Kim, Jiyoung

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Jiyoung Kim serves as Associate Professor in the Department of Materials Science and Engineering. His research interests include:

  • Gate Stack Engineering for the Next Generation Complementary
  • Metal-Oxide-Semiconductor (CMOS) Applications
  • Nano-structure Materials and Devices for Nanoelectronics
  • Novel Atomic Layer Deposition (ALD) Applications
  • Novel Memory Device Materials, Fabrication and Applications
  • Nano-sensor Fabrication and Applications

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Recent Submissions

Now showing 1 - 20 of 21
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    Engineering The Palladium-WSe₂ Interface Chemistry for Field Effect Transistors with High-Performance Hole Contacts
    (Amer Chemical Soc, 2018-12-07) Smyth, Christopher M.; Walsh, Lee A.; Bolshakov, Pavel; Catalano, Massimo; Addou, Rafik; Wang, Luhua; Kim, Jiyoung; Kim, Moon J.; Young, Chadwin D.; Hinkle, Christopher L.; Wallace, Robert M.; 0000-0001-5566-4806 (Wallace, RM); 0000-0003-0690-7423 (Young, CD); 0000-0003-2781-5149 (Kim, J); 0000-0002-6688-8626 (Walsh, LA); 0000-0002-5485-6600 (Hinkle, CD); 0000-0002-5454-0315 (Addou, R); 70133685 (Kim, J); Smyth, Christopher M.; Walsh, Lee A.; Bolshakov, Pavel; Catalano, Massimo; Addou, Rafik; Wang, Luhua; Kim, Jiyoung; Kim, Moon J.; Young, Chadwin D.; Hinkle, Christopher L.; Wallace, Robert M.
    Palladium has been widely employed as a hole contact to WSe₂ and has enabled, at times, the highest WSe₂ transistor performance. However, there are orders of magnitude variation across the literature in Pd-WSe₂ contact resistance and I-ON/I-OFF ratios with no true understanding of how to consistently achieve high-performance contacts. In this work, WSe₂ transistors with impressive I-ON/I-OFF ratios of 10(6) and Pd-WSe₂ Schottky diodes with near-zero variability are demonstrated utilizing Ohmic-like Pd contacts through deliberate control of the interface chemistry. The increased concentration of a PdSeₓ intermetallic is correlated with an Ohmic band alignment and concomitant defect passivation, which further reduces the contact resistance, variability, and barrier height inhomogeneity. The lowest contact resistance occurs when a 60 min post-metallization anneal at 400 degrees C in forming gas (FG) is performed. X-ray photoelectron spectroscopy indicates this FG anneal produces 3x the concentration of PdSeₓ and an Ohmic band alignment, in contrast to that detected after annealing in ultrahigh vacuum, during which a 0.2 eV hole Schottky barrier forms. Raman spectroscopy and scanning transmission electron microscopy highlight the necessity of the fabrication step to achieve high-performance contacts as no PdSeₓ forms, and WSe₂ is unperturbed by room temperature Pd deposition. However, at least one WSe₂ layer is consumed by the necessary interface reactions that form PdSeₓ requiring strategic exploitation of a sacrificial WSe₂ layer during device fabrication. The interface chemistry and structural properties are correlated with Pd-WSe₂ diode and transistor performance, and the recommended processing steps are provided to enable reliable high-performance contact formation.
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    Ferroelectric Hf₀․₅Zr₀․₅O₂ Thin Films: A Review of Recent Advances
    (Springer, 2018-09-28) Kim, Si Joon; Mohan, Jaidah; Summerfelt, Scott R.; Kim, Jiyoung; 0000-0003-2781-5149 (Kim, J); 70133685 (Kim, J); Mohan, Jaidah; Kim, Jiyoung
    Ferroelectricity in HfO₂-based materials, especially Hf₀․₅Zr₀․₅O₂ (HZO), is today one of the most attractive topics because of its wide range of applications in ferroelectric random-access memory, ferroelectric field-effect transistors, ferroelectric tunneling junctions, steep-slope devices, and synaptic devices. The main reason for this increasing interest is that, when compared with conventional ferroelectric materials, HZO is compatible with complementary metal-oxide-semiconductor flow [even back-end of the line thermal budget] and can exhibit robust ferroelectricity even at extremely thin (<10nm) thicknesses. In this report, recent advances in the ferroelectric properties of HZO thin films since the first report in 2011, including doping effects, mechanical stress effects, interface effects, and ferroelectric film thickness effects, are comprehensively reviewed.
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    Realization of Spatially Addressable Library by a Novel Combinatorial Approach on Atomic Layer Deposition: A Case Study of Zinc Oxide
    (American Chemical Society, 2019-05-07) Kim, Harrison Sejoon; Lee, Joy S.; Kim, S. J.; Lee, Jaebeom; Lucero, Antonio T.; Sung, M. M.; Kim, Jiyoung; 0000-0003-2781-5149 (Kim, J); 0000-0002-6488-5915 (Kim, HS); 70133685 (Kim, J); Kim, Harrison Sejoon; Lee, Joy S.; Lee, Jaebeom; Lucero, Antonio T.; Kim, Jiyoung
    Though the synthesis of libraries of multicomponent metal oxide systems is prevalent using the combinatorial approach, the combinatorial approach has been rarely realized in studying simple metal oxides, especially applied to the atomic layer deposition (ALD) technique. In this literature, a novel combinatorial approach technique is utilized within an ALD grown simple metal oxide to synthesize a "spatially addressable combinatorial library". The two key factors in gradients were defined during the ALD process: (1) the process temperature and (2) a nonuniform flow of pulsed gases inside a cross-flow reactor. To validate the feasibility of our novel combinatorial approach, a case study of zinc oxide (ZnO), a simple metal oxide whose properties are well-known, is performed. Because of the induced gradient, the ZnO (002) crystallite size was found to gradually vary across a 100 mm wafer (10-20 nm) with a corresponding increase in the normalized Raman E 2 /A 1 peak intensity ratio. The findings agree well with the visible grain size observed from scanning electron microscope. The novel combinatorial approach provides a means of systematical interpretation of the combined effect of the two gradients, especially in the analysis of the microstructure of ZnO crystals. Moreover, the combinatorial library reveals that the process temperature, rather than the crystal size, plays the most significant role in determining the electrical conductivity of ZnO. © 2019 American Chemical Society.
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    ZnO Composite Nanolayer with Mobility Edge Quantization for Multi-Value Logic Transistors
    (Nature Publishing Group, 2019-04-30) Lee, L.; Hwang, Jeongwoon; Jung, J. W.; Kim, J.; Lee, H. -I; Heo, S.; Yoon, M.; Choi, S.; Van Long, N.; Park, J.; Jeong, J. W.; Kim, Jiyoung; Kim, K. R.; Kim, D. H.; Im, S.; Lee, B. H.; Cho, Kyeongjae; Sung, M. M.; 0000-0003-2781-5149 (Kim, J); 0000-0003-2698-7774 (Cho, K); 70133685 (Kim, J); 369148996084659752200 (Cho, K); Hwang, Jeongwoon; Kim, Jiyoung; Cho, Kyeongjae
    A quantum confined transport based on a zinc oxide composite nanolayer that has conducting states with mobility edge quantization is proposed and was applied to develop multi-value logic transistors with stable intermediate states. A composite nanolayer with zinc oxide quantum dots embedded in amorphous zinc oxide domains generated quantized conducting states at the mobility edge, which we refer to as “mobility edge quantization”. The unique quantized conducting state effectively restricted the occupied number of carriers due to its low density of states, which enable current saturation. Multi-value logic transistors were realized by applying a hybrid superlattice consisting of zinc oxide composite nanolayers and organic barriers as channels in the transistor. The superlattice channels produced multiple states due to current saturation of the quantized conducting state in the composite nanolayers. Our multi-value transistors exhibited excellent performance characteristics, stable and reliable operation with no current fluctuation, and adjustable multi-level states. ©2019, The Author(s).
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    High-κ Dielectric on ReS₂: In-Situ Thermal Versus Plasma-Enhanced Atomic Layer Deposition of Al₂O₃
    (MDPI AG, 2019-03-30) Khosravi, Ava; Addou, Rafik; Catalano, Massimo; Kim, Jiyoung; Wallace, Robert M.; 0000-0003-2781-5149 (Kim, J); 0000-0001-5566-4806 (Wallace, RM); 0000-0001-9901-9809 (Khosravi, A); 0000-0002-5454-0315 (Addou, R); 70133685 (Kim, J); Khosravi, Ava; Addou, Rafik; Catalano, Massimo; Kim, Jiyoung; Wallace, Robert M.
    We report an excellent growth behavior of a high-κ dielectric on ReS₂ , a two-dimensional (2D) transition metal dichalcogenide (TMD). The atomic layer deposition (ALD) of an Al₂O₃ thin film on the UV-Ozone pretreated surface of ReS₂ yields a pinhole free and conformal growth. In-situ half-cycle X-ray photoelectron spectroscopy (XPS) was used to monitor the interfacial chemistry and ex-situ atomic force microscopy (AFM) was used to evaluate the surface morphology. A significant enhancement in the uniformity of the Al₂O₃ thin film was deposited via plasma-enhanced atomic layer deposition (PEALD), while pinhole free Al₂O₃ was achieved using a UV-Ozone pretreatment. The ReS₂ substrate stays intact during all different experiments and processes without any formation of the Re oxide. This work demonstrates that a combination of the ALD process and the formation of weak S-O bonds presents an effective route for a uniform and conformal high-κ dielectric for advanced devices based on 2D materials. © 2019 by the authors.
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    Top-Down Fabrication of High-Uniformity Nanodiamonds by Self-Assembled Block Copolymer Masks
    (Nature Publishing Group) Bersin, E.; Cotlet, M.; Doerk, G.; Lienhard, B.; Zheng, J; Kim, Harrison Sejoon; Byun, Young-Chui; Nam, C. -Y.; Kim, Jiyoung; Black, C. T.; Englund, D.; 0000-0003-2781-5149 (Kim, J); 70133685 (Kim, J); Kim, Harrison Sejoon; Byun, Young-Chui; Kim, Jiyoung
    Nanodiamonds hosting colour centres are a promising material platform for various quantum technologies. The fabrication of non-aggregated and uniformly-sized nanodiamonds with systematic integration of single quantum emitters has so far been lacking. Here, we present a top-down fabrication method to produce 30.0 ± 5.4 nm uniformly-sized single-crystal nanodiamonds by block copolymer self-assembled nanomask patterning together with directional and isotropic reactive ion etching. We show detected emission from bright single nitrogen vacancy centres hosted in the fabricated nanodiamonds. The lithographically precise patterning of large areas of diamond by self-assembled masks and their release into uniformly sized nanodiamonds open up new possibilities for quantum information processing and sensing. ©2019, The Author(s).
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    Ferroelectric TiN/Hf₀.₅Zr₀.₅O₂/Tin Capacitors with Low-Voltage Operation and High Reliability for Next-Generation FRAM Applications
    (Institute of Electrical and Electronics Engineers Inc.) Kim, Si Joon; Mohan, Jaidah; Young, Chadwin D.; Colombo, Luigi; Kim, Jiyoung; Summerfelt, S. R.; San, T.; 0000-0003-0690-7423 (Young, CD); 0000-0003-2781-5149 (Kim, J); 70133685 (Kim, J); Kim, Si Joon; Mohan, Jaidah; Young, Chadwin D.; Colombo, Luigi; Kim, Jiyoung
    In this study, we investigated the ferroelectric properties of Hf₀.₅Zr₀.₅O₂ (HZO) thin films with different thicknesses (5-20 nm) deposited by atomic layer deposition for the development of future ferroelectric random access memory cells. HZO-based capacitors with a thickness of 5 nm exhibited a switching polarization of ~13 μC/cm² and a ferroelectric saturation voltage of 1.0 V as extracted from the pulse write/read measurements. Furthermore, we performed fatigue measurements and we found no degradation up to 10¹⁰ switching cycles at 1.2 V.
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    Effect of Film Thickness on the Ferroelectric and Dielectric Properties of Low-Temperature (400 ⁰C) Hf₀.₅Zr₀.₅O₂ Films
    (American Institute of Physics) Kim, Si Joon; Mohan. Jaidah; Lee, Jaebeom; Lee, Joy S.; Lucero, Antonion T.; Young, Chandwin D.; Colombo, Luigi; Summerfelt, Scott R.; San, Tamer; Kim, Jiyoung; Kim, Si Joon; Mohan. Jaidah; Lee, Jaebeom; Lee, Joy S.; Lucero, Antonion T.; Young, Chandwin D.; Colombo, Luigi; Kim, Jiyoung
    We report on the effect of the Hf₀.₅Zr₀.₅O₂ (HZO) film thickness on the ferroelectric and dielectric properties using pulse write/read measurements. HZO films of thicknesses ranging from 5 to 20 nm were annealed at 400 ⁰C for 1min in a nitrogen ambient to be compatible with the back-end of the line thermal budget. As the HZO film thickness decreases, low-voltage operation (1.0V or less) can be achieved without the dead layer effect, although switching polarization (P_{sw}) tends to decrease due to the smaller grain size. Meanwhile, for 20-nm-thick HZO films prepared under the identical stress (similar TiN top electrode thickness and thermal budget), the P_{sw} and dielectric constant are reduced because of additional monoclinic phase formation.
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    Large Ferroelectric Polarization of TiN/Hf₀․₅Zr₀․₅0₂ Capacitors Due to Stress-Induced Crystallization at Low Thermal Budget
    (Amer Inst Physics, 2018-10-22) Kim, Si Joon; Narayan, Dushyant; Lee, Jae-Gil; Mohan, Jaidah; Lee, Joy S.; Lee, Jaebeom; Kim, Harrison S.; Byun, Young-Chul; Lucero, Antonio T.; Young, Chadwin D.; Summerfelt, Scott R.; San, Tamer; Colombo, Luigi; Kim, Jiyoung; 0000-0001-7335-1053 (Lee, JS); 0000-0001-9477-5728 (Byun, Y-C); 0000-0003-0690-7423 (Young, CD); 0000-0003-2781-5149 (Kim, J); 70133685 (Kim, J); Kim, Si Joon; Narayan, Dushyant; Lee, Jae-Gil; Mohan, Jaidah; Lee, Joy S.; Lee, Jaebeom; Kim, Harrison S.; Byun, Young-Chul; Lucero, Antonio T.; Young, Chadwin D.; Kim, Jiyoung
    We report on atomic layer deposited Hf₀․₅Zr₀․₅0₂ (HZO)-based capacitors which exhibit excellent ferroelectric (FE) characteristics featuring a large switching polarization (45 μC/cm²) and a low FE saturation voltage (~1.5V) as extracted from pulse write/read measurements. The large FE polarization in HZO is achieved by the formation of a non-centrosymmetric orthorhombic phase, which is enabled by the TiN top electrode (TE) having a thickness of at least 90nm. The TiN films are deposited at room temperature and annealed at 400 ⁰C in an inert environment for at least 1 min in a rapid thermal annealing system. The room-temperature deposited TiN TE acts as a tensile stressor on the HZO film during the annealing process. The stress-inducing TiN TE is shown to inhibit the formation of the monoclinic phase during HZO crystallization, forming an orthorhombic phase that generates a large FE polarization, even at low process temperatures.
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    Nucleation and Growth of WSe₂: Enabling Large Grain Transition Metal Dichalcogenides
    (IOP Publishing Ltd, 2017-09-22) 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.; 0000-0002-2910-2938 (Liang, C); Yue, Ruoyu; Nie, Yifan; Walsh, Lee A.; Addou, Rafik; Liang, Chaoping; Lu, Ning; Barton, Adam T.; Zhu, Hui; Che, Zifan; Barrera, Diego; Cheng, Lanxia; Chabal, Yves J.; Hsu, Julia W. P.; Kim, Jiyoung; Kim, Moon J.; Wallace, Robert M.; Cho, Kyeongjae; Hinkle, Christopher L.
    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, the fundamental nucleation and growth behavior of WSe₂ is investigated through a detailed experimental design combined with on-lattice, diffusion-based first principles kinetic modeling to enable large area TMD growth. A three-stage adsorption-diffusion-attachment mechanism is identified and the adatom stage is revealed to play a significant role in the nucleation behavior. To limit the nucleation density and promote 2D layered growth, it is necessary to have a low metal flux in conjunction with an elevated substrate temperature. At the same time, providing a Se-rich environment further limits the formation of W-rich nuclei which suppresses vertical growth and promotes 2D growth. The fundamental understanding gained through this investigation has enabled an increase of over one order of magnitude in grain size for WSe₂ thus far, and provides valuable insight into improving the growth of other TMD compounds by MBE and other growth techniques such as chemical vapor deposition (CVD).
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    Impurity and Silicate Formation Dependence on O₃ Pulse Time and the Growth Temperature in Atomic-Layer-Deposited La₂O₃ Thin Films
    (American Institute of Physics Inc, 2018-09-24) Park, Tae Joo; Byun, Young-Byun; Wallace, Robert M.; Kim, Jiyoung; Park, Tae Joo; Byun, Young-Byun; Wallace, Robert M.; Kim, Jiyoung
    Atomic-layer-deposited La₂O₃ films were grown on Si with different O₃ pulse times and growth temperatures. The interfacial reactions and impurity behaviors were observed using in situ X-ray photoelectron spectroscopy. Longer pulse time of O₃ formed the solid SiO₂ interfacial barrier layer, which suppressed La-silicate formation. Meanwhile, the carboxyl compound acting as an impurity phase was replaced with LaCO₃ on increasing the O₃ pulse time due to further oxidation and reaction of La. Higher growth temperatures enhanced La-silicate formation by mixed diffusion of Si and La₂O₃, during which most of the La₂O₃ phase was consumed at 400 °C. C and N impurities decreased with increasing growth temperature and completely disappear at 400 °C.
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    Organic-Inorganic Hybrid Semiconductor Thin Films Deposited Using Molecular-Atomic Layer Deposition (MALD)
    (Royal Society of Chemistry) Huang, Jie; Zhang, Hengji; Lucero, Antonio; Cheng, Lanxia; KC, Santosh; Wang, Jian; Hsu, Julia W. P.; Cho, Kyeongjae; Kim, Jiyoung; 0000 0003 8600 0978 (Hsu, JWP); 0000-0003-2698-7774 (Cho, K); 0000-0003-2781-5149 (Kim, J); Huang, Jie; Zhang, Hengji; Lucero, Antonio; Cheng, Lanxia; KC, Santosh; Wang, Jian; Hsu, Julia W. P.; Cho, Kyeongjae; Kim, Jiyoung
    Molecular-atomic layer deposition (MALD) is employed to fabricate hydroquinone (HQ)/diethyl zinc (DEZ) organic-inorganic hybrid semiconductor thin films with accurate thickness control, sharp interfaces, and low deposition temperature. Self-limiting growth is observed for both HQ and DEZ precursors. The growth rate remains constant at approximately 2.8 Å per cycle at 150°C. The hybrid materials exhibit n-type semiconducting behavior with a field effect mobility of approximately 5.7 cm² V⁻¹ s⁻¹ and an on/off ratio of over 103 following post annealing at 200°C in nitrogen. The resulting films are characterized using ellipsometry, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), UV-Vis spectroscopy, transistor behavior, and Hall-effect measurements. Density functional theory (DFT) and many-body perturbation theory within the GW approximation are also performed to assist the explanation and understanding of the experimental results. This research offers n-channel materials as valuable candidates for efficient organic CMOS devices. © 2016.
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    Hydroquinone-ZnO Nano-Laminate Deposited by Molecular-Atomic Layer Deposition
    (American Institute of Physics Inc) Huang, Jie; Lucero, Antonio T.; Cheng, Lanxia; Hwang, Hyeon Jun; Ha, M. -W; Kim, Jiyoung; 70133685 (Kim, J)
    In this study, we have deposited organic-inorganic hybrid semiconducting hydroquinone (HQ)/zinc oxide (ZnO) superlattices using molecular-atomic layer deposition, which enables accurate control of film thickness, excellent uniformity, and sharp interfaces at a low deposition temperature (150 °C). Self-limiting growth of organic layers is observed for the HQ precursor on ZnO surface. Nano-laminates were prepared by varying the number of HQ to ZnO cycles in order to investigate the physical and electrical effects of different HQ to ZnO ratios. It is indicated that the addition of HQ layer results in enhanced mobility and reduced carrier concentration. The highest Hall mobility of approximately 2.3 cm²/V·s and the lowest n-type carrier concentration of approximately 1.0 × 10¹⁸/cm³ were achieved with the organic-inorganic superlattice deposited with a ratio of 10 ZnO cycles to 1 HQ cycle. This study offers an approach to tune the electrical transport characteristics of ALD ZnO matrix thin films using an organic dopant. Moreover, with organic embedment, this nano-laminate material may be useful for flexible electronics.
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    Low Temperature Synthesis of Graphite on Ni Films Using Inductively Coupled Plasma Enhanced CVD
    (Royal Soc Chemistry) 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; A-5283-2008 (Wallace, RM); A-2297-2010 (Kim, MJ); 70133685 (Kim, J)
    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 380 ⁰C, using inductively coupled plasma enhanced chemical vapor deposition. Raman analysis shows that the grown graphite films are of good quality as determined by a low I-D/I-G ratio, ~0.43, for thicknesses ranging from a few layers of graphene to several nanometer thick graphitic films. The growth of graphite films was also studied as a function of time, precursor gas pressure, hydrogen concentration, substrate temperature and plasma power. We found that graphitic films can be synthesized on polycrystalline thin Ni films on SiO₂/Si substrates after only 10 seconds at a substrate temperature as low as 200 ⁰C. The amount of hydrogen radicals, adjusted by changing the hydrogen to methane gas ratio and pressure, was found to dramatically affect the quality of graphite films due to their dual role as a catalyst and an etchant. We also find that a plasma power of about 50 W is preferred in order to minimize plasma induced graphite degradation.
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    A Crystalline Oxide Passivation for Al₂O₃/AlGaN/GaN
    (American Institute of Physics Inc.) Qin, Xiaoye; Dong, Hong; Kim, Jiyoung; Wallace, Robert M.; A-5283-2008 (Wallace, RM)
    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 remote N₂+O₂ plasma pretreatments resulting in a stable crystalline oxide. The impact of the oxide on the interface state density is studied by capacitance voltage (C-V) measurements. It is found that a remote plasma exposure at 550⁰ C shows the smallest frequency dispersion. Crystalline oxide formation may provide a novel passivation method for high quality AlGaN/GaN devices.
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    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.; 70133685 (Kim, J)
    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 epitaxy after thermal desorption of a protective As or Sb layer and subsequent atomic layer deposition (ALD) of Al₂O₃. An antimony protective layer is found to be more favorable compared to an arsenic capping layer as it prevents As alloys from forming with the GaSb substrate. The evolution of oxide free GaSb/Al₂O₃ interface is investigated by "half-cycle" ALD reactions of trimethyl aluminum and deionized water.
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    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.; 70133685 (Kim, J)
    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 contamination from the MoS₂ surface and also functionalizes the MoS₂ surface through the formation of a weak sulfur-oxygen bond without any evidence of molybdenum-sulfur bond disruption. This is supported by first principles density functional theory calculations which show that oxygen bonded to a surface sulfur atom while the sulfur is simultaneously back-bonded to three molybdenum atoms is a thermodynamically favorable configuration. The adsorbed oxygen increases the reactivity of MoS₂ surface and provides nucleation sites for atomic layer deposition of Al₂O₃. The enhanced nucleation is found to be dependent on the thin film deposition temperature.
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    In Situ Study of the Role of Substrate Temperature during Atomic Layer Deposition of HfO2 on InP
    (2013-10-16) Dong, Hong; Santosh, KC; Qin, Xiaoye; Brennan, Barry; McDonnell, Steven; Zhernokletov, Dmitry; Hinkle, Christopher L.; Kim, Jiyoung; Cho, Kyeongjie; Wallace, Robert M.; 70133685 (Kim, J)
    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 using in situ X-ray photoelectron spectroscopy. The removal of In-oxide is found to be more efficient at higher ALD temperatures. The P oxidation states on native oxide and acid etched samples are seen to change, with the total P-oxide concentration remaining constant, after 10 cycles of ALD HfO₂ at different temperatures. An (NH₄)₂ S treatment is seen to effectively remove native oxides and passivate the InP surfaces independent of substrate temperature studied (200°C, 250°C and 300°C) before and after the ALD process. Density functional theory modeling provides insight into the mechanism of the changes in the P-oxide chemical states.
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    Selective Atomic Layer Deposition with Electron-Beam Patterned Self-Assembled Monolayers
    Huang, Jie; Lee, Mingun; Kim, Jiyoung; 70133685 (Kim, J)
    The authors selectively deposited nanolines of titanium oxide (TiO(2)) through atomic layer deposition (ALD) using an octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM) as a nucleation inhibition layer. Electron-beam (e-beam) patterning is used to prepare nanoline patterns in the OTS SAM on SiO(2)/Si substrates suitable for selective ALD. The authors have investigated the effect of an e-beam dose on the pattern width of the selectively deposited TiO(2) lines. A high dose (e. g., 20 nC/cm) causes broadening of the linewidth possibly due to scattering, while a low dose (e. g., 5 nC/cm) results in a low TiO(2) deposition rate because of incomplete exposure of the OTS SAMs. The authors have confirmed that sub-30 nm isolated TiO(2) lines can be achieved by selective ALD combined with OTS patterned by EBL at an accelerating voltage of 2 kV and line dose of 10 nC/cm. This research offers a new approach for patterned gate dielectric layer fabrication, as well as potential applications for nanosensors and solar cells.
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    Investigation of interfacial oxidation control using sacrificial metallic Al and La passivation layers on InGaAs
    (2012-05-25) Brennan, Barry; Milojevic, Marko; Contreras-Guerrero, Roccio; Kim, Hyun-Chul; Lopez-Lopez, Maximo; Kim, Jiyoung; Wallace, Robert M.; 70133685 (Kim, J)
    The ability of metallic Al and La interlayers to control the oxidation of InGaAs substrates is examined by monochromatic x-ray photoelectron spectroscopy (XPS) and compared to the interfacial chemistry of atomic layer deposition (ALD) of Al2O3 directly on InGaAs surfaces. Al and La layers were deposited by electron-beam and effusion cell evaporators, respectively, on In0.53Ga0.47As samples with and without native oxides present. It was found that both metals are extremely efficient at scavenging oxygen from III-V native oxides, which are removed below XPS detection limits prior to ALD growth. However, metallic Ga//In/As species are simultaneously observed to form at the semiconductor-metal interface. Upon introduction of the samples to the ALD chamber, these metal bonds are seen to oxidize, leading to Ga/In-O bond growth that cannot be controlled by subsequent trimethyl-aluminum (TMA) exposures. Deposition on an oxide-free InGaAs surface results in both La and Al atoms displacing group III atoms near the surface of the semiconductor. The displaced substrate atoms tend to partially oxidize and leave both metallic and III-V oxide species trapped below the interlayers where they cannot be "cleaned-up" by TMA. For both Al and La layers the level of Ga-O bonding detected at the interface appears larger then that seen following ALD directly on a clean surface.

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