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Ren H, Zhu T, Feng L, Wu Q, Wang K, Yun X, Zhu H, Chen J, Wei B, Ni H, Xu X, Zhang Z, Wu X. Atomic Valence Reversal-Induced Polarization Resonance Spurs Highly Efficient Electromagnetic Wave Absorption in α-Fe 2O 3@Carbon Microtubes. NANO LETTERS 2024; 24:3525-3531. [PMID: 38466128 DOI: 10.1021/acs.nanolett.4c00532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
Variegation and complexity of polarization relaxation loss in many heterostructured materials provide available mechanisms to seek a strong electromagnetic wave (EMW) absorption performance. Here we construct a unique heterostructured compound that bonds α-Fe2O3 nanosheets of the (110) plane on carbon microtubes (CMTs). Through effective alignment between the Fermi energy level of CMTs and the conduction band position of α-Fe2O3 nanosheets at the interface, we attain substantial polarization relaxation loss via novel atomic valence reversal between Fe(III) ↔ Fe(III-) induced with periodic electron injection from conductive CMTs under EMW irradiation to give α-Fe2O3 nanosheets. Such heterostructured materials possess currently reported minimum reflection loss of -84.01 dB centered at 10.99 GHz at a thickness of 3.19 mm and an effective absorption bandwidth (reflection loss ≤ -10 dB) of 7.17 GHz (10.83-18 GHz) at 2.65 mm. This work provides an effective strategy for designing strong EMW absorbers by combining highly efficient electron injection and atomic valence reversal.
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Affiliation(s)
- Hengdong Ren
- National Laboratory of Solid States Microstructures and School of Physics, Nanjing University, Nanjing 210093, China
| | - Tongshuai Zhu
- National Laboratory of Solid States Microstructures and School of Physics, Nanjing University, Nanjing 210093, China
- College of Science, China University of Petroleum (East China), Qingdao 266580, China
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao 266580, China
| | - Lei Feng
- National Laboratory of Solid States Microstructures and School of Physics, Nanjing University, Nanjing 210093, China
| | - Qifan Wu
- National Laboratory of Solid States Microstructures and School of Physics, Nanjing University, Nanjing 210093, China
| | - Ka Wang
- National Laboratory of Solid States Microstructures and School of Physics, Nanjing University, Nanjing 210093, China
| | - Xinjie Yun
- National Laboratory of Solid States Microstructures and School of Physics, Nanjing University, Nanjing 210093, China
| | - Haogang Zhu
- National Laboratory of Solid States Microstructures and School of Physics, Nanjing University, Nanjing 210093, China
| | - Jian Chen
- National Laboratory of Solid States Microstructures and Research Institute of Superconductor Electronics, Nanjing University, Nanjing 210093, China
| | - Baojun Wei
- College of Science, China University of Petroleum (East China), Qingdao 266580, China
| | - Hao Ni
- College of Science, China University of Petroleum (East China), Qingdao 266580, China
| | - Xiaobing Xu
- College of Electronic Engineering, Nanjing Xiaozhuang University, Nanjing 211171, China
| | - Zhiyong Zhang
- National Laboratory of Solid States Microstructures and School of Physics, Nanjing University, Nanjing 210093, China
| | - Xinglong Wu
- National Laboratory of Solid States Microstructures and School of Physics, Nanjing University, Nanjing 210093, China
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2
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Badawy G, Bakkers EPAM. Electronic Transport and Quantum Phenomena in Nanowires. Chem Rev 2024; 124:2419-2440. [PMID: 38394689 PMCID: PMC10941195 DOI: 10.1021/acs.chemrev.3c00656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2023] [Revised: 01/26/2024] [Accepted: 02/08/2024] [Indexed: 02/25/2024]
Abstract
Nanowires are natural one-dimensional channels and offer new opportunities for advanced electronic quantum transport experiments. We review recent progress on the synthesis of nanowires and methods for the fabrication of hybrid semiconductor/superconductor systems. We discuss methods to characterize their electronic properties in the context of possible future applications such as topological and spin qubits. We focus on group III-V (InAs and InSb) and group IV (Ge/Si) semiconductors, since these are the most developed, and give an outlook on other potential materials.
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Affiliation(s)
- Ghada Badawy
- Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
| | - Erik P. A. M. Bakkers
- Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
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3
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Zhang N, Yan J, Wang L, Zhang J, Zhang Z, Miao T, Zheng C, Jiang Z, Hu H, Zhong Z. Hexagonal-Ge Nanostructures with Direct-Bandgap Emissions in a Si-Based Light-Emitting Metasurface. ACS NANO 2024; 18:328-336. [PMID: 38147566 DOI: 10.1021/acsnano.3c06279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2023]
Abstract
Si-based emitters have been of great interest as an ideal light source for monolithic optical-electronic integrated circuits (MOEICs) on Si substrates. However, the general Si-based material is a diamond structure of cubic lattice with an indirect band gap, which cannot emit light efficiently. Here, hexagonal-Ge (H-Ge) nanostructures within a light-emitting metasurface consisting of a cubic-SiGe nanodisk array are reported. The H-Ge nanostructure is naturally formed within the cubic-Ge epitaxially grown on Si (001) substrates due to the strain-induced nanoscale crystal structure transformation assisted by far-from-equilibrium growth conditions. The direct-bandgap features of H-Ge nanostructures are observed and discussed, including a rather strong and linearly power-dependent photoluminescence (PL) peak around 1562 nm at room temperature and temperature-insensitive PL spectrum near room temperature. Given the direct-bandgap nature, the heterostructure of H-Ge/C-Ge, and the compatibility with the sophisticated Si technology, the H-Ge nanostructure has great potential for innovative light sources and other functional devices, particularly in Si-based MOEICs.
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Affiliation(s)
- Ningning Zhang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, P. R. China
- Key Laboratory of Analog Integrated Circuits and Systems, Ministry of Education, School of Microelectronics, Xidian University, Xi'an 710071, P. R. China
| | - Jia Yan
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, P. R. China
| | - Liming Wang
- Key Laboratory of Analog Integrated Circuits and Systems, Ministry of Education, School of Microelectronics, Xidian University, Xi'an 710071, P. R. China
| | - Jiarui Zhang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, P. R. China
| | - Zhifang Zhang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, P. R. China
| | - Tian Miao
- Key Laboratory of Analog Integrated Circuits and Systems, Ministry of Education, School of Microelectronics, Xidian University, Xi'an 710071, P. R. China
| | - Changlin Zheng
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, P. R. China
| | - Zuimin Jiang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, P. R. China
| | - Huiyong Hu
- Key Laboratory of Analog Integrated Circuits and Systems, Ministry of Education, School of Microelectronics, Xidian University, Xi'an 710071, P. R. China
| | - Zhenyang Zhong
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, P. R. China
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4
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Forrer N, Nigro A, Gadea G, Zardo I. Influence of Different Carrier Gases, Temperature, and Partial Pressure on Growth Dynamics of Ge and Si Nanowires. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:2879. [PMID: 37947724 PMCID: PMC10650493 DOI: 10.3390/nano13212879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 10/23/2023] [Accepted: 10/29/2023] [Indexed: 11/12/2023]
Abstract
The broad and fascinating properties of nanowires and their synthesis have attracted great attention as building blocks for functional devices at the nanoscale. Silicon and germanium are highly interesting materials due to their compatibility with standard CMOS technology. Their combination provides optimal templates for quantum applications, for which nanowires need to be of high quality, with carefully designed dimensions, crystal phase, and orientation. In this work, we present a detailed study on the growth kinetics of silicon (length 0.1-1 μm, diameter 10-60 nm) and germanium (length 0.06-1 μm, diameter 10-500 nm) nanowires grown by chemical vapor deposition applying the vapour-liquid-solid growth method catalysed by gold. The effects of temperature, partial pressure of the precursor gas, and different carrier gases are analysed via scanning electron microscopy. Argon as carrier gas enhances the growth rate at higher temperatures (120 nm/min for Ar and 48 nm/min H2), while hydrogen enhances it at lower temperatures (35 nm/min for H2 and 22 nm/min for Ar) due to lower heat capacity. Both materials exhibit two growth regimes as a function of the temperature. The tapering rate is about ten times lower for silicon nanowires than for germanium ones. Finally, we identify the optimal conditions for nucleation in the nanowire growth process.
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Affiliation(s)
- Nicolas Forrer
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland; (N.F.); (A.N.); (G.G.)
| | - Arianna Nigro
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland; (N.F.); (A.N.); (G.G.)
| | - Gerard Gadea
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland; (N.F.); (A.N.); (G.G.)
- Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Ilaria Zardo
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland; (N.F.); (A.N.); (G.G.)
- Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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5
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Varley JB, Ray KG, Lordi V. Dangling Bonds as Possible Contributors to Charge Noise in Silicon and Silicon-Germanium Quantum Dot Qubits. ACS APPLIED MATERIALS & INTERFACES 2023; 15:43111-43123. [PMID: 37651689 DOI: 10.1021/acsami.3c06725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Abstract
Spin qubits based on Si and Si1-xGex quantum dot architectures exhibit among the best coherence times of competing quantum computing technologies, yet they still suffer from charge noise that limit their qubit gate fidelities. Identifying the origins of these charge fluctuations is therefore a critical step toward improving Si quantum-dot-based qubits. Here, we use hybrid functional calculations to investigate possible atomistic sources of charge noise, focusing on charge trapping at Si and Ge dangling bonds (DBs). We evaluate the role of global and local environment in the defect levels associated with DBs in Si, Ge, and Si1-xGex alloys, and consider their trapping and excitation energies within the framework of configuration coordinate diagrams. We additionally consider the influence of strain and oxidation in charge-trapping energetics by analyzing Si and GeSi DBs in SiO2 and strained Si layers in typical Si1-xGex quantum dot heterostructures. Our results identify that Ge dangling bonds are more problematic charge-trapping centers both in typical Si1-xGex alloys and associated oxidation layers, and they may be exacerbated by compositional inhomogeneities. These results suggest the importance of alloy homogeneity and possible passivation schemes for DBs in Si-based quantum dot qubits and are of general relevance to mitigating possible trap levels in other Si, Ge, and Si1-xGex-based metal-oxide-semiconductor stacks and related devices.
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Affiliation(s)
- Joel B Varley
- Materials Science Division, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Keith G Ray
- Materials Science Division, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Vincenzo Lordi
- Materials Science Division, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
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6
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Zhang Z, Xiang Y, Zhu Z. Electronic Characteristics, Stability and Water Oxidation Selectivity of High-Index BiVO 4 Facets for Photocatalytic Application: A First Principle Study. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:2023. [PMID: 37446539 DOI: 10.3390/nano13132023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 06/26/2023] [Accepted: 07/04/2023] [Indexed: 07/15/2023]
Abstract
Some high-index facets of BiVO4, such as (012), (210), (115), (511), (121), (132) and (231), exhibit much better photocatalytic performance than conventional (010) and (110) surfaces for water splitting. However, the detailed mechanisms and stability of improved photocatalytic performance for these high-index BiVO4 surfaces are still not clear, which is important for designing photocatalysts with high efficiency. Here, based on first principle calculation, we carried out a systematic theoretical research on BiVO4 with different surfaces, especially high-index facets. The results show that all of the high-index facets in our calculated systems show an n-type behavior, and the band edge positions indicate that all of the high-index facets have enough ability to produce O2 without external bias. Electronic structures, band alignments and formation enthalpy indicate that (012), (115) and (132) could be equivalent to (210), (511) and (231), respectively, in the calculation. Oxidation and reduction potential show that only (132)/(231) is stable without strongly oxidative conditions, and the Gibbs free energy indicates that (012)/(210), (115)/(511), (121) and (132)/(231) have lower overpotential than (010) and (110). Our calculation is able to unveil insights into the effects of the surface, including electronic structures, overpotential and stability during the reaction process.
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Affiliation(s)
- Zhiyuan Zhang
- College of Advanced Interdisciplinary Studies & Hunan Provincial Key Laboratory of Novel Nano Optoelectronic Information Materials and Devices, National University of Defense Technology, 410073 Changsha, China
- Nanhu Laser Laboratory, National University of Defense Technology, Changsha 410073, China
| | - Yuqi Xiang
- College of Advanced Interdisciplinary Studies & Hunan Provincial Key Laboratory of Novel Nano Optoelectronic Information Materials and Devices, National University of Defense Technology, 410073 Changsha, China
- Nanhu Laser Laboratory, National University of Defense Technology, Changsha 410073, China
| | - Zhihong Zhu
- College of Advanced Interdisciplinary Studies & Hunan Provincial Key Laboratory of Novel Nano Optoelectronic Information Materials and Devices, National University of Defense Technology, 410073 Changsha, China
- Nanhu Laser Laboratory, National University of Defense Technology, Changsha 410073, China
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7
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Domínguez-Flores F, Melander MM. Approximating constant potential DFT with canonical DFT and electrostatic corrections. J Chem Phys 2023; 158:144701. [PMID: 37061493 DOI: 10.1063/5.0138197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/17/2023] Open
Abstract
The complexity of electrochemical interfaces has led to the development of several approximate density functional theory (DFT)-based schemes to study reaction thermodynamics and kinetics as a function of electrode potential. While fixed electrode potential conditions can be simulated with grand canonical ensemble DFT (GCE-DFT), various electrostatic corrections on canonical, constant charge DFT are often applied instead. In this work, we present a systematic derivation and analysis of the different electrostatic corrections on canonical DFT to understand their physical validity, implicit assumptions, and scope of applicability. Our work highlights the need to carefully address the suitability of a given model for the problem under study, especially if physical or chemical insight in addition to reaction energetics is sought. In particular, we analytically show that the different corrections cannot differentiate between electrostatic interactions and covalent or charge-transfer interactions. By numerically testing different models for CO2 adsorption on a single-atom catalyst as a function of the electrode potential, we further show that computed capacitances, dipole moments, and the obtained physical insight depend sensitively on the chosen approximation. These features limit the scope, generality, and physical insight of these corrective schemes despite their proven practicality for specific systems and energetics. Finally, we suggest guidelines for choosing different electrostatic corrections and propose the use of conceptual DFT to develop more general approximations for electrochemical interfaces and reactions using canonical DFT.
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Affiliation(s)
- Fabiola Domínguez-Flores
- Department of Chemistry, Nanoscience Center, University of Jyväskylä, FI-40014 Jyväskylä, Finland
| | - Marko M Melander
- Department of Chemistry, Nanoscience Center, University of Jyväskylä, FI-40014 Jyväskylä, Finland
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8
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Liu X, Zhao C, Niu C, Jia Y. Computational and experimental studies on band alignment of ZnO/In xGa 2-xO 3/GaN heterojunctions. J Chem Phys 2023; 158:134720. [PMID: 37031125 DOI: 10.1063/5.0134277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/10/2023] Open
Abstract
The ZnO/GaN heterojunctions are extensively investigated now, owing to their good luminescent properties and devisable capability to form efficient hybrid structures. An electron-blocking layer inserted into heterojunctions can greatly change their properties. In this work, n-ZnO/β-InxGa2-xO3/p-GaN heterojunctions have been successfully formed using atomic layer deposition methods. We show that the doping of In can effectively tune the band edges of the heterojunctions. First-principle calculations reveal that the bandgap of bulk β-InxGa2-xO3 shrinks linearly with the increase in In contents, accompanied by an upward movement of the valence band maximum and a downward movement of the conduction band minimum. As the indium concentrations increase, the valence band offsets show an upward movement at both the InxGa2-xO3/GaN and ZnO/InxGa2-xO3 interfaces, while the conduction band offsets present different trends. A broad, reddish yellow-green emission appears after In doping, which verifies the effect of band alignment. What is more, we show that the amorphization of InxGa2-xO3 can play an important role in tuning the band edge. This work provides access to a series of band offsets tunable heterojunctions and can be used for the further design of direct white light-emitting diodes without any phosphors, based on this structure.
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Affiliation(s)
- Xilai Liu
- International Laboratory for Quantum Functional Materials of Henan, and School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450001, China
| | - Chunxiang Zhao
- International Laboratory for Quantum Functional Materials of Henan, and School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450001, China
| | - Chunyao Niu
- International Laboratory for Quantum Functional Materials of Henan, and School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450001, China
| | - Yu Jia
- International Laboratory for Quantum Functional Materials of Henan, and School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450001, China
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9
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Wind L, Sistani M, Böckle R, Smoliner J, Vukŭsić L, Aberl J, Brehm M, Schweizer P, Maeder X, Michler J, Fournel F, Hartmann JM, Weber WM. Composition Dependent Electrical Transport in Si 1-x Ge x Nanosheets with Monolithic Single-Elementary Al Contacts. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2204178. [PMID: 36135726 DOI: 10.1002/smll.202204178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 08/25/2022] [Indexed: 06/16/2023]
Abstract
Si1-x Gex is a key material in modern complementary metal-oxide-semiconductor and bipolar devices. However, despite considerable efforts in metal-silicide and -germanide compound material systems, reliability concerns have so far hindered the implementation of metal-Si1-x Gex junctions that are vital for diverse emerging "More than Moore" and quantum computing paradigms. In this respect, the systematic structural and electronic properties of Al-Si1-x Gex heterostructures, obtained from a thermally induced exchange between ultra-thin Si1-x Gex nanosheets and Al layers are reported. Remarkably, no intermetallic phases are found after the exchange process. Instead, abrupt, flat, and void-free junctions of high structural quality can be obtained. Interestingly, ultra-thin interfacial Si layers are formed between the metal and Si1-x Gex segments, explaining the morphologic stability. Integrated into omega-gated Schottky barrier transistors with the channel length being defined by the selective transformation of Si1-x Gex into single-elementary Al leads, a detailed analysis of the transport is conducted. In this respect, a report on a highly versatile platform with Si1-x Gex composition-dependent properties ranging from highly transparent contacts to distinct Schottky barriers is provided. Most notably, the presented abrupt, robust, and reliable metal-Si1-x Gex junctions can open up new device implementations for different types of emerging nanoelectronic, optoelectronic, and quantum devices.
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Affiliation(s)
- Lukas Wind
- Institute of Solid State Electronics, Technische Universität Wien, Gußhausstraße 25-25a, Vienna, 1040, Austria
| | - Masiar Sistani
- Institute of Solid State Electronics, Technische Universität Wien, Gußhausstraße 25-25a, Vienna, 1040, Austria
| | - Raphael Böckle
- Institute of Solid State Electronics, Technische Universität Wien, Gußhausstraße 25-25a, Vienna, 1040, Austria
| | - Jürgen Smoliner
- Institute of Solid State Electronics, Technische Universität Wien, Gußhausstraße 25-25a, Vienna, 1040, Austria
| | - Lada Vukŭsić
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University, Altenberger Straße 69, Linz, 4040, Austria
| | - Johannes Aberl
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University, Altenberger Straße 69, Linz, 4040, Austria
| | - Moritz Brehm
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University, Altenberger Straße 69, Linz, 4040, Austria
| | - Peter Schweizer
- Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Mechanics of Materials and Nanostructures, Feuerwerkstrasse 39, Thun, 3602, Switzerland
| | - Xavier Maeder
- Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Mechanics of Materials and Nanostructures, Feuerwerkstrasse 39, Thun, 3602, Switzerland
| | - Johann Michler
- Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Mechanics of Materials and Nanostructures, Feuerwerkstrasse 39, Thun, 3602, Switzerland
| | - Frank Fournel
- CEA-LETI, University Grenoble Alpes, 17 Avenue des Martyrs, Grenoble, 38000, France
| | - Jean-Michel Hartmann
- CEA-LETI, University Grenoble Alpes, 17 Avenue des Martyrs, Grenoble, 38000, France
| | - Walter M Weber
- Institute of Solid State Electronics, Technische Universität Wien, Gußhausstraße 25-25a, Vienna, 1040, Austria
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10
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Zhang Z, Song Y, Xiang Y, Zhu Z. Vacancy defect engineered BiVO 4 with low-index surfaces for photocatalytic application: a first principles study. RSC Adv 2022; 12:31317-31325. [PMID: 36349004 PMCID: PMC9623612 DOI: 10.1039/d2ra04890f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 10/18/2022] [Indexed: 06/16/2023] Open
Abstract
BiVO4 has been widely investigated as a photocatalyst material for water splitting due to its outstanding photocatalytic properties. In order to further improve its photocatalytic efficiency, it is necessary to conduct an in-depth study of improvement strategies, such as defect engineering. By focusing on the (001) and (011) surfaces, we carried out a systematic theoretical research on pristine and defective systems, including Bi, V and O vacancies. Based on density functional theory (DFT), the electronic properties, band alignments and Gibbs free energy of pristine and defective BiVO4 have been analyzed. The electronic structures of the (001) and (011) surfaces show different band gaps, and O vacancies make the BiVO4 become an n-type semiconductor, while Bi and V vacancies tend to form a p-type semiconductor. Moreover, the band edge positions indicate that holes are indeed easily accumulated on the (011) surface while electrons tend to accumulate on (001). However, the (011) surface with Bi and V vacancies does not have enough oxidation potential to oxidize water. The reaction free energy shows that O and Bi vacancies could lower the overpotential to some extent.
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Affiliation(s)
- Zhiyuan Zhang
- College of Advanced Interdisciplinary Studies & Hunan Provincial Key Laboratory of Novel Nano Optoelectronic Information Materials and Devices, National University of Defense Technology 410073 Changsha Hunan P. R. China
| | - Yingchao Song
- College of Advanced Interdisciplinary Studies & Hunan Provincial Key Laboratory of Novel Nano Optoelectronic Information Materials and Devices, National University of Defense Technology 410073 Changsha Hunan P. R. China
| | - Yuqi Xiang
- College of Advanced Interdisciplinary Studies & Hunan Provincial Key Laboratory of Novel Nano Optoelectronic Information Materials and Devices, National University of Defense Technology 410073 Changsha Hunan P. R. China
| | - Zhihong Zhu
- College of Advanced Interdisciplinary Studies & Hunan Provincial Key Laboratory of Novel Nano Optoelectronic Information Materials and Devices, National University of Defense Technology 410073 Changsha Hunan P. R. China
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11
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Ye Z, Zhang C, Galli G. Photoelectron spectra of water and simple aqueous solutions at extreme conditions. Faraday Discuss 2022; 236:352-363. [DOI: 10.1039/d2fd00003b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Determining the electronic structure of aqueous solutions at extreme conditions is an important step towards understanding chemical bonding and reactions in water under pressure (P) and at high temperature (T)....
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12
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Tani K, Okumura T, Oda K, Deura M, Ido T. On-chip optical interconnection using integrated germanium light emitters and photodetectors. OPTICS EXPRESS 2021; 29:28021-28036. [PMID: 34614942 DOI: 10.1364/oe.432324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 08/02/2021] [Indexed: 06/13/2023]
Abstract
Germanium (Ge) is an attractive material for monolithic light sources and photodetectors, but it is not easy to integrate Ge light sources and photodetectors because their optimum device structures differ. In this study, we developed a monolithically integrated Ge light emitting diode (LED) that enables current injection at high density and a Ge photodiode (PD) having low dark current, and we fabricated an on-chip optical interconnection system consisting of the Ge LED, Ge PD, and Si waveguide. We investigated the properties of the fabricated Ge LED and PD and demonstrated on-chip optical interconnection.
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13
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Chen P, Zhang N, Peng K, Zhang L, Yan J, Jiang Z, Zhong Z. Artificial Graphene on Si Substrates: Fabrication and Transport Characteristics. ACS NANO 2021; 15:13703-13711. [PMID: 34286957 DOI: 10.1021/acsnano.1c04995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Artificial graphene (AG) based on a honeycomb lattice of semiconductor quantum dots (QDs) has been of great interest for exploration and applications of massless Dirac Fermions in semiconductors thanks to the tunable interplay between the carrier interactions and the honeycomb topology. Here, an innovative strategy to realize AG on Si substrates is developed by fabricating a honeycomb lattice of Au nanodisks on a Si/GeSi quantum well. The lateral potential modulation induced by the nanoscale Au/Si Schottky junction results in the formation of quantum dots arranged in a honeycomb lattice to form AG. Nonlinear current-voltage curves of the AG reveal conductance phase transitions with switch on/off voltages, a large electric hysteresis loop, and a strong sharp current peak accompanied by a group of differential-conductance peaks and negative differential conductance around the switch-on voltage, which can be modulated by temperature and light. These features are interpreted by a model based on the Coulomb blockade effect, the collective resonant tunneling, and the coupling of holes in the AG. Our results not only demonstrate an approach to the formation but also will greatly stimulate the characterizations and the applications of innovative semiconductor-based AG.
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Affiliation(s)
- Peizong Chen
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, People's Republic of China
| | - Ningning Zhang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, People's Republic of China
| | - Kun Peng
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, People's Republic of China
| | - Lijian Zhang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, People's Republic of China
| | - Jia Yan
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, People's Republic of China
| | - Zuimin Jiang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, People's Republic of China
| | - Zhenyang Zhong
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, People's Republic of China
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14
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Chan SC, Cheng YL, Chang BK, Hong CW. The origins of charge separation in anisotropic facet photocatalysts investigated through first-principles calculations. RSC Adv 2021; 11:18500-18508. [PMID: 35480943 PMCID: PMC9033447 DOI: 10.1039/d1ra01711j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Accepted: 05/13/2021] [Indexed: 11/21/2022] Open
Abstract
It was recently discovered that the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) can be completed on the {110} and {001} facets, respectively, of a 18-facet SrTiO3 mono-crystal. The effective charge separation is attributed to the facet junction at the interface between two arbitrary anisotropic crystal planes. Theoretical estimation of the built-in potential at the facet junction can greatly improve understanding of the mechanism. This work employs density functional theory (DFT) calculations to investigate such potential at the (110)/(100) facet junction in SrTiO3 crystals. The formation of the facet junction is verified by a calculated work function difference between the (110) and (100) planes, which form p-type and n-type segments of the junction, respectively. The built-in potential is estimated at about 2.9 V. As a result, with the ultra high built-in potential, electrons and holes can effectively transfer to different anisotropic planes to complete both photo-oxidative and photo-reductive reactions.
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Affiliation(s)
- Shun-Chiao Chan
- Department of Power Mechanical Engineering, National Tsing Hua University Hsinchu City 300 Taiwan
| | - Yu-Lin Cheng
- Department of Power Mechanical Engineering, National Tsing Hua University Hsinchu City 300 Taiwan
| | - Bor Kae Chang
- Department of Chemical & Materials Engineering, National Central University Taoyuan City 320 Taiwan
| | - Che-Wun Hong
- Department of Power Mechanical Engineering, National Tsing Hua University Hsinchu City 300 Taiwan
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15
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Marri I, Amato M, Bertocchi M, Ferretti A, Varsano D, Ossicini S. Surface chemistry effects on work function, ionization potential and electronic affinity of Si(100), Ge(100) surfaces and SiGe heterostructures. Phys Chem Chem Phys 2020; 22:25593-25605. [PMID: 33164017 DOI: 10.1039/d0cp04013d] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We combine density functional theory and many body perturbation theory to investigate the electronic properties of Si(100) and Ge(100) surfaces terminated with halogen atoms (-I, -Br, -Cl, -F) and other chemical functionalizations (-H, -OH, -CH3) addressing the absolute values of their work function, electronic affinity and ionization potential. Our results point out that electronic properties of functionalized surfaces strongly depend on the chemisorbed species and much less on the surface crystal orientation. The presence of halogens at the surface always leads to an increment of the work function, ionization potential and electronic affinity with respect to fully hydrogenated surfaces. On the contrary, the presence of polar -OH and -CH3 groups at the surface leads to a reduction of the aforementioned quantities with respect to the H-terminated system. Starting from the work functions calculated for the Si and Ge passivated surfaces, we apply a simple model to estimate the properties of functionalized SiGe surfaces. The possibility of modulating the work function by changing the chemisorbed species and composition is predicted. The effects induced by different terminations on the band energy line-up profile of SiGe surfaces are then analyzed. Interestingly, our calculations predict a type-II band offset for the H-terminated systems and a type-I band offset for the other cases.
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Affiliation(s)
- Ivan Marri
- Department of Sciences and Methods for Engineering, University of Modena e Reggio Emilia, 42122 Reggio Emilia, Italy.
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16
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A Silicon-Compatible Synaptic Transistor Capable of Multiple Synaptic Weights toward Energy-Efficient Neuromorphic Systems. ELECTRONICS 2019. [DOI: 10.3390/electronics8101102] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In order to resolve the issue of tremendous energy consumption in conventional artificial intelligence, hardware-based neuromorphic system is being actively studied. Although various synaptic devices for the system have been proposed, they have shown limits in terms of endurance, reliability, energy efficiency, and Si processing compatibility. In this work, we design a synaptic transistor with short-term and long-term plasticity, high density, high reliability and energy efficiency, and Si processing compatibility. The synaptic characteristics of the device are closely examined and validated through technology computer-aided design (TCAD) device simulation. Consequently, full synaptic functions with high energy efficiency have been realized.
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17
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Abstract
Germanium has long been regarded as a promising laser material for silicon based opto-electronics. It is CMOS-compatible and has a favourable band structure, which can be tuned by strain or alloying with Sn to become direct, as it was found to be required for interband semiconductor lasers. Here, we report lasing in the mid-infrared region (from λ = 3.20 μm up to λ = 3.66 μm) in tensile strained Ge microbridges uniaxially loaded above 5.4% up to 5.9% upon optical pumping, with a differential quantum efficiency close to 100% with a lower bound of 50% and a maximal operating temperature of 100 K. We also demonstrate the effect of a non-equilibrium electron distribution in k-space which reveals the importance of directness for lasing. With these achievements the strained Ge approach is shown to compare well to GeSn, in particular in terms of efficiency. Germanium (based) lasers are a promising route towards a fully CMOS-compatible light source, key to the further development of silicon photonics. Here, the authors realize lasing from strained germanium microbridges up to 100 K, finding a quantum efficiency close to 100%.
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18
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Strain engineering of transverse electric and transverse magnetic mode of material gain in GeSn/SiGeSn quantum wells. Sci Rep 2019; 9:3316. [PMID: 30824800 PMCID: PMC6397312 DOI: 10.1038/s41598-019-40146-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Accepted: 01/25/2019] [Indexed: 11/15/2022] Open
Abstract
8-band k · p Hamiltonian together with envelope function approximation and planewave expansion method are applied to calculate the electronic band structure and material gain for Ge1−wSnw/SiyGe1−x−ySnx/Ge1−wSnw quantum wells (QWs) grown on virtual Ge1-zSnz substrates integrated with Si platform. It is clearly shown how both the emission wavelength in this material system can be controlled by the content of virtual substrate and the polarization of emitted light can be controlled via the built-in strain. In order to systematically demonstrate these possibilities, the transverse electric (TE) and transverse magnetic (TM) modes of material gain, and hence the polarization degree, are calculated for Ge1−wSnw/SiyGe1−x−ySnx/Ge1−wSnw (QWs) with the strain varying from tensile (ε = +1.5%) to compressive (ε = −0.9%). It has been predicted that the polarization can be changed from 100% TE to 80% TM. In addition, it has been shown that SiyGe1−x−ySnx barriers, lattice matched to the virtual Ge1-zSnz substrate (condition: y = 3.66(x-z)), may ensure a respectable quantum confinement for electrons and holes in this system. With such material features Ge1−wSnw/SiyGe1−x−ySnx/Ge1−wSnw QW structure unified with Ge1-zSnz/Si platform may be considered as a very prospective one for light polarization engineering.
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19
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Theoretical investigation of structural, electronic and optical properties of (BeS)1/(BeSe)1, (BeSe)1/(BeTe)1 and (BeS)1/(BeTe)1 superlattices under pressure. Chem Phys Lett 2018. [DOI: 10.1016/j.cplett.2018.10.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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20
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O'Rourke C, Mujahed SY, Kumarasinghe C, Miyazaki T, Bowler DR. Structural properties of silicon-germanium and germanium-silicon core-shell nanowires. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:465303. [PMID: 30284970 DOI: 10.1088/1361-648x/aae617] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Core-shell nanowires made of Si and Ge can be grown experimentally with excellent control for different sizes of both core and shell. We have studied the structural properties of Si/Ge and Ge/Si core-shell nanowires aligned along the [Formula: see text] direction, with diameters up to 10.2 nm and varying core to shell ratios, using linear scaling density functional theory. We show that Vegard's law, which is often used to predict the axial lattice constant, can lead to an error of up to 1%, underlining the need for a detailed ab initio atomistic treatment of the nanowire structure. We analyse the character of the intrinsic strain distribution and show that, regardless of the composition or bond direction, the Si core or shell always expands. In contrast, the strain patterns in the Ge shell or core are highly sensitive to the location, composition and bond direction. The highest strains are found at heterojunction interfaces and the surfaces of the nanowires. This detailed understanding of the atomistic structure and strain paves the way for studies of the electronic properties of core-shell nanowires and investigations of doping and structure defects.
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Affiliation(s)
- Conn O'Rourke
- London Centre for Nanotechnology, University College London, 17-19 Gordon St, London, WC1H 0AH, United Kingdom. International Centre for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
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21
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Shapera EP, Schleife A. Database‐Driven Materials Selection for Semiconductor Heterojunction Design. ADVANCED THEORY AND SIMULATIONS 2018. [DOI: 10.1002/adts.201800075] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Ethan P. Shapera
- Department of Physics University of Illinois at Urbana‐Champaign Urbana IL 61801 USA
| | - André Schleife
- Department of Materials Science and Engineering Frederick Seitz Materials Research Laboratory National Center for Supercomputing Applications University of Illinois at Urbana‐Champaign Urbana IL 61801 USA
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22
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Pilania G, McClellan KJ, Stanek CR, Uberuaga BP. Physics-informed machine learning for inorganic scintillator discovery. J Chem Phys 2018; 148:241729. [DOI: 10.1063/1.5025819] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- G. Pilania
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - K. J. McClellan
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - C. R. Stanek
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - B. P. Uberuaga
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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23
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Zhou Y, Wang H, Liu Y, Gao X, Song H. Applicability of Kerker preconditioning scheme to the self-consistent density functional theory calculations of inhomogeneous systems. Phys Rev E 2018; 97:033305. [PMID: 29776145 DOI: 10.1103/physreve.97.033305] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Indexed: 06/08/2023]
Abstract
The Kerker preconditioner, based on the dielectric function of homogeneous electron gas, is designed to accelerate the self-consistent field (SCF) iteration in the density functional theory calculations. However, a question still remains regarding its applicability to the inhomogeneous systems. We develop a modified Kerker preconditioning scheme which captures the long-range screening behavior of inhomogeneous systems and thus improves the SCF convergence. The effectiveness and efficiency is shown by the tests on long-z slabs of metals, insulators, and metal-insulator contacts. For situations without a priori knowledge of the system, we design the a posteriori indicator to monitor if the preconditioner has suppressed charge sloshing during the iterations. Based on the a posteriori indicator, we demonstrate two schemes of the self-adaptive configuration for the SCF iteration.
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Affiliation(s)
- Yuzhi Zhou
- Laboratory of Computational Physics, Huayuan Road 6, Beijing 100088, People's Republic of China
- Institute of Applied Physics and Computational Mathematics, Fenghao East Road 2, Beijing 100094, People's Republic of China
- CAEP Software Center for High Performance Numerical Simulation, Huayuan Road 6, Beijing 100088, People's Republic of China
| | - Han Wang
- Institute of Applied Physics and Computational Mathematics, Fenghao East Road 2, Beijing 100094, People's Republic of China
- CAEP Software Center for High Performance Numerical Simulation, Huayuan Road 6, Beijing 100088, People's Republic of China
| | - Yu Liu
- Institute of Applied Physics and Computational Mathematics, Fenghao East Road 2, Beijing 100094, People's Republic of China
- CAEP Software Center for High Performance Numerical Simulation, Huayuan Road 6, Beijing 100088, People's Republic of China
| | - Xingyu Gao
- Laboratory of Computational Physics, Huayuan Road 6, Beijing 100088, People's Republic of China
- Institute of Applied Physics and Computational Mathematics, Fenghao East Road 2, Beijing 100094, People's Republic of China
- CAEP Software Center for High Performance Numerical Simulation, Huayuan Road 6, Beijing 100088, People's Republic of China
| | - Haifeng Song
- Institute of Applied Physics and Computational Mathematics, Fenghao East Road 2, Beijing 100094, People's Republic of China
- CAEP Software Center for High Performance Numerical Simulation, Huayuan Road 6, Beijing 100088, People's Republic of China
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24
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Jiang J, Sun J, Gao J, Zhang R. Analysis of threshold current of uniaxially tensile stressed bulk Ge and Ge/SiGe quantum well lasers. OPTICS EXPRESS 2017; 25:26714-26727. [PMID: 29092155 DOI: 10.1364/oe.25.026714] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 10/07/2017] [Indexed: 06/07/2023]
Abstract
We propose and design uniaxially tensile stressed bulk Ge and Ge/SiGe quantum well lasers with the stress along <100> direction. The micro-bridge structure is adapted for introducing uniaxial stress in Ge/SiGe quantum well. To enhance the fabrication tolerance, full-etched circular gratings with high reflectivity bandwidths of ~500 nm are deployed in laser cavities. We compare and analyze the density of state, the number of states between Γ- and L-points, the carrier injection efficiency, and the threshold current density for the uniaxially tensile stressed bulk Ge and Ge/SiGe quantum well lasers. Simulation results show that the threshold current density of the Ge/SiGe quantum well laser is much higher than that of the bulk Ge laser, even combined with high uniaxial tensile stress owing to the larger number of states between Γ- and L- points and extremely low carrier injection efficiency. Electrical transport simulation reveals that the reduced effective mass of the hole and the small conduction band offset cause the low carrier injection efficiency of the Ge/SiGe quantum well laser. Our theoretical results imply that unlike III-V material, uniaxially tensile stressed bulk Ge outperforms a Ge/SiGe quantum well with the same strain level and is a promising approach for Si-compatible light sources.
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25
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Caro MA, Lopez-Acevedo O, Laurila T. Redox Potentials from Ab Initio Molecular Dynamics and Explicit Entropy Calculations: Application to Transition Metals in Aqueous Solution. J Chem Theory Comput 2017; 13:3432-3441. [DOI: 10.1021/acs.jctc.7b00314] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Miguel A. Caro
- Department
of Electrical Engineering and Automation, Aalto University, 02150 Espoo, Finland
- COMP
Centre of Excellence in Computational Nanoscience, Department of Applied
Physics, Aalto University, Espoo, 02150Finland
| | - Olga Lopez-Acevedo
- COMP
Centre of Excellence in Computational Nanoscience, Department of Applied
Physics, Aalto University, Espoo, 02150Finland
- Departamento
de Ciencias Básicas, Universidad de Medellín, 050026 Medellín, Colombia
| | - Tomi Laurila
- Department
of Electrical Engineering and Automation, Aalto University, 02150 Espoo, Finland
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26
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Wang W, Janotti A, Van de Walle CG. Phase transformations upon doping in WO 3. J Chem Phys 2017; 146:214504. [PMID: 28595405 PMCID: PMC5656041 DOI: 10.1063/1.4984581] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 05/11/2017] [Indexed: 12/21/2022] Open
Abstract
High levels of doping in WO3 have been experimentally observed to lead to structural transformation towards higher symmetry phases. We explore the structural phase diagram with charge doping through first-principles methods based on hybrid density functional theory, as a function of doping the room-temperature monoclinic phase transitions to the orthorhombic, tetragonal, and finally cubic phase. Based on a decomposition of energies into electronic and strain contributions, we attribute the transformation to a gain in energy resulting from a lowering of the conduction band on an absolute energy scale.
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Affiliation(s)
- Wennie Wang
- Materials Department, University of California, Santa Barbara, California 93106-5050, USA
| | - Anderson Janotti
- Materials Department, University of California, Santa Barbara, California 93106-5050, USA
| | - Chris G Van de Walle
- Materials Department, University of California, Santa Barbara, California 93106-5050, USA
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27
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Computational Predictions for Single Chain Chalcogenide-Based One-Dimensional Materials. NANOMATERIALS 2017; 7:nano7050115. [PMID: 28513537 PMCID: PMC5449996 DOI: 10.3390/nano7050115] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 04/24/2017] [Accepted: 05/02/2017] [Indexed: 11/24/2022]
Abstract
Exfoliation of multilayered materials has led to an abundance of new two-dimensional (2D) materials and to their fabrication by other means. These materials have shown exceptional promise for many applications. In a similar fashion, we can envision starting with crystalline polymeric (multichain) materials and exfoliate single-chain, one-dimensional (1D) materials that may also prove useful. We use electronic structure methods to elucidate the properties of such 1D materials: individual chains of chalcogens, of silicon dichalcogenides and of sulfur nitrides. The results indicate reasonable exfoliation energies in the case of polymeric three-dimensional (3D) materials. Quantum confinement effects lead to large band gaps and large exciton binding energies. The effects of strain are quantified and heterojunction band offsets are determined. Possible applications would entail 1D materials on 3D or 2D substrates.
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28
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Wang Z, Wang S, Yin Y, Liu T, Lin D, Li DH, Yang X, Jiang Z, Zhong Z. Promising features of low-temperature grown Ge nanostructures on Si(001) substrates. NANOTECHNOLOGY 2017; 28:115701. [PMID: 28140355 DOI: 10.1088/1361-6528/aa5b3d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
High-quality Ge nanostructures are obtained by molecular beam epitaxy of Ge on Si(001) substrates at 200 °C and ex situ annealing at 400 °C. Their structural properties are comprehensively characterized by atomic force microscopy, transmission electron microscopy and Raman spectroscopy. It is disclosed that they are almost defect free except for some defects at the Ge/Si interface and in the subsequent Si capping layer. The misfit strain in the nanostructure is substantially relaxed. Dramatically strong photoluminescence (PL) from the Ge nanostructures is observed. Detailed analyses on the power- and temperature-dependent PL spectra, together with a self-consistent calculation, indicate the confinement and the high quantum efficiency of excitons within the Ge nanostructures. Our results demonstrate that the Ge nanostructures obtained via the present feasible route may have great potential in optoelectronic devices for monolithic optical-electronic integration circuits.
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Affiliation(s)
- Ze Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, People's Republic of China. Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
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29
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Péan E, Vidal J, Jobic S, Latouche C. Presentation of the PyDEF post-treatment Python software to compute publishable charts for defect energy formation. Chem Phys Lett 2017. [DOI: 10.1016/j.cplett.2017.01.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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30
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Xue KH, Fonseca LRC, Miao XS. Ferroelectric fatigue in layered perovskites from self-energy corrected density functional theory. RSC Adv 2017. [DOI: 10.1039/c7ra01650f] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We employed GGA-1/2 to investigate the band alignment between platinum and various layered perovskite Aurivillius ferroelectrics. A model is proposed for ferroelectric fatigue in bismuth titanate based on our calculation.
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Affiliation(s)
- Kan-Hao Xue
- School of Optical and Electronic Information
- Huazhong University of Science and Technology
- Wuhan 430074
- China
- Wuhan National Laboratory for Optoelectronics
| | | | - Xiang-Shui Miao
- School of Optical and Electronic Information
- Huazhong University of Science and Technology
- Wuhan 430074
- China
- Wuhan National Laboratory for Optoelectronics
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31
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Xiao B, Yu XF, Cheng JB. Atomic Insight into the Origin of Various Operation Voltages of Cation-Based Resistance Switches. ACS APPLIED MATERIALS & INTERFACES 2016; 8:31978-31985. [PMID: 27800674 DOI: 10.1021/acsami.6b10056] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Low operation voltage (VSET), which means low power consumption and good stability, is one of the most important factors in designing the resistance switches with high performance. However, the atomic details for the various VSET values of such devices are still lacking, which hinders their further improvement. In the present study, by taking Ag/Ta2O5/Pt (VSET = 0.6 V) and Cu/Ta2O5/Pt (VSET = 2.0 V) as the examples, we have examined the switching mechanisms of these two cation-based devices by using first principle simulation. Several possible reasons have been addressed to explain the much lower VSET of Ag/Ta2O5/Pt than that of Cu/Ta2O5/Pt: (i) the faster diffusion of Ag ions in Ta2O5 compared to Cu ions; (ii) the more preferable nucleation process of Ag ions at Pt/Ta2O5 interface compared to Cu ions; (iii) the lower Schottky barrier height (SBH) of Ag/Ta2O5/Pt than that of Cu/Ta2O5/Pt. On the basis of these results, several key factors have been suggested to design the cation-based resistance switches (oxidizable-metal/Ta2O5/inert-metal) with low VSET values: (i) the weak interaction strength between oxidizable metal ions and Ta2O5 surface; (ii) the low formation energy of oxidizable metal ions on inert electrode; (iii) the low SBH, which could be controlled by tuning the ambient water pressure during the device fabrication process.
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Affiliation(s)
- Bo Xiao
- The Laboratory of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Yantai University , Yantai 264005, China
| | - Xue-Fang Yu
- The Laboratory of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Yantai University , Yantai 264005, China
| | - Jian-Bo Cheng
- The Laboratory of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Yantai University , Yantai 264005, China
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32
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Fabini DH, Labram JG, Lehner AJ, Bechtel JS, Evans HA, Van der Ven A, Wudl F, Chabinyc ML, Seshadri R. Main-Group Halide Semiconductors Derived from Perovskite: Distinguishing Chemical, Structural, and Electronic Aspects. Inorg Chem 2016; 56:11-25. [DOI: 10.1021/acs.inorgchem.6b01539] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
| | | | - Anna J. Lehner
- Institute for Applied Materials, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
- Fraunhofer-Institut für Werkstoffmechanik, 79108 Freiburg, Germany
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33
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Silvestri L, Ladouceur F. Role of AlN Polarity in the Band Alignment of AlN(0001)/Diamond(100) Heterojunctions: A First-Principles Study. J Phys Chem Lett 2016; 7:1534-1538. [PMID: 27063922 DOI: 10.1021/acs.jpclett.6b00285] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We present a comprehensive first-principles study of the band alignment at AlN(0001)/diamond(100) heterojunctions, considering two different polarities of the AlN and taking into account atomic relaxation at the interface. Our simulations show that the valence-band offset reduces dramatically from about 1.6 eV for one polarity to 0.6 eV for the other, changing the corresponding band alignment from staggered (type II) to straddling (type I). Our findings have important consequences for the design of many applications, most notably solid state UV-emitting devices.
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Affiliation(s)
- Leonardo Silvestri
- School of Electrical Engineering and Telecommunications, University of New South Wales , Sydney NSW 2052, Australia
| | - François Ladouceur
- School of Electrical Engineering and Telecommunications, University of New South Wales , Sydney NSW 2052, Australia
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34
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Virgilio M, Grosso G. Strain-modulated Ge superlattices. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:485305. [PMID: 26569138 DOI: 10.1088/0953-8984/27/48/485305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We present a numerical study of the electronic and optical properties of a model single-element superlattice made of a periodic sequence of relaxed and strained regions of a germanium crystal, realized by means of an externally applied strain. We adopt the tight-binding model to evaluate the strain-driven modifications of the band structure and the optical properties. Superlattice band gaps, spatial confinement of near-gap valence and conduction states, and analysis of their symmetry character, have been obtained for different superlattice periodicities and strain intensities. Our results indicate that, for suitable choices of spatial periodicity and strain values, type-I and direct-gap superlattices, with strong dipole matrix elements, can be realized. Conceptually, we demonstrate that Ge single-element strained superlattices could be active materials for novel Si-compatible optical devices.
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Affiliation(s)
- Michele Virgilio
- Dipartimento di Fisica 'E Fermi', Università di Pisa, Largo Pontecorvo 3, I-56127 Pisa, Italy. NEST, Istituto Nanoscienze-CNR, P.za San Silvestro 12, I-56127 Pisa, Italy
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35
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Laubscher M, Küfner S, Kroll P, Bechstedt F. Amorphous Ge quantum dots embedded in crystalline Si: ab initio results. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:405302. [PMID: 26402441 DOI: 10.1088/0953-8984/27/40/405302] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We study amorphous Ge quantum dots embedded in a crystalline Si matrix through structure modeling and simulation using ab initio density functional theory including spin-orbit interaction and quasiparticle effects. Three models are generated by replacing a spherical region within diamond Si by Ge atoms and creating a disordered bond network with appropriate density inside the Ge quantum dot. After total-energy optimisations of the atomic geometry we compute the electronic and optical properties. We find three major effects: (i) the resulting nanostructures adopt a type-I heterostructure character; (ii) the lowest optical transitions occur only within the Ge quantum dots, and do not involve or cross the Ge-Si interface. (iii) for larger amorphous Ge quantum dots, with diameters of about 2.0 and 2.7 nm, absorption peaks appear in the mid-infrared spectral region. These are promising candidates for intense luminescence at photon energies below the gap energy of bulk Ge.
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Affiliation(s)
- M Laubscher
- Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany
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36
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Fei ET, Chen X, Zang K, Huo Y, Shambat G, Miller G, Liu X, Dutt R, Kamins TI, Vuckovic J, Harris JS. Investigation of germanium quantum-well light sources. OPTICS EXPRESS 2015; 23:22424-22430. [PMID: 26368212 DOI: 10.1364/oe.23.022424] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In this paper, we report a broad investigation of the optical properties of germanium (Ge) quantum-well devices. Our simulations show a significant increase of carrier density in the Ge quantum wells. Photoluminescence (PL) measurements show the enhanced direct-bandgap radiative recombination rates due to the carrier density increase in the Ge quantum wells. Electroluminescence (EL) measurements show the temperature-dependent properties of our Ge quantum-well devices, which are in good agreement with our theoretical models. We also demonstrate the PL measurements of Ge quantum-well microdisks using tapered-fiber collection method and quantify the optical loss of the Ge quantum-well structure from the measured PL spectra for the first time.
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Singh AK, Mathew K, Zhuang HL, Hennig RG. Computational Screening of 2D Materials for Photocatalysis. J Phys Chem Lett 2015; 6:1087-98. [PMID: 26262874 DOI: 10.1021/jz502646d] [Citation(s) in RCA: 232] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Two-dimensional (2D) materials exhibit a range of extraordinary electronic, optical, and mechanical properties different from their bulk counterparts with potential applications for 2D materials emerging in energy storage and conversion technologies. In this Perspective, we summarize the recent developments in the field of solar water splitting using 2D materials and review a computational screening approach to rapidly and efficiently discover more 2D materials that possess properties suitable for solar water splitting. Computational tools based on density-functional theory can predict the intrinsic properties of potential photocatalyst such as their electronic properties, optical absorbance, and solubility in aqueous solutions. Computational tools enable the exploration of possible routes to enhance the photocatalytic activity of 2D materials by use of mechanical strain, bias potential, doping, and pH. We discuss future research directions and needed method developments for the computational design and optimization of 2D materials for photocatalysis.
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Affiliation(s)
- Arunima K Singh
- †Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, United States
| | - Kiran Mathew
- †Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, United States
- ‡Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, United States
| | - Houlong L Zhuang
- †Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, United States
| | - Richard G Hennig
- †Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, United States
- ‡Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, United States
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38
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Kharche N, Muckerman JT, Hybertsen MS. First-principles approach to calculating energy level alignment at aqueous semiconductor interfaces. PHYSICAL REVIEW LETTERS 2014; 113:176802. [PMID: 25379929 DOI: 10.1103/physrevlett.113.176802] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Indexed: 06/04/2023]
Abstract
A first-principles approach is demonstrated for calculating the relationship between an aqueous semiconductor interface structure and energy level alignment. The physical interface structure is sampled using density functional theory based molecular dynamics, yielding the interface electrostatic dipole. The GW approach from many-body perturbation theory is used to place the electronic band edge energies of the semiconductor relative to the occupied 1b1 energy level in water. The application to the specific cases of nonpolar (101¯0) facets of GaN and ZnO reveals a significant role for the structural motifs at the interface, including the degree of interface water dissociation and the dynamical fluctuations in the interface Zn-O and O-H bond orientations. These effects contribute up to 0.5 eV.
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Affiliation(s)
- Neerav Kharche
- Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973-5000, USA
| | - James T Muckerman
- Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973-5000, USA
| | - Mark S Hybertsen
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973-5000, USA
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39
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Rohling N, Russ M, Burkard G. Hybrid spin and valley quantum computing with singlet-triplet qubits. PHYSICAL REVIEW LETTERS 2014; 113:176801. [PMID: 25379928 DOI: 10.1103/physrevlett.113.176801] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Indexed: 06/04/2023]
Abstract
The valley degree of freedom in the electronic band structure of silicon, graphene, and other materials is often considered to be an obstacle for quantum computing (QC) based on electron spins in quantum dots. Here we show that control over the valley state opens new possibilities for quantum information processing. Combining qubits encoded in the singlet-triplet subspace of spin and valley states allows for universal QC using a universal two-qubit gate directly provided by the exchange interaction. We show how spin and valley qubits can be separated in order to allow for single-qubit rotations.
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Affiliation(s)
- Niklas Rohling
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
| | - Maximilian Russ
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
| | - Guido Burkard
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
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40
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Misch LM, Brgoch J, Birkel A, Mates TE, Stucky GD, Seshadri R. Rapid Microwave Preparation and ab Initio Studies of the Stability of the Complex Noble Metal Oxides La2BaPdO5 and La2BaPtO5. Inorg Chem 2014; 53:2628-34. [DOI: 10.1021/ic4030124] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Lauren M. Misch
- Materials
Research Laboratory, University of California, Santa Barbara, California 93106, United States
- Department
of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States
| | - Jakoah Brgoch
- Materials
Research Laboratory, University of California, Santa Barbara, California 93106, United States
| | - Alexander Birkel
- Materials
Research Laboratory, University of California, Santa Barbara, California 93106, United States
| | - Thomas E. Mates
- Materials
Department, University of California, Santa Barbara, California 93106, United States
| | - Galen D. Stucky
- Department
of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States
- Materials
Department, University of California, Santa Barbara, California 93106, United States
| | - Ram Seshadri
- Department
of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States
- Materials
Department, University of California, Santa Barbara, California 93106, United States
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41
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Amato M, Palummo M, Rurali R, Ossicini S. Silicon–Germanium Nanowires: Chemistry and Physics in Play, from Basic Principles to Advanced Applications. Chem Rev 2013; 114:1371-412. [DOI: 10.1021/cr400261y] [Citation(s) in RCA: 137] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Michele Amato
- Institut d’Electronique Fondamentale, UMR8622, CNRS, Université Paris-Sud, 91405 Orsay, France
| | - Maurizia Palummo
- European
Theoretical Spectroscopy Facility (ETSF), Dipartimento di Fisica, Università di Roma, “Tor Vergata”, Via della Ricerca
Scientifica 1, 00133 Roma, Italy
| | - Riccardo Rurali
- Institut de Ciència de Materials de Barcelona (ICMAB−CSIC), Campus de Bellaterra, 08193 Bellaterra, Barcelona, Spain
| | - Stefano Ossicini
- “Centro S3”, CNR-Istituto di Nanoscienze, Via Campi 213/A, 41125 Modena, Italy
- Dipartimento di Scienze e Metodi dell’Ingegneria, Centro Interdipartimentale En&Tech, Università di Modena e Reggio Emilia, Via Amendola 2 Pad. Morselli, I-42100 Reggio Emilia, Italy
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42
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Jiang H, Shen YC. Ionization potentials of semiconductors from first-principles. J Chem Phys 2013; 139:164114. [DOI: 10.1063/1.4826321] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Ares N, Golovach VN, Katsaros G, Stoffel M, Fournel F, Glazman LI, Schmidt OG, De Franceschi S. Nature of tunable hole g factors in quantum dots. PHYSICAL REVIEW LETTERS 2013; 110:046602. [PMID: 25166183 DOI: 10.1103/physrevlett.110.046602] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Revised: 10/12/2012] [Indexed: 05/27/2023]
Abstract
We report an electric-field-induced giant modulation of the hole g factor in SiGe nanocrystals. The observed effect is ascribed to a so-far overlooked contribution to the g factor that stems from the mixing between heavy- and light-hole wave functions. We show that the relative displacement between the confined heavy- and light-hole states, occurring upon application of the electric field, alters their mixing strength leading to a strong nonmonotonic modulation of the g factor.
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Affiliation(s)
- N Ares
- SPSMS, CEA-INAC/UJF-Grenoble 1, 17 Rue des Martyrs, F-38054 Grenoble Cedex 9, France
| | - V N Golovach
- SPSMS, CEA-INAC/UJF-Grenoble 1, 17 Rue des Martyrs, F-38054 Grenoble Cedex 9, France and Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstrasse 20, D-01069 Dresden, Germany and IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao, Spain and Centro de Física de Materiales (CFM-MPC), Centro Mixto CSIC-UPV/EHU, Manuel de Lardizabal 5, E-20018 San Sebastián, Spain
| | - G Katsaros
- SPSMS, CEA-INAC/UJF-Grenoble 1, 17 Rue des Martyrs, F-38054 Grenoble Cedex 9, France and Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstrasse 20, D-01069 Dresden, Germany and Johannes Kepler University, Institute of Semiconductor and Solid State Physics, Altenbergerstrasse 69, 4040 Linz, Austria
| | - M Stoffel
- Université de Lorraine, Institut Jean Lamour, UMR CNRS 7198, Nancy-Université, BP 239, F-54506 Vandoeuvre-les-Nancy, France
| | - F Fournel
- CEA, LETI, MINATEC, 17 Rue des Martyrs, F-38054 Grenoble Cedex 9, France
| | - L I Glazman
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
| | - O G Schmidt
- Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstrasse 20, D-01069 Dresden, Germany
| | - S De Franceschi
- SPSMS, CEA-INAC/UJF-Grenoble 1, 17 Rue des Martyrs, F-38054 Grenoble Cedex 9, France
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Halilov SV, Huang XY, Hytha M, Stephenson R, Yiptong A, Takeuchi H, Cody N, Mears RJ. Tunneling through superlattices: the effect of anisotropy and kinematic coupling. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:495801. [PMID: 23148049 DOI: 10.1088/0953-8984/24/49/495801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The tunneling of carriers in stratified superlattice systems is analyzed in terms of the constituent effective mass tensor. The focus is on the effects on the tunneling which are caused by the side regions of an intervening barrier. Depending on the covalency and work function in the constituent layers of a superlattice, it is concluded that the kinematics in the regions on either side determined by the effective carrier mass and its interference with the band offset at heterojunctions leads to either a constructive or a destructive effect on the tunneling current. As an example, Si(1-x)Ge(x)/Si and Al(x)Ga(1-x)As/GaAs superlattices are demonstrated to reduce the tunneling current at certain fractional thicknesses and stoichiometries of the constituent slabs without affecting the lateral mobility. The findings show, in general, how manipulation of the carrier's effective mass tensor through stoichiometric/structural modulation of the heterostructure may be used to control the tunneling current through a given potential barrier, given that the characteristic de Broglie wavelength exceeds all the constituent dimensions, thus offering a method complementary to high-k technologies.
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Affiliation(s)
- S V Halilov
- Mears Technologies, 189 Wells Avenue, Newton, MA 02459, USA.
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45
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Amato M, Ossicini S, Rurali R. Electron transport in SiGe alloy nanowires in the ballistic regime from first-principles. NANO LETTERS 2012; 12:2717-2721. [PMID: 22545577 DOI: 10.1021/nl204313v] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Silicon-germanium alloying is emerging as one of the most promising strategies to engineer heat transport at the nanoscale. Here, we perform first-principles electron transport calculations to assess at what extent such approach can be followed without worsening the electrical conduction properties of the system, providing then a path toward high-efficiency thermoelectric materials.
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Affiliation(s)
- Michele Amato
- Dipartimento di Scienze e Metodi dell'Ingegneria, Centro Interdipartimentale En&Tech, Universitá di Modena e Reggio Emilia, Via Amendola 2 Pad. Morselli, I-42100 Reggio Emilia, Italy
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Yu B, Zebarjadi M, Wang H, Lukas K, Wang H, Wang D, Opeil C, Dresselhaus M, Chen G, Ren Z. Enhancement of thermoelectric properties by modulation-doping in silicon germanium alloy nanocomposites. NANO LETTERS 2012; 12:2077-82. [PMID: 22435933 DOI: 10.1021/nl3003045] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Modulation-doping was theoretically proposed and experimentally proved to be effective in increasing the power factor of nanocomposites (Si(80)Ge(20))(70)(Si(100)B(5))(30) by increasing the carrier mobility but not the figure-of-merit (ZT) due to the increased thermal conductivity. Here we report an alternative materials design, using alloy Si(70)Ge(30) instead of Si as the nanoparticles and Si(95)Ge(5) as the matrix, to increase the power factor but not the thermal conductivity, leading to a ZT of 1.3 ± 0.1 at 900 °C.
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Affiliation(s)
- Bo Yu
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
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47
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Nah J, Dillen DC, Varahramyan KM, Banerjee SK, Tutuc E. Role of confinement on carrier transport in Ge-Si(x)Ge(1-x) core-shell nanowires. NANO LETTERS 2012; 12:108-112. [PMID: 22111925 DOI: 10.1021/nl2030695] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We examine the impact of shell content and the associated hole confinement on carrier transport in Ge-Si(x)Ge(1-x) core-shell nanowires (NWs). Using NWs with different Si(x)Ge(1-x) shell compositions (x = 0.5 and 0.7), we fabricate NW field-effect transistors (FETs) with highly doped source/drain and examine their characteristics dependence on shell content. The results demonstrate a 2-fold higher mobility at room temperature, and a 3-fold higher mobility at 77K in the NW FETs with higher (x = 0.7) Si shell content by comparison to those with lower (x = 0.5) Si shell content. Moreover, the carrier mobility shows a stronger temperature dependence in Ge-Si(x)Ge(1-x) core-shell NWs with high Si content, indicating a reduced charge impurity scattering. The results establish that carrier confinement plays a key role in realizing high mobility core-shell NW FETs.
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Affiliation(s)
- Junghyo Nah
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas, Austin, Texas 78758, USA
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48
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49
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Huang R, Yin H, Liang J, Hobart KD, Sturm JC, Suo Z. Relaxation of a Strained Elastic Film on a Viscous Layer. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-695-l3.14.1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTExperiments were conducted with SiGe film islands on a layer of borophosphorosilicate glass (BPSG). Initially the SiGe is under compression. Upon annealing, the glass flows and the SiGe islands relax by both inplane expansion and wrinkling. This paper provides a two-dimensional (2D) model for inplane expansion. The results from the model are compared with the experiments with small SiGe islands. The effect of winkling, which is ignored in the present model, is discussed qualitatively.
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50
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Sturm J, Xiao X, Mi Q, Lenchyshyn L, Thewalt M. Luminescence Processes in Si1-xGex/Si Heterostructures Grown by Chemical Vapor Deposition. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-298-69] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AbstractWell-resolved band-edge exciton photoluminescence (PL) has been observed in strained Si1-xGex. heterostructures grown on Si(100) by rapid thermal chemical vapor deposition. The luminescence is due to shallow-impurity bound excitons at low temperatures (under 20K) and at higher temperatures is due to free excitons or electron-hole plasmas, depending on the pump power. The luminescence can also be electrically pumped, with both the electroluminescence and PL persisting above room temperature in samples with a sufficient bandgap offset. Loss of carrier confinement and subsequent non-radiative recombination outside the Si1-xGex. is found to be the reason for reduced PL and EL at high temperature.
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