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De Palma AC, Peng X, Arash S, Gao FY, Baldini E, Li X, Yu ET. Elucidating Piezoelectricity and Strain in Monolayer MoS 2 at the Nanoscale Using Kelvin Probe Force Microscopy. Nano Lett 2024; 24:1835-1842. [PMID: 38315833 DOI: 10.1021/acs.nanolett.3c03100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2024]
Abstract
Strain engineering modifies the optical and electronic properties of atomically thin transition metal dichalcogenides. Highly inhomogeneous strain distributions in two-dimensional materials can be easily realized, enabling control of properties on the nanoscale; however, methods for probing strain on the nanoscale remain challenging. In this work, we characterize inhomogeneously strained monolayer MoS2 via Kelvin probe force microscopy and electrostatic gating, isolating the contributions of strain from other electrostatic effects and enabling the measurement of all components of the two-dimensional strain tensor on length scales less than 100 nm. The combination of these methods is used to calculate the spatial distribution of the electrostatic potential resulting from piezoelectricity, presenting a powerful way to characterize inhomogeneous strain and piezoelectricity that can be extended toward a variety of 2D materials.
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Affiliation(s)
- Alex C De Palma
- Materials Science and Engineering Program, Texas Materials Institute, University of Texas at Austin, Austin, Texas 78712, United States
| | - Xinyue Peng
- Department of Physics and Center for Complex Quantum Systems, University of Texas at Austin, Austin, Texas 78712, United States
| | - Saba Arash
- Department of Physics and Center for Complex Quantum Systems, University of Texas at Austin, Austin, Texas 78712, United States
| | - Frank Y Gao
- Department of Physics and Center for Complex Quantum Systems, University of Texas at Austin, Austin, Texas 78712, United States
| | - Edoardo Baldini
- Department of Physics and Center for Complex Quantum Systems, University of Texas at Austin, Austin, Texas 78712, United States
| | - Xiaoqin Li
- Department of Physics and Center for Complex Quantum Systems, University of Texas at Austin, Austin, Texas 78712, United States
| | - Edward T Yu
- Materials Science and Engineering Program, Texas Materials Institute, University of Texas at Austin, Austin, Texas 78712, United States
- Microelectronics Research Center, Department of Electrical and Computer Engineering, University of Texas at Austin, Austin, Texas 78758, United States
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2
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Cossio G, Barbosa R, Korgel B, Yu ET. Massively Scalable Self-Assembly of Nano and Microparticle Monolayers via Aerosol Assisted Deposition. Adv Mater 2024; 36:e2309775. [PMID: 37983639 DOI: 10.1002/adma.202309775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 11/01/2023] [Indexed: 11/22/2023]
Abstract
An extremely rapid process for self-assembling well-ordered, nano, and microparticle monolayers via a novel aerosolized method is presented. The novel technique can reach monolayer self-assembly rates as high as 268 cm2 min-1 from a single aerosolizing source and methods to reach faster monolayer self-assembly rates are outlined. A new physical mechanism describing the self-assembly process is presented and new insights enabling high-efficiency nanoparticle monolayer self-assembly are developed. In addition, well-ordered monolayer arrays from particles of various sizes, surface functionality, and materials are fabricated. This new technique enables a 93× increase in monolayer self-assembly rates compared to the current state of the art and has the potential to provide an extremely low-cost option for submicron nanomanufacturing.
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Affiliation(s)
- Gabriel Cossio
- Microelectronics Research Center, University of Texas at Austin, Chandra Department of Electrical and Computer Engineering, Austin, TX, 78758, USA
| | - Raul Barbosa
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, TX, 78712, USA
| | - Brian Korgel
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, TX, 78712, USA
| | - Edward T Yu
- Microelectronics Research Center, University of Texas at Austin, Chandra Department of Electrical and Computer Engineering, Austin, TX, 78758, USA
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3
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Yang H, Wang Y, Zou X, Bai R, Wu Z, Han S, Chen T, Hu S, Zhu H, Chen L, Zhang DW, Lee JC, Lu X, Zhou P, Sun Q, Yu ET, Akinwande D, Ji L. Wafer-Scale Synthesis of WS 2 Films with In Situ Controllable p-Type Doping by Atomic Layer Deposition. Research (Wash D C) 2021; 2021:9862483. [PMID: 34957405 PMCID: PMC8672204 DOI: 10.34133/2021/9862483] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 11/09/2021] [Indexed: 11/24/2022]
Abstract
Wafer-scale synthesis of p-type TMD films is critical for its commercialization in next-generation electro/optoelectronics. In this work, wafer-scale intrinsic n-type WS2 films and in situ Nb-doped p-type WS2 films were synthesized through atomic layer deposition (ALD) on 8-inch α-Al2O3/Si wafers, 2-inch sapphire, and 1 cm2 GaN substrate pieces. The Nb doping concentration was precisely controlled by altering cycle number of Nb precursor and activated by postannealing. WS2 n-FETs and Nb-doped p-FETs with different Nb concentrations have been fabricated using CMOS-compatible processes. X-ray photoelectron spectroscopy, Raman spectroscopy, and Hall measurements confirmed the effective substitutional doping with Nb. The on/off ratio and electron mobility of WS2 n-FET are as high as 105 and 6.85 cm2 V−1 s−1, respectively. In WS2 p-FET with 15-cycle Nb doping, the on/off ratio and hole mobility are 10 and 0.016 cm2 V−1 s−1, respectively. The p-n structure based on n- and p- type WS2 films was proved with a 104 rectifying ratio. The realization of controllable in situ Nb-doped WS2 films paved a way for fabricating wafer-scale complementary WS2 FETs.
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Affiliation(s)
- Hanjie Yang
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Yang Wang
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Xingli Zou
- State Key Laboratory of Advanced Special Steel, School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China
| | - Rongxu Bai
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Zecheng Wu
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Sheng Han
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Tao Chen
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Shen Hu
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Hao Zhu
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Lin Chen
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - David W Zhang
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Jack C Lee
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, 78758 Texas, USA
| | - Xionggang Lu
- State Key Laboratory of Advanced Special Steel, School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China
| | - Peng Zhou
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Qingqing Sun
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Edward T Yu
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, 78758 Texas, USA
| | - Deji Akinwande
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, 78758 Texas, USA
| | - Li Ji
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
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4
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Yang H, Wang Y, Zou X, Bai RX, Han S, Wu Z, Han Q, Zhang Y, Zhu H, Chen L, Lu X, Sun Q, Lee JC, Yu ET, Akinwande D, Ji L. Growth Mechanisms and Morphology Engineering of Atomic Layer-Deposited WS 2. ACS Appl Mater Interfaces 2021; 13:43115-43122. [PMID: 34473473 DOI: 10.1021/acsami.1c13467] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Transition-metal dichalcogenides (TMDs) have attracted intense research interest for a broad range of device applications. Atomic layer deposition (ALD), a CMOS compatible technique, can enable the preparation of high-quality TMD films on 8 to 12 in. wafers for large-scale circuit integration. However, the ALD growth mechanisms are still not fully understood. In this work, we systematically investigated the growth mechanisms for WS2 and found them to be strongly affected by nucleation density and film thickness. Transmission electron microscope imaging reveals the coexistence and competition of lateral and vertical growth mechanisms at different growth stages, and the critical thicknesses for each mechanism are obtained. The in-plane lateral growth mode dominates when the film thickness remains less than 5.6 nm (8 layers), while the vertical growth mode dominates when the thickness is greater than 20 nm. From the resulting understanding of these growth mechanisms, the conditions for film deposition were optimized and a maximum grain size of 108 nm was achieved. WS2-based field-effect transistors were fabricated with electron mobility and on/off current ratio up to 3.21 cm2 V-1 s-1 and 105, respectively. Particularly, this work proves the capability of synthesis of TMD films in a wafer scale with excellent controllability of thickness and morphology, enabling many potential applications other than transistors, such as nanowire- or nanosheet-based supercapacitors, batteries, sensors, and catalysis.
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Affiliation(s)
- Hanjie Yang
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Yang Wang
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Xingli Zou
- State Key Laboratory of Advanced Special Steel, School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China
| | - Rong-Xu Bai
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Sheng Han
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Zecheng Wu
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Qi Han
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Yu Zhang
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Hao Zhu
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Lin Chen
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Xionggang Lu
- State Key Laboratory of Advanced Special Steel, School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China
| | - Qingqing Sun
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Jack C Lee
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin 78758, Texas, United States
| | - Edward T Yu
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin 78758, Texas, United States
| | - Deji Akinwande
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin 78758, Texas, United States
| | - Li Ji
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
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5
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Liu R, Peng X, Han X, Mak CH, Cheng KC, Permatasari Santoso S, Shen HH, Ruan Q, Cao F, Yu ET, Chu PK, Hsu HY. Cost-effective liquid-junction solar devices with plasma-implanted Ni/TiN/CNF hierarchically structured nanofibers. J Electroanal Chem (Lausanne) 2021. [DOI: 10.1016/j.jelechem.2021.115167] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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6
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Abstract
Nanosphere lithography offers a rapid, low-cost approach for patterning of large-area two-dimensional periodic nanostructures. However, a complete understanding of the nanosphere self-assembly process is necessary to enable further development and scaling of this technology. The self-assembly of nanospheres into two-dimensional periodic arrays has previously been attributed solely to the Marangoni force; however, we demonstrate that the ζ potential of the nanosphere solution is critically important for successful self-assembly to occur. We discuss and demonstrate how this insight can be used to greatly increase self-assembled 2D periodic array areas while decreasing patterning time and cost. As a representative application, we fabricate antireflection nanostructures on a transparent flexible polymer substrate suitable for use as a large-area (270 cm2), broadband, omnidirectional antireflection film.
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Affiliation(s)
- Gabriel Cossio
- Department of Electrical and Computer Engineering, The University of Texas at Austin, 10100 Burnet Road, Building 160, Austin, Texas 78758, United States
| | - Edward T Yu
- Department of Electrical and Computer Engineering, The University of Texas at Austin, 10100 Burnet Road, Building 160, Austin, Texas 78758, United States
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7
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Gawlik B, Barrera C, Yu ET, Sreenivasan SV. Hyperspectral imaging for high-throughput, spatially resolved spectroscopic scatterometry of silicon nanopillar arrays. Opt Express 2020; 28:14209-14221. [PMID: 32403464 DOI: 10.1364/oe.388158] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 02/23/2020] [Indexed: 06/11/2023]
Abstract
Modern high-throughput nanopatterning techniques, such as nanoimprint lithography, make it possible to fabricate arrays of nanostructures (features with dimensions of 10's to 100's of nm) over large area substrates (cm2 to m2 scale) such as Si wafers, glass sheets, and flexible roll-to-roll webs. The ability to make such large-area nanostructure arrays (LNAs) has created an extensive design space, enabling a wide array of applications including optical devices, such as wire-grid polarizers, transparent conductors, color filters, and anti-reflection surfaces, and building blocks for electronic components, such as ultracapacitors, sensors, and memory storage architectures. However, existing metrology methods will have trouble scaling alongside fabrication methods. Scanning electron microscopy (SEM) and atomic force microscopy (AFM), for instance, have micron scale fields of view (FOV) that preclude comprehensive characterization of LNAs, which may be manufactured at m2 per minute rates. Scatterometry approaches have larger FOVs (typically 100's of µm to a few mm), but traditional scatterometry systems measure samples one point at a time, which also makes them too slow for large-scale LNA manufacturing. In this work, we demonstrate parallelization of the traditional spectroscopic scatterometry approach using hyperspectral imaging, increasing the throughput of the technique by a factor of 106-107. We demonstrate this approach by using hyperspectral imaging and inverse modeling of reflectance spectra to derive 3-dimensional geometric data for Si nanopillar array structures over both mm and cm-scale with µm-scale spatial resolution. This work suggests that geometric measurements for a variety of LNAs can be performed with the potential for high speed over large areas which may be critical for future LNA manufacturing.
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8
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Gawlik BM, Cossio G, Kwon H, Jurado Z, Palacios B, Singhal S, Alù A, Yu ET, Sreenivasan SV. Structural coloration with hourglass-shaped vertical silicon nanopillar arrays. Opt Express 2018; 26:30952-30968. [PMID: 30469985 DOI: 10.1364/oe.26.030952] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 10/07/2018] [Indexed: 06/09/2023]
Abstract
We demonstrate that arrays of hourglass-shaped nanopillars patterned into crystalline silicon substrates exhibit vibrant, highly controllable reflective structural coloration. Unlike structures with uniform sidewall profiles, the hourglass profile defines two separate regions on the pillar: a head and a body. The head acts as a suspended Mie resonator and is responsible for resonant reflectance, while the body acts to suppress broadband reflections from the surface. The combination of these effects gives rise to vibrant colors. The size of the nanopillars can be tuned to provide a variety of additive colors, including the RGB primaries. Experimental results are shown for nanopillar arrays fabricated using nanoimprint lithography and plasma etching. A finite difference time domain (FDTD) model is validated against these results and is used to elucidate the electromagnetic response of the nanopillars. Furthermore, a COMSOL model is used to investigate the angle dependence of the reflectance. In view of display applications, a genetic algorithm is used to optimize the nanopillar geometries for RGB color reflective pixels, showing that nearly all of the sRGB color space and most of the Adobe RGB color space can be covered with this technique.
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9
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Liao J, Ji L, Zhang J, Gao N, Li P, Huang K, Yu ET, Kang J. Influence of the Substrate to the LSP Coupling Wavelength and Strength. Nanoscale Res Lett 2018; 13:280. [PMID: 30203155 PMCID: PMC6134573 DOI: 10.1186/s11671-018-2691-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 08/28/2018] [Indexed: 06/08/2023]
Abstract
Three kinds of typical structures, hemi-/spherical nanoparticles/nanoparticle dimers on the substrate and spherical nanoparticles/nanoparticle dimers half-buried into the substrate, are used for FDTD simulation to theoretically discuss the influence of the substrate to the localized surface plasmon (LSP) coupling when the metal nanoparticles/nanoparticle dimers are locating near a substrate. Simulated results show that the dependencies between the LSP coupling wavelength and the refractive index of the substrate for different structures are not the same, which can be attributed to the different polarization field distributions of LSPs. When light is incident from different directions, the LSP coupling strength are not the same as well and the ratios of the scattering peak intensities depend on the position of the metal nanoparticles or nanoparticle dimers. These phenomenon can be explained by the difference of the local driving electric field intensities which is modulated by the interface between the air and the substrate.
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Affiliation(s)
- Jiawei Liao
- Fujian Provincial Key Laboratory of Semiconductors and Applications, Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices, Department of Physics, Xiamen University, Xiamen, 361005 People’s Republic of China
| | - Li Ji
- Department of Electrical and Computer Engineering, Microelectronic Research Center, The University of Texas at Austin, Austin, TX 78758 USA
| | - Jin Zhang
- Inspection and Quarantine Technology Center, Xiamen Entry-Exit Inspection and Quarantine Bureau of the People’s Republic of China, Xiamen, 361026 People’s Republic of China
| | - Na Gao
- Fujian Provincial Key Laboratory of Semiconductors and Applications, Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices, Department of Physics, Xiamen University, Xiamen, 361005 People’s Republic of China
| | - Penggang Li
- Fujian Provincial Key Laboratory of Semiconductors and Applications, Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices, Department of Physics, Xiamen University, Xiamen, 361005 People’s Republic of China
| | - Kai Huang
- Fujian Provincial Key Laboratory of Semiconductors and Applications, Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices, Department of Physics, Xiamen University, Xiamen, 361005 People’s Republic of China
| | - Edward T. Yu
- Department of Electrical and Computer Engineering, Microelectronic Research Center, The University of Texas at Austin, Austin, TX 78758 USA
| | - Junyong Kang
- Fujian Provincial Key Laboratory of Semiconductors and Applications, Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices, Department of Physics, Xiamen University, Xiamen, 361005 People’s Republic of China
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10
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Ji L, Hsu HY, Lee JC, Bard AJ, Yu ET. High-Performance Photodetectors Based on Solution-Processed Epitaxial Grown Hybrid Halide Perovskites. Nano Lett 2018; 18:994-1000. [PMID: 29303584 DOI: 10.1021/acs.nanolett.7b04445] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Hybrid organic-inorganic halide perovskites (HOIPs) have recently attracted tremendous attention because of their excellent semiconducting and optoelectronic properties, which exist despite their morphology and crystallinity being far inferior to those of more mature semiconductors, such as silicon and III-V compound semiconductors. Heteroepitaxy can provide a route to achieving high-performance HOIP devices when high crystalline quality and smooth morphology are required, but work on heteroepitaxial HOIPs has not previously been reported. Here, we demonstrate epitaxial growth of methylammonium lead iodide (MAPbI3) on single crystal KCl substrates with smooth morphology and the highest carrier recombination lifetime (∼213 ns) yet reported for nonsingle crystalline MAPbI3. Experimental Raman spectra agree well with theoretical calculations, presenting in particular a sharp peak at 290 cm-1 for the torsional mode of the organic cations, a marker of orientational order and typically lacking in previous reports. Photodetectors were fabricated showing excellent performance, confirming the high quality of the epitaxial MAPbI3 thin films. This work provides a new strategy to enhance the performance of all HOIPs-based devices.
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Affiliation(s)
| | - Hsien-Yi Hsu
- School of Energy and Environment, City University of Hong Kong , Hong Kong, China
- Shenzhen Research Institute of City University of Hong Kong, Shen Zhen, 518057, China
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11
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Zou X, Ji L, Yang X, Lim T, Yu ET, Bard AJ. Electrochemical Formation of a p–n Junction on Thin Film Silicon Deposited in Molten Salt. J Am Chem Soc 2017; 139:16060-16063. [DOI: 10.1021/jacs.7b09090] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xingli Zou
- Center
for Electrochemistry, Department of Chemistry, The University of Texas at Austin, Austin, 78712 Texas, United States
| | - Li Ji
- Center
for Electrochemistry, Department of Chemistry, The University of Texas at Austin, Austin, 78712 Texas, United States
- Microelectronics
Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, 78758 Texas, United States
| | - Xiao Yang
- Center
for Electrochemistry, Department of Chemistry, The University of Texas at Austin, Austin, 78712 Texas, United States
| | - Taeho Lim
- Center
for Electrochemistry, Department of Chemistry, The University of Texas at Austin, Austin, 78712 Texas, United States
| | - Edward T. Yu
- Microelectronics
Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, 78758 Texas, United States
| | - Allen J. Bard
- Center
for Electrochemistry, Department of Chemistry, The University of Texas at Austin, Austin, 78712 Texas, United States
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12
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Yang X, Ji L, Zou X, Lim T, Zhao J, Yu ET, Bard AJ. Toward Cost-Effective Manufacturing of Silicon Solar Cells: Electrodeposition of High-Quality Si Films in a CaCl 2 -based Molten Salt. Angew Chem Int Ed Engl 2017; 56:15078-15082. [PMID: 28902971 DOI: 10.1002/anie.201707635] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Indexed: 11/06/2022]
Abstract
Electrodeposition of Si films from a Si-containing electrolyte is a cost-effective approach for the manufacturing of solar cells. Proposals relying on fluoride-based molten salts have suffered from low product quality due to difficulties in impurity control. Here we demonstrate the successful electrodeposition of high-quality Si films from a CaCl2 -based molten salt. Soluble SiIV -O anions generated from solid SiO2 are electrodeposited onto a graphite substrate to form a dense film of crystalline Si. Impurities in the deposited Si film are controlled at low concentrations (both B and P are less than 1 ppm). In the photoelectrochemical measurements, the film shows p-type semiconductor character and large photocurrent. A p-n junction fabricated from the deposited Si film exhibits clear photovoltaic effects. This study represents the first step to the ultimate goal of developing a cost-effective manufacturing process for Si solar cells based on electrodeposition.
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Affiliation(s)
- Xiao Yang
- Center for Electrochemistry, Department of Chemistry, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Li Ji
- Center for Electrochemistry, Department of Chemistry, The University of Texas at Austin, Austin, TX, 78712, USA.,Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX, 78758, USA
| | - Xingli Zou
- Center for Electrochemistry, Department of Chemistry, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Taeho Lim
- Center for Electrochemistry, Department of Chemistry, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Ji Zhao
- Center for Electrochemistry, Department of Chemistry, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Edward T Yu
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX, 78758, USA
| | - Allen J Bard
- Center for Electrochemistry, Department of Chemistry, The University of Texas at Austin, Austin, TX, 78712, USA
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13
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Yang X, Ji L, Zou X, Lim T, Zhao J, Yu ET, Bard AJ. Toward Cost‐Effective Manufacturing of Silicon Solar Cells: Electrodeposition of High‐Quality Si Films in a CaCl
2
‐based Molten Salt. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201707635] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Xiao Yang
- Center for Electrochemistry Department of Chemistry The University of Texas at Austin Austin TX 78712 USA
| | - Li Ji
- Center for Electrochemistry Department of Chemistry The University of Texas at Austin Austin TX 78712 USA
- Microelectronics Research Center Department of Electrical and Computer Engineering The University of Texas at Austin Austin TX 78758 USA
| | - Xingli Zou
- Center for Electrochemistry Department of Chemistry The University of Texas at Austin Austin TX 78712 USA
| | - Taeho Lim
- Center for Electrochemistry Department of Chemistry The University of Texas at Austin Austin TX 78712 USA
| | - Ji Zhao
- Center for Electrochemistry Department of Chemistry The University of Texas at Austin Austin TX 78712 USA
| | - Edward T. Yu
- Microelectronics Research Center Department of Electrical and Computer Engineering The University of Texas at Austin Austin TX 78758 USA
| | - Allen J. Bard
- Center for Electrochemistry Department of Chemistry The University of Texas at Austin Austin TX 78712 USA
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14
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Brennan CJ, Ghosh R, Koul K, Banerjee SK, Lu N, Yu ET. Out-of-Plane Electromechanical Response of Monolayer Molybdenum Disulfide Measured by Piezoresponse Force Microscopy. Nano Lett 2017; 17:5464-5471. [PMID: 28763615 DOI: 10.1021/acs.nanolett.7b02123] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Two-dimensional (2D) materials have recently been theoretically predicted and experimentally confirmed to exhibit electromechanical coupling. Specifically, monolayer and few-layer molybdenum disulfide (MoS2) have been measured to be piezoelectric within the plane of their atoms. This work demonstrates and quantifies a nonzero out-of-plane electromechanical response of monolayer MoS2 and discusses its possible origins. A piezoresponse force microscope was used to measure the out-of-plane deformation of monolayer MoS2 on Au/Si and Al2O3/Si substrates. Using a vectorial background subtraction technique, we estimate the effective out-of-plane piezoelectric coefficient, d33eff, for monolayer MoS2 to be 1.03 ± 0.22 pm/V when measured on the Au/Si substrate and 1.35 ± 0.24 pm/V when measured on Al2O3/Si. This is on the same order as the in-plane coefficient d11 reported for monolayer MoS2. Interpreting the out-of-plane response as a flexoelectric response, the effective flexoelectric coefficient, μeff*, is estimated to be 0.10 nC/m. Analysis has ruled out the possibility of elastic and electrostatic forces contributing to the measured electromechanical response. X-ray photoelectron spectroscopy detected some contaminants on both MoS2 and its substrate, but the background subtraction technique is expected to remove major contributions from the unwanted contaminants. These measurements provide evidence that monolayer MoS2 exhibits an out-of-plane electromechanical response and our analysis offers estimates of the effective piezoelectric and flexoelectric coefficients.
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Affiliation(s)
- Christopher J Brennan
- Microelectronics Research Center, University of Texas at Austin , Austin, Texas 78758, United States
- Department of Electrical and Computer Engineering, University of Texas at Austin , Austin, Texas 78701, United States
| | - Rudresh Ghosh
- Microelectronics Research Center, University of Texas at Austin , Austin, Texas 78758, United States
- Department of Electrical and Computer Engineering, University of Texas at Austin , Austin, Texas 78701, United States
| | - Kalhan Koul
- Microelectronics Research Center, University of Texas at Austin , Austin, Texas 78758, United States
- Department of Electrical and Computer Engineering, University of Texas at Austin , Austin, Texas 78701, United States
| | - Sanjay K Banerjee
- Microelectronics Research Center, University of Texas at Austin , Austin, Texas 78758, United States
- Department of Electrical and Computer Engineering, University of Texas at Austin , Austin, Texas 78701, United States
- Texas Materials Institute, University of Texas at Austin , Austin, Texas 78712, United States
| | - Nanshu Lu
- Microelectronics Research Center, University of Texas at Austin , Austin, Texas 78758, United States
- Department of Electrical and Computer Engineering, University of Texas at Austin , Austin, Texas 78701, United States
- Texas Materials Institute, University of Texas at Austin , Austin, Texas 78712, United States
- Center for Mechanics of Solids, Structures, and Materials, Department of Aerospace Engineering and Engineering Mechanics, University of Texas at Austin , Austin, Texas 78712, United States
- Department of Biomedical Engineering, University of Texas at Austin , Austin, Texas 78712, United States
| | - Edward T Yu
- Microelectronics Research Center, University of Texas at Austin , Austin, Texas 78758, United States
- Department of Electrical and Computer Engineering, University of Texas at Austin , Austin, Texas 78701, United States
- Texas Materials Institute, University of Texas at Austin , Austin, Texas 78712, United States
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15
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Ji L, Hsu HY, Li X, Huang K, Zhang Y, Lee JC, Bard AJ, Yu ET. Localized dielectric breakdown and antireflection coating in metal-oxide-semiconductor photoelectrodes. Nat Mater 2017; 16:127-131. [PMID: 27820811 DOI: 10.1038/nmat4801] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 08/01/2016] [Indexed: 06/06/2023]
Abstract
Silicon-based photoelectrodes for solar fuel production have attracted great interest over the past decade, with the major challenge being silicon's vulnerability to corrosion. A metal-insulator-semiconductor architecture, in which an insulator film serves as a protection layer, can prevent corrosion but must also allow low-resistance carrier transport, generally leading to a trade-off between stability and efficiency. In this work, we propose and demonstrate a general method to decouple the two roles of the insulator by employing localized dielectric breakdown. This approach allows the insulator to be thick, which enhances stability, while enabling low-resistance carrier transport as required for efficiency. This method can be applied to various oxides, such as SiO2 and Al2O3. In addition, it is suitable for silicon, III-V compounds, and other optical absorbers for both photocathodes and photoanodes. Finally, the thick metal-oxide layer can serve as a thin-film antireflection coating, which increases light absorption efficiency.
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Affiliation(s)
- Li Ji
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, USA
- Center for Electrochemistry, Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Hsien-Yi Hsu
- Center for Electrochemistry, Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Xiaohan Li
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Kai Huang
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Ye Zhang
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Jack C Lee
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Allen J Bard
- Center for Electrochemistry, Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Edward T Yu
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, USA
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16
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Hsu HY, Ji L, Du M, Zhao J, Yu ET, Bard AJ. Optimization of Lead-free Organic–inorganic Tin(II) Halide Perovskite Semiconductors by Scanning Electrochemical Microscopy. Electrochim Acta 2016. [DOI: 10.1016/j.electacta.2016.10.049] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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17
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Hu C, McDaniel MD, Jiang A, Posadas A, Demkov AA, Ekerdt JG, Yu ET. A Low-Leakage Epitaxial High-κ Gate Oxide for Germanium Metal-Oxide-Semiconductor Devices. ACS Appl Mater Interfaces 2016; 8:5416-5423. [PMID: 26859048 DOI: 10.1021/acsami.5b10661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Germanium (Ge)-based metal-oxide-semiconductor field-effect transistors are a promising candidate for high performance, low power electronics at the 7 nm technology node and beyond. However, the availability of high quality gate oxide/Ge interfaces that provide low leakage current density and equivalent oxide thickness (EOT), robust scalability, and acceptable interface state density (D(it)) has emerged as one of the most challenging hurdles in the development of such devices. Here we demonstrate and present detailed electrical characterization of a high-κ epitaxial oxide gate stack based on crystalline SrHfO3 grown on Ge (001) by atomic layer deposition. Metal-oxide-Ge capacitor structures show extremely low gate leakage, small and scalable EOT, and good and reducible D(it). Detailed growth strategies and postgrowth annealing schemes are demonstrated to reduce Dit. The physical mechanisms behind these phenomena are studied and suggest approaches for further reduction of D(it).
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Affiliation(s)
- Chengqing Hu
- Microelectronics Research Center, The University of Texas at Austin , Austin, Texas 78758, United States
| | | | - Aiting Jiang
- Microelectronics Research Center, The University of Texas at Austin , Austin, Texas 78758, United States
| | | | | | | | - Edward T Yu
- Microelectronics Research Center, The University of Texas at Austin , Austin, Texas 78758, United States
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18
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Hsu HY, Ji L, Ahn HS, Zhao J, Yu ET, Bard AJ. A Liquid Junction Photoelectrochemical Solar Cell Based on p-Type MeNH3PbI3 Perovskite with 1.05 V Open-Circuit Photovoltage. J Am Chem Soc 2015; 137:14758-64. [DOI: 10.1021/jacs.5b09758] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Hsien-Yi Hsu
- Center
for Electrochemistry, Department of Chemistry, and ‡Microelectronics
Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Li Ji
- Center
for Electrochemistry, Department of Chemistry, and ‡Microelectronics
Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Hyun S. Ahn
- Center
for Electrochemistry, Department of Chemistry, and ‡Microelectronics
Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Ji Zhao
- Center
for Electrochemistry, Department of Chemistry, and ‡Microelectronics
Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Edward T. Yu
- Center
for Electrochemistry, Department of Chemistry, and ‡Microelectronics
Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Allen J. Bard
- Center
for Electrochemistry, Department of Chemistry, and ‡Microelectronics
Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
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19
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Zhang Z, Dillen DC, Tutuc E, Yu ET. Strain and Hole Gas Induced Raman Shifts in Ge-Si(x)Ge(1-x) Core-Shell Nanowires Using Tip-Enhanced Raman Spectroscopy. Nano Lett 2015; 15:4303-4310. [PMID: 26053999 DOI: 10.1021/acs.nanolett.5b00176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report tip-enhanced and conventional Raman spectroscopy studies of Ge-Si0.5Ge0.5 core-shell nanowires in which we observe two distinct Ge-Ge vibrational mode Raman peaks associated with vibrations in the Ge nanowire core and at the Ge-Si0.5Ge0.5 interface at which a quantum-confined hole gas is formed. Tip enhanced Raman measurements show dramatically increased sensitivity to the modes at the Ge-Si0.5Ge0.5 interface and a shift in position of this mode due to plasmonic field localization at the tip apex and the resulting change in phonon self-energy caused by increased coupling between phonons and intervalence-band carrier transitions.
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Affiliation(s)
- Zhongjian Zhang
- Microelectronics Research Center, University of Texas, 10100 Burnet Rd, Building 160, Austin, Texas 78758, United States
| | - David C Dillen
- Microelectronics Research Center, University of Texas, 10100 Burnet Rd, Building 160, Austin, Texas 78758, United States
| | - Emanuel Tutuc
- Microelectronics Research Center, University of Texas, 10100 Burnet Rd, Building 160, Austin, Texas 78758, United States
| | - Edward T Yu
- Microelectronics Research Center, University of Texas, 10100 Burnet Rd, Building 160, Austin, Texas 78758, United States
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20
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Park KW, Krivoy EM, Nair HP, Bank SR, Yu ET. Cross-sectional scanning thermal microscopy of ErAs/GaAs superlattices grown by molecular beam epitaxy. Nanotechnology 2015; 26:265701. [PMID: 26057323 DOI: 10.1088/0957-4484/26/26/265701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Scanning thermal microscopy has been implemented in a cross-sectional geometry, and its application for quantitative, nanoscale analysis of thermal conductivity is demonstrated in studies of an ErAs/GaAs nanocomposite superlattice. Spurious measurement effects, attributable to local thermal transport through air, were observed near large step edges, but could be eliminated by thermocompression bonding to an additional structure. Using this approach, bonding of an ErAs/GaAs superlattice grown on GaAs to a silicon-on-insulator wafer enabled thermal signals to be obtained simultaneously from Si, SiO2, GaAs, and ErAs/GaAs superlattice. When combined with numerical modeling, the thermal conductivity of the ErAs/GaAs superlattice measured using this approach was 11 ± 4 W m(-1) K(-1).
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Affiliation(s)
- K W Park
- Microelectronics Research Center, University of Texas at Austin, 10100 Burnet Rd., Austin, TX 78758, USA
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21
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Ji L, McDaniel MD, Wang S, Posadas AB, Li X, Huang H, Lee JC, Demkov AA, Bard AJ, Ekerdt JG, Yu ET. A silicon-based photocathode for water reduction with an epitaxial SrTiO3 protection layer and a nanostructured catalyst. Nat Nanotechnol 2015; 10:84-90. [PMID: 25437745 DOI: 10.1038/nnano.2014.277] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Accepted: 10/22/2014] [Indexed: 06/04/2023]
Abstract
The rapidly increasing global demand for energy combined with the environmental impact of fossil fuels has spurred the search for alternative sources of clean energy. One promising approach is to convert solar energy into hydrogen fuel using photoelectrochemical cells. However, the semiconducting photoelectrodes used in these cells typically have low efficiencies and/or stabilities. Here we show that a silicon-based photocathode with a capping epitaxial oxide layer can provide efficient and stable hydrogen production from water. In particular, a thin epitaxial layer of strontium titanate (SrTiO3) was grown directly on Si(001) by molecular beam epitaxy. Photogenerated electrons can be transported easily through this layer because of the conduction-band alignment and lattice match between single-crystalline SrTiO3 and silicon. The approach was used to create a metal-insulator-semiconductor photocathode that, under a broad-spectrum illumination at 100 mW cm(-2), exhibits a maximum photocurrent density of 35 mA cm(-2) and an open circuit potential of 450 mV; there was no observable decrease in performance after 35 hours of operation in 0.5 M H2SO4. The performance of the photocathode was also found to be highly dependent on the size and spacing of the structured metal catalyst. Therefore, mesh-like Ti/Pt nanostructured catalysts were created using a nanosphere lithography lift-off process and an applied-bias photon-to-current efficiency of 4.9% was achieved.
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Affiliation(s)
- Li Ji
- 1] Microelectronics Research Center, Department of Electrical and Computer Engineering, University of Texas at Austin, Texas 78712, USA [2] Center for Electrochemistry, Department of Chemistry and Biochemistry, University of Texas at Austin, Texas 78712, USA
| | - Martin D McDaniel
- Department of Chemical Engineering, University of Texas at Austin, Texas 78712, USA
| | - Shijun Wang
- Center for Electrochemistry, Department of Chemistry and Biochemistry, University of Texas at Austin, Texas 78712, USA
| | - Agham B Posadas
- Department of Physics, University of Texas at Austin, Texas 78712, USA
| | - Xiaohan Li
- Microelectronics Research Center, Department of Electrical and Computer Engineering, University of Texas at Austin, Texas 78712, USA
| | - Haiyu Huang
- Microelectronics Research Center, Department of Electrical and Computer Engineering, University of Texas at Austin, Texas 78712, USA
| | - Jack C Lee
- Microelectronics Research Center, Department of Electrical and Computer Engineering, University of Texas at Austin, Texas 78712, USA
| | | | - Allen J Bard
- Center for Electrochemistry, Department of Chemistry and Biochemistry, University of Texas at Austin, Texas 78712, USA
| | - John G Ekerdt
- Department of Chemical Engineering, University of Texas at Austin, Texas 78712, USA
| | - Edward T Yu
- Microelectronics Research Center, Department of Electrical and Computer Engineering, University of Texas at Austin, Texas 78712, USA
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22
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Gao N, Lin W, Chen X, Huang K, Li S, Li J, Chen H, Yang X, Ji L, Yu ET, Kang J. Quantum state engineering with ultra-short-period (AlN)m/(GaN)n superlattices for narrowband deep-ultraviolet detection. Nanoscale 2014; 6:14733-14739. [PMID: 25352426 DOI: 10.1039/c4nr04286g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Ultra-short-period (AlN)m/(GaN)n superlattices with tunable well and barrier atomic layer numbers were grown by metal-organic vapour phase epitaxy, and employed to demonstrate narrowband deep ultraviolet photodetection. High-resolution transmission electron microscopy and X-ray reciprocal space mapping confirm that superlattices containing well-defined, coherently strained GaN and AlN layers as thin as two atomic layers (∼ 0.5 nm) were grown. Theoretical and experimental results demonstrate that an optical absorption band as narrow as 9 nm (210 meV) at deep-ultraviolet wavelengths can be produced, and is attributable to interband transitions between quantum states along the [0001] direction in ultrathin GaN atomic layers isolated by AlN barriers. The absorption wavelength can be precisely engineered by adjusting the thickness of the GaN atomic layers because of the quantum confinement effect. These results represent a major advance towards the realization of wavelength selectable and narrowband photodetectors in the deep-ultraviolet region without any additional optical filters.
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Affiliation(s)
- Na Gao
- Department of Physics, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Xiamen University, Xiamen, 361005, China.
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23
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Hu C, McDaniel MD, Posadas A, Demkov AA, Ekerdt JG, Yu ET. Highly controllable and stable quantized conductance and resistive switching mechanism in single-crystal TiO2 resistive memory on silicon. Nano Lett 2014; 14:4360-7. [PMID: 25072099 DOI: 10.1021/nl501249q] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
TiO2 is being widely explored as an active resistive switching (RS) material for resistive random access memory. We report a detailed analysis of the RS characteristics of single-crystal anatase-TiO2 thin films epitaxially grown on silicon by atomic layer deposition. We demonstrate that although the valence change mechanism is responsible for the observed RS, single-crystal anatase-TiO2 thin films show electrical characteristics that are very different from the usual switching behaviors observed for polycrystalline or amorphous TiO2 and instead very similar to those found in electrochemical metallization memory. In addition, we demonstrate highly stable and reproducible quantized conductance that is well controlled by application of a compliance current and that suggests the localized formation of conducting Magnéli-like nanophases. The quantized conductance observed results in multiple well-defined resistance states suitable for implementation of multilevel memory cells.
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Affiliation(s)
- Chengqing Hu
- Microelectronics Research Center, ‡Department of Electrical and Computer Engineering, §Department of Chemical Engineering, and ∥Department of Physics, The University of Texas at Austin , Austin, Texas 78758, United States
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24
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Li PC, Chang JC, La Porta A, Yu ET. Fabrication of birefringent nanocylinders for single-molecule force and torque measurement. Nanotechnology 2014; 25:235304. [PMID: 24850364 DOI: 10.1088/0957-4484/25/23/235304] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Optically anisotropic subwavelength scale dielectric particles have been shown to enable studies of the mechanical properties of bio-molecules via optical trapping and manipulation. However, techniques emphasized to date for fabrication of such particles generally suffer from limited uniformity and control over particle dimensions, or low throughput and high cost. Here, an approach for rapid, low-cost, fabrication of large quantities of birefringent quartz nanocylinders with dimensions optimized for optical torque wrench experiments is described. For a typical process, 10(8) or more quartz cylinders with diameters of 500 nm and heights of 800 nm, with uniformity of ±5% in each dimension, can be fabricated over ∼10 cm(2) areas, for binding to a single bio-molecule, and harvested for use in optical trapping experiments. Use of these structures to measure extensional and torsional dynamics of single DNA molecules is demonstrated with measured forces and torques shown to be in very good agreement with previously reported results.
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Affiliation(s)
- Ping-Chun Li
- Microelectronics Research Center, 10100 Burnet Road, Austin, TX 78758, USA
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25
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Ji L, Chang YF, Fowler B, Chen YC, Tsai TM, Chang KC, Chen MC, Chang TC, Sze SM, Yu ET, Lee JC. Integrated one diode-one resistor architecture in nanopillar SiOx resistive switching memory by nanosphere lithography. Nano Lett 2014; 14:813-818. [PMID: 24369783 DOI: 10.1021/nl404160u] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We report on a highly compact, one diode-one resistor (1D-1R) nanopillar device architecture for SiOx-based ReRAM fabricated using nanosphere lithography (NSL). The intrinsic SiOx-based resistive switching element and Si diode are self-aligned on an epitaxial silicon wafer using NSL and a deep-Si-etch process without conventional photolithography. AC-pulse response in 50 ns regime, multibit operation, and good reliability are demonstrated. The NSL process provides a fast and economical approach to large-scale patterning of high-density 1D-1R ReRAM with good potential for use in future applications.
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Affiliation(s)
- Li Ji
- Microelectronics Research Center, The University of Texas at Austin , Austin, Texas 78758, United States
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26
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McPheeters CO, Yu ET. Computational analysis of thin film InGaAs/GaAs quantum well solar cells with back side light trapping structures. Opt Express 2012; 20:A864-A878. [PMID: 23326834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Simulations of thin film (~2.5 µm thick) InGaAs/GaAs quantum well solar cells with various back side reflective and planar, symmetric scattering structures used for light trapping have been performed using rigorous coupled-wave analysis. Two-dimensional periodic metal/dielectric scattering structures were numerically optimized for Airmass 0 photocurrent generation for each device structure. The simulation results indicate that the absorption spectra of devices with both reflective and scattering structures are largely determined by the Fabry-Perot resonance characteristics of the thin film device structure. The scattering structures substantially increase absorption in the quantum wells at wavelengths longer than the GaAs absorption edge through a combination of coupling to modes of the thin film device structures and by reducing parasitic metal absorption compared to planar metal reflectors. For Airmass 0 illumination and 100% carrier collection, the estimated short-circuit current density of devices with In(0.3)Ga(0.7)As/GaAs quantum wells improves by up to 4.6 mA/cm(2) (15%) relative to a GaAs homojunction device, with the improvement resulting approximately equally from scattering of light into thin film modes and reduction of metal absorption compared to a planar reflective layer.
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Affiliation(s)
- Claiborne O McPheeters
- Microelectronics Research Center, Department of Electrical and Computer Engineering, University of Texas, Austin, 10100 Burnet Rd, Bldg 160, Austin, TX 78758, USA
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27
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Hu D, McPheeters CCO, Yu ET, Schaadt DM. Improvement of performance of InAs quantum dot solar cell by inserting thin AlAs layers. Nanoscale Res Lett 2011; 6:83. [PMID: 21711628 PMCID: PMC3212232 DOI: 10.1186/1556-276x-6-83] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/26/2010] [Accepted: 01/12/2011] [Indexed: 05/31/2023]
Abstract
A new measure to enhance the performance of InAs quantum dot solar cell is proposed and measured. One monolayer AlAs is deposited on top of InAs quantum dots (QDs) in multistack solar cells. The devices were fabricated by molecular beam epitaxy. In situ annealing was intended to tune the QD density. A set of four samples were compared: InAs QDs without in situ annealing with and without AlAs cap layer and InAs QDs in situ annealed with and without AlAs cap layer. Atomic force microscopy measurements show that when in situ annealing of QDs without AlAs capping layers is investigated, holes and dashes are present on the device surface, while capping with one monolayer AlAs improves the device surface. On unannealed samples, capping the QDs with one monolayer of AlAs improves the spectral response, the open-circuit voltage and the fill factor. On annealed samples, capping has little effect on the spectral response but reduces the short-circuit current, while increasing the open-circuit voltage, the fill factor and power conversion efficiency.
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Affiliation(s)
- Dongzhi Hu
- Institut für Angewandte Physik/DFG-Center for Functional Nanostructures, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Claiborne CO McPheeters
- Department of Electrical and Computer Engineering, Microelectronics Research Center, University of Texas at Austin, Austin, TX 78758, USA
| | - Edward T Yu
- Department of Electrical and Computer Engineering, Microelectronics Research Center, University of Texas at Austin, Austin, TX 78758, USA
| | - Daniel M Schaadt
- Institut für Angewandte Physik/DFG-Center for Functional Nanostructures, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
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28
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Abstract
We demonstrate the ability to precisely control the alignment and placement of large numbers of InAs nanowires from solution onto very narrow, prepatterned electrodes using dielectrophoresis. An understanding of dielectrophoretic behavior associated with such electrode geometries is essential to development of approaches for assembly of intricate nanowire systems. The influence of signal frequency and electrode design on nanowire manipulation and placement is examined. Signal frequencies in the range of 10 MHz are found to yield high percentages of aligned nanowires on electrodes with dimensions similar to that of the nanowire. Strategies for further improvement of nanowire alignment are suggested and analyzed.
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Affiliation(s)
- Sourobh Raychaudhuri
- Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093, USA
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29
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Abstract
We report new fundamental insights into InAs nanowire (NW) nucleation and evolution on InAs (111)B surfaces using organometallic vapor phase epitaxy and present the first experimental demonstration of two distinct NW growth regimes, defined by the direction of substrate-NW adatom exchange, that lead to nonlinear growth rates. We show that the NW elongation rate and morphology in these two growth regimes are governed by the relative difference between the In adatom diffusion lengths on the growth substrate surface and on the NW sidewalls, resulting in strong growth rate dependence on the NW length. These results indicate that surface solid-phase diffusion of In adatoms is a key process in InAs NW growth, which is also supported by diameter-dependent growth rates. These developments enable rational growth of axial and radial NW heterostructures.
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Affiliation(s)
- Shadi A Dayeh
- Department of Electrical and Computer Engineering, University of California at San Diego, La Jolla, California 92093-0407, USA.
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30
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Affiliation(s)
- Shadi A Dayeh
- Department of Electrical and Computer Engineering, University of California-San Diego, La Jolla, CA 92093, USA
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31
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Dayeh SA, Susac D, Kavanagh KL, Yu ET, Wang D. Field dependent transport properties in InAs nanowire field effect transistors. Nano Lett 2008; 8:3114-3119. [PMID: 18783282 DOI: 10.1021/nl801256p] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We present detailed studies of the field dependent transport properties of InAs nanowire field-effect transistors. Transconductance dependence on both vertical and lateral fields is discussed. Velocity-field plots are constructed from a large set of output and transfer curves that show negative differential conductance behavior and marked mobility degradation at high injection fields. Two dimensional electrothermal simulations at current densities similar to those measured in the InAs NWFET devices indicate that a significant temperature rise occurs in the channel due to enhanced phonon scattering that leads to the observed mobility degradation. Scanning transmission electron microscopy measurements on devices operated at high current densities reveal arsenic vaporization and crystal deformation in the subject nanowires.
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Affiliation(s)
- Shadi A Dayeh
- Department of Electrical and Computer Engineering, University of California San Diego, La Jolla, California 92093, USA
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Abstract
A novel design is presented for a nanowire/polymer hybrid photodiode. n-InP nanowires are grown directly onto an indium tin oxide (ITO) electrode to increase carrier collection efficiency and to eliminate the need for an expensive substrate. Experiments show that an ohmic contact is achieved between the nanowires and the ITO electrode. The nanowires are then enveloped by a high hole mobility conjugated polymer, poly(3-hexylthiophene). Compared to the control polymer-only device, the inclusion of InP nanowires increases the forward bias current conduction by 6-7 orders of magnitude. A high rectification ratio of 155 is achieved in these photodiodes along with a low ideality factor of 1.31. The hybrid device produces a photoresponse with a fill factor of 0.44, thus showing promise as an alternative to current polymer solar cell designs.
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Affiliation(s)
- Clint J Novotny
- Department of Electrical and Computer Engineering, University of California-San Diego, La Jolla, CA 92093, USA
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Affiliation(s)
- Shadi A Dayeh
- Department of Electrical and Computer Engineering, University of California San Diego, 9500 Gilman Dr., La Jolla, CA 92093, USA
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Abstract
We have studied the dependence of Au-assisted InAs nanowire (NW) growth on InAs(111)B substrates as a function of substrate temperature and input V/III precursor ratio using organometallic vapor-phase epitaxy. Temperature-dependent growth was observed within certain temperature windows that are highly dependent on input V/III ratios. This dependence was found to be a direct consequence of the drop in NW nucleation and growth rate with increasing V/III ratio at a constant growth temperature due to depletion of indium at the NW growth sites. The growth rate was found to be determined by the local V/III ratio, which is dependent on the input precursor flow rates, growth temperature, and substrate decomposition. These studies advance understanding of the key processes involved in III-V NW growth, support the general validity of the vapor-liquid-solid growth mechanism for III-V NWs, and improve rational control over their growth morphology.
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Affiliation(s)
- Shadi A Dayeh
- Department of Electrical and Computer Engineering, University of California-San Diego, La Jolla, California 92093, USA
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Abstract
Single-crystal InAs nanowires (NWs) are synthesized using metal-organic chemical vapor deposition (MOCVD) and fabricated into NW field-effect transistors (NWFETs) on a SiO(2)/n(+)-Si substrate with a global n(+)-Si back-gate and sputtered SiO(x)/Au underlap top-gate. For top-gate NWFETs, we have developed a model that allows accurate estimation of characteristic NW parameters, including carrier field-effect mobility and carrier concentration by taking into account series and leakage resistances, interface state capacitance, and top-gate geometry. Both the back-gate and the top-gate NWFETs exhibit room-temperature field-effect mobility as high as 6580 cm(2) V(-1) s(-1), which is the lower-bound value without interface-capacitance correction, and is the highest mobility reported to date in any semiconductor NW.
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Affiliation(s)
- Shadi A Dayeh
- Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, CA 92093-0407, USA
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Yu ET, Juinio-Meñez MA, Monje VD. Sequence variation in the ribosomal DNA internal transcribed spacer of Tridacna crocea. Mar Biotechnol (NY) 2000; 2:511-516. [PMID: 14961174 DOI: 10.1007/s101260000033] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
DNA-based genetic markers are needed to augment existing allozyme markers in the assessment of genetic diversity of wild giant clam populations. The dearth of polymorphic mitochondrial DNA regions amplified from known universal polymerase chain reaction (PCR) primers has led us to search other regions of the genome for viable sources of DNA polymorphism. We have designed tridacnid-specific PCR primers for the amplification of internal transcribed spacer regions. Sequences of the first internal transcribed spacer segment (ITS-1) revealed very high polymorphism, showing 29% variation arising from base substitutions alone. Preliminary restriction analysis of the ITS regions using 8 restriction enzymes revealed cryptic changes in the DNA sequence. These mutations are promising as marker tools for differentiating geographically separated populations. Such variation in the ITS region can possibly be used for population genetic analysis.
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Affiliation(s)
- E T Yu
- Institute of Chemistry, University of the Philippines, Diliman, Quezon City, Philippines.
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Affiliation(s)
- Edward T. Yu
- Department of Electrical and Computer Engineering, University of California at San Diego, La Jolla, California 92093-0407
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Yu ET, Phillips MC, Chow DH, Collins DA, Wang MW, McCaldin JO, McGill TC. Interfacial reactions and band offsets in the AlSb/GaSb/ZnTe material system. Phys Rev B Condens Matter 1992; 46:13379-13388. [PMID: 10003385 DOI: 10.1103/physrevb.46.13379] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Ting DZ, Yu ET, McGill TC. Effect of band mixing on hole-tunneling times in GaAs/AlAs double-barrier heterostructures. Phys Rev B Condens Matter 1992; 45:3576-3582. [PMID: 10001937 DOI: 10.1103/physrevb.45.3576] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Ting DZ, Yu ET, McGill TC. Multiband treatment of quantum transport in interband tunnel devices. Phys Rev B Condens Matter 1992; 45:3583-3592. [PMID: 10001938 DOI: 10.1103/physrevb.45.3583] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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