Stacey Bent

All Publications

• Theoretical and Experimental Studies of CoGa Catalysts for the Hydrogenation of CO2 to Methanol CATALYSIS LETTERS Singh, J. A., Cao, A., Schumann, J., Wang, T., Norskov, J. K., Abild-Pedersen, F., Bent, S. F. 2018; 148 (12): 3583–91

  View details for DOI 10.1007/s10562-018-2542-x

  View details for Web of Science ID 000449257700001

• Encapsulating perovskite solar cells to withstand damp heat and thermal cycling SUSTAINABLE ENERGY & FUELS Cheacharoen, R., Boyd, C. C., Burkhard, G. F., Leijtens, T., Raiford, J. A., Bush, K. A., Bent, S. F., McGehee, M. D. 2018; 2 (11): 2398–2406

  View details for DOI 10.1039/c8se00250a

  View details for Web of Science ID 000448425900018

• In situ observation of phase changes of a silica-supported cobalt catalyst for the Fischer-Tropsch process by the development of a synchrotron-compatible insitu/operando powder X-ray diffraction cell. Journal of synchrotron radiation Hoffman, A. S., Singh, J. A., Bent, S. F., Bare, S. R. 2018; 25 (Pt 6): 1673–82

  Abstract

  In situ characterization of catalysts gives direct insight into the working state of the material. Here, the design and performance characteristics of a universal insitu synchrotron-compatible X-ray diffraction cell capable of operation at high temperature and high pressure, 1373 K, and 35 bar, respectively, are reported. Its performance is demonstrated by characterizing a cobalt-based catalyst used in a prototypical high-pressure catalytic reaction, the Fischer-Tropsch synthesis, using X-ray diffraction. Cobalt nanoparticles supported on silica were studied insitu during Fischer-Tropsch catalysis using syngas, H2 and CO, at 723 K and 20 bar. Post reaction, the Co nanoparticles were carburized at elevated pressure, demonstrating an increased rate of carburization compared with atmospheric studies.

  View details for DOI 10.1107/S1600577518013942

  View details for PubMedID 30407177

• Tin-lead halide perovskites with improved thermal and air stability for efficient all-perovskite tandem solar cells SUSTAINABLE ENERGY & FUELS Leijtens, T., Prasanna, R., Bush, K. A., Eperon, G. E., Raiford, J. A., Gold-Parker, A., Wolf, E. J., Swifter, S. A., Boyd, C. C., Wang, H., Toney, M. F., Bent, S. F., McGehee, M. D. 2018; 2 (11): 2450–59

  View details for DOI 10.1039/c8se00314a

  View details for Web of Science ID 000448425900009

• Optical modeling of wide-bandgap perovskite and perovskite/silicon tandem solar cells using complex refractive indices for arbitrary-bandgap perovskite absorbers OPTICS EXPRESS Manzoor, S., Haeusele, J., Bush, K. A., Palmstrom, A. F., Carpenter, J., Yu, Z. J., Bent, S. F., Mcgehee, M. D., Holman, Z. C. 2018; 26 (21): 27441–60

  View details for DOI 10.1364/OE.26.027441

  View details for Web of Science ID 000447287700048

• Minimizing Current and Voltage Losses to Reach 25% Efficient Monolithic Two-Termina Perovskite-Silicon Tandem Solar Cells ACS ENERGY LETTERS Bush, K. A., Manzoor, S., Frohna, K., Yu, Z. J., Raiford, J. A., Palmstrom, A. F., Wang, H., Prasanna, R., Bent, S. F., Holman, Z. C., McGehee, M. D. 2018; 3 (9): 2173–80

  View details for DOI 10.1021/acsenergylett.8b01201

  View details for Web of Science ID 000445052900023

• Formation and Ripening of Self-Assembled Multilayers from the Vapor-Phase Deposition of Dodecanethiol on Copper Oxide CHEMISTRY OF MATERIALS Bergsman, D. S., Liu, T., Closser, R. G., Nardi, K. L., Draeger, N., Hausmann, D. M., Bent, S. F. 2018; 30 (16): 5694–5703

  View details for DOI 10.1021/acs.chemmater.8b02150

  View details for Web of Science ID 000443526300022

• Interfacial Effects of Tin Oxide Atomic Layer Deposition in Metal Halide Perovskite Photovoltaics ADVANCED ENERGY MATERIALS Palmstrom, A. F., Raiford, J. A., Prasanna, R., Bush, K. A., Sponseller, M., Cheacharoen, R., Minichetti, M. C., Bergsman, D. S., Leijtens, T., Wang, H., Bulovic, V., McGehee, M. D., Bent, S. F. 2018; 8 (23)

  View details for DOI 10.1002/aenm.201800591

  View details for Web of Science ID 000441741900012

• Molecular Layer Deposition of a Highly Stable Silicon Oxycarbide Thin Film Using an Organic Chlorosilane and Water ACS APPLIED MATERIALS & INTERFACES Closser, R. G., Bergsman, D. S., Bent, S. F. 2018; 10 (28): 24266–74

  Abstract

  In this study, molecular layer deposition (MLD) was used to deposit ultrathin films of methylene-bridged silicon oxycarbide (SiOC) using bis(trichlorosilyl)methane and water as precursors at room temperature. By utilizing bifunctional trichlorosilane precursors, films of SiOC can be deposited in a layer-by-layer manner, wherein a water co-reactant circumvents the need for plasma, high temperatures, or highly oxidizing precursors. In this manner, films could be grown without the degradation commonly seen in other SiOC deposition methods. Saturation behavior for both precursors was confirmed for the MLD process, and a constant growth rate of 0.5 ± 0.1 Å/cycle was determined. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy were used to verify the reaction between precursors and to gain insight into the final film composition. Unlike most MLD films, which grow polymers in a linear fashion, XPS analysis indicates that neighboring silanol groups within the films tend to condense, forming a highly cross-linked network structure, whereby, on average, two-thirds of silanol groups undergo a condensation reaction. Further indication of cross-linking is seen by XPS during in situ annealing, which shows exceptional temperature stability of the film up to 600 °C in vacuum, in contrast to linear SiOC films, which are known to degrade below this temperature. The films also exhibit high chemical stability against acids, bases, and solvents. A film density of 1.4 g/cm3 was measured by X-ray reflectivity, while the dielectric constant and refractive index were determined to be 2.6 ± 0.3 and 1.6 ± 0.1, respectively, at a 633 nm wavelength. The low dielectric constant, high ease of deposition, and exceptional thermal and chemical stabilities of this MLD SiOC film suggest that it may have potential applications for electronic devices.

  View details for DOI 10.1021/acsami.8b06057

  View details for Web of Science ID 000439528400094

  View details for PubMedID 29965720

• Atomic and Molecular Layer Deposition of Hybrid Mo-Thiolate Thin Films with Enhanced Catalytic Activity ADVANCED FUNCTIONAL MATERIALS MacIsaac, C., Schneider, J. R., Closser, R. G., Hellstern, T. R., Bergsman, D. S., Park, J., Liu, Y., Sinclair, R., Bent, S. F. 2018; 28 (26)

  View details for DOI 10.1002/adfm.201800852

  View details for Web of Science ID 000436104800016

• Copper interstitial recombination centers in Cu3N PHYSICAL REVIEW B Yee, Y., Inoue, H., Hultqvist, A., Hanifi, D., Salleo, A., Magyari-Kope, B., Nishi, Y., Bent, S. F., Clemens, B. M. 2018; 97 (24)

  View details for DOI 10.1103/PhysRevB.97.245201

  View details for Web of Science ID 000434016100006

• Area-Selective Atomic Layer Deposition of Metal Oxides on Noble Metals through Catalytic Oxygen Activation CHEMISTRY OF MATERIALS Singh, J. A., Thissen, N. W., Kim, W., Johnson, H., Kessels, W. M., Bol, A. A., Bent, S. F., Mackus, A. M. 2018; 30 (3): 663–70

  Abstract

  Area-selective atomic layer deposition (ALD) is envisioned to play a key role in next-generation semiconductor processing and can also provide new opportunities in the field of catalysis. In this work, we developed an approach for the area-selective deposition of metal oxides on noble metals. Using O2 gas as co-reactant, area-selective ALD has been achieved by relying on the catalytic dissociation of the oxygen molecules on the noble metal surface, while no deposition takes place on inert surfaces that do not dissociate oxygen (i.e., SiO2, Al2O3, Au). The process is demonstrated for selective deposition of iron oxide and nickel oxide on platinum and iridium substrates. Characterization by in situ spectroscopic ellipsometry, transmission electron microscopy, scanning Auger electron spectroscopy, and X-ray photoelectron spectroscopy confirms a very high degree of selectivity, with a constant ALD growth rate on the catalytic metal substrates and no deposition on inert substrates, even after 300 ALD cycles. We demonstrate the area-selective ALD approach on planar and patterned substrates and use it to prepare Pt/Fe2O3 core/shell nanoparticles. Finally, the approach is proposed to be extendable beyond the materials presented here, specifically to other metal oxide ALD processes for which the precursor requires a strong oxidizing agent for growth.

  View details for DOI 10.1021/acs.chemmater.7b03818

  View details for Web of Science ID 000425840500016

  View details for PubMedID 29503508

  View details for PubMedCentralID PMC5828705

• Photoelectrochemical Water Oxidation by GaAs Nanowire Arrays Protected with Atomic Layer Deposited NiO (x) Electrocatalysts Zeng, J., Xu, X., Parameshwaran, V., Baker, J., Bent, S., Wong, H., Clemens, B. SPRINGER. 2018: 932–37

  View details for DOI 10.1007/s11664-017-5824-y

  View details for Web of Science ID 000419791800005

• Understanding the Active Sites of CO Hydrogenation on Pt-Co Catalysts Prepared Using Atomic Layer Deposition JOURNAL OF PHYSICAL CHEMISTRY C Singh, J. A., Yang, N., Liu, X., Tsai, C., Stone, K. H., Johnson, B., Koh, A., Bent, S. F. 2018; 122 (4): 2184–94

  View details for DOI 10.1021/acs.jpcc.7b10541

  View details for Web of Science ID 000424316200036

• Thermal adsorption-enhanced atomic layer etching of Si3N4 JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Kim, W., Sung, D., Oh, S., Woo, J., Lim, S., Lee, H., Bent, S. F. 2018; 36 (1)

  View details for DOI 10.1116/1.5003271

  View details for Web of Science ID 000418961400030

• The Role of Sodium in Tuning Product Distribution in Syngas Conversion by Rh Catalysts CATALYSIS LETTERS Yang, N., Liu, X., Asundi, A. S., Norskov, J. K., Bent, S. F. 2018; 148 (1): 289–97

  View details for DOI 10.1007/s10562-017-2223-1

  View details for Web of Science ID 000419901300031

• Photoactivated Molecular Layer Deposition through Iodo-Ene Coupling Chemistry CHEMISTRY OF MATERIALS Lillethorup, M., Bergsman, D. S., Sandoval, T. E., Bent, S. F. 2017; 29 (23): 9897–9906

  View details for DOI 10.1021/acs.chemmater.7b01780

  View details for Web of Science ID 000418206600007

• Nanoengineering Heterogeneous Catalysts by Atomic Layer Deposition. Annual review of chemical and biomolecular engineering Singh, J. A., Yang, N., Bent, S. F. 2017; 8: 41-62

  Abstract

  A new generation of catalysts is needed to meet society's energy and resource requirements. Current catalyst synthesis does not fully achieve optimum control of composition, size, and structure. Atomic layer deposition (ALD) is an emerging technique that allows for synthesis of highly controlled catalysts in the form of films, nanoparticles, and single sites. The addition of ALD coatings can also be used to introduce promoters and improve the stability of traditional catalysts. Evolving research shows promise for applying ALD to understand catalytically active sites and create next-generation catalysts using advanced 3D nanostructures.

  View details for DOI 10.1146/annurev-chembioeng-060816-101547

  View details for PubMedID 28301732

• Adsorption of Homotrifunctional 1,2,3-Benzenetriol on a Ge(100)-2 × 1 Surface. Langmuir Sandoval, T. E., Bent, S. F. 2017

  Abstract

  The adsorption of the homotrifunctional 1,2,3-benzenetriol on Ge(100)-2 × 1 has been investigated by density functional theory calculations, Fourier transform infrared spectroscopy, and X-ray-photoelectron spectroscopy. The results show that the adsorption can occur through OH dissociation of all three hydroxyl groups, and that all three reaction pathways are kinetically and thermodynamically favorable. A coverage-dependent analysis shows that at low coverage, the molecule reacts to form a mix of trifold and dually bound adsorbates. As the coverage increases, the reactions are limited to dissociative adsorption through single and dual attachments. Calculations on the three possible dually bound configurations further reveals that the dissociative adsorption of the third hydroxyl group is limited by geometrical constraints to only two reaction channels. Finally, the proximity between OH-groups in the molecule favors intra- and intermolecular hydrogen bonding, which stabilizes singly and dually bound adsorbate configurations and limits the reactivity of the functional groups.

  View details for DOI 10.1021/acs.langmuir.7b00872

  View details for PubMedID 28574269

• Formation of Germa-ketenimine on the Ge(100) Surface by Adsorption of tert-Butyl Isocyanide. Journal of the American Chemical Society Shong, B., Yoo, J. S., Sandoval, T. E., Bent, S. F. 2017

  Abstract

  Reactions of the (100) surfaces of Ge and Si with organic molecules have been generally understood within the concept of "dimers" formed by the 2 × 1 surface reconstruction. In this work, the adsorption of tert-butyl isocyanide on the Ge(100)-2 × 1 surface at large exposures is investigated under ultrahigh vacuum conditions. A combination of infrared spectroscopy, X-ray photoelectron spectroscopy, and temperature-programmed desorption experiments along with dispersion-corrected density functional theory calculations is used to determine the surface products. Upon adsorption of a dense monolayer of tert-butyl isocyanide, a product whose structure resembles a germa-ketenimine (N=C=Ge) with σ donation toward and π back-donation from the Ge(100) surface appears. Formation of this structure involves divalent-type surface Ge atoms that arise from cleavage of the Ge(100)-2 × 1 surface dimers. Our results reveal an unprecedented class of reactions of organic molecules at the Ge(100) surface.

  View details for DOI 10.1021/jacs.7b04755

  View details for PubMedID 28560877

• Ultrathin light absorbers based on plasmonic nanocomposites SPIE Newsroom Hägglund, C., Bent, S., F.

  View details for DOI 10.1117/2.1201309.005135

• Correcting defects in area selective molecular layer deposition JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Closser, R. G., Bergsman, D. S., Ruelas, L., Hashemi, F. S., Bent, S. F. 2017; 35 (3)

  View details for DOI 10.1116/1.4980049

  View details for Web of Science ID 000401122700031

• Effect of Backbone Chemistry on the Structure of Polyurea Films Deposited by Molecular Layer Deposition CHEMISTRY OF MATERIALS Bergsman, D. S., Closser, R. G., Tassone, C. J., Clemens, B. M., Nordlund, D., Bent, S. F. 2017; 29 (3): 1192-1203

  View details for DOI 10.1021/acs.chemmater.6b04530

  View details for Web of Science ID 000394924100037

• Incomplete elimination of precursor ligands during atomic layer deposition of zinc-oxide, tin-oxide, and zinc-tin-oxide. journal of chemical physics Mackus, A. J., MacIsaac, C., Kim, W., Bent, S. F. 2017; 146 (5): 052802-?

  Abstract

  For atomic layer deposition (ALD) of doped, ternary, and quaternary materials achieved by combining multiple binary ALD processes, it is often difficult to correlate the material properties and growth characteristics with the process parameters due to a limited understanding of the underlying surface chemistry. In this work, in situ Fourier transform infrared (FTIR) spectroscopy was employed during ALD of zinc-oxide, tin-oxide, and zinc-tin-oxide (ZTO) with the precursors diethylzinc (DEZ), tetrakis(dimethylamino)tin (TDMASn), and H2O. The main aim was to investigate the molecular basis for the nucleation delay during ALD of ZTO, observed when ZnO ALD is carried out after SnO2 ALD. Gas-phase FTIR spectroscopy showed that dimethylamine, the main reaction product of the SnO2 ALD process, is released not only during SnO2 ALD but also when depositing ZnO after SnO2, indicating incomplete removal of the ligands of the TDMASn precursor from the surface. Transmission FTIR spectroscopy performed during ALD on SiO2 powder revealed that a significant fraction of the ligands persist during both SnO2 and ZnO ALD. These observations provide experimental evidence for a recently proposed mechanism, based on theoretical calculations, suggesting that the elimination of precursor ligands is often not complete. In addition, it was found that the removal of precursor ligands by H2O exposure is even less effective when ZnO ALD is carried out after SnO2 ALD, which likely causes the nucleation delay in ZnO ALD during the deposition of ZTO. The underlying mechanisms and the consequences of the incomplete elimination of precursor ligands are discussed.

  View details for DOI 10.1063/1.4961459

  View details for PubMedID 28178803

• Buffer Layer Point Contacts for CIGS Solar Cells Using Nanosphere Lithography and Atomic Layer Deposition IEEE JOURNAL OF PHOTOVOLTAICS Hultqvist, A., Sone, T., Bent, S. F. 2017; 7 (1): 322-328

  View details for DOI 10.1109/JPHOTOV.2016.2627621

  View details for Web of Science ID 000395836800046

• Photoanodes for Photoelectrochemical Water Splitting. Nano letters Narkeviciute, I., Chakthranont, P., Mackus, A. J., Hahn, C., Pinaud, B. A., Bent, S. F., Jaramillo, T. F. 2016; 16 (12): 7565-7572

  Abstract

  Nanostructured core-shell Si-Ta3N5 photoanodes were designed and synthesized to overcome charge transport limitations of Ta3N5 for photoelectrochemical water splitting. The core-shell devices were fabricated by atomic layer deposition of amorphous Ta2O5 onto nanostructured Si and subsequent nitridation to crystalline Ta3N5. Nanostructuring with a thin shell of Ta3N5 results in a 10-fold improvement in photocurrent compared to a planar device of the same thickness. In examining thickness dependence of the Ta3N5 shell from 10 to 70 nm, superior photocurrent and absorbed-photon-to-current efficiencies are obtained from the thinner Ta3N5 shells, indicating minority carrier diffusion lengths on the order of tens of nanometers. The fabrication of a heterostructure based on a semiconducting, n-type Si core produced a tandem photoanode with a photocurrent onset shifted to lower potentials by 200 mV. CoTiOx and NiOx water oxidation cocatalysts were deposited onto the Si-Ta3N5 to yield active photoanodes that with NiOx retained 50-60% of their maximum photocurrent after 24 h chronoamperometry experiments and are thus among the most stable Ta3N5 photoanodes reported to date.

  View details for PubMedID 27960454

• Selective Deposition of Dielectrics: Limits and Advantages of Alkanethiol Blocking Agents on Metal-Dielectric Patterns. ACS applied materials & interfaces Minaye Hashemi, F. S., Birchansky, B. R., Bent, S. F. 2016; 8 (48): 33264-33272

  Abstract

  Area selective atomic layer deposition has the potential to significantly improve current fabrication approaches by introducing a bottom-up process in which robust and conformal thin films are selectively deposited onto patterned substrates. In this paper, we demonstrate selective deposition of dielectrics on metal/dielectric patterns by protecting metal surfaces using alkanethiol blocking layers. We examine alkanethiol self-assembled monolayers (SAMs) with two different chain lengths deposited both in vapor and in solution and show that in both systems, thiols have the ability to block surfaces against dielectric deposition. We show that thiol molecules can displace Cu oxide, opening possibilities for easier sample preparation. A vapor-deposited alkanethiol SAM is shown to be more effective than a solution-deposited SAM in blocking ALD, even after only 30 s of exposure. The vapor deposition also results in a much better thiol regeneration process and may facilitate deposition of the SAMs on porous or three-dimensional structures, allowing for the fabrication of next generation electronic devices.

  View details for PubMedID 27934166

• Selective Deposition of Dielectrics: Limits and Advantages of Alkanethiol Blocking Agents on Metal-Dielectric Patterns ACS APPLIED MATERIALS & INTERFACES Hashemi, F. S., Birchansky, B. R., Bent, S. F. 2016; 8 (48): 33264-33272

  View details for DOI 10.1021/acsami.6b09960

  View details for Web of Science ID 000389624600073

• Tandem Core-Shell Si-Ta3N5 Photoanodes for Photoelectrochemical Water Splitting NANO LETTERS Narkeviciute, I., Chakthranont, P., Mackus, A. J., Hahn, C., Pinaud, B. A., Bent, S. F., Jaramillo, T. F. 2016; 16 (12): 7565-7572

  View details for DOI 10.1021/acs.nanolett.6b03408

  View details for Web of Science ID 000389963200037

• Perovskite-perovskite tandem photovoltaics with optimized band gaps SCIENCE Eperon, G. E., Leijtens, T., Bush, K. A., Prasanna, R., Green, T., Wang, J. T., McMeekin, D. P., Volonakis, G., Milot, R. L., May, R., Palmstrom, A., Slotcavage, D. J., Belisle, R. A., Patel, J. B., Parrott, E. S., Sutton, R. J., Ma, W., Moghadam, F., Conings, B., Babayigit, A., Boyen, H., Bent, S., Giustino, F., Herz, L. M., Johnston, M. B., McGehee, M. D., Snaith, H. J. 2016; 354 (6314): 861-865

  Abstract

  We demonstrate four- and two-terminal perovskite-perovskite tandem solar cells with ideally matched band gaps. We develop an infrared-absorbing 1.2-electron volt band-gap perovskite, FA0.75Cs0.25Sn0.5Pb0.5I3, that can deliver 14.8% efficiency. By combining this material with a wider-band gap FA0.83Cs0.17Pb(I0.5Br0.5)3 material, we achieve monolithic two-terminal tandem efficiencies of 17.0% with >1.65-volt open-circuit voltage. We also make mechanically stacked four-terminal tandem cells and obtain 20.3% efficiency. Notably, we find that our infrared-absorbing perovskite cells exhibit excellent thermal and atmospheric stability, not previously achieved for Sn-based perovskites. This device architecture and materials set will enable "all-perovskite" thin-film solar cells to reach the highest efficiencies in the long term at the lowest costs.

  View details for DOI 10.1126/science.aaf9717

  View details for Web of Science ID 000388531900034

  View details for PubMedID 27856902

• Impact of Conformality and Crystallinity for Ultrathin 4 nm Compact TiO2 Layers in Perovskite Solar Cells ADVANCED MATERIALS INTERFACES Roelofs, K. E., Pool, V. L., Bobb-Semple, D. A., Palmstrom, A. F., Santra, P. K., Van Campen, D. G., Toney, M. F., Bent, S. F. 2016; 3 (21)

  View details for DOI 10.1002/admi.201600580

  View details for Web of Science ID 000393772400015

• Sequential Regeneration of Self-Assembled Monolayers for Highly Selective Atomic Layer Deposition ADVANCED MATERIALS INTERFACES Hashemi, F. S., Bent, S. F. 2016; 3 (21)

  View details for DOI 10.1002/admi.201600464

  View details for Web of Science ID 000393772400010

• Molecular Ligands Control Superlattice Structure and Crystallite Orientation in Colloidal Quantum Dot Solids CHEMISTRY OF MATERIALS Santra, P. K., Palmstrom, A. F., Tassone, C. J., Bent, S. F. 2016; 28 (19): 7072-7081

  View details for DOI 10.1021/acs.chemmater.6b03076

  View details for Web of Science ID 000385336500032

• Adsorption of heterobifunctional 4-nitrophenol on the Ge(100)-2 x 1 surface SURFACE SCIENCE Shong, B., Hellstern, T. R., Bent, S. F. 2016; 650: 279-284

  View details for DOI 10.1016/j.susc.2015.04.007

  View details for Web of Science ID 000377837800035

• Tailoring Mixed-Halide, Wide-Gap Perovskites via Multistep Conversion Process ACS APPLIED MATERIALS & INTERFACES Bae, D., Palmstrom, A., Roelofs, K., Mei, B., Chorkendorff, I., Bent, S. F., Vesborg, P. C. 2016; 8 (23): 14301-14306

  Abstract

  Wide-band-gap mixed-halide CH3NH3PbI3-XBrX-based solar cells have been prepared by means of a sequential spin-coating process. The spin-rate for PbI2 as well as its repetitive deposition are important in determining the cross-sectional shape and surface morphology of perovskite, and, consequently, J-V performance. A perovskite solar cell converted from PbI2 with a dense bottom layer and porous top layer achieved higher device performance than those of analogue cells with a dense PbI2 top layer. This work demonstrates a facile way to control PbI2 film configuration and morphology simply by modification of spin-coating parameters without any additional chemical or thermal post-treatment.

  View details for DOI 10.1021/acsami.6b01246

  View details for Web of Science ID 000378195000001

  View details for PubMedID 27227816

• A Process for Topographically Selective Deposition on 3D Nanostructures by Ion Implantation ACS NANO Kim, W., Hashemi, F. S., Mackus, A. J., Singh, J., Kim, Y., Bobb-Semple, D., Fan, Y., Kaufman-Osborn, T., Godet, L., Bent, S. F. 2016; 10 (4): 4451-4458

  Abstract

  Area-selective atomic layer deposition (AS-ALD) is attracting increasing interest because of its ability to enable both continued dimensional scaling and accurate pattern placement for next-generation nanoelectronics. Here we report a strategy for depositing material onto three-dimensional (3D) nanostructures with topographic selectivity using an ALD process with the aid of an ultrathin hydrophobic surface layer. Using ion implantation of fluorocarbons (CFx), a hydrophobic interfacial layer is formed, which in turn causes significant retardation of nucleation during ALD. We demonstrate the process for Pt ALD on both blanket and 2D patterned substrates. We extend the process to 3D structures, demonstrating that this method can achieve selective anisotropic deposition, selectively inhibiting Pt deposition on deactivated horizontal regions while ensuring that only vertical surfaces are decorated during ALD. The efficacy of the approach for metal oxide ALD also shows promise, though further optimization of the implantation conditions is required. The present work advances practical applications that require area-selective coating of surfaces in a variety of 3D nanostructures according to their topographical orientation.

  View details for DOI 10.1021/acsnano.6b00094

  View details for Web of Science ID 000375245000063

  View details for PubMedID 26950397

• Intrinsic Selectivity and Structure Sensitivity of Rhodium Catalysts for C2+ Oxygenate Production. Journal of the American Chemical Society Yang, N., Medford, A. J., Liu, X., Studt, F., Bligaard, T., Bent, S. F., Nørskov, J. K. 2016; 138 (11): 3705-3714

  Abstract

  Synthesis gas (CO + H2) conversion is a promising route to converting coal, natural gas, or biomass into synthetic liquid fuels. Rhodium has long been studied as it is the only elemental catalyst that has demonstrated selectivity to ethanol and other C2+ oxygenates. However, the fundamentals of syngas conversion over rhodium are still debated. In this work a microkinetic model is developed for conversion of CO and H2 into methane, ethanol, and acetaldehyde on the Rh (211) and (111) surfaces, chosen to describe steps and close-packed facets on catalyst particles. The model is based on DFT calculations using the BEEF-vdW functional. The mean-field kinetic model includes lateral adsorbate-adsorbate interactions, and the BEEF-vdW error estimation ensemble is used to propagate error from the DFT calculations to the predicted rates. The model shows the Rh(211) surface to be ∼6 orders of magnitude more active than the Rh(111) surface, but highly selective toward methane, while the Rh(111) surface is intrinsically selective toward acetaldehyde. A variety of Rh/SiO2 catalysts are synthesized, tested for catalytic oxygenate production, and characterized using TEM. The experimental results indicate that the Rh(111) surface is intrinsically selective toward acetaldehyde, and a strong inverse correlation between catalytic activity and oxygenate selectivity is observed. Furthermore, iron impurities are shown to play a key role in modulating the selectivity of Rh/SiO2 catalysts toward ethanol. The experimental observations are consistent with the structure-sensitivity predicted from theory. This work provides an improved atomic-scale understanding and new insight into the mechanism, active site, and intrinsic selectivity of syngas conversion over rhodium catalysts and may also guide rational design of alloy catalysts made from more abundant elements.

  View details for DOI 10.1021/jacs.5b12087

  View details for PubMedID 26958997

• Growth, intermixing, and surface phase formation for zinc tin oxide nanolaminates produced by atomic layer deposition JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Hagglund, C., Grehl, T., Tanskanen, J. T., Yee, Y. S., Mullings, M. N., Mackus, A. J., Maclsaac, C., Clemens, B. M., Brongersma, H. H., Bent, S. F. 2016; 34 (2)

  View details for DOI 10.1116/1.4941411

  View details for Web of Science ID 000372352300038

• Strong Coupling of Plasmon and Nanocavity Modes for Dual-Band, Near-Perfect Absorbers and Ultrathin Photovoltaics ACS PHOTONICS Haegglund, C., Zeltzer, G., Ruiz, R., Wangperawong, A., Roelofs, K. E., Bent, S. F. 2016; 3 (3): 456-463

  View details for DOI 10.1021/acsphotonics.5b00651

  View details for Web of Science ID 000372479500022

• Polysulfide ligand exchange on zinc sulfide nanocrystal surfaces for improved film formation APPLIED SURFACE SCIENCE Herron, S. M., Lawal, Q. O., Bent, S. F. 2015; 359: 106-113

  View details for DOI 10.1016/j.apsusc.2015.10.059

  View details for Web of Science ID 000366220600016

• Quantifying Geometric Strain at the PbS QD-TiO2 Anode Interface and Its Effect on Electronic Structures NANO LETTERS Trejo, O., Roelofs, K. E., Xu, S., Logar, M., Sarangi, R., Nordlund, D., Dadlani, A. L., Kravec, R., Dasgupta, N. P., Bent, S. F., Prinz, F. B. 2015; 15 (12): 7829-7836

  View details for DOI 10.1021/acs.nanolett.5b02373

  View details for Web of Science ID 000366339600008

  View details for PubMedID 26554814

• Deep recombination centers in Cu2ZnSnSe4 revealed by screened-exchange hybrid density functional theory PHYSICAL REVIEW B Yee, Y. S., Magyari-Koepe, B., Nishi, Y., Bent, S. F., Clemens, B. M. 2015; 92 (19)

  View details for DOI 10.1103/PhysRevB.92.195201

  View details for Web of Science ID 000364016300003

• Formation of Continuous Pt Films on the Graphite Surface by Atomic Layer Deposition with Reactive O-3 CHEMISTRY OF MATERIALS Lee, H., Bent, S. F. 2015; 27 (19): 6802-6809

  View details for DOI 10.1021/acs.chemmater.5b03076

  View details for Web of Science ID 000362920700041

• Self-Correcting Process for High Quality Patterning by Atomic Layer Deposition. ACS nano Minaye Hashemi, F. S., Prasittichai, C., Bent, S. F. 2015; 9 (9): 8710-8717

  Abstract

  Nanoscale patterning of materials is widely used in a variety of device applications. Area selective atomic layer deposition (ALD) has shown promise for deposition of patterned structures with subnanometer thickness control. However, the current process is limited in its ability to achieve good selectivity for thicker films formed at higher number of ALD cycles. In this report, we demonstrate a strategy for achieving selective film deposition via a self-correcting process on patterned Cu/SiO2 substrates. We employ the intrinsically selective adsorption of octadecylphosphonic acid self-assembled monolayers on Cu over SiO2 surfaces to selectively create a resist layer only on Cu. ALD is then performed on the patterns to deposit a dielectric film. A mild etchant is subsequently used to selectively remove any residual dielectric film deposited on the Cu surface while leaving the dielectric film on SiO2 unaffected. The selectivity achieved after this treatment, measured by compositional analysis, is found to be 10 times greater than for conventional area selective ALD.

  View details for DOI 10.1021/acsnano.5b03125

  View details for PubMedID 26181140

• Creating Highly Active Atomic Layer Deposited NiO Electrocatalysts for the Oxygen Evolution Reaction ADVANCED ENERGY MATERIALS Nardi, K. L., Yang, N., Dickens, C. F., Strickler, A. L., Bent, S. F. 2015; 5 (17)

  View details for DOI 10.1002/aenm.201500412

  View details for Web of Science ID 000361226700004

• Increased Quantum Dot Loading by pH Control Reduces Interfacial Recombination in Quantum-Dot-Sensitized Solar Cells. ACS nano Roelofs, K. E., Herron, S. M., Bent, S. F. 2015; 9 (8): 8321-8334

  Abstract

  The power conversion efficiency of quantum-dot-sensitized solar cells (QDSSCs) hinges on interfacial charge transfer. Increasing quantum dot (QD) loading on the TiO2 anode has been proposed as a means to block recombination of electrons in the TiO2 to the hole transport material; however, it is not known whether a corresponding increase in QD-mediated recombination processes might lead to an overall higher rate of recombination. In this work, a 3-fold increase in PbS QD loading was achieved by the addition of an aqueous base to negatively charge the TiO2 surface during Pb cation deposition. Increased QD loading improved QDSSC device efficiencies through both increased light absorption and an overall reduction in recombination. Unexpectedly, we also found increased QD size had the detrimental effect of increasing recombination. Kinetic modeling of the effect of QD size on interfacial charge transfer processes provided qualitative agreement with the observed variation in recombination lifetimes. These results demonstrate a robust method of improving QD loading, identify the specific mechanisms by which increased QD deposition impacts device performance, and provide a framework for future efforts optimizing the device architecture of QDSSCs.

  View details for DOI 10.1021/acsnano.5b02853

  View details for PubMedID 26244426

• Increased Quantum Dot Loading by pH Control Reduces Interfacial Recombination in Quantum-Dot-Sensitized Solar Cells ACS NANO Roelofs, K. E., Herron, S. M., Bent, S. F. 2015; 9 (8): 8321-8334

  View details for DOI 10.1021/acsnano.5b02853

  View details for Web of Science ID 000360323300061

• Reducing interface recombination for Cu(In,Ga)Se-2 by atomic layer deposited buffer layers APPLIED PHYSICS LETTERS Hultqvist, A., Li, J. V., Kuciauskas, D., Dippo, P., Contreras, M. A., Levi, D. H., Bent, S. F. 2015; 107 (3)

  View details for DOI 10.1063/1.4927096

  View details for Web of Science ID 000358675600070

• Unidirectional Adsorption of Bifunctional 1,4-Phenylene Diisocyanide on the Ge(100)-2 x 1 Surface JOURNAL OF PHYSICAL CHEMISTRY LETTERS Shong, B., Sandoval, T. E., Crow, A. M., Bent, S. F. 2015; 6 (6): 1037-1041

  View details for DOI 10.1021/acs.jpclett.5b00098

  View details for Web of Science ID 000351563100022

• Unidirectional Adsorption of Bifunctional 1,4-Phenylene Diisocyanide on the Ge(100)-2 × 1 Surface. journal of physical chemistry letters Shong, B., Sandoval, T. E., Crow, A. M., Bent, S. F. 2015; 6 (6): 1037-1041

  Abstract

  Adsorption of bifunctional organic molecules on semiconductor surfaces is important for surface modification; however, most bifunctional molecules previously studied have yielded mixtures of singly and dually tethered adsorbates. Here we report the adsorption of bifunctional 1,4-phenylene diisocyanide (PDI) on the Ge(100)-2 × 1 surface, in which singly bound adsorbates are selectively produced. As shown by polarized multiple internal reflection infrared spectroscopy experiments and density functional theory calculations, PDI adsorbates form a single C-dative bonding configuration through one of the isocyanide functionalities, retaining one unreacted isocyanide moiety per adsorbate. The angle of the molecular axis is ∼30° from the surface normal. The delocalized π* molecular orbital of the free molecule is also preserved upon adsorption. These results demonstrate the potential usefulness of isocyanide adsorbates as a means toward selective organic functionalization of semiconductor surfaces.

  View details for DOI 10.1021/acs.jpclett.5b00098

  View details for PubMedID 26262866

• ALD of Ultrathin Ternary Oxide Electrocatalysts for Water Splitting ACS CATALYSIS Pickrahn, K. L., Garg, A., Bent, S. F. 2015; 5 (3): 1609-1616

  View details for DOI 10.1021/cs501532b

  View details for Web of Science ID 000350843500026

• Improving Performance in Colloidal Quantum Dot Solar Cells by Tuning Band Alignment through Surface Dipole Moments JOURNAL OF PHYSICAL CHEMISTRY C Santra, P. K., Palmstrom, A. F., Tanskanen, J. T., Yang, N., Bent, S. F. 2015; 119 (6): 2996-3005

  View details for DOI 10.1021/acs.jpcc.5b00341

  View details for Web of Science ID 000349578400011

• Applications of ALD MnO to electrochemical water splitting PHYSICAL CHEMISTRY CHEMICAL PHYSICS Pickrahn, K. L., Gorlin, Y., Seitz, L. C., Garg, A., Nordlund, D., Jaramillo, T. F., Bent, S. F. 2015; 17 (21): 14003-14011

  Abstract

  Atomic layer deposition (ALD) is an attractive method to deposit uniform catalytic films onto high surface area electrodes. One interesting material for ALD synthesis is MnOx, a promising earth-abundant catalyst for the oxygen evolution reaction (OER). It has previously been shown that catalysts beginning as MnO synthesized using ALD on smooth glassy carbon (s-GC) electrodes and Mn2O3 obtained upon annealing MnO on s-GC are active OER catalysts. Here, we use ALD to deposit MnO on high surface area GC (HSA-GC) substrates, forming an active catalyst on a geometric surface area basis. We then characterize three types of catalysts, HSA-GC MnO, s-GC MnO, and annealed MnO (Mn2O3), using cyclic voltammetry (CV), scanning electron microscopy (SEM), and ex situ X-ray absorption spectroscopy (XAS). We show that under OER conditions, all three catalysts oxidize to similar surface states with a mixture of Mn(3+)/Mn(4+) and that MnOx surface area effects can account for the observed differences in the catalytic activity. We also demonstrate the need for a high surface area support for high OER activity on a geometric basis.

  View details for DOI 10.1039/c5cp00843c

  View details for Web of Science ID 000354946200025

  View details for PubMedID 25946998

• Atomic layer deposition in nanostructured photovoltaics: tuning optical, electronic and surface properties NANOSCALE Palmstrom, A. F., Santra, P. K., Bent, S. F. 2015; 7 (29): 12266-12283

  Abstract

  Nanostructured materials offer key advantages for third-generation photovoltaics, such as the ability to achieve high optical absorption together with enhanced charge carrier collection using low cost components. However, the extensive interfacial areas in nanostructured photovoltaic devices can cause high recombination rates and a high density of surface electronic states. In this feature article, we provide a brief review of some nanostructured photovoltaic technologies including dye-sensitized, quantum dot sensitized and colloidal quantum dot solar cells. We then introduce the technique of atomic layer deposition (ALD), which is a vapor phase deposition method using a sequence of self-limiting surface reaction steps to grow thin, uniform and conformal films. We discuss how ALD has established itself as a promising tool for addressing different aspects of nanostructured photovoltaics. Examples include the use of ALD to synthesize absorber materials for both quantum dot and plasmonic solar cells, to grow barrier layers for dye and quantum dot sensitized solar cells, and to infiltrate coatings into colloidal quantum dot solar cell to improve charge carrier mobilities as well as stability. We also provide an example of monolayer surface modification in which adsorbed ligand molecules on quantum dots are used to tune the band structure of colloidal quantum dot solar cells for improved charge collection. Finally, we comment on the present challenges and future outlook of the use of ALD for nanostructured photovoltaics.

  View details for DOI 10.1039/c5nr02080h

  View details for Web of Science ID 000358207700002

• Highly Textured Tin(II) Sulfide Thin Films Formed from Sheetlike Nanocrystal Inks CHEMISTRY OF MATERIALS Herron, S. M., Tanskanen, J. T., Roelofs, K. E., Bent, S. F. 2014; 26 (24): 7106-7113

  View details for DOI 10.1021/cm503666y

  View details for Web of Science ID 000347139700025

• Thermally Activated Reactions of Nitrobenzene at the Ge(100)-2 x 1 Surface JOURNAL OF PHYSICAL CHEMISTRY C Shong, B., Bent, S. F. 2014; 118 (50): 29224-29233

  View details for DOI 10.1021/jp505352k

  View details for Web of Science ID 000346759300034

• Bifacial solar cell with SnS absorber by vapor transport deposition APPLIED PHYSICS LETTERS Wangperawong, A., Hsu, P., Yee, Y., Herron, S. M., Clemens, B. M., Cui, Y., Bent, S. F. 2014; 105 (17)

  View details for DOI 10.1063/1.4898092

  View details for Web of Science ID 000344588600079

• Improving Area-Selective Molecular Layer Deposition by Selective SAM Removal ACS APPLIED MATERIALS & INTERFACES Prasittichai, C., Pickrahn, K. L., Hashemi, F. S., Bergsman, D. S., Bent, S. F. 2014; 6 (20): 17831-17836

  View details for DOI 10.1021/am504441e

  View details for Web of Science ID 000343684200060

• Improving area-selective molecular layer deposition by selective SAM removal. ACS applied materials & interfaces Prasittichai, C., Pickrahn, K. L., Hashemi, F. S., Bergsman, D. S., Bent, S. F. 2014; 6 (20): 17831-17836

  Abstract

  Area selective molecular layer deposition (MLD) is a promising technique for achieving micro- or nanoscale patterned organic structures. However, this technique still faces challenges in attaining high selectivity, especially at large MLD cycle numbers. Here, we illustrate a new strategy for achieving high quality patterns in selective film deposition on patterned Cu/Si substrates. We employed the intrinsically selective adsorption of an octadecylphosphonic acid self-assembled monolayer (SAM) on Cu over Si surfaces to selectively create a resist layer only on Cu. MLD was then performed on the patterns to deposit organic films predominantly on the Si surface, with only small amounts growing on the Cu regions. A negative potential bias was subsequently applied to the pattern to selectively desorb the layer of SAMs electrochemically from the Cu surface while preserving the MLD films on Si. Selectivity could be enhanced up to 30-fold after this treatment.

  View details for DOI 10.1021/am504441e

  View details for PubMedID 25290370

• Coverage-Dependent Adsorption of Bifunctional Molecules: Detailed Insights into Interactions between Adsorbates JOURNAL OF PHYSICAL CHEMISTRY C Shong, B., Brogaard, R. Y., Sandoval, T. E., Bent, S. F. 2014; 118 (41): 23811-23820

  View details for DOI 10.1021/jp507349k

  View details for Web of Science ID 000343333600043

• Nanoscale Limitations in Metal Oxide Electrocatalysts for Oxygen Evolution NANO LETTERS Viswanathan, V., Pickrahn, K. L., Luntz, A. C., Bent, S. F., Norskov, J. K. 2014; 14 (10): 5853-5857

  View details for DOI 10.1021/nl502775u

  View details for Web of Science ID 000343016400059

• Nanostructuring Materials for Solar-to-Hydrogen Conversion JOURNAL OF PHYSICAL CHEMISTRY C Guer, T. M., Bent, S. F., Prinz, F. B. 2014; 118 (37): 21301-21315

  View details for DOI 10.1021/jp500966u

  View details for Web of Science ID 000342118500001

• Structural evolution of platinum thin films grown by atomic layer deposition JOURNAL OF APPLIED PHYSICS Geyer, S. M., Methaapanon, R., Johnson, R., Brennan, S., Toney, M. F., Clemens, B., Bent, S. 2014; 116 (6)

  View details for DOI 10.1063/1.4892104

  View details for Web of Science ID 000341179400073

• Effect of O-3 on Growth of Pt by Atomic Layer Deposition JOURNAL OF PHYSICAL CHEMISTRY C Lee, H., Pickrahn, K. L., Bent, S. F. 2014; 118 (23): 12325-12332

  View details for DOI 10.1021/jp502596n

  View details for Web of Science ID 000337497400027

• A brief review of atomic layer deposition: from fundamentals to applications MATERIALS TODAY Johnson, R. W., Hultqvist, A., Bent, S. F. 2014; 17 (5): 236-246

  View details for DOI 10.1016/j.mattod.2014.04.026

  View details for Web of Science ID 000338412300017

• A New Resist for Area Selective Atomic and Molecular Layer Deposition on Metal-Dielectric Patterns JOURNAL OF PHYSICAL CHEMISTRY C Hashemi, F. S., Prasittichai, C., Bent, S. F. 2014; 118 (20): 10957-10962

  View details for DOI 10.1021/jp502669f

  View details for Web of Science ID 000336509400049

• Correlating Growth Characteristics in Atomic Layer Deposition with Precursor Molecular Structure: The Case of Zinc Tin Oxide CHEMISTRY OF MATERIALS Tanskanen, J. T., Hagglund, C., Bent, S. F. 2014; 26 (9): 2795-2802

  View details for DOI 10.1021/cm403913r

  View details for Web of Science ID 000336020700007

• An atomic layer deposition chamber for in situ x-ray diffraction and scattering analysis REVIEW OF SCIENTIFIC INSTRUMENTS Geyer, S. M., Methaapanon, R., Johnson, R. W., Kim, W., Van Campen, D. G., Metha, A., Bent, S. F. 2014; 85 (5)

  Abstract

  The crystal structure of thin films grown by atomic layer deposition (ALD) will determine important performance properties such as conductivity, breakdown voltage, and catalytic activity. We report the design of an atomic layer deposition chamber for in situ x-ray analysis that can be used to monitor changes to the crystal structural during ALD. The application of the chamber is demonstrated for Pt ALD on amorphous SiO2 and SrTiO3 (001) using synchrotron-based high resolution x-ray diffraction, grazing incidence x-ray diffraction, and grazing incidence small angle scattering.

  View details for DOI 10.1063/1.4876484

  View details for Web of Science ID 000337104600078

  View details for PubMedID 24880424

• Strong Carbon-Surface Dative Bond Formation by tert-Butyl Isocyanide on the Ge(100)-2 x 1 Surface JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Shong, B., Wong, K. T., Bent, S. F. 2014; 136 (16): 5848-5851

  Abstract

  Carbon dative bond formation between an organic molecule and a semiconductor surface is reported here for the first time. Our studies show that the adsorption of tert-butyl isocyanide on the (100) surface of germanium, measured using Fourier transform infrared spectroscopy, temperature-programmed desorption, and density functional theory calculations, occurs via formation of a dative bond to the surface through the isocyanide carbon. The experimentally observed adsorption energy of 26.8 kcal/mol is the largest among any organic molecule dative bonded on the Ge(100)-2 × 1 surface studied to date. The dative-bonded adsorbate is characterized by a N≡C stretching frequency significantly blue-shifted from that of the free molecule. Moreover, the adsorbate N≡C vibrational frequency red-shifts back toward that of the free molecule upon increasing coverage. These spectroscopic effects are attributed to σ-donation of the isocyanide lone pair electrons to the surface.

  View details for DOI 10.1021/ja500742a

  View details for Web of Science ID 000335086100008

  View details for PubMedID 24725248

• Thin film characterization of zinc tin oxide deposited by thermal atomic layer deposition THIN SOLID FILMS Mullings, M. N., Haegglund, C., Tanskanen, J. T., Yee, Y., Geyer, S., Bent, S. F. 2014; 556: 186-194

  View details for DOI 10.1016/j.tsf.2014.01.068

  View details for Web of Science ID 000333085700029

• Interface Engineering in Inorganic-Absorber Nanostructured Solar Cells JOURNAL OF PHYSICAL CHEMISTRY LETTERS Roelofs, K. E., Brennan, T. P., Bent, S. F. 2014; 5 (2): 348-360

  View details for DOI 10.1021/jz4023656

  View details for Web of Science ID 000330017800014

• Interface Engineering in Inorganic-Absorber Nanostructured Solar Cells. journal of physical chemistry letters Roelofs, K. E., Brennan, T. P., Bent, S. F. 2014; 5 (2): 348-360

  Abstract

  Nanostructured solar cells have the potential to provide a low-cost alternative to more traditional thin film solar cell technologies. Of particular interest are nanostructured solar cells with inorganic semiconductor absorbers, due to their favorable absorption properties. Such devices include quantum-dot-sensitized solar cells (QDSSCs), extremely thin absorber solar cells (ETASCs), and colloidal quantum dot solar cells (CQDSCs). However, these device architectures suffer from high rates of internal recombination and other problems associated with their extensive internal surface areas. Interfacial surface treatments have proven to be a highly effective means to improve the electronic properties of these devices, leading to overall gains in efficiencies. In this Perspective, we focus on three types of interfacial modification: band alignment by molecular dipole layers, improved CQD film mobilities by ligand exchange, and reduced recombination by interfacial inorganic layers. Select examples in each of these categories are highlighted to provide a detailed look at the underlying mechanisms. We believe that surface modification studies in these devices-QDSSCs, ETASCs, and CQDSCs-are of interest not only to these fields, but also to the broader photovoltaics community.

  View details for DOI 10.1021/jz4023656

  View details for PubMedID 26270710

• Interface engineering in inorganic-absorber nanostructured solar cells J. Phys. Chem. Lett., Invited Perspective article Roelofs, K., E., Brennan, T., P., Bent, S., F. 2014; 5: 348−360

  View details for DOI dx.doi.org/10.1021/jz4023656

• Selective metal deposition at graphene line defects by atomic layer deposition. Nature communications Kim, K., Lee, H., Johnson, R. W., Tanskanen, J. T., Liu, N., Kim, M., Pang, C., Ahn, C., Bent, S. F., Bao, Z. 2014; 5: 4781-?

  Abstract

  One-dimensional defects in graphene have a strong influence on its physical properties, such as electrical charge transport and mechanical strength. With enhanced chemical reactivity, such defects may also allow us to selectively functionalize the material and systematically tune the properties of graphene. Here we demonstrate the selective deposition of metal at chemical vapour deposited graphene's line defects, notably grain boundaries, by atomic layer deposition. Atomic layer deposition allows us to deposit Pt predominantly on graphene's grain boundaries, folds and cracks due to the enhanced chemical reactivity of these line defects, which is directly confirmed by transmission electron microscopy imaging. The selective functionalization of graphene defect sites, together with the nanowire morphology of deposited Pt, yields a superior platform for sensing applications. Using Pt-graphene hybrid structures, we demonstrate high-performance hydrogen gas sensors at room temperature and show its advantages over other evaporative Pt deposition methods, in which Pt decorates the graphene surface non-selectively.

  View details for DOI 10.1038/ncomms5781

  View details for PubMedID 25179368

• Area Selective Molecular Layer Deposition of Polyurea Films ACS APPLIED MATERIALS & INTERFACES Prasittichai, C., Zhou, H., Bent, S. F. 2013; 5 (24): 13391-13396

  Abstract

  Patterned organic thin films with submicrometer features are of great importance in applications such as nanoelectronics and optoelectronics. We present here a new approach for creating patterned organic films using area selective molecular layer deposition (MLD). MLD is a technique that allows for conformal deposition of nanoscale organic thin films with exceptional control over vertical thickness and composition. By expanding the technique to allow for area selective MLD, lateral patterning of the film can be achieved. In this work, polyurea thin films were deposited by alternating pulses of 1,4-phenylenediisocyanate (PDIC) and ethylenediamine (ED) in a layer-by-layer fashion with a linear growth rate of 5.3 Å/cycle. Studies were carried out to determine whether self-assembled monolayer (SAM) formed from octadecyltrichlorosilane (ODTS) could block MLD on silicon substrates. Results show that the MLD process is impeded by the SAM. To test lateral patterning in MLD, SAMs were patterned onto silicon substrates using two different approaches. In one approach, SiO2-coated Si(100) substrates were patterned with an ODTS SAM by soft lithography in a well-controlled environment. In the second approach, patterned ODTS SAM was formed on H-Si/SiO2 patterned wafers by employing the chemically selective adsorption of ODTS on SiO2 over H-Si. Auger electron spectroscopy results revealed that the polyurea film is deposited predominantly on the ODTS-free regions of both patterned substrates, indicating sufficient blocking of MLD by the ODTS SAM layer to replicate the pattern. The method we describe here offers a novel approach for fabricating high quality, three-dimensional organic structures.

  View details for DOI 10.1021/am4043195

  View details for Web of Science ID 000329137400080

  View details for PubMedID 24229350

• Formation of Stable Nitrene Surface Species by the Reaction of Adsorbed Phenyl Isocyanate at the Ge(100)-2 x 1 Surface LANGMUIR Wong, K. T., Tanskanen, J. T., Bent, S. F. 2013; 29 (51): 15842-15850

  Abstract

  The reaction of phenyl isocyanate (PIC) following adsorption at the Ge(100)-2 × 1 surface has been investigated both experimentally and theoretically by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption, quantum chemical calculations, and molecular dynamics simulations. PIC initially adsorbs by [2 + 2] cycloaddition across the C═N bond of the isocyanate, as previously reported, but this initial product converts to a second product on the time scale of minutes at room temperature. The experimental and theoretical results show that the second product formed is phenylnitrene (C6H5N) covalently bonded to the germanium surface via a single Ge-N bond. This conclusion is further supported by FTIR spectroscopy experiments and density functional theory calculations using phenyl isocyanate-(15)N and phenyl-d5 isocyanate.

  View details for DOI 10.1021/la4036216

  View details for Web of Science ID 000329137000015

  View details for PubMedID 24359033

• Adsorption of Trimethyl Phosphite at the Ge(100)-2 x 1 Surface by Nucleophilic Reaction JOURNAL OF PHYSICAL CHEMISTRY C Wong, K. T., Shong, B., Sun, W., Bent, S. F. 2013; 117 (50): 26628-26635

  View details for DOI 10.1021/jp408538e

  View details for Web of Science ID 000328920500025

• TiO2 Conduction Band Modulation with In2O3 Recombination Barrier Layers in Solid-State Dye-Sensitized Solar Cells JOURNAL OF PHYSICAL CHEMISTRY C Brennan, T. P., Tanskanen, J. T., Roelofs, K. E., To, J. W., Nguyen, W. H., Bakke, J. R., Ding, I., Hardin, B. E., Sellinger, A., McGehee, M. D., Bent, S. F. 2013; 117 (46): 24138-24149

  View details for DOI 10.1021/jp406789k

  View details for Web of Science ID 000327557300006

• Dynamical Orientation of Large Molecules on Oxide Surfaces and its Implications for Dye-Sensitized Solar Cells CHEMISTRY OF MATERIALS Brennan, T. P., Tanskanen, J. T., Bakke, J. R., Nguyen, W. H., Nordlund, D., Toney, M. F., McGehee, M. D., Sellinger, A., Bent, S. F. 2013; 25 (21): 4354-4363

  View details for DOI 10.1021/cm402609k

  View details for Web of Science ID 000327045000026

• Tin oxide atomic layer deposition from tetrakis(dimethylamino)tin and water JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Mullings, M. N., Haegglund, C., Bent, S. F. 2013; 31 (6)

  View details for DOI 10.1116/1.4812717

  View details for Web of Science ID 000327253900028

• Highly Stable Ultrathin Carbosiloxane Films by Molecular Layer Deposition JOURNAL OF PHYSICAL CHEMISTRY C Zhou, H., Bent, S. F. 2013; 117 (39): 19967-19973

  View details for DOI 10.1021/jp4058725

  View details for Web of Science ID 000326300700020

• Insights into the Surface Chemistry of Tin Oxide Atomic Layer Deposition from Quantum Chemical Calculations JOURNAL OF PHYSICAL CHEMISTRY C Tanskanen, J. T., Bent, S. F. 2013; 117 (37): 19056-19062

  View details for DOI 10.1021/jp4063324

  View details for Web of Science ID 000330162600031

• Adsorption of Structural and Stereoisomers of Cyclohexanediamine at the Ge(100)-2 x 1 Surface: Geometric Effects in Adsorption on a Semiconductor Surface JOURNAL OF PHYSICAL CHEMISTRY C Wong, K. T., Bent, S. F. 2013; 117 (37): 19063-19073

  View details for DOI 10.1021/jp406423n

  View details for Web of Science ID 000330162600032

• Size Dependent Effects in Nucleation of Ru and Ru Oxide Thin Films by Atomic Layer Deposition Measured by Synchrotron Radiation X-ray Diffraction CHEMISTRY OF MATERIALS Methaapanon, R., Geyer, S. M., Brennan, S., Bent, S. F. 2013; 25 (17): 3458-3463

  View details for DOI 10.1021/cm401585k

  View details for Web of Science ID 000330097900007

• Competing geometric and electronic effects in adsorption of phenylenediamine structural isomers on the Ge(100)-2 x 1 surface SURFACE SCIENCE Kachian, J. S., Squires, K. H., Bent, S. F. 2013; 615: 72-79

  View details for DOI 10.1016/j.susc.2013.03.024

  View details for Web of Science ID 000321409400010

• Semiconductor surface functionalization for advances in electronics, energy conversion, and dynamic systems JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Teplyakov, A. V., Bent, S. F. 2013; 31 (5)

  View details for DOI 10.1116/1.4810784

  View details for Web of Science ID 000324388800011

• Vapor transport deposition and epitaxy of orthorhombic SnS on glass and NaCl substrates APPLIED PHYSICS LETTERS Wangperawong, A., Herron, S. M., Runser, R. R., Haegglund, C., Tanskanen, J. T., Lee, H., Clemens, B. M., Bent, S. F. 2013; 103 (5)

  View details for DOI 10.1063/1.4816746

  View details for Web of Science ID 000322723000041

• Cross-Linked Ultrathin Polyurea Films via Molecular Layer Deposition MACROMOLECULES Zhou, H., Toney, M. F., Bent, S. F. 2013; 46 (14): 5638-5643

  View details for DOI 10.1021/ma400998m

  View details for Web of Science ID 000322417100026

• Atomic layer deposition of CdO and CdxZn1-xO films MATERIALS CHEMISTRY AND PHYSICS Bakke, J. R., Haegglund, C., Jung, H. J., Sinclair, R., Bent, S. F. 2013; 140 (2-3): 465-471

  View details for DOI 10.1016/j.matchemphys.2013.03.038

  View details for Web of Science ID 000320837700008

• Self-assembly based plasmonic arrays tuned by atomic layer deposition for extreme visible light absorption. Nano letters Hägglund, C., Zeltzer, G., Ruiz, R., Thomann, I., Lee, H., Brongersma, M. L., Bent, S. F. 2013; 13 (7): 3352-3357

  Abstract

  Achieving complete absorption of visible light with a minimal amount of material is highly desirable for many applications, including solar energy conversion to fuel and electricity, where benefits in conversion efficiency and economy can be obtained. On a fundamental level, it is of great interest to explore whether the ultimate limits in light absorption per unit volume can be achieved by capitalizing on the advances in metamaterial science and nanosynthesis. Here, we combine block copolymer lithography and atomic layer deposition to tune the effective optical properties of a plasmonic array at the atomic scale. Critical coupling to the resulting nanocomposite layer is accomplished through guidance by a simple analytical model and measurements by spectroscopic ellipsometry. Thereby, a maximized absorption of light exceeding 99% is accomplished, of which up to about 93% occurs in a volume-equivalent thickness of gold of only 1.6 nm. This corresponds to a record effective absorption coefficient of 1.7 × 10(7) cm(-1) in the visible region, far exceeding those of solid metals, graphene, dye monolayers, and thin film solar cell materials. It is more than a factor of 2 higher than that previously obtained using a critically coupled dye J-aggregate, with a peak width exceeding the latter by 1 order of magnitude. These results thereby substantially push the limits for light harvesting in ultrathin, nanoengineered systems.

  View details for DOI 10.1021/nl401641v

  View details for PubMedID 23805835

• Self-Assembly Based Plasmonic Arrays Tuned by Atomic Layer Deposition for Extreme Visible Light Absorption NANO LETTERS Haegglund, C., Zeltzer, G., Ruiz, R., Thomann, I., Lee, H., Brongersma, M. L., Bent, S. F. 2013; 13 (7): 3352-3357

  Abstract

  Achieving complete absorption of visible light with a minimal amount of material is highly desirable for many applications, including solar energy conversion to fuel and electricity, where benefits in conversion efficiency and economy can be obtained. On a fundamental level, it is of great interest to explore whether the ultimate limits in light absorption per unit volume can be achieved by capitalizing on the advances in metamaterial science and nanosynthesis. Here, we combine block copolymer lithography and atomic layer deposition to tune the effective optical properties of a plasmonic array at the atomic scale. Critical coupling to the resulting nanocomposite layer is accomplished through guidance by a simple analytical model and measurements by spectroscopic ellipsometry. Thereby, a maximized absorption of light exceeding 99% is accomplished, of which up to about 93% occurs in a volume-equivalent thickness of gold of only 1.6 nm. This corresponds to a record effective absorption coefficient of 1.7 × 10(7) cm(-1) in the visible region, far exceeding those of solid metals, graphene, dye monolayers, and thin film solar cell materials. It is more than a factor of 2 higher than that previously obtained using a critically coupled dye J-aggregate, with a peak width exceeding the latter by 1 order of magnitude. These results thereby substantially push the limits for light harvesting in ultrathin, nanoengineered systems.

  View details for DOI 10.1021/nl401641v

  View details for Web of Science ID 000321884300057

• Fabrication of organic interfacial layers by molecular layer deposition: Present status and future opportunities JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Zhou, H., Bent, S. F. 2013; 31 (4)

  View details for DOI 10.1116/1.4804609

  View details for Web of Science ID 000321516400003

• Highly sensitive, patternable organic films at the nanoscale made by bottom-up assembly. ACS applied materials & interfaces Zhou, H., Blackwell, J. M., Lee, H., Bent, S. F. 2013; 5 (9): 3691-3696

  Abstract

  Nanoscale patterning of organic thin films is of great interest for next-generation technologies. To keep pace with the demands of state-of-the-art lithography, both the sensitivity and resolution of the patternable thin films need to be improved. Here we report a highly sensitive polyurea film grown by bottom-up assembly via the molecular layer deposition (MLD) technique, which allows for high-resolution patterning at the nanoscale. The MLD process used in this work provides an exceptionally high degree of control over the film thickness and composition and also offers high coating conformality. The polyurea film was formed by urea coupling reactions between 1,4-diisocyanatobutane and 2,2'-(propane-2,2-diyldioxy)diethanamine precursors and deposited in a layer-by-layer fashion. Acid-labile ketal groups were incorporated into the backbone of the polymer chains to ensure chemically amplified cleaving reactions when combined with photoacid, which was generated by electron-beam activation of triphenylsulfonium triflate soaked into the polyurea film. With electron-beam lithography, sub-100 μC/cm(2) sensitivity and sub-100 nm resolution were demonstrated using this new bottom-up assembly approach to resist fabrication.

  View details for DOI 10.1021/am4002887

  View details for PubMedID 23594160

• Effect of Al2O3 Recombination Barrier Layers Deposited by Atomic Layer Deposition in Solid-State CdS Quantum Dot-Sensitized Solar Cells JOURNAL OF PHYSICAL CHEMISTRY C Roelofs, K. E., Brennan, T. P., Dominguez, J. C., Bailie, C. D., Margulis, G. Y., Hoke, E. T., McGehee, M. D., Bent, S. F. 2013; 117 (11): 5584-5592

  View details for DOI 10.1021/jp311846r

  View details for Web of Science ID 000316773000009

• Growth of Pt Nanowires by Atomic Layer Deposition on Highly Ordered Pyrolytic Graphite NANO LETTERS Lee, H., Baeck, S. H., Jaramillo, T. F., Bent, S. F. 2013; 13 (2): 457-463

  Abstract

  The formation of Pt nanowires (NWs) by atomic layer deposition on highly ordered pyrolytic graphite (HOPG) is investigated. Pt is deposited only at the step edges of HOPG and not on the basal planes, leading to the formation of laterally aligned Pt NWs. A growth model involving a morphological transition from 0-D to 1-D structures via coalescence is presented. The width of the NWs grows at a rate greater than twice the vertical growth rate. This asymmetry is ascribed to the wetting properties of Pt on HOPG as influenced by the formation of graphene oxide. A difference in Pt growth kinetics based on crystallographic orientation may also contribute.

  View details for DOI 10.1021/nl303803p

  View details for Web of Science ID 000315079500021

  View details for PubMedID 23317031

• One-Dimensional Pattern Formation of Adsorbed Molecules on the Ge(100)-2 X 1 Surface Driven by Nearest-Neighbor Effects JOURNAL OF PHYSICAL CHEMISTRY C Shong, B., Bent, S. F. 2013; 117 (2): 949-955

  View details for DOI 10.1021/jp3078503

  View details for Web of Science ID 000313932800024

• In Vacuo Photoemission Studies of Platinum Atomic Layer Deposition Using Synchrotron Radiation JOURNAL OF PHYSICAL CHEMISTRY LETTERS Geyer, S. M., Methaapanon, R., Shong, B., Pianetta, P. A., Bent, S. F. 2013; 4 (1): 176-179

  View details for DOI 10.1021/jz301475z

  View details for Web of Science ID 000313142000029

• Efficiency enhancement of solid-state PbS quantum dot-sensitized solar cells with Al2O3 barrier layer JOURNAL OF MATERIALS CHEMISTRY A Brennan, T. P., Trejo, O., Roelofs, K. E., Xu, J., Prinz, F. B., Bent, S. F. 2013; 1 (26): 7566-7571

  View details for DOI 10.1039/c3ta10903h

  View details for Web of Science ID 000320245400004

• Novel photoresist thin films with in-situ photoacid generator by molecular layer deposition Conference on Advances in Resist Materials and Processing Technology XXX Zhou, H., Bent, S. F. SPIE-INT SOC OPTICAL ENGINEERING. 2013

  View details for DOI 10.1117/12.2011572

  View details for Web of Science ID 000323247200027

• Formation of stable nitrene surface species by reaction of adsorbed phenyl isocyanate at the Ge(100)-2×1 surface Langmuir Wong, K., T., Tanskanen, J., T., Bent, S., F. 2013; 29: 15842−15850

  View details for DOI dx.doi.org/10.1021/la4036216

• Fabrication of organic interfacial layers by molecular layer deposition: present status and future opportunities J. Vac. Sci. Technol., invited review Zhou, H., Bent, S., F. 2013; 31: 040801

  View details for DOI 10.1116/1.4804609

• Insights into the surface chemistry of tin oxide atomic layer deposition from quantum chemical calculations J. Phys. Chem. C Tanskanen, J., T., Bent, S., F. 2013; 117: 19056−19062

  View details for DOI dx.doi.org/10.1021/jp4063324

• Portable atomic layer deposition reactor for in situ synchrotron photoemission studies REVIEW OF SCIENTIFIC INSTRUMENTS Methaapanon, R., Geyer, S. M., Hagglund, C., Pianetta, P. A., Bent, S. F. 2013; 84 (1)

  View details for DOI 10.1063/1.4773230

  View details for Web of Science ID 000314729100063

  View details for PubMedID 23387692

• Cross-linked ultrathin polyurea films via molecular layer deposition Macromolecules Zhou, H., Toney, M., F., Bent, S., F. 2013; 46: 5638−5643

  View details for DOI dx.doi.org/10.1021/ma400998m

• Highly stable ultrathin carbosiloxane films by molecular layer deposition J. Phys. Chem.C Zhou, H., Bent, S., F. 2013; 117: 19967−19973

  View details for DOI dx.doi.org/10.1021/jp4058725

• Size dependent effects in nucleation of Ru and Ru oxide thin films by atomic layer deposition measured by synchrotron radiation x-ray diffraction Chem. Mat Methaapanon, R., Geyer, S., M., Brennan, S., Bent, S., F. 2013; 25: 58−3463

  View details for DOI dx.doi.org/10.1021/cm401585k

• The dynamical orientation of large molecules on oxide surfaces and its implications for dye-sensitized solar cells Chem. Mat. Brennan, T., P., Tanskanen, J., T., Bakke, J., R., Nguyen, W., H., Nordlund, D., Toney, M., F., Bent, S. F. 2013; 25: 4354−4363

  View details for DOI dx.doi.org/10.1021/cm402609k

• Tin oxide atomic layer deposition from tetrakis(dimethylamino)tin and water J. Vac. Sci. Technol. A Mullings, M., N., Hagglund, C., Bent, S., F. 2013; 31: 061503

  View details for DOI http://dx.doi.org/10.1116/1.4812717

• 1D pattern formation of adsorbed molecules on the Ge(100)-2 × 1 surface driven by nearest neighbor effects J. Phys. Chem. C Shong, B., Bent, S., F. 2013; 2 (117): 949-955
• Vapor transport deposition and epitaxy of orthorhombic SnS on glass and NaCl substrates Appl. Phys. Lett Wangperawong, A., Herron, S., M., Runser, R., R., Hägglund, C., Tanskanen, J., Lee, H., B. R., Bent, S. F. 2013; 103: 052105

  View details for DOI http://dx.doi.org/10.1063/1.4816746

• Adsorption of trimethyl phosphite at the Ge(100)-2×1 surface by nucleophilic reaction J. Phys. Chem. C Wong, K., T., Shong, B., S., Sun, W., Bent, S., F. 2013; 117: 26628−26635

  View details for DOI dx.doi.org/10.1021/jp408538e

• Adsorption of structural and stereoisomers of cyclohexanediamineat the Ge(100)-2 × 1 surface: geometric effects in adsorption on a semiconductor surface J. Phys. Chem. C Wong, K., T., Bent, S., F. 2013; 117: 19063−19073

  View details for DOI dx.doi.org/10.1021/jp406423n

• Portable atomic layer deposition reactor for in situ synchrotron photoemission studies. Review of scientific instruments Methaapanon, R., Geyer, S. M., Hagglund, C., Pianetta, P. A., Bent, S. F. 2013; 84 (1): 015104-?

  Abstract

  We report the design of a portable atomic layer deposition (ALD) reactor that can be integrated into synchrotron facilities for in situ synchrotron photoemission studies. The design allows for universal installation of the system onto different beam line end stations. The ALD reactor operates as a fully functional, low vacuum deposition system under the conditions of a typical ALD reactor while allowing the samples to be analyzed in an ultrahigh vacuum (UHV) chamber through a quick transfer without vacuum break. This system not only minimizes the exposure of the UHV chamber to the ALD reactants, but it also eliminates the necessity of a beam alignment step after installation. The system has been successfully installed at the synchrotron and tested in the mechanistic studies of platinum ALD following individual half reaction cycles.

  View details for DOI 10.1063/1.4773230

  View details for PubMedID 23387692

• Dissociative Adsorption of Dimethyl Sulfoxide at the Ge(100)-2 x 1 Surface JOURNAL OF PHYSICAL CHEMISTRY C Wong, K. T., Chopra, S. N., Bent, S. F. 2012; 116 (50): 26422-26430

  View details for DOI 10.1021/jp309418e

  View details for Web of Science ID 000312519600035

• Power losses in bilayer inverted small molecule organic solar cells APPLIED PHYSICS LETTERS Trinh, C., Bakke, J. R., Brennan, T. P., Bent, S. F., Navarro, F., Bartynski, A., Thompson, M. E. 2012; 101 (23)

  View details for DOI 10.1063/1.4769440

  View details for Web of Science ID 000312243900099

• Nucleation-Controlled Growth of Nanoparticles by Atomic Layer Deposition CHEMISTRY OF MATERIALS Lee, H., Mullings, M. N., Jiang, X., Clemens, B. M., Bent, S. F. 2012; 24 (21): 4051-4059

  View details for DOI 10.1021/cm3014978

  View details for Web of Science ID 000311239300008

• Active MnOx Electrocatalysts Prepared by Atomic Layer Deposition for Oxygen Evolution and Oxygen Reduction Reactions ADVANCED ENERGY MATERIALS Pickrahn, K. L., Park, S. W., Gorlin, Y., Lee, H., Jaramillo, T. F., Bent, S. F. 2012; 2 (10): 1269-1277

  View details for DOI 10.1002/aenm.201200230

  View details for Web of Science ID 000309595900016

• Single versus Dual Attachment in the Adsorption of Diisocyanates at the Ge(100)-2 x 1 Surface JOURNAL OF PHYSICAL CHEMISTRY C Wong, K. T., Chopra, S. N., Bent, S. F. 2012; 116 (23): 12670-12679

  View details for DOI 10.1021/jp302930g

  View details for Web of Science ID 000305356200038

• Transition in the Molecular Orientation of Phenol Adsorbates on the Ge(100)-2 x 1 Surface JOURNAL OF PHYSICAL CHEMISTRY C Shong, B., Bent, S. F. 2012; 116 (14): 7925-7930

  View details for DOI 10.1021/jp3009767

  View details for Web of Science ID 000302591300039

• TiO2-SnO2:F interfacial electronic structure investigated by soft x-ray absorption spectroscopy PHYSICAL REVIEW B Kronawitter, C. X., Kapilashrami, M., Bakke, J. R., Bent, S. F., Chuang, C., Pong, W., Guo, J., Vayssieres, L., Mao, S. S. 2012; 85 (12)

  View details for DOI 10.1103/PhysRevB.85.125109

  View details for Web of Science ID 000301336900003

• Reaction of Hydroquinone and p-Benzoquinone with the Ge(100)-2 x 1 Surface JOURNAL OF PHYSICAL CHEMISTRY C Shong, B., Wong, K. T., Bent, S. F. 2012; 116 (7): 4705-4713

  View details for DOI 10.1021/jp210804v

  View details for Web of Science ID 000301156500044

• Microstructure-Dependent Nucleation in Atomic Layer Deposition of Pt on TiO2 CHEMISTRY OF MATERIALS Lee, H., Bent, S. F. 2012; 24 (2): 279-286

  View details for DOI 10.1021/cm202764b

  View details for Web of Science ID 000299367500006

• The importance of dye chemistry and TiCl4 surface treatment in the behavior of Al2O3 recombination barrier layers deposited by atomic layer deposition in solid-state dye-sensitized solar cells PHYSICAL CHEMISTRY CHEMICAL PHYSICS Brennan, T. P., Bakke, J. R., Ding, I., Hardin, B. E., Nguyen, W. H., Mondal, R., Bailie, C. D., Margulis, G. Y., Hoke, E. T., Sellinger, A., McGehee, M. D., Bent, S. F. 2012; 14 (35): 12130-12140

  Abstract

  Atomic layer deposition (ALD) was used to fabricate Al(2)O(3) recombination barriers in solid-state dye-sensitized solar cells (ss-DSSCs) employing an organic hole transport material (HTM) for the first time. Al(2)O(3) recombination barriers of varying thickness were incorporated into efficient ss-DSSCs utilizing the Z907 dye adsorbed onto a 2 μm-thick nanoporous TiO(2) active layer and the HTM spiro-OMeTAD. The impact of Al(2)O(3) barriers was also studied in devices employing different dyes, with increased active layer thicknesses, and with substrates that did not undergo the TiCl(4) surface treatment. In all instances, electron lifetimes (as determined by transient photovoltage measurements) increased and dark current was suppressed after Al(2)O(3) deposition. However, only when the TiCl(4) treatment was eliminated did device efficiency increase; in all other instances efficiency decreased due to a drop in short-circuit current. These results are attributed in the former case to the similar effects of Al(2)O(3) ALD and the TiCl(4) surface treatment whereas the insulating properties of Al(2)O(3) hinder charge injection and lead to current loss in TiCl(4)-treated devices. The impact of Al(2)O(3) barrier layers was unaffected by doubling the active layer thickness or using an alternative ruthenium dye, but a metal-free donor-π-acceptor dye exhibited a much smaller decrease in current due to its higher excited state energy. We develop a model employing prior research on Al(2)O(3) growth and dye kinetics that successfully predicts the reduction in device current as a function of ALD cycles and is extendable to different dye-barrier systems.

  View details for DOI 10.1039/c2cp42388j

  View details for Web of Science ID 000307648700014

  View details for PubMedID 22850593

• The low temperature atomic layer deposition of ruthenium and the effect of oxygen exposure JOURNAL OF MATERIALS CHEMISTRY Methaapanon, R., Geyer, S. M., Lee, H., Bent, S. F. 2012; 22 (48): 25154-25160

  View details for DOI 10.1039/c2jm35332f

  View details for Web of Science ID 000311970800023

• Growth characteristics, material properties, and optical properties of zinc oxysulfide films deposited by atomic layer deposition JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Bakke, J. R., Tanskanen, J. T., Haegglund, C., Pakkanen, T. A., Bent, S. F. 2012; 30 (1)

  View details for DOI 10.1116/1.3664758

  View details for Web of Science ID 000298992800035

• Atomic Layer Deposition of CdS Quantum Dots for Solid-State Quantum Dot Sensitized Solar Cells ADVANCED ENERGY MATERIALS Brennan, T. P., Ardalan, P., Lee, H., Bakke, J. R., Ding, I., McGehee, M. D., Bent, S. F. 2011; 1 (6): 1169-1175

  View details for DOI 10.1002/aenm.201100363

  View details for Web of Science ID 000297056500031

• Electron Enrichment in 3d Transition Metal Oxide Hetero-Nanostructures NANO LETTERS Kronawitter, C. X., Bakke, J. R., Wheeler, D. A., Wang, W., Chang, C., Antoun, B. R., Zhang, J. Z., Guo, J., Bent, S. F., Mao, S. S., Vayssieres, L. 2011; 11 (9): 3855-3861

  Abstract

  Direct experimental observation of spontaneous electron enrichment of metal d orbitals in a new transition metal oxide heterostructure with nanoscale dimensionality is reported. Aqueous chemical synthesis and vapor phase deposition are combined to fabricate oriented arrays of high-interfacial-area hetero-nanostructures comprised of titanium oxide and iron oxide nanomaterials. Synchrotron-based soft X-ray spectroscopy techniques with high spectral resolution are utilized to directly probe the titanium and oxygen orbital character of the interfacial region's occupied and unoccupied densities of states. These data demonstrate the interface to possess electrons in Ti 3d bands and an emergent degree of orbital hybridization that is absent in parent oxide reference crystals. The carrier dynamics of the hetero-nanostructures are studied by ultrafast transient absorption spectroscopy, which reveals the presence of a dense manifold of states, the relaxations from which exhibit multiple exponential decays whose magnitudes depend on their energetic positions within the electronic structure.

  View details for DOI 10.1021/nl201944h

  View details for Web of Science ID 000294790200060

  View details for PubMedID 21834542

• Three-dimensional nanojunction device models for photovoltaics APPLIED PHYSICS LETTERS Wangperawong, A., Bent, S. F. 2011; 98 (23)

  View details for DOI 10.1063/1.3595411

  View details for Web of Science ID 000291658900066

• Influence of organozinc ligand design on growth and material properties of ZnS and ZnO deposited by atomic layer deposition JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Tanskanen, J. T., Bakke, J. R., Pakkanen, T. A., Bent, S. F. 2011; 29 (3)

  View details for DOI 10.1116/1.3572232

  View details for Web of Science ID 000289689000019

• Coverage dependence of glycine adsorption on the Ge(100)-2 x 1 surface SURFACE SCIENCE Kachian, J. S., Jung, S. J., Kim, S., Bent, S. F. 2011; 605 (7-8): 760-769

  View details for DOI 10.1016/j.susc.2011.01.015

  View details for Web of Science ID 000288841200016

• Effects of Self-Assembled Monolayers on Solid-State CdS Quantum Dot Sensitized Solar Cells ACS NANO Ardalan, P., Brennan, T. P., Lee, H., Bakke, J. R., Ding, I., McGehee, M. D., Bent, S. F. 2011; 5 (2): 1495-1504

  Abstract

  Quantum dot sensitized solar cells (QDSSCs) are of interest for solar energy conversion because of their tunable band gap and promise of stable, low-cost performance. We have investigated the effects of self-assembled monolayers (SAMs) with phosphonic acid headgroups on the bonding and performance of cadmium sulfide (CdS) solid-state QDSSCs. CdS quantum dots ∼2 to ∼6 nm in diameter were grown on SAM-passivated planar or nanostructured TiO(2) surfaces by successive ionic layer adsorption and reaction (SILAR), and photovoltaic devices were fabricated with spiro-OMeTAD as the solid-state hole conductor. X-ray photoelectron spectroscopy, Auger electron spectroscopy, ultraviolet-visible spectroscopy, scanning electron microscopy, transmission electron microscopy, water contact angle measurements, ellipsometry, and electrical measurements were employed to characterize the materials and the resulting device performance. The data indicate that the nature of the SAM tailgroup does not significantly affect the uptake of CdS quantum dots on TiO(2) nor their optical properties, but the presence of the SAM does have a significant effect on the photovoltaic device performance. Interestingly, we observe up to ∼3 times higher power conversion efficiencies in devices with a SAM compared to those without the SAM.

  View details for DOI 10.1021/nn103371v

  View details for Web of Science ID 000287553800093

  View details for PubMedID 21299223

• Aqueous bath process for deposition of Cu2ZnSnS4 photovoltaic absorbers THIN SOLID FILMS Wangperawong, A., King, J. S., Herron, S. M., Tran, B. P., Pangan-Okimoto, K., Bent, S. F. 2011; 519 (8): 2488-2492

  View details for DOI 10.1016/j.tsf.2010.11.040

  View details for Web of Science ID 000287631500017

• Molecular Layer Deposition of Functional Thin Films for Advanced Lithographic Patterning ACS APPLIED MATERIALS & INTERFACES Zhou, H., Bent, S. F. 2011; 3 (2): 505-511

  Abstract

  Photoresist materials comprise one of the main challenges faced by lithography to meet the requirements of electronic device size scaling. Here we report for the first time the use of molecular layer deposition (MLD) to produce photoresist materials with controllable placement of functional moieties. Polyurea resists films are deposited by MLD using urea coupling reactions between 1,4-phenylene diisocyanate (PDIC) and ethylenediamine (ED) or 2,2'-(propane-2,2-diylbis(oxy))diethanamine (PDDE) monomers in a layer-by-layer fashion with a linear growth rate, allowing acid-labile groups to be incorporated into the film at well-controlled positions. The films are deposited with stoichiometric compositions and have highly uniform surface morphology as investigated using atomic force microscopy. We show that acid treatment can cleave the backbone of the polyurea film at positions where the acid-labile groups are embedded. We further show that after soaking the polyurea film with photoacid generator (PAG), it acts as a photoresist material and we present several UV patterning demonstrations. This approach presents a new way to make molecularly designed resist films for lithography.

  View details for DOI 10.1021/am1010805

  View details for Web of Science ID 000287639400055

  View details for PubMedID 21302918

• Tuning the reactivity of semiconductor surfaces by functionalization with amines of different basicity PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Bent, S. F., Kachian, J. S., Rodriguez-Reyes, J. C., Teplyakov, A. V. 2011; 108 (3): 956-960

  Abstract

  Surface functionalization of semiconductors has been the backbone of the newest developments in microelectronics, energy conversion, sensing device design, and many other fields of science and technology. Over a decade ago, the notion of viewing the surface itself as a chemical reagent in surface reactions was introduced, and adding a variety of new functionalities to the semiconductor surface has become a target of research for many groups. The electronic effects on the substrate have been considered as an important consequence of chemical modification. In this work, we shift the focus to the electronic properties of the functional groups attached to the surface and their role on subsequent reactivity. We investigate surface functionalization of clean Si(100)-2 × 1 and Ge(100)-2 × 1 surfaces with amines as a way to modify their reactivity and to fine tune this reactivity by considering the basicity of the attached functionality. The reactivity of silicon and germanium surfaces modified with ethylamine (CH(3)CH(2)NH(2)) and aniline (C(6)H(5)NH(2)) is predicted using density functional theory calculations of proton attachment to the nitrogen of the adsorbed amine to differ with respect to a nucleophilic attack of the surface species. These predictions are then tested using a model metalorganic reagent, tetrakis(dimethylamido)titanium (((CH(3))(2)N)(4)Ti, TDMAT), which undergoes a transamination reaction with sufficiently nucleophilic amines, and the reactivity tests confirm trends consistent with predicted basicities. The identity of the underlying semiconductor surface has a profound effect on the outcome of this reaction, and results comparing silicon and germanium are discussed.

  View details for DOI 10.1073/pnas.1006656107

  View details for Web of Science ID 000286310300016

  View details for PubMedID 21068370

• Disulfide Passivation of the Ge(100)-2 x 1 Surface LANGMUIR Kachian, J. S., Tannaci, J., Wright, R. J., Tilley, T. D., Bent, S. F. 2011; 27 (1): 179-186

  Abstract

  Understanding the bonding of sulfur at the germanium surface is important to developing good passivation routes for germanium-based electronic devices. The adsorption behavior of ethyl disulfide (EDS) and 1,8-naphthalene disulfide (NDS) at the Ge(100)-2 × 1 surface has been studied under ultrahigh vacuum conditions to investigate both their fundamental reactivity and their effectiveness as passivants of this surface. X-ray photoelectron spectroscopy, multiple internal reflection-infrared spectroscopy, and density functional theory results indicate that both molecules adsorb via S-S dissociation at room temperature. Upon exposure to ambient air, the thiolate adlayer remains intact for both EDS- and NDS-functionalized surfaces, indicating the stability of this surface attachment. Although both systems resist oxidation compared to the bare Ge(100)-2 × 1 surface, the Ge substrate is significantly oxidized in all cases (17-57% relative to the control), with the NDS-passivated surface undergoing up to two times more oxidation than the EDS-passivated surface at the longest air exposure times studied. The difference in passivation capability is attributed to the difference in surface coverage on Ge(100)-2 × 1, where EDS adsorption leads to a saturation coverage 17% higher than that for NDS/Ge(100)-2 × 1.

  View details for DOI 10.1021/la103614f

  View details for Web of Science ID 000285560400025

  View details for PubMedID 21141841

• Nanoengineering and interfacial engineering of photovoltaics by atomic layer deposition NANOSCALE Bakke, J. R., Pickrahn, K. L., Brennan, T. P., Bent, S. F. 2011; 3 (9): 3482-3508

  Abstract

  Investment into photovoltaic (PV) research has accelerated over the past decade as concerns over energy security and carbon emissions have increased. The types of PV technology in which the research community is actively engaged are expanding as well. This review focuses on the burgeoning field of atomic layer deposition (ALD) for photovoltaics. ALD is a self-limiting thin film deposition technique that has demonstrated usefulness in virtually every sector of PV technology including silicon, thin film, tandem, organic, dye-sensitized, and next generation solar cells. Further, the specific applications are not limited. ALD films have been deposited on planar and nanostructured substrates and on inorganic and organic devices, and vary in thickness from a couple of angstroms to over 100 nm. The uses encompass absorber materials, buffer layers, passivating films, anti-recombination shells, and electrode modifiers. Within the last few years, the interest in ALD as a PV manufacturing technique has increased and the functions of ALD have expanded. ALD applications have yielded fundamental understanding of how devices operate and have led to increased efficiencies or to unique architectures for some technologies. This review also highlights new developments in high throughput ALD, which is necessary for commercialization. As the demands placed on materials for the next generation of PV become increasingly stringent, ALD will evolve into an even more important method for research and fabrication of solar cell devices.

  View details for DOI 10.1039/c1nr10349k

  View details for Web of Science ID 000294472600004

  View details for PubMedID 21799978

• Optical Response of 3D Nano-Architecture Solar Cells and Integration with 3D Device Physics Conference on Next Generation (Nano) Photonic and Cell Technologies for Solar Energy Conversion II Wangperawong, A., Haegglund, C., Bent, S. F. SPIE-INT SOC OPTICAL ENGINEERING. 2011

  View details for DOI 10.1117/12.893168

  View details for Web of Science ID 000303797800013

• Atomic layer deposition of CdxZn1-xS films JOURNAL OF MATERIALS CHEMISTRY Bakke, J. R., Tanskanen, J. T., Jung, H. J., Sinclair, R., Bent, S. F. 2011; 21 (3): 743-751

  View details for DOI 10.1039/c0jm02786c

  View details for Web of Science ID 000285749900021

• Adsorption Behavior of Bifunctional Molecules on Ge(100)-2 x 1: Comparison of Mercaptoethanol and Mercaptamine JOURNAL OF PHYSICAL CHEMISTRY C Kachian, J. S., Bent, S. F. 2010; 114 (50): 22230-22236

  View details for DOI 10.1021/jp1085894

  View details for Web of Science ID 000285236800047

• Deposition of Ultrathin Polythiourea Films by Molecular Layer Deposition CHEMISTRY OF MATERIALS Loscutoff, P. W., Lee, H., Bent, S. F. 2010; 22 (19): 5563-5569

  View details for DOI 10.1021/cm1016239

  View details for Web of Science ID 000282471000019

• Molecular Level Insights into Atomic Layer Deposition of CdS by Quantum Chemical Calculations JOURNAL OF PHYSICAL CHEMISTRY C Tanskanen, J. T., Bakke, J. R., Bent, S. F., Pakkanen, T. A. 2010; 114 (39): 16618-16624

  View details for DOI 10.1021/jp105911p

  View details for Web of Science ID 000282209800070

• Reaction of tert-butyl isocyanate and tert-butyl isothiocyanate at the Ge(100)-2 x 1 Surface SURFACE SCIENCE Loscutoff, P. W., Wong, K. T., Bent, S. F. 2010; 604 (19-20): 1791-1799

  View details for DOI 10.1016/j.susc.2010.07.007

  View details for Web of Science ID 000281993200040

• Reaction of Phenyl Isocyanate and Phenyl Isothiocyanate with the Ge(100)-2 x 1 Surface JOURNAL OF PHYSICAL CHEMISTRY C Loscutoff, P. W., Wong, K. T., Bent, S. F. 2010; 114 (33): 14193-14201

  View details for DOI 10.1021/jp104388a

  View details for Web of Science ID 000280961800032

• Atomic Layer Deposition of CdS Films CHEMISTRY OF MATERIALS Bakke, J. R., Jung, H. J., Tanskanen, J. T., Sinclair, R., Bent, S. F. 2010; 22 (16): 4669-4678

  View details for DOI 10.1021/cm100874f

  View details for Web of Science ID 000280855100021

• Atomic layer deposition of ZnS via in situ production of H2S THIN SOLID FILMS BAKKE, J. R., King, J. S., Jung, H. J., Sinclair, R., Bent, S. F. 2010; 518 (19): 5400-5408

  View details for DOI 10.1016/j.tsf.2010.03.074

  View details for Web of Science ID 000279885700009

• ALD Growth Characteristics of ZnS Films Deposited from Organozinc and Hydrogen Sulfide Precursors LANGMUIR Tanskanen, J. T., Bakke, J. R., Bent, S. F., Pakkanen, T. A. 2010; 26 (14): 11899-11906

  Abstract

  Growth characteristics of zinc sulfide thin films deposited from dialkylzinc and H(2)S reactants by the atomic layer deposition technique have been investigated by quantum chemical methods. The steady-state growth of the films was simulated by studying the reaction of the Zn precursor with the hydrogenated sulfur-terminated (111) surface of zincblende ZnS and then by investigating the chemisorption of hydrogen sulfide on the surface formed by the metal exposure. The behavior of the dissociatively chemisorbed Zn precursors on the growth surface is of particular significance for the film deposition process, since the film growth is limited by the Zn deposition step. Hydrogen sulfide exposure results in the replacement of the surface alkyl groups by SH surface species, whose vibrational features are useful in the experimental verification of the developed growth mechanisms.

  View details for DOI 10.1021/la101128w

  View details for Web of Science ID 000279756700043

  View details for PubMedID 20553010

• Comparative Study of Titanium Dioxide Atomic Layer Deposition on Silicon Dioxide and Hydrogen-Terminated Silicon JOURNAL OF PHYSICAL CHEMISTRY C Methaapanon, R., Bent, S. F. 2010; 114 (23): 10498-10504

  View details for DOI 10.1021/jp1013303

  View details for Web of Science ID 000278479700025

• Reaction Mechanism, Bonding, and Thermal Stability of 1-Alkanethiols Self-Assembled on Halogenated Ge Surfaces LANGMUIR Ardalan, P., Sun, Y., Pianetta, P., Musgrave, C. B., Bent, S. F. 2010; 26 (11): 8419-8429

  Abstract

  We have employed synchrotron radiation photoemission spectroscopy to study the reaction mechanism, surface bonding, and thermal stability of 1-octadecanethiolate (ODT) self-assembled monolayers (SAMs) at Cl- and Br-terminated Ge(100) surfaces. Density functional theory (DFT) calculations were also carried out for the same reactions. From DFT calculations, we have found that adsorption of 1-octadecanethiol on the halide-terminated surface via hydrohalogenic acid elimination is kinetically favorable on both Cl- and Br-terminated Ge surfaces at room temperature, but the reactions are more thermodynamically favorable at Cl-terminated Ge surfaces. After ODT SAM formation at room temperature, photoemission spectroscopy experiments show that Ge(100) and (111) surfaces contain monothiolates and possibly dithiolates together with unbound thiol and atomic sulfur. Small coverages of residual halide are also observed, consistent with predictions by DFT. Annealing studies in ultrahigh vacuum show that the Ge thiolates are thermally stable up to 150 degrees C. The majority of the surface thiolates are converted to sulfide and carbide upon annealing to 350 degrees C. By 430 degrees C, no sulfur remains on the surface, whereas Ge carbide is stable to above 470 degrees C.

  View details for DOI 10.1021/la904864c

  View details for Web of Science ID 000277928100104

  View details for PubMedID 20433151

• Atomic Layer Deposition (ALD) Co-Deposited Pt-Ru Binary and Pt Skin Catalysts for Concentrated Methanol Oxidation CHEMISTRY OF MATERIALS Jiang, X., Guer, T. N., Prinz, F. B., Bent, S. F. 2010; 22 (10): 3024-3032

  View details for DOI 10.1021/cm902904u

  View details for Web of Science ID 000277635000002

• Periodic Trends in Organic Functionalization of Group IV Semiconductor Surfaces ACCOUNTS OF CHEMICAL RESEARCH Kachian, J. S., Wong, K. T., Bent, S. F. 2010; 43 (2): 346-355

  Abstract

  Organic functionalization of group IV semiconductor surfaces provides a means to precisely control the interfacial properties of some of the most technologically important electronic materials in use today. The 2 x 1 reconstructed group IV (100) surfaces in ultrahigh vacuum, in particular, have a well-defined surface that allows adsorbate-surface interactions to be studied in detail. Surface dimers containing a strong sigma- and weak pi-bond form upon reconstruction of the group IV (100) surfaces, imparting a rich surface reactivity, which allows useful analogies to be made between reactions at the surface and those in classic organic chemistry. To date, most studies have focused on single substrates and a limited number of adsorbate functional groups. In this Account, we bring together experimental and theoretical results from several studies to investigate broader trends in thermodynamics and kinetics of organic molecules reacted with group IV (100)-2 x 1 surfaces. By rationalizing these trends in terms of simple periodic properties, we aim to provide guidelines by which to understand the chemical origin of the observed trends and predict how related molecules or functionalities will react. Results of experimental and theoretical studies are used to show that relative electronegativities and orbital overlap correlate well with surface-adsorbate covalent bond strength, while orbital overlap together with donor electronegativity and acceptor electron affinity correlate with surface-adsorbate dative bond strength. Using such simple properties as predictive tools is limited, of course, but theoretical calculations fill in some of the gaps. The predictive power inherent in periodic trends may be put to use in designing molecules for applications where controlled attachment of organic molecules to semiconductor surfaces is needed. Organic functionalization may facilitate the semiconductor industry's transition from traditional silicon-based architectures to other materials, such as germanium, that offer better electrical properties. Potential applications also exist in other fields ranging from organic and molecular electronics, where control of interfacial properties may allow coupling of traditional semiconductor technology with such developing technologies, to biosensors and nanoscale lithography, where the functionality imparted to the surface may be used directly. Knowledge of thermodynamic and kinetic trends and the fundamental basis of these trends may enable effective development of new functionalization strategies for such applications.

  View details for DOI 10.1021/ar900251s

  View details for Web of Science ID 000274765400018

  View details for PubMedID 20041705

• Sputtered Pt-Ru Alloys as Catalysts for Highly Concentrated Methanol Oxidation JOURNAL OF THE ELECTROCHEMICAL SOCIETY Jiang, X., Guer, T. M., Prinz, F. B., Bent, S. F. 2010; 157 (3): B314-B319

  View details for DOI 10.1149/1.3273081

  View details for Web of Science ID 000274321900021

• Fabrication of organic thin films for copper diffusion barrier layers using molecular layer deposition Loscutoff, P., W., Clendenning, S., B., Bent, S., F. 2010
• A CHEMICAL BATH PROCESS FOR DEPOSITING Cu2ZnSnS4 PHOTOVOLTAIC ABSORBERS 35th IEEE Photovoltaic Specialists Conference Wangperawong, A., King, J. S., Herron, S. M., Tran, B. P., Pangan-Okimoto, K., Bent, S. F. IEEE. 2010: 1986–1989

  View details for Web of Science ID 000287579502051

• ALD co-deposited and core-shell Ru-Pt catalysts for concentrated methanol oxidation Chem. Mat Jiang, X., Gür, T., M., Prinz, F., B., Bent, S., F. 2010; 22: 3024-3032
• Formation of Organic Nanoscale Laminates and Blends by Molecular Layer Deposition ACS NANO Loscutoff, P. W., Zhou, H., Clendenning, S. B., Bent, S. F. 2010; 4 (1): 331-341

  Abstract

  Nanoscale organic films are important for many applications. We report on a system of molecular layer deposition that allows for the deposition of conformal organic films with thickness and composition control at the subnanometer length scale. Nanoscale polyurea films are grown on silica substrates in a layer-by-layer fashion by dosing 1,4-phenylene diisocyanate (PDIC) and ethylenediamine (ED) in the gas phase. Ellipsometry measurements indicate that the film growth occurs at a constant growth rate, with film thicknesses consistent with molecular distances calculated using density functional theory. Characterization of the films by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy reveals formation of stable polyurea films with nearly stoichiometric composition, and transmission electron microscopy indicates that the films uniformly coat the substrate surface. Subnanometer control over the film composition was demonstrated using 2,2'-thiobis(ethylamine) (TBEA) as an alternate diamine to vary the composition of the films. By substituting TBEA for ED, blended films, with homogeneous composition through the film, and nanolaminates, with discrete layers of differing film chemistry, were created.

  View details for DOI 10.1021/nn901013r

  View details for Web of Science ID 000273863400043

  View details for PubMedID 20000603

• Area Selective Atomic Layer Deposition by Microcontact Printing with a Water-Soluble Polymer JOURNAL OF THE ELECTROCHEMICAL SOCIETY Mullings, M. N., Lee, H., Marchack, N., Jiang, X., Chen, Z., Gorlin, Y., Lin, K., Bent, S. F. 2010; 157 (12): D600-D604

  View details for DOI 10.1149/1.3491376

  View details for Web of Science ID 000283938300050

• Catalysts with Pt Surface Coating by Atomic Layer Deposition for Solid Oxide Fuel Cells JOURNAL OF THE ELECTROCHEMICAL SOCIETY Shim, J. H., Jiang, X., Bent, S. F., Prinz, F. B. 2010; 157 (6): B793-B797

  View details for DOI 10.1149/1.3368787

  View details for Web of Science ID 000277260200023

• Area-Selective ALD with Soft Lithographic Methods: Using Self-Assembled Monolayers to Direct Film Deposition JOURNAL OF PHYSICAL CHEMISTRY C Jiang, X., Bent, S. F. 2009; 113 (41): 17613-17625

  View details for DOI 10.1021/jp905317n

  View details for Web of Science ID 000270459900007

• Photochemical Covalent Attachment of Alkene-Derived Monolayers onto Hydroxyl-Terminated Silica LANGMUIR ter Maat, J., Regeling, R., Yang, M., Mullings, M. N., Bent, S. F., Zuilhof, H. 2009; 25 (19): 11592-11597

  Abstract

  The functionalization of optically transparent substrates is of importance, for example, in the field of biosensing. In this article, a new method for modification of silica surfaces is presented that is based on a photochemical reaction of terminal alkenes with the surface. This yields highly hydrophobic surfaces, which are thermally stable up to at least 400 degrees C. The formed monolayer provides chemical passivation of the underlying surface, according to studies showing successful blocking of platinum atomic layer deposition (ALD). The reaction is photochemically initiated, requiring light with a wavelength below 275 nm. X-ray photoelectron spectroscopy and infrared spectroscopy studies show that the alkenes initially bind to the surface hydroxyl groups in Markovnikov fashion. At prolonged reaction times (>5 h), however, oligomerization occurs, resulting in layer growth normal to the surface. The photochemical nature of the reaction enables the use of photolithography as a tool to constructively pattern silica surfaces. Atomic force microscopy shows that the features of the photomask are well transferred. The newly developed method can complement existing patterning methods on silica that are based on soft lithography.

  View details for DOI 10.1021/la901551t

  View details for Web of Science ID 000270136900061

  View details for PubMedID 19583192

• Growth Process of Polyaniline Thin Films Formed by Hot Wire CVD CHEMICAL VAPOR DEPOSITION Zaharias, G. A., Bent, S. F. 2009; 15 (4-6): 133-141

  View details for DOI 10.1002/cvde.200806743

  View details for Web of Science ID 000267727400010

• Sulfur versus Oxygen Reactivity of Organic Molecules at the Ge(100)-2x1 Surface JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Kachian, J. S., Bent, S. F. 2009; 131 (20): 7005-7015

  Abstract

  The adsorption behavior of sulfur- versus oxygen-containing organic molecules, including ethanol, ethanethiol, diethyl ether, and diethyl sulfide, at the Ge(100)-2 x 1 surface was investigated using a combination of multiple internal reflection infrared (MIR-IR) spectroscopy and density functional theory (DFT). The results show that ethanol and ethanethiol both adsorb via Ch-H dissociation at 310 K, where Ch (chalcogen) is either S or O. DFT calculations indicate that S-H dissociation is both kinetically and thermodynamically favored over O-H dissociation. IR spectra of diethyl ether and diethyl sulfide reveal that both molecules adsorb via dative bonding through the heteroatom for temperatures up to approximately 255 and 335 K, respectively, and reversibly desorb at higher temperatures. From these desorption temperatures, the S-Ge dative bond of a sulfide is calculated to be 5.9 kcal/mol stronger than the O-Ge dative bond of an ether, a trend consistent with results from DFT calculations. Moreover, for all of the molecules studied, SGe dative bonds are found to be stronger than O-Ge dative bonds, with the magnitude of the difference increasing with substitution of bulkier groups on the Ch atom of the adsorbate. Calculations on diethyl selenide show that the Se-Ge dative bond is slightly stronger than the S-Ge dative bond.

  View details for DOI 10.1021/ja808066t

  View details for Web of Science ID 000266484700043

  View details for PubMedID 19413324

• Controlling Atomic Layer Deposition of TiO2 in Aerogels through Surface Functionalization CHEMISTRY OF MATERIALS Ghosal, S., Baumann, T. F., King, J. S., Kucheyev, S. O., Wang, Y., Worsley, M. A., Biener, J., Bent, S. F., Hamza, A. V. 2009; 21 (9): 1989-1992

  View details for DOI 10.1021/cm900636s

  View details for Web of Science ID 000265781000034

• Formation of Alkanethiolate Self-Assembled Monolayers at Halide-Terminated Ge Surfaces LANGMUIR Ardalan, P., Musgrave, C. B., Bent, S. F. 2009; 25 (4): 2013-2025

  Abstract

  We have studied Ge halide passivation and formation of 1-octadecanethiolate self-assembled monolayers (SAMs) at Cl- and Br-terminated Ge(100) and Ge(111) surfaces. The results of water contact angle measurements, ellipsometry, transmission infrared spectroscopy, X-ray photoelectron spectroscopy, and Auger electron spectroscopy show that good quality 1-alkanethiolate SAMs can be achieved at both Cl- and Br-terminated surfaces via direct Ge-S bonds. The quality of the SAMs depends on the concentration and the solvent of the 1-alkanethiol solution. Moreover, SAMs formed at Ge(100) surfaces have higher water contact angles, thicknesses, and ambient stability than those formed at Ge(111) surfaces. Surface passivation and light are found to play an important role in the packing and stability of the SAMs. Furthermore, well-packed SAMs can be retrieved by repassivation after degradation due to ambient exposure. This work presents novel routes for Ge surface passivation.

  View details for DOI 10.1021/la803468e

  View details for Web of Science ID 000263373600023

  View details for PubMedID 19152272

• Metal Alloy Catalysts with Pt Surface Coating by Atomic Layer Deposition for Intermediate Temperature Ceramic Fuel Cells 5th Symposium on Atomic Layer Deposition held as part of the 216th Meeting of the Electrochemical-Society (ECS) Shim, J. H., Jiang, X., Bent, S., Prinz, F. B. ELECTROCHEMICAL SOC INC. 2009: 323–32

  View details for DOI 10.1149/1.3205067

  View details for Web of Science ID 000337731900031

• Effects of Surface Functionalization on Titanium Dioxide Atomic Layer Deposition on Ge Surfaces 5th Symposium on Atomic Layer Deposition held as part of the 216th Meeting of the Electrochemical-Society (ECS) Ardalan, P., Musgrave, C. B., Bent, S. F. ELECTROCHEMICAL SOC INC. 2009: 131–39

  View details for DOI 10.1149/1.3205050

  View details for Web of Science ID 000337731900014

• Ultralow loading Pt nanocatalysts prepared by atomic layer deposition on carbon aerogels NANO LETTERS King, J. S., Wittstock, A., Biener, J., Kucheyev, S. O., Wang, Y. M., Baumann, T. F., Giri, S. K., Hamza, A. V., Baeumer, M., Bent, S. F. 2008; 8 (8): 2405-2409

  Abstract

  Using atomic layer deposition (ALD), we show that Pt nanoparticles can be deposited on the inner surfaces of carbon aerogels (CA). The resultant Pt-loaded materials exhibit high catalytic activity for the oxidation of CO even at loading levels as low as approximately 0.05 mg Pt/cm2. We observe a conversion efficiency of nearly 100% in the 150-250 degrees C temperatures range, and the total conversion rate seems to be limited only by the thermal stability of the CA support in ambient oxygen. The ALD approach described here is universal in nature, and can be applied to the design of new catalytic materials for a variety of applications, including fuel cells, hydrogen storage, pollution control, green chemistry, and liquid fuel production.

  View details for DOI 10.1021/nl801299z

  View details for Web of Science ID 000258440700051

  View details for PubMedID 18636780

• Application of atomic layer deposition of platinum to solid oxide fuel cells CHEMISTRY OF MATERIALS Jiang, X., Huang, H., Prinz, F. B., Bent, S. F. 2008; 20 (12): 3897-3905

  View details for DOI 10.1021/cm7033189

  View details for Web of Science ID 000256854800020

• Formation of an oxide-free Ge/TiO2 interface by atomic layer deposition on brominated Ge APPLIED PHYSICS LETTERS Ardalan, P., Pickett, E. R., Harris, J. S., Marshall, A. F., Bent, S. F. 2008; 92 (25)

  View details for DOI 10.1063/1.2951608

  View details for Web of Science ID 000257231200043

• Plasma ash processing solutions for advanced interconnect technology 28th Dry Process Symposium (DPS) Fuller, N. C., Worsley, M. A., Tai, L., Bent, S., Labelle, C., Arnold, J., Dalton, T. ELSEVIER SCIENCE SA. 2008: 3558–63

  View details for DOI 10.1016/j.tsf.2007.08.071

  View details for Web of Science ID 000255421900025

• Surface patterning: Silicon falls into line NATURE NANOTECHNOLOGY Bent, S. F. 2008; 3 (4): 185-186

  View details for DOI 10.1038/nnano.2008.79

  View details for Web of Science ID 000254744300003

  View details for PubMedID 18654496

• Silicon falls into line Nature Nanotechnology Bent, S., F. 2008; 3: 185-186
• Pt-Ru Alloys Deposited by Sputtering as Catalysts for Methanol Oxidation 8th Symposium on Proton Exchange Membrane Fuel Cells Jiang, X., Prinz, F. B., Bent, S. F. ELECTROCHEMICAL SOCIETY INC. 2008: 605–12

  View details for DOI 10.1149/1.2981895

  View details for Web of Science ID 000271859300058

• Spatial control over atomic layer deposition using microcontact-printed resists 16th European Conference on Chemical Vapor Deposition Jiang, X., Chen, R., Bent, S. F. ELSEVIER SCIENCE SA. 2007: 8799–8807

  View details for DOI 10.1016/j.surfcoat.2007.04.126

  View details for Web of Science ID 000249340400002

• A model neural interface based on functional chemical stimulation BIOMEDICAL MICRODEVICES Mehenti, N. Z., Fishman, H. A., Bent, S. F. 2007; 9 (4): 579-586

  Abstract

  While functional electrical stimulation has been applied to treat a variety of neurological disorders, it cannot mimic function that is primarily achieved using neurochemical means. In this work, we present a neurotransmitter-based prosthetic interface in the form of a flexible microdevice that selectively releases chemical pulses through an aperture in a polymer membrane. The release profiles through the aperture are controlled by microfluidic switching in an underlying channel network. The profiles have been characterized using fluorescence microscopy as a function of pulse duration and frequency. Hippocampal neurons were cultured on the microdevices and cell stimulation via glutamate delivery was detected using calcium imaging. The release properties could be tuned to repeatedly elicit discrete action potentials in cells seeded proximate to the aperture, including single cell stimulation at 2 Hz. This model neural interface based on functional chemical stimulation may provide the biomimetic platform necessary to restore physiological pathways and function that electrical stimulation cannot fundamentally address.

  View details for DOI 10.1007/s10544-007-9069-z

  View details for Web of Science ID 000248007500016

  View details for PubMedID 17520371

• Heads or tails: Which is more important in molecular self-assembly? ACS NANO Bent, S. F. 2007; 1 (1): 10-12

  Abstract

  Self-assembled monolayers can modify the functionality of the surfaces on which they assemble. Because they alter the surface properties, self-assembled monolayers can be used for a multitude of applications. Understanding the forces that drive the formation of a self-assembled monolayer on a given surface remains an important area of investigation. A new paper discusses some of the considerations for self-assembly on semiconductors. The results highlight the tradeoffs between achieving crystalline packing of the tail groups and forming commensurate bonding between the head groups and the underlying surface. Where the emphasis should be placed depends on the application, but obtaining both interfacial and intermolecular ordering may be possible.

  View details for DOI 10.1021/nn700118k

  View details for Web of Science ID 000252012200007

  View details for PubMedID 19203125

• Spatial cues for the enhancement of retinal pigment epithelial cell function in potential transplants BIOMATERIALS Lee, C. J., Fishman, H. A., Bent, S. F. 2007; 28 (13): 2192-2201

  Abstract

  Retinal pigment epithelial (RPE) cellular morphology and function are vital to the health of the retina. In age-related macular degeneration, RPE dysfunction and changes in Bruch's membrane occur. Thus, a potential cure is a dual-layer biomimetic transplant consisting of a layer of healthy RPE cells cultured on a support membrane. In this study, we investigated human anterior lens capsule as a replacement for Bruch's membrane and also explored different seeding methods as ways of inducing the desired cellular morphology and function. Using in vitro assays, we demonstrated that RPE cells cultured on lens capsule exhibited epithelial characteristics, such as the presence of actin belts and the formation of tight junctions in the monolayer. Bovine photoreceptor outer segments were also incubated with the RPE cells in order to quantify the binding and ingestion activity of the RPE cells. With these assays, we determined that cells seeded by centrifugation appeared to possess the most epithelial-like morphology, with the shortest overall length and the smallest elongation. They also exhibited enhanced metabolic activity, with a 1.5-fold increase over conventional gravity seeding. Thus, the spatial cues provided by centrifugation may assist cells in assuming native RPE function. Therefore, a dual-layer transplant, with RPE cells organized by centrifugation onto lens capsule, appears promising in achieving native retinal function.

  View details for DOI 10.1016/j.biomaterials.2007.01.018

  View details for Web of Science ID 000244947100004

  View details for PubMedID 17267030

• Thin collagen film scaffolds for retinal epithelial cell culture BIOMATERIALS Lu, J. T., Lee, C. J., Bent, S. F., Fishman, H. A., Sabelman, E. E. 2007; 28 (8): 1486-1494

  Abstract

  Collagen films have been used in biological implantation and surgical grafts. The development of thin collagen films on the order of 10 microm thick that ensure a planar distribution of implanted cells is a necessary step towards surgical grafts for treatment of age-related macular degeneration (AMD). Here, collagen films were manufactured on a Teflon support to a thickness of 2.4+/-0.2 microm, comparable to that of native Bruch's membrane. Because one important function of Bruch's membrane is allowing the flow of nutrients and waste to and from the retinal pigment epithelium the diffusion properties of the collagen films were studied using blind-well chambers. The diffusion coefficient of the collagen film was determined to be 4.1 x 10(-10)cm(2)/s for 71,200 Da dextran molecules. Viability studies utilizing the blind-well chambers also confirmed that nutrient transport through the films was sufficient to sustain retinal pigment epithelial (RPE) cells. The films were bioassayed in a RPE cell culture model to confirm cell attachment and viability. RPE cells were shown to form an epithelial phenotype and were able to phagocytize photoreceptor outer segments.

  View details for DOI 10.1016/j.biomaterials.2006.11.023

  View details for Web of Science ID 000244130000004

  View details for PubMedID 17161864

• Carbon-oxygen coupling in the reaction of formaldehyde on Ge(100)-2x1 JOURNAL OF PHYSICAL CHEMISTRY C Filler, M. A., Musgrave, C. B., Bent, S. F. 2007; 111 (4): 1739-1746

  View details for DOI 10.1021/jp064820v

  View details for Web of Science ID 000245005500029

• ALD resist formed by vapor-deposited self-assembled monolayers LANGMUIR Hong, J., Porter, D. W., Sreenivasan, R., McIntyre, P. C., Bent, S. F. 2007; 23 (3): 1160-1165

  Abstract

  A new process of applying molecular resists to block HfO2 and Pt atomic layer deposition has been investigated. Monolayer films are formed from octadecyltrichlorosilane (ODTS) or tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane (FOTS) and water vapor on native silicon oxide surfaces and from 1-octadecene on hydrogen-passivated silicon surfaces through a low-pressure chemical vapor deposition process. X-ray photoelectron spectroscopy data indicates that surfaces blocked by these monolayer resists can prevent atomic layer deposition of both HfO2 and Pt successfully. Time-dependent studies show that the ODTS monolayers continue to improve in blocking ability for as long as 48 h of formation time, and infrared spectroscopy measurements confirm an evolution of packing order over these time scales.

  View details for DOI 10.1021/la0606401

  View details for Web of Science ID 000243684100033

  View details for PubMedID 17241027

• Thermal control of amide product distributions at the Ge(100)-2x1 surface JOURNAL OF PHYSICAL CHEMISTRY C Keung, A. J., Filler, M. A., Bent, S. F. 2007; 111 (1): 411-419

  View details for DOI 10.1021/jp065278d

  View details for Web of Science ID 000244993800060

• Area-selective atomic layer deposition of platinum on YSZ substrates using microcontact printed SAMs JOURNAL OF THE ELECTROCHEMICAL SOCIETY Jiang, X., Bent, S. F. 2007; 154 (12): D648-D656

  View details for DOI 10.1149/1.2789301

  View details for Web of Science ID 000250504600043

• Spatial clues for the enhancement of retinal pigment epithelial cell function in potential implants Biomaterials Lee, C., J., Fishman, H., A., Bent, S., F. 2007; 28: 2192-2201
• Effect of radical species density and ion bombardment during ashing of extreme ultralow-kappa interlevel dielectric materials JOURNAL OF APPLIED PHYSICS Worsley, M. A., Bent, S. F., Fuller, N. C., Tai, T. L., Doyle, J., Rothwell, M., Dalton, T. 2007; 101 (1)

  View details for DOI 10.1063/1.2405123

  View details for Web of Science ID 000243585200017

• Characterization of neutral species densities in dual frequency capacitively coupled photoresist ash plasmas by optical emission actinometry JOURNAL OF APPLIED PHYSICS Worsley, M. A., Bent, S. F., Fuller, N. C., Dalton, T. 2006; 100 (8)

  View details for DOI 10.1063/1.2358303

  View details for Web of Science ID 000241721900013

• Highly stable monolayer resists for atomic layer deposition on germanium and silicon CHEMISTRY OF MATERIALS Chen, R., Bent, S. F. 2006; 18 (16): 3733-3741

  View details for DOI 10.1021/cm0607785

  View details for Web of Science ID 000239396900021

• A model retinal interface based on directed neuronal growth for single cell stimulation BIOMEDICAL MICRODEVICES Mehenti, N. Z., Tsien, G. S., Leng, T., Fishman, H. A., Bent, S. F. 2006; 8 (2): 141-150

  Abstract

  In this work, we use cell micropatterning technologies to direct neuronal growth to individual electrodes, and demonstrate that such an approach can achieve selective stimulation and lower stimulation thresholds than current field-effect based retinal prostheses. Rat retinal ganglion cells (RGCs) were purified through immunopanning techniques, and microcontact printing (microCP) was applied to align and pattern laminin on a microelectrode array, on which the RGCs were seeded and extended neurites along the pattern to individual electrodes. The stimulation threshold currents of RGCs micropatterned to electrodes were found to be significantly less than those of non-patterned RGCs over a wide range of electrode-soma distances, as determined with calcium imaging techniques. Moreover, the stimulation threshold for micropatterned cells was found to be independent of electrode-soma distance, and there was no significant effect of microCP on cell excitability. The effects of additional stimulation parameters, such as electrode size and pulse duration, on threshold currents were determined. The stimulation results quantitatively demonstrate the potential benefits of a retinal prosthetic interface based on directed neuronal growth.

  View details for DOI 10.1007/s10544-006-7709-3

  View details for Web of Science ID 000237486500006

  View details for PubMedID 16688573

• Detecting free radicals during the hot wire chemical vapor deposition of amorphous silicon carbide films using single-source precursors JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Zaharias, G. A., Duan, H. L., Bent, S. F. 2006; 24 (3): 542-549

  View details for DOI 10.1116/1.2194023

  View details for Web of Science ID 000238091300023

• Characterization of polyconjugated thin films synthesized by hot-wire chemical vapor deposition of aniline 3rd International Conference on Hot-Wire CVD (Cat-CVD) Process Zaharias, G. A., Shi, H. H., Bent, S. F. ELSEVIER SCIENCE SA. 2006: 341–45

  View details for DOI 10.1016/j.tsf.2005.07.145

  View details for Web of Science ID 000235979600084

• Chemistry for positive pattern transfer using area-selective atomic layer deposition ADVANCED MATERIALS Chen, R., Bent, S. F. 2006; 18 (8): 1086-?

  View details for DOI 10.1002/adma.200502470

  View details for Web of Science ID 000237371800023

• Formation of surface-bound acyl groups by reaction of acyl halides on Ge(100)-2x1 JOURNAL OF PHYSICAL CHEMISTRY B Filler, M. A., Keung, A. J., Porter, D. W., Bent, S. F. 2006; 110 (9): 4115-4124

  Abstract

  We have investigated the reaction of a series of acyl halides, including acetyl chloride, acetyl bromide, acetyl-d3 chloride, benzoyl chloride, and pivaloyl chloride, on Ge(100)-2x1 with multiple internal reflection infrared (MIR-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). Infrared spectra following saturation exposures of acetyl chloride and acetyl bromide to Ge(100)-2x1 at 310 K are nearly identical, both exhibiting strong nu(C=O) stretching peaks near 1685 cm-1 and no vibrational modes in the nu(Ge-H) region. These data provide strong evidence for the presence of a surface-bound acetyl group on Ge(100)-2x1, which results from a C-X dissociation reaction (where X=Cl, Br). For acetyl chloride, DFT calculations predict that the barrier to C-Cl dissociation is only 1 kcal/mol above a chlorine-bound precursor state and is considerably smaller than barriers leading to the [2+2] C=O cycloaddition and alpha-CH dissociation products. In addition to the C-X dissociation product, both infrared and photoelectron results point to the presence of a second structure for acetyl halides where the oxygen of the surface-bound acetyl group donates charge to a nearby surface atom. This interaction is not observed for benzoyl chloride and pivaloyl chloride.

  View details for DOI 10.1021/jp055685+

  View details for Web of Science ID 000235944500045

  View details for PubMedID 16509705

• Determination of human lens capsule permeability and its feasibility as a replacement for Bruch's membrane BIOMATERIALS Lee, C. J., Vroom, J. A., Fishman, H. A., Bent, S. F. 2006; 27 (8): 1670-1678

  Abstract

  We have investigated human anterior lens capsule as a potential replacement for Bruch's membrane as a treatment for age-related macular degeneration. Any substrate to replace Bruch's membrane should possess certain characteristics to maintain proper function of the overlying retina. One of the important properties of Bruch's membrane is allowing the flow of nutrients and waste between the retinal pigment epithelium and the choriocapillaris. Here, we measured the permeability of the lens capsule by studying the diffusion of various molecular weight FITC-dextran molecules. Expressions for extraction of diffusion coefficients from concentration vs. time data from a blind-well chamber apparatus were derived for both a single and double membrane experiments. The diffusion coefficients in the lens capsule were found to be in the range of 10(-6) to 10(-10)cm2/s. We demonstrated a power law relationship, with the diffusion coefficient possessing a -0.6 order dependence on molecular weight. The molecular weight exclusion limit was determined to be 150+/-40 kDa. We have compared this value with reported values of Bruch's membrane molecular weight exclusion limit and find that the lens capsule has the potential to act as a substitute Bruch's membrane.

  View details for DOI 10.1016/j.biomaterials.2005.09.008

  View details for Web of Science ID 000234731900055

  View details for PubMedID 16199085

• Carboxylic acid chemistry at the Ge(100)-2 x 1 interface: Bidentate bridging structure formation on a semiconductor surface JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Filler, M. A., Van Deventer, J. A., Keung, A. J., Bent, S. F. 2006; 128 (3): 770-779

  Abstract

  The reactions of acetic acid, acetic-d3 acid-d, and formic acid with the Ge(100)-2 x 1 surface have been investigated using multiple internal reflection Fourier transform infrared (MIR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. The infrared and photoelectron data provide experimental evidence for an O-H dissociation product at 310 K. DFT calculations indicate that the O-H dissociation pathway is significantly favored, both kinetically and thermodynamically, over other potential reaction pathways. All of the carboxylic acids studied exhibit unexpected vibrational modes between 1400 and 1525 cm(-1), which are attributed to the presence of a bidentate bridging structure where both oxygen atoms interact directly with the surface.

  View details for DOI 10.1021/ja0549502

  View details for Web of Science ID 000234815000040

  View details for PubMedID 16417366

• Reactivity of the germanium surface: Chemical passivation and functionalization ANNUAL REVIEW OF PHYSICAL CHEMISTRY Loscutoff, P. W., Bent, S. F. 2006; 57: 467-495

  Abstract

  With the rapidly changing materials needs of modern microelectronics, germanium provides an opportunity for future-generation devices. Controlling germanium interfaces will be essential for this purpose. We review germanium surface reactivity, beginning with a description of the most commonly used surfaces, Ge(100) and Ge(111). An analysis of oxide formation shows why the poor oxide properties have hindered practical use of germanium to date. This is followed by an examination of alternate means of surface passivation, with particular attention given to sulfide, chloride, and hydride termination. Specific tailoring of the interface properties is possible through organic functionalization. The few solution functionalization methods that have been studied are reviewed. Vacuum functionalization has been studied to a much greater extent, with dative bonding and cycloaddition reactions emerging as principle reaction mechanisms. These are reviewed through molecular reaction studies that demonstrate the versatility of the germanium surface.

  View details for DOI 10.1146/annurev.physchem.56.092503.141307

  View details for Web of Science ID 000237668700016

  View details for PubMedID 16599818

• Analysis of plasma-induced modification of ULK and eULK materials: Dual damascene processing challenges for 45nm (kappa <= 2.4) and beyond BEOL technologies PROCEEDINGS OF THE IEEE 2006 INTERNATIONAL INTERCONNECT TECHNOLOGY CONFERENCE Fuller, N. C., Worsley, M. A., Nitta, S., Dalton, T., Tai, T. L., Bent, S., Magbitang, T., Dubois, G., Miller, R., Volksen, W., Sankar, M., Purushothaman, S. 2006: 24-26

  View details for Web of Science ID 000238974400007

• Area selective atomic layer deposition by soft lithography Chen, R., Kim, H., Porter, D., W., McIntyre, P., C., Bent, S., F. 2006
• Tertiary amide chemistry at the Ge(100)-2 x 1 surface SURFACE SCIENCE Keung, A. J., Filler, M. A., Porter, D. W., Bent, S. F. 2005; 599 (1-3): 41-54

  View details for DOI 10.1016/j.susc.2005.09.035

  View details for Web of Science ID 000234132600006

• Ethylenediamine on Ge(100)-2 x 1: The role of interdimer interactions JOURNAL OF PHYSICAL CHEMISTRY B Kim, A., Filler, M. A., Kim, S., Bent, S. F. 2005; 109 (42): 19817-19822

  Abstract

  We have investigated the reaction of the bifunctional molecule ethylenediamine on Ge(100)-2 x 1 using multiple internal reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations. Ethylenediamine exhibits different adsorption behavior than simple methylamines on the Ge(100)-2 x 1 surface. At low coverages, ethylenediamine undergoes dissociative chemisorption via an interdimer dual N-H dissociation reaction. As coverage increases, the N-H dissociation reaction is inhibited and formation of a Ge-N dative-bonded structure dominates.

  View details for DOI 10.1021/jp054340o

  View details for Web of Science ID 000232857900037

  View details for PubMedID 16853562

• Detection of open or closed porosity in low-kappa dielectrics by solvent diffusion MICROELECTRONIC ENGINEERING Worsley, M. A., Roberts, M., Bent, S. F., GATES, S. M., Shaw, T., Volksen, W., Miller, R. 2005; 82 (2): 113-118

  View details for DOI 10.1016/j.mee.2005.06.007

  View details for Web of Science ID 000232945100003

• The influence of filament material on radical production in hot wire chemical vapor deposition of a-Si : H THIN SOLID FILMS Duan, H. L., Bent, S. F. 2005; 485 (1-2): 126-134

  View details for DOI 10.1016/j.tsf.2005.03.038

  View details for Web of Science ID 000230607700019

• Achieving area-selective atomic layer deposition on patterned substrates by selective surface modification APPLIED PHYSICS LETTERS Chen, R., Kim, H., McIntyre, P. C., Porter, D. W., Bent, S. F. 2005; 86 (19)

  View details for DOI 10.1063/1.1922076

  View details for Web of Science ID 000229397900026

• Layer-by-layer growth on Ge(100) via spontaneous urea coupling reactions JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Kim, A., Filler, M. A., Kim, S., Bent, S. F. 2005; 127 (16): 6123-6132

  Abstract

  We have demonstrated the layer-by-layer growth, via a urea coupling reaction between two bifunctional molecules, ethylenediamine and 1,4-phenylene diisocyanate, to form an ultrathin film on Ge(100)-2 x 1 at room temperature under vacuum conditions. The initial adsorption and subsequent growth of each layer was studied with multiple internal reflection Fourier transform infrared (MIR-FTIR) spectroscopy. Ethylenediamine reacts with Ge(100)-2 x 1 to produce a surface-bound amine group which is available for additional reaction. Subsequent exposure of 1,4-phenylene diisocyanate leads to a spontaneous urea coupling reaction between the surface-bound amine and the highly reactive isocyanate functional group. Three bands at 1665, 1512, and 1306 cm(-)(1) are characteristic of a urea linkage and provide evidence of the coupling reaction. The coupling procedure can be repeated in a binary fashion to create covalently bound ultrathin films at room temperature, and in the present work, we demonstrate the successful growth of four layers. In addition, we have found that an initial exposure of 1,4-phenylene diisocyanate to Ge(100)-2 x 1 produces an isocyanate-functionalized surface which, upon exposure to ethylenediamine, also forms urea linkages. This layer-by-layer deposition method provides a strategy with which to design and produce precisely tailored organic materials at semiconductor interfaces.

  View details for DOI 10.1021/ja042751x

  View details for Web of Science ID 000228602600077

  View details for PubMedID 15839714

• Effect of plasma interactions with low-kappa films as a function of porosity, plasma, chemistry, and temperature JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B Worsley, M. A., Bent, S. F., GATES, S. M., Fuller, N. C., Volksen, W., Steen, M., Dalton, T. 2005; 23 (2): 395-405

  View details for DOI 10.1116/1.1861038

  View details for Web of Science ID 000228788600011

• Investigation of self-assembled monolayer resists for hafnium dioxide atomic layer deposition CHEMISTRY OF MATERIALS Chen, R., Kim, H., McIntyre, P. C., Bent, S. F. 2005; 17 (3): 536-544

  View details for DOI 10.1021/cm0486666

  View details for Web of Science ID 000226804000011

• Quantum chemistry based statistical mechanical model of hydrogen desorption from Si(100)-2 x 1, Ge(100)-2 x 1, and SiGe alloy surfaces JOURNAL OF PHYSICAL CHEMISTRY B Mui, C., Bent, S. F., Musgrave, C. B. 2004; 108 (47): 18243-18253

  View details for DOI 10.1021/jp0379493

  View details for Web of Science ID 000225227700021

• Directed retinal nerve cell growth for use in a retinal prosthesis interface INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE Leng, T., Wu, P., Mehenti, N. Z., Bent, S. F., Marmor, M. F., Blumenkranz, M. S., Fishman, H. A. 2004; 45 (11): 4132-4137

  Abstract

  Retinal prosthetic devices that use microelectrode arrays to stimulate retinal nerve cells may provide a viable treatment for degenerative retinal diseases. Current devices are based on electrical field-effect stimulation of remaining functional neural elements. However, the distance between target neurons and electrodes limits the potential density of electrodes and the ability to stimulate specific types of retinal neurons that contribute to visual perceptions. This study was conducted to investigate the use of microcontact printing (muCP) to direct cultured or explant retinal ganglion cell (RGC) neurites to precise and close stimulation positions and to evaluate the cell types that grow from a retinal explant.RGCs and whole retinal explants were isolated from postnatal day-7 Sprague-Dawley rats using immunopanning purification and microdissection, respectively. Aligned muCP was used to direct the growth of RGC neurites from pure cultures (n=105) and retinal explants (n=64) along laminin patterns and to individual microelectrodes. Immunofluorescence stains (n=39) were used to determine the cell types that grew out from the retinal explants.RGC neurite growth was directed reproducibly along aligned laminin micropatterns to individual microelectrodes in pure RGC cultures and from full-thickness explanted rat retinas in 92% of experiments, neurites from pure RGC cultures extended along the laminin lines with an average length of 263 +/- 118 microm (SD; n=27) after 24 hours. Neurites from retinal explants extended in more than 80% of experiments and were observed to grow to an average length of 279 +/- 78 microm (n=64) after 2 days in culture. These neurites grew up to 3 mm after 1 month of culture on the laminin micropatterns. Immunohistochemical stains demonstrated that extended processes from both RGCs and glial cells grew out of retinal explants onto stamped laminin lines.Using muCP to pattern surfaces with growth factors, individual neuronal processes from pure RGC culture and whole retinal explants can be directed to discrete sites on a microelectronic chip surface. By directing RGC neurite processes to specific sites, single cell stimulation becomes possible. This may allow discrete populations of retinal neurons to be addressed so that physiologic retinal processing of visual information can be achieved.

  View details for DOI 10.1167/iovs.03-1335

  View details for Web of Science ID 000224678200039

  View details for PubMedID 15505066

• A density functional theory study on the effect of Ge alloying on hydrogen desorption from SiGe alloy surfaces JOURNAL OF PHYSICAL CHEMISTRY B Mui, C., Bent, S. F., Musgrave, C. B. 2004; 108 (20): 6336-6350

  Abstract

  We have used density functional theory to investigate hydrogen desorption from SiGe alloy surfaces, and the effect of Ge alloying on the kinetics of hydrogen desorption via the prepairing and interdimer mechanisms. We find that the calculated activation barriers of the prepairing mechanism are affected by the surface atom bonded to the desorbing hydrogen atoms. On the other hand, our calculations show that the activation barrier for hydrogen desorption via the 2H interdimer mechanism is affected by all four surface atoms of the two neighboring dimers. For the 4H interdimer mechanism, we have shown that the activation barrier for hydrogen desorption is not significantly higher than the endothermicity of hydrogen desorption. We also find that the calculated activation barriers of the interdimer mechanisms are generally lower than those of the prepairing mechanism. In addition, our calculations show that surface Ge atoms on neighboring dimers on SiGe alloy surfaces have a minor effect on the calculated activation barriers of both the prepairing and interdimer mechanisms, which indicates that the effect of Ge alloying on hydrogen desorption is local in nature. We also discuss the effects of cluster size and constraints on the calculated reaction energies and activation barriers of hydrogen desorption via the two mechanisms.

  View details for DOI 10.1021/jp037948a

  View details for Web of Science ID 000221455000031

  View details for PubMedID 18950120

• Self-assembled monolayer resist for atomic layer deposition of HfO2 and ZrO2 high-kappa gate dielectrics APPLIED PHYSICS LETTERS Chen, R., Kim, H., McIntyre, P. C., Bent, S. F. 2004; 84 (20): 4017-4019

  View details for DOI 10.1063/1.1751211

  View details for Web of Science ID 000221269800021

• Controlling cell adhesion on human tissue by soft lithography LANGMUIR Lee, C. J., Blumenkranz, M. S., Fishman, H. A., Bent, S. F. 2004; 20 (10): 4155-4161

  Abstract

  Soft lithographic techniques are widely used for fundamental biological applications. This study investigates the extension of soft lithography for use on human tissue to create a biological implant by systematically studying the effect of pattern size on cellular morphology. We focus on mimicking a key layer of the physiological retina with an organized monolayer of epithelial cells to act as a new treatment for age-related macular degeneration. We show that epithelial cells can be confined to cytophilic islands defined on lens capsule by the inhibitory polymer poly(vinyl alcohol). In addition, as the size of the cytophilic islands grows, both the fraction of islands with cells attached and the number of cells adhered to each island increase. High densities of cell adhesion and single cell attachment per island were achieved with a 25 microm pattern size. Over time, the cells spread over the 5 microm wide barriers to form a confluent monolayer that may eventually serve as a functional retinal implant. With the ability to apply soft lithography to tissue samples, human tissue may become a universal membrane substrate for other ocular diseases or in tissue engineering applications elsewhere in the body.

  View details for DOI 10.1021/la035467c

  View details for Web of Science ID 000221319400049

  View details for PubMedID 15969410

• A quantum chemistry based statistical mechanical model of hydrogen desorption from Si(100)‑2x1, Ge(100)‑2x1, and SiGe alloy surfaces J. Phys. Chem. B Mui, C., Bent, S., F., Musgrave, C., B. 2004; 108: 12559-12565
• Hot wire chemical vapor deposition as a novel synthetic method for electroactive organic thin films Symposium on Flexible Electronics-Materials and Device Technology held at the 2004 MRS Spring Meeting Zaharias, G. A., Shi, H. H., Bent, S. F. MATERIALS RESEARCH SOCIETY. 2004: 361–366

  View details for Web of Science ID 000224425500047

• Controlling area-selective atomic layer deposition of HfO2 dielectric by self-assembled monolayers Symposium on Integration of Advanced Micro-and Nanoelectronic Devices held at the 2004 MRS Spring Meeting Chen, R., Kim, H., McIntyre, P. C., Bent, S. F. MATERIALS RESEARCH SOCIETY. 2004: 57–62

  View details for Web of Science ID 000224411400009

• Hot wire chemical vapor deposition as a novel synthetic method for electroactive organic thin films Zaharias, G., A., Shi, H., H., Bent, S., F. 2004
• Pushing the limits of artificial vision IEEE Potentials Mehenti, N., Z., Fishman, H., A., Bent, S., F. 2004; 23: 21-23
• Controlling area-selective atomic layer deposition of HfO2 dielectric by self-assembled monolayers Chen, R., Kim, H., McIntyre, P., C., Bent, S., F. 2004
• Reactions of nitriles at semiconductor surfaces JOURNAL OF PHYSICAL CHEMISTRY B Mui, C., Filler, M. A., Bent, S. F., Musgrave, C. B. 2003; 107 (44): 12256-12267

  View details for DOI 10.1021/jp034864t

  View details for Web of Science ID 000186282200030

• The artificial synapse chip: A flexible retinal interface based on directed retinal cell growth and neurotransmitter stimulation ARTIFICIAL ORGANS Peterman, M. C., Mehenti, N. Z., Bilbao, K. V., Lee, C. J., Leng, T., Noolandi, J., Bent, S. F., Blumenkranz, M. S., Fishman, H. A. 2003; 27 (11): 975-985

  Abstract

  The Artificial Synapse Chip is an evolving design for a flexible retinal interface that aims to improve visual resolution of an electronic retinal prosthesis by addressing cells individually and mimicking the physiological stimulation achieved in synaptic transmission. We describe three novel approaches employed in the development of the Artificial Synapse Chip: (i) micropatterned substrates to direct retinal cell neurite growth to individual stimulation sites; (ii) a prototype retinal interface based on localized neurotransmitter delivery; and (iii) the use of soft materials to fabricate these devices. By patterning the growth of cells to individual stimulation sites, we can improve the selectivity of stimulation and decrease the associated power requirements. Moreover, we have microfabricated a neurotransmitter delivery system based on a 5- micro m aperture in a 500-nm-thick silicon nitride membrane overlying a microfluidic channel. This device can release neurotransmitter volumes as small as 2 pL, demonstrating the possibility of chemical-based prostheses. Finally, we have fabricated and implanted an equivalent device using soft flexible materials that conform to the retinal tissue more effectively. As many of the current retinal prosthesis devices use hard materials and electrical excitation at a lower resolution, our approach may provide more physiologic retinal stimulation.

  View details for Web of Science ID 000186491900003

  View details for PubMedID 14616516

• The surface as molecular reagent: organic chemistry at the semiconductor interface PROGRESS IN SURFACE SCIENCE Filler, M. A., Bent, S. F. 2003; 73 (1-3): 1-56

  View details for DOI 10.1016/S0079-6816(03)00035-2

  View details for Web of Science ID 000185414300001

• Localized neurotransmitter release for use in a prototype retinal interface INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE Peterman, M. C., Bloom, D. M., Lee, C., Bent, S. F., Marmor, M. E., Blumenkranz, M. S., Fishman, H. A. 2003; 44 (7): 3144-3149

  Abstract

  Current neural prostheses use electricity as the mode of stimulation, yet information transfer in neural circuitry is primarily through chemical transmitters. To address this disparity, this study was conducted to devise a prototype interface for a retinal prosthetic based on localized chemical delivery. The goal was to determine whether fluidic delivery through microfabricated apertures could be used to stimulate at single-cell dimensions.A drug delivery system was microfabricated based on a 5- or 10- microm aperture in a 500-nm thick silicon nitride membrane to localize and limit transmitter release. The aperture overlies a microfluidic delivery channel in a silicone elastomer. To demonstrate the effectiveness of this transmitter-based prosthesis, rat pheochromocytoma cells (PC12 cell line) were grown on the surface of the device to test the precision of stimulation, using bradykinin as a stimulant and measuring fluorescence from the calcium indicator, fluo-4.The extent of stimulation could be controlled accurately by varying the concentration of stimulant, from a single cell adjacent to the aperture to a broad area of cells. The stimulation radius was as small as 10 microm, corresponding to stimulation volumes as small as 2 pL. The relationship between the extent of stimulation and concentration was linear.The demonstration of localized chemical stimulation of excitable cells illustrates the potential of this technology for retinal prostheses. Although this is only a proof of concept of neurotransmitter stimulation for a retinal prosthesis, it is a significant first step toward mimicking neurotransmitter release during synaptic transmission.

  View details for DOI 10.1167/iovs.02-1097

  View details for Web of Science ID 000183795800048

  View details for PubMedID 12824264

• Reactions of cyclic aliphatic and aromatic amines on Ge(100)-2x1 and Si(100)-2x1 JOURNAL OF PHYSICAL CHEMISTRY B Wang, G. T., Mui, C., Tannaci, J. F., Filler, M. A., Musgrave, C. B., Bent, S. F. 2003; 107 (21): 4982-4996

  View details for DOI 10.1021/jp026864j

  View details for Web of Science ID 000183066000014

• Competition and selectivity in the reaction of nitriles on Ge(100)-2x1 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Filler, M. A., Mui, C., Musgrave, C. B., Bent, S. F. 2003; 125 (16): 4928-4936

  Abstract

  We have experimentally investigated bonding of the nitrile functional group (R-Ctbd1;N:) on the Ge(100)-2x1 surface with multiple internal reflection infrared spectroscopy. Density functional theory calculations are used to help explain trends in the data. Several probe molecules, including acetonitrile, 2-propenenitrile, 3-butenenitrile, and 4-pentenenitrile, were studied to elucidate the factors controlling selectivity and competition on this surface. It is found that acetonitrile does not react on the Ge(100)-2x1 surface at room temperature, a result that can be understood with thermodynamic and kinetic arguments. A [4+2] cycloaddition product through the conjugated pi system and a [2+2] C=C cycloaddition product through the alkene are found to be the dominant surface adducts for the multifunctional molecule 2-propenenitrile. These two surface products are evidenced, respectively, by an extremely intense nu(C=C=N), or ketenimine stretch, at 1954 cm(-)(1) and the nu(Ctbd1;N) stretch near 2210 cm(-)(1). While the non-conjugated molecules 3-butenenitrile and 4-pentenenitrile are not expected to form a [4+2] cycloaddition product, both show vibrational modes near 1954 cm(-)(1). Additional investigation suggests that 3-butenenitrile can isomerize to 2-butenenitrile, a conjugated nitrile, before introduction into the vacuum chamber, explaining the presence of the vibrational modes near 1954 cm(-)(1). Pathways directly involving only the nitrile functional group are thermodynamically unfavorable at room temperature on Ge(100)-2x1, demonstrating that this functional group may prove useful as a vacuum-compatible protecting group.

  View details for DOI 10.1021/ja027887e

  View details for Web of Science ID 000182331800052

  View details for PubMedID 12696912

• The study of modified layers in SiCOH dielectrics using spectroscopic ellipsometry Worsley, M., A., Bent, S., F., Gates, S., M., Kumar, K., Dalton, T., Hedrick, J., C. 2003
• The study of modified layers in SiCOH dielectrics using spectroscopic ellipsometry Symposium on Materials, Technology and Reliability for Advanced Interconnects and Low-k Dielectrics held at the 2003 MRS Spring Meeting Worsley, M. A., Bent, S. F., GATES, S. M., Kumar, K., Dalton, T., Hedrick, J. C. MATERIALS RESEARCH SOCIETY. 2003: 235–239

  View details for Web of Science ID 000187620400033

• Reaction of cyclic aliphatic and aromatic amines on Ge(100)-2x1 and Si(100)-2x1 J. Phys. Chem. B Wang, G., T., Mui, C., Tannaci, J., F., Filler, M., A., Musgrave, C., B., Bent, S., F. 2003; 107: 4982
• Microcontact printing on human tissue for retinal cell transplantation ARCHIVES OF OPHTHALMOLOGY Lee, C. J., Huie, P., Leng, T., Peterman, M. C., Marmor, M. F., Blumenkranz, M. S., Bent, S. F., Fishman, H. A. 2002; 120 (12): 1714-1718

  Abstract

  To demonstrate that microcontact printing, a modern materials fabrication technique, can be used to engineer the surface of human tissue and to show that inhibitory molecules can be used to pattern the growth of retinal pigment epithelial cells or iris pigment epithelial cells on human lens capsule for transplantation.Photolithographic techniques were used to fabricate photoresist-coated silicon substrates into molds. Poly(dimethylsiloxane)stamps for microcontact printing were made from these molds. The poly(dimethylsiloxane) stamps were then used to "wet-transfer" growth inhibitory molecules to the surface of prepared human lens capsules that were obtained during cataract surgery. Human retinal pigment epithelial and rabbit iris pigment epithelial cells were grown on a lens capsule substrate in the presence and absence of a patterned array of inhibitory factors.We found that human lens capsule could be microprinted with a precision similar to that obtained on glass or synthetic polymers. Retinal pigment epithelial cells and iris pigment epithelial cells cultured onto an untreated lens capsule showed spreading and formed into fusiform-appearing cells. In contrast, cells cultured on a lens capsule with a hexagonal micropattern of growth inhibitory molecules retained an epithelioid form within the inhibitory hexagons.Inhibitory growth molecules can be micropatterned onto human lens capsule, and these micropatterns can control the organization of retinal pigment epithelial cells or iris pigment epithelial cells cultured onto the lens capsule surface.Microprinting on autologous human tissue may facilitate efforts to effectively organize cell cultures and transplantations for the replacement of vital ocular tissues such as the retinal pigment epithelium in age-related macular degeneration.

  View details for Web of Science ID 000179737900014

  View details for PubMedID 12470147

• Detecting reactive species in hot wire chemical vapor deposition CURRENT OPINION IN SOLID STATE & MATERIALS SCIENCE Duan, H. L., Zaharias, G. A., Bent, S. F. 2002; 6 (5): 471-477

  View details for Web of Science ID 000179963800014

• Competition and selectivity of organic reactions on semiconductor surfaces: Reaction of unsaturated ketones on Si(100)-2x1 and Ge(100)-2x1 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Wang, G. T., Mui, C., Musgrave, C. B., Bent, S. F. 2002; 124 (30): 8990-9004

  Abstract

  A combined experimental and theoretical study of a model system of multifunctional unsaturated ketones, including ethyl vinyl ketone (EVK), 2-cyclohexen-1-one, and 5-hexen-2-one, on the Si(100)-2 x 1 and Ge(100)-2 x 1 surfaces was performed in order to probe the factors controlling the competition and selectivity of organic reactions on clean semiconductor surfaces. Multiple internal reflection infrared spectroscopy data and density functional theory calculations indicate that EVK and 2-cyclohexen-1-one undergo selective [4 + 2] hetero-Diels-Alder and [4 + 2] trans cycloaddition reactions on the Ge(100)-2 x 1 surface at room temperature. In contrast, on the Si(100)-2 x 1 surface, evidence is seen for significant ene and possibly [2 + 2] C=O cycloaddition side products. The greater selectivity of these compounds on Ge(100) versus Si(100) is explained by differences between the two surfaces in both thermodynamic factors and kinetic factors. With 5-hexen-2-one, for which [4 + 2] cycloaddition is not possible, a small [2 + 2] C=C cycloaddition product is observed on Ge(100) and possibly Si(100), even though the [2 + 2] C=C transition state is calculated to be the highest barrier reaction by several kilocalories per mole. The results suggest that, due to the high reactivity of clean semiconductor surfaces, thermodynamic selectivity and control will play important roles in their selective functionalization, favoring the use of Ge for selective attachment of multifunctional organics.

  View details for DOI 10.1021/ja026330w

  View details for Web of Science ID 000177074400049

  View details for PubMedID 12137555

• Proton transfer reactions on semiconductor surfaces JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Mui, C., Han, J. H., Wang, G. T., Musgrave, C. B., Bent, S. F. 2002; 124 (15): 4027-4038

  Abstract

  The concept of proton affinity on semiconductor surfaces has been explored through an investigation of the chemistry of amines on the Ge(100)-2 x 1, Si(100)-2 x 1, and C(100)-2 x 1 surfaces. Multiple internal reflection Fourier transform infrared (MIR-FTIR) spectroscopy, temperature programmed desorption (TPD), and density functional theory (DFT) calculations were used in the studies. We find that methylamine, dimethylamine, and trimethylamine undergo molecular chemisorption on the Ge(100)-2 x 1 surface through the formation of Ge-N dative bonds. In contrast, primary and secondary amines react on the Si(100)-2 x 1 surface via N-H dissociation. Since N-H dissociation of amines at semiconductor surfaces mimics a proton-transfer reaction, the difference in chemical reactivities of the Ge(100)-2 x 1 and Si(100)-2 x 1 surfaces toward N-H dissociation can be interpreted as a decrease of proton affinity down a group in the periodic table. The trend in proton affinities of the two surfaces is explained in terms of thermodynamics and kinetics. Solid-state effects on the C(100)-2 x 1 surface and the surface proton affinity concept are discussed based on our theoretical predictions.

  View details for DOI 10.1021/ja0171512

  View details for Web of Science ID 000175014000046

  View details for PubMedID 11942841

• Attaching organic layers to semiconductor surfaces JOURNAL OF PHYSICAL CHEMISTRY B Bent, S. F. 2002; 106 (11): 2830-2842

  View details for DOI 10.1021/jp012995t

  View details for Web of Science ID 000174551500005

• Organic functionalization of group IV semiconductor surfaces: principles, examples, applications, and prospects SURFACE SCIENCE Bent, S. F. 2002; 500 (1-3): 879-903

  View details for Web of Science ID 000175303400039

• Effect of filament material on the decomposition of SiH4 in hot wire CVD of Si-based films Duan, H., L., Zaharias, G., A., Bent, S., F. 2002
• Effect of filament material on the decomposition of SiH4 in hot wire CVD of Si-based films AMORPHOUS AND HETEROGENEOUS SILICON-BASED FILMS-2002 Duan, H. L., Zaharias, G. A., Bent, S. F. 2002; 715: 21-30

  View details for Web of Science ID 000179162400003

• Example of a thermodynamically controlled reaction on a semiconductor surface: Acetone on Ge(100)-2 x 1 JOURNAL OF PHYSICAL CHEMISTRY B Wang, G. T., Mui, C., Musgrave, C. B., Bent, S. F. 2001; 105 (50): 12559-12565

  View details for DOI 10.1021/jp013058o

  View details for Web of Science ID 000172945700019

• pi bond versus radical character of the diamond (100)-2 x 1 surface Taiwan Diamond 2000: Taiwan International Di amond and Related Materials Science and Technology Symposium RUSSELL, J. N., Butler, J. E., Wang, G. T., Bent, S. F., Hovis, J. S., Hamers, R. J., D'Evelyn, M. P. ELSEVIER SCIENCE SA. 2001: 147–51

  View details for Web of Science ID 000171822100010

• The effect of filament temperature on the gaseous radicals in the hot wire decomposition of silane 1st International Conference on Cat-CVD (Hot Wire CVD) Process Duan, H. L., Zaharias, G. A., Bent, S. F. ELSEVIER SCIENCE SA. 2001: 36–41

  View details for Web of Science ID 000171625000007

• Reactions of methylamines at the Si(100)-2x1 surface JOURNAL OF CHEMICAL PHYSICS Mui, C., Wang, G. T., Bent, S. F., Musgrave, C. B. 2001; 114 (22): 10170-10180

  View details for Web of Science ID 000168998000057

• Effect of a methyl-protecting group on the adsorption of pyrrolidine on Si(100)-2 x 1 JOURNAL OF PHYSICAL CHEMISTRY B Wang, G. T., Mui, C., Musgrave, C. B., Bent, S. F. 2001; 105 (16): 3295-3299

  View details for Web of Science ID 000168441900020

• Chemical engineering: Poised for progress CHEMICAL & ENGINEERING NEWS Bent, S. F. 2001; 79 (13): 58-58

  View details for Web of Science ID 000167717100045

• Probing radicals in hot wire decomposition of silane using single photon ionization APPLIED PHYSICS LETTERS Duan, H. L., Zaharias, G. A., Bent, S. F. 2001; 78 (12): 1784-1786

  View details for Web of Science ID 000167436300046

• The effect of a methyl protecting group on the adsorption of pyrrolidine on Si(100)-2x1 J. Phys. Chem. B Wang, G., T., Mui, C., Musgrave, C., B., Bent, S., F. 2001; 105: 3295
• Identification of growth precursors in hot wire CVD of amorphous silicon films Duan, H., L., Zaharias, G., A., Bent, S., F. 2001
• Temperature effects in the hot wire chemical vapor deposition of amorphous hydrogenated silicon carbon alloy JOURNAL OF APPLIED PHYSICS Lee, M. S., Bent, S. F. 2000; 87 (9): 4600-4610

  View details for Web of Science ID 000086724100084

• Interaction of C-6 cyclic hydrocarbons with a Si(100)-2x1 surface: Adsorption and hydrogenation reactions JOURNAL OF PHYSICAL CHEMISTRY B Kong, M. J., Teplyakov, A. V., Jagmohan, J., Lyubovitsky, J. G., Mui, C., Bent, S. F. 2000; 104 (14): 3000-3007

  View details for Web of Science ID 000086599700005

• A theoretical study of the structure and thermochemistry of 1,3-butadiene on the Ge/Si(100)-2 x 1 surface JOURNAL OF PHYSICAL CHEMISTRY A Mui, C., Bent, S. F., Musgrave, C. B. 2000; 104 (11): 2457-2462

  View details for Web of Science ID 000086025300040

• Functionalization of diamond(100) by Diels-Alder chemistry JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Wang, G. T., Bent, S. F., RUSSELL, J. N., Butler, J. E., D'Evelyn, M. P. 2000; 122 (4): 744-745

  View details for Web of Science ID 000085165200038

• Cycloaddition of cyclopentadiene and dicyclopentadiene on Si(100)-2x1: Comparison of monomer and dimer adsorption JOURNAL OF PHYSICAL CHEMISTRY B Wang, G. T., Mui, C., Musgrave, C. B., Bent, S. F. 1999; 103 (32): 6803-6808

  View details for Web of Science ID 000082111200022

• Adsorption of ethylene on the Ge(100)-2 x 1 surface: Coverage and time-dependent behavior JOURNAL OF CHEMICAL PHYSICS Lal, P., Teplyakov, A. V., Noah, Y., Kong, M. J., Wang, G. T., Bent, S. F. 1999; 110 (21): 10545-10553

  View details for Web of Science ID 000080369100036

• In situ diagnostics of methane/hydrogen plasma interactions with Si(100) Duan, H., L., Bent, S., F. 1999
• NEXAFS studies of adsorption of benzene on Si(100)-2 x 1 SURFACE SCIENCE Kong, M. J., Teplyakov, A. V., Lyubovitsky, J. G., Bent, S. F. 1998; 411 (3): 286-293

  View details for Web of Science ID 000075878600013

• Evidence for a retro-Diels-Alder reaction on a single crystalline surface: Butadienes on Ge(100) JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Teplyakov, A. V., Lal, P., Noah, Y. A., Bent, S. F. 1998; 120 (29): 7377-7378

  View details for Web of Science ID 000075176000038

• Spectroscopic and thermal studies of a-SiC : H film growth: Comparison of mono-, tri-, and tetramethylsilane JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Lee, M. S., Bent, S. F. 1998; 16 (3): 1658-1663

  View details for Web of Science ID 000074150500049

• Diels-Alder reactions of butadienes with the Si(100)-2x1 surface as a dienophile: Vibrational spectroscopy, thermal desorption and near edge x-ray absorption fine structure studies JOURNAL OF CHEMICAL PHYSICS Teplyakov, A. V., Kong, M. J., Bent, S. F. 1998; 108 (11): 4599-4606

  View details for Web of Science ID 000072489200028

• Spectroscopic and thermal studies of a-SiC:H film growth: comparison of mono-, tri-, and tetramethylsilane J. Vac. Sci. Technol. A Lee, M., S., Bent, S., F. 1998; 16: 1658
• Temperature-dependent studies of a-SiC:H growth by remote plasma CVD using methylsilanes Lee, M., S., Lal, P., Bent, S., F. 1998
• Etching, insertion, and abstraction reactions of atomic deuterium with amorphous silicon hydride films JOURNAL OF PHYSICAL CHEMISTRY B Chiang, C. M., GATES, S. M., Lee, S. S., Kong, M., Bent, S. F. 1997; 101 (46): 9537-9547

  View details for Web of Science ID A1997YG46300018

• Vibrational spectroscopic studies of Diels-Alder reactions with the Si(100)-2x1 surface as a dienophile JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Teplyakov, A. V., Kong, M. J., Bent, S. F. 1997; 119 (45): 11100-11101

  View details for Web of Science ID A1997YG27300033

• Bonding and thermal reactivity in thin a-SiC:H films grown by methylsilane CVD JOURNAL OF PHYSICAL CHEMISTRY B Lee, M. S., Bent, S. F. 1997; 101 (45): 9195-9205

  View details for Web of Science ID A1997YF25500010

• Bonding and thermal reactivity in thin a-SiC:H films grown by methylsilane CVD J. Phys. Chem. B Lee, M., S., Bent, S., F. 1997; B101: 9195
• Infrared study of the reactions of atomic deuterium with amorphous silicon monohydride JOURNAL OF PHYSICAL CHEMISTRY Lee, S. S., Kong, M. J., Bent, S. F., Chiang, C. M., GATES, S. M. 1996; 100 (51): 20015-20020

  View details for Web of Science ID A1996VZ91200038

• Infrared spectroscopy of methyl groups on silicon CHEMICAL PHYSICS LETTERS Kong, M. J., Lee, K. S., Lyubovitsky, J., Bent, S. F. 1996; 263 (1-2): 1-7

  View details for Web of Science ID A1996VW24400001

• Hydrogen recombinative desorption dynamics Laser Spectroscopy and Photochemistry on Metal Surfaces Bent, S., F., Michelsen, H., A., Zare, R., N. edited by Dai, H.-L., Ho, W. World Scientific, New Jersey. 1995
• Synthesis, layer assembly, and fluorescence dynamics of poly(phenylene vinylene) oligomer phosphonates Katz, H., E., Shane (Bent), S., F., Wilson, W., L., Schilling, M., L., Ungashe, S., B. 1994
• Synthesis, layer assembly, and fluorescence dynamics of poly(phenylene vinylene) oligomer phosphonates J. Am. Chem. Soc. Katz, H., E., Bent, S., F., Wilson, W., L., Schilling, M., L., Ungashe, S. 1994; 116: 6631
• Structural characterization of self-assembled multilayers by FTIR Chem. Mater. Bent, S., F., Schilling, M., L., Wilson, W., L., Katz, H., E., Harris, A., L. 1994; 6: 122
• Photoluminescence studies of self-assembled phenylene vinylene oligomer films Polym. Prepr. (Am. Chem. Soc., Div. Polym. Chem.) Shane (Bent), S., F., Wilson, W., L., Katz, H., E., Schilling, M., L., Ungashe, S. 1994; 35: 315
• Structural studies of zirconium alkylphosphonate monolayers and multilayer assemblies Langmuir. Schilling, M., L., Katz, H., E., Stein, S., M., Shane (Bent), S., F., Wilson, W., L., Ungashe, S., B. 1993; 9: 2156
• Control of polarity and supramolecular optical effects in rigid surface assemblies Polym. Prepr. (Am. Chem. Soc., Div. Polym. Chem.) Katz, H., E., Schilling, M., L., Ungashe, S., B., Shane (Bent), S., Scheller, G., Wilson, W., L. 1993; 34: 793
• Recombinative desorption of H2 on Si(100)-(2x1) and Si(111)-(7x7): comparison of internal state distributions J. Chem. Phys Shane (Bent), S., F., Kolasinski, K., W., Zare, R., N. 1992; 97: 1520
• Internal-state distributions of recombinative hydrogen desorption from Si(100) J. Chem. Phys Kolasinski, K., W., Shane (Bent), S., F., Zare, R., N. 1992; 96: 3995
• Internal-state distributions of H2 desorbed from mono- and dihydride species on Si(100) J. Chem. Phys Shane (Bent), S., F., Kolasinski, K., W., Zare, R., N. 1992; 97: 3704
• A state-specific study of hydrogen desorption from Si(100)-(2x1): comparison of disilane and hydrogen adsorption J. Vac. Sci. Technol Shane (Bent), S., F., Kolasinski, K., W., Zare, R., N. 1992; A10: 2287
• Probing the dynamics of hydrogen recombination on Si(100) J. Chem. Phys Kolasinski, K., W., Shane, S., F., Zare, R., N. 1991; 95: 5482
• Surface vibrational energy relaxation by coupling to electron-hole pairs: c(2x2)-CO/Cu(100) Shane (Bent), S., F., Rothberg, L., Dubois, L., H., Levinos, N., J., Morin, M., Harris, A., L 1990
• Vibrational energy transfer to metal surfaces probed by sum generation: CO/Cu(100) and CH3S/Ag(111) J. Electron Spectrosc. Related Phenom Harris, A., L., Levinos, N., J., Rothberg, L., Dhar, L., H., Shane (Bent), S., F., Morin, M. 1990; 54/55: 5
• Rotational population and alignment distributions for inelastic scattering and trapping/desorption of NO on Pt(111) J. Chem. Phys Jacobs, D., C., Kolasinski, K., W., Shane (Bent), S., F., Zare, R., N. 1989; 91: 3182
• The electronic state-selective photodissociation of CH2BrI at 248, 210, and 193 nm J. Chem. Phys Butler, L., J., Hintsa, E., J., Shane (Bent), S., F., Lee, Y., T. 1987; 86: 2051