Now showing items 1-20 of 24

    • Covalent Nitrogen Doping in Molecular Beam Epitaxy-Grown and Bulk WSe₂ 

      Khosravi, Ava; Addou, Rafik; Smyth, Christopher M.; Yue, Ruoyu; Cormier, Christopher R.; Kim, Jiyoung; Hinkle, Christopher L.; Wallace, Robert M. (American Institute of Physics Inc, 2018-10-22)
      Covalent p-type doping of WSe₂ thin films grown by molecular beam epitaxy and WSe₂ exfoliated from bulk crystals is achieved via remote nitrogen plasma exposure. X-ray photoelectron and Raman spectroscopies indicate ...
    • Nucleation and Growth of WSe₂: Enabling Large Grain Transition Metal Dichalcogenides 

      Yue, Ruoyu; Nie, Yifan; Walsh, Lee A.; Addou, Rafik; Liang, Chaoping; Lu, Ning; Barton, Adam T.; Zhu, Hui; Che, Zifan; Barrera, Diego; Cheng, Lanxia; Cha, Pil-Ryung; Chabal, Yves J.; Hsu, Julia W. P.; Kim, Jiyoung; Kim, Moon J.; Colombo, Luigi; Wallace, Robert M.; Cho, Kyeongjae; Hinkle, Christopher L. (IOP Publishing Ltd, 2017-09-22)
      The limited grain size (< 200 nm) for transition metal dichalcogenides (TMDs) grown by molecular beam epitaxy (MBE) reported in the literature thus far is unsuitable for high-performance device applications. In this work, ...
    • A Crystalline Oxide Passivation on In₀․₅₃Ga₀․₄₇As (100) 

      Qin, Xiaoye; Wang, W. -E; Droopad, R.; Rodder, M. S.; Wallace, Robert M. (American Institute of Physics Inc, 2018-09-24)
      The passivation of In₀․₅₃Ga₀․₄₇As surfaces is highly desired for transistor performance. In this study, the feasibility of a crystalline oxide passivation on In₀․₅₃Ga₀․₄₇As (100) is demonstrated experimentally. The (3 × ...
    • A Kinetic Monte Carlo Simulation Method of Van Der Waals Epitaxy for Atomistic Nucleation-Growth Processes of Transition Metal Dichalcogenides 

      Nie, Yifan; Liang, Chaoping; Cha, Pil-Ryung; Colombo, Luigi; Wallace, Robert M.; Cho, Kyeongjae (Nature Publishing Group, 2018-08-31)
      Controlled growth of crystalline solids is critical for device applications, and atomistic modeling methods have been developed for bulk crystalline solids. Kinetic Monte Carlo (KMC) simulation method provides detailed ...
    • Al₂O₃ on WSe₂ by Ozone Based Atomic Layer Deposition: Nucleation and Interface Study 

      Azcatl, Angelica; Wang, Qingxiao; Kim, Moon J.; Wallace, Robert M.
      In this work, the atomic layer deposition process using ozone and trimethylaluminum (TMA) for the deposition of Al₂O₃ films on WSe₂ was investigated. It was found that the ozone-based atomic layer deposition enhanced the ...
    • Tuning Electronic Transport in Epitaxial Graphene-Based Van Der Waals Heterostructures 

      Lin, Yu-Chuan; Li, Jun; de la Barrera, Sergio,C.; Eichfeld, Sarah M.; Nie, Yifan; Addou, Rafik; Mende, Patrick C.; Wallace, Robert M.; Cho, Kyeongjae; Feenstra, Randall M.; Robinson, Joshua A.
      Two-dimensional tungsten diselenide (WSe₂) has been used as a component in atomically thin photovoltaic devices, field effect transistors, and tunneling diodes in tandem with graphene. In some applications it is necessary ...
    • Oxidation of GaSb(100) and its Control Studied by Scanning Tunneling Microscopy and Spectroscopy 

      Makela, J.; Tuominen, M.; Yasir, M.; Kuzmin, M.; Dahl, J.; Punkkinen, M. P. J.; Laukkanen, P.; Kokko, K.; Wallace, Robert M.
      Atomic-scale knowledge and control of oxidation of GaSb(100), which is a potential interface for energy-efficient transistors, are still incomplete, largely due to an amorphous structure of GaSb(100) oxides. We elucidate ...
    • In Situ Plasma Enhanced Atomic Layer Deposition Half Cycle Study of Al₂O₃ on AlGaN/GaN High Electron Mobility Transistors 

      Qin, Xiaoye; Wallace, Robert M.
      A half cycle study of plasma enhanced atomic layer deposited (PEALD) Al₂O₃ on AlGaN is investigated using in situ X-ray photoelectron spectroscopy, low energy ion scattering, and ex situ electrical characterizations. A ...
    • Low Temperature Synthesis of Graphite on Ni Films Using Inductively Coupled Plasma Enhanced CVD 

      Cheng, Lanxia; Yun, Kayoung; Lucero, Antonio; Huang, Jie; Meng, Xin; Lian, Guoda; Nam, Ho-Seok; Wallace, Robert M.; Kim, Moon J.; Venugopal, Archana; Colombo, Luigi; Kim, Jiyoung
      Controlled synthesis of graphite at low temperatures is a desirable process for a number of applications. Here, we present a study on the growth of thin graphite films on polycrystalline Ni films at low temperatures, about ...
    • Atomically Thin Resonant Tunnel Diodes Built from Synthetic van der Waals Heterostructures 

      Lin, Yu-Chuan; Ghosh, Ram Krishna; Addou, Rafik; Lu, Ning; Eichfeld, Sarah M.; Zhu, Hui; Li, Ming-Yang; Peng, Xin; Kim, Moon J.; Li, Lain-Jong; Wallace, Robert M.; Datta, Suman; Robinson, Joshua A.
      Vertical integration of two-dimensional van der Waals materials is predicted to lead to novel electronic and optical properties not found in the constituent layers. Here, we present the direct synthesis of two unique, ...
    • High Quality HfO₂/p-GaSb(001) Metal-Oxide-Semiconductor Capacitors with 0.8 Nm Equivalent Oxide Thickness 

      Barth, Michael; Rayner, G. Bruce,Jr.; McDonnell, Stephen; Wallace, Robert M.; Bennett, Brian R.; Engel-Herbert, Roman; Datta, Suman
      We investigate in-situ cleaning of GaSb surfaces and its effect on the electrical performance of p-type GaSb metal-oxide-semiconductor capacitor (MOSCAP) using a remote hydrogen plasma. Ultrathin HfO₂ films grown by atomic ...
    • A Crystalline Oxide Passivation for Al₂O₃/AlGaN/GaN 

      Qin, Xiaoye; Dong, Hong; Kim, Jiyoung; Wallace, Robert M.
      In situ X-ray photoelectron spectroscopy and low energy electron diffraction are performed to study the formation of a crystalline oxide on the AlGaN surface. The oxidation of the AlGaN surface is prepared by annealing and ...
    • Accumulation Capacitance Frequency Dispersion of Ⅲ-Ⅴ Metal-Insulator-Semiconductor Devices due to Disorder Induced Gap States 

      Galatage, R. V.; Zhernokletov, Dmitry M.; Dong, Hong; Brennan, Barry; Hinkle, Christopher L.; Wallace, Robert M.; Vogel, E. M. (American Institute of Physics Inc., 2014-07-07)
      The origin of the anomalous frequency dispersion in accumulation capacitance of metal-insulator-semiconductor devices on InGaAs and InP substrates is investigated using modeling, electrical characterization, and chemical ...
    • GaSb Oxide Thermal Stability Studied by Dynamic-XPS 

      McDonnell, Steven; Brennan, Barry; Bursa, Emin; Wallace, Robert M.; Winkler, K.; Baumann, P.
      The thermal decomposition of the native GaSb oxides is studied using time resolved x-ray photoelectron spectroscopy with a temperature resolution of better than 1 K. The expected transfer of oxygen from Sb-O to Ga-O before ...
    • Selectivity of Metal Oxide Atomic Layer Deposition on Hydrogen Terminated and Oxidized Si(001)-(2x1) Surface 

      Longo, Roberto C.; McDonnell, Stephen; Dick, D.; Wallace, Robert M.; Chabal, Yves J.; Owen, James H. G.; Ballard, Josh B.; Randall, John N.; Cho, Kyeongjae (A V S Amer Inst Physics, 2014-02-10)
      In this work, the authors used density-functional theory methods and x-ray photoelectron spectroscopy to study the chemical composition and growth rate of HfO₂, Al₂O₃, and TiO₂ thin films grown by in-situ atomic layer ...
    • Investigation of Arsenic and Antimony Capping Layers, and Half Cycle Reactions During Atomic Layer Deposition of Al₂O₃ on GaSb(100) 

      Zhernokletov, Dmitry M.; Dong, Hong; Brennan, Barry; Kim, Jiyoung; Wallace, Robert M.; Yakimov, M.; Tokranov, V.; Oktyabrsky, S.
      In-situ monochromatic x-ray photoelectron spectroscopy, low energy electron diffraction, ion scattering spectroscopy, and transmission electron microscopy are used to examine the GaSb(100) surfaces grown by molecular beam ...
    • MoS₂ Functionalization for Ultra-Thin Atomic Layer Deposited Dielectrics 

      Azcatl, Angelica; McDonnell, Stephen; KC, Santosh; Peng, Xin; Dong, Hong; Qin, Xiaoye; Addou, Rafik; Mordi, Greg I.; Lu, Ning; Kim, Jiyoung; Kim, Moon J.; Cho, Kyeongjae; Wallace, Robert M.
      The effect of room temperature ultraviolet-ozone (UV-O₃) exposure of MoS₂ on the uniformity of subsequent atomic layer deposition of Al₂O₃ is investigated. It is found that a UV-O₃ pre-treatment removes adsorbed carbon ...
    • Chemical and Electrical Characterization of the HfO2/InAlAs Interface 

      Brennan, Barry; Galatage, Rohit V.; Thomas, K.; Pelucchi, E.; Hurley, P. K.; Kim, Jiyoung; Hinkle, Christopher L.; Vogel, E. M.; Wallace, Robert M.
      InAlAs has the potential to be used as a barrier layer in buried channel quantum well field effect transistor devices due to favorable lattice-matching and carrier confinement properties with InGaAs. Field effect device ...
    • In Situ Study of the Role of Substrate Temperature during Atomic Layer Deposition of HfO2 on InP 

      Dong, Hong; Santosh, KC; Qin, Xiaoye; Brennan, Barry; McDonnell, Steven; Zhernokletov, Dmitry; Hinkle, Christopher L.; Kim, Jiyoung; Cho, Kyeongjie; Wallace, Robert M. (2013-10-16)
      The dependence of the "self cleaning" effect of the substrate oxides on substrate temperature during atomic layer deposition (ALD) of HfO₂ on various chemically treated and native oxide InP (100) substrates is investigated ...
    • In Situ Study of E-Beam Al And Hf Metal Deposition on Native Oxide InP (100) 

      Dong, Hong; Santosh, KC; Azcatl, Angelica; Cabrera, Wilfredo; Qin, Xiaoye; Brennan, Barry; Zhernokletov, Dmitry; Cho, Kyeongjie; Wallace, Robert M.
      The interfacial chemistry of thin Al (∼3 nm) and Hf (∼2 nm) metal films deposited by electron beam (e-beam) evaporation on native oxide InP (100) samples at room temperature and after annealing has been studied by in situ ...