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Charnas A, Zhang Z, Lin Z, Zheng D, Zhang J, Si M, Ye PD. Review-Extremely Thin Amorphous Indium Oxide Transistors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2304044. [PMID: 37957006 DOI: 10.1002/adma.202304044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Revised: 09/30/2023] [Indexed: 11/21/2023]
Abstract
Amorphous oxide semiconductor transistors have been a mature technology in display panels for upward of a decade, and have recently been considered as promising back-end-of-line compatible channel materials for monolithic 3D applications. However, achieving high-mobility amorphous semiconductor materials with comparable performance to traditional crystalline semiconductors has been a long-standing problem. Recently it has been found that greatly reducing the thickness of indium oxide, enabled by an atomic layer deposition (ALD) process, can tune its material properties to achieve high mobility, high drive current, high on/off ratio, and enhancement-mode operation at the same time, beyond the capabilities of conventional oxide semiconductor materials. In this work, the history leading to the re-emergence of indium oxide, its fundamental material properties, growth techniques with a focus on ALD, state-of-the-art indium oxide device research, and the bias stability of the devices are reviewed.
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Affiliation(s)
- Adam Charnas
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - Zhuocheng Zhang
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - Zehao Lin
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - Dongqi Zheng
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - Jie Zhang
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - Mengwei Si
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
- Department of Electronic Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Peide D Ye
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
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2
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Bangolla HK, Yusuf Fakhri M, Lin CH, Cheng CM, Lu YH, Fu TY, Selvarasu P, Ulaganathan RK, Sankar R, Chen RS. Electrical and optoelectronic anisotropy and surface electron accumulation in ReS 2 nanostructures. NANOSCALE 2023. [PMID: 38047470 DOI: 10.1039/d3nr04830f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
Two interesting electronic transport properties including in-plane anisotropy and nonhomogeneous carrier distribution were observed in ReS2 nanoflakes. The electrical conductivity defined by the current parallel to the b-axis (‖b) is 32 times higher than that perpendicular to the b-axis (⊥b). Similar anisotropy was also observed in optoelectronic properties in which the ratio of responsivity ‖b to ⊥b reaches 20. In addition, conductivity and thermal activation energy with substantial thickness dependence were observed, which indicates a surface-dominant 2D transport in ReS2 nanoflakes. The presence of surface electron accumulation (SEA) in ReS2 has been confirmed by angle-resolved photoemission spectroscopy and scanning tunneling spectroscopy. The electron concentration (∼1019 cm-3) at the surface is over three orders of magnitude higher than that of the bulks. Sulfur vacancies which are sensitive to air molecules are suggested to be the major factor resulting in SEA and high conductivity in ReS2 nanostructures.
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Affiliation(s)
- Hemanth Kumar Bangolla
- Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 10607, Taiwan.
| | - Muhammad Yusuf Fakhri
- Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 10607, Taiwan.
| | - Ching-Hsuan Lin
- Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 10607, Taiwan.
| | - Cheng-Maw Cheng
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
- Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan
- Taiwan Consortium of Emergent Crystalline Materials, National Science and Technology Council, Taipei 10601, Taiwan
| | - Yi-Hung Lu
- Department of Physics, National Taiwan Normal University, Taipei 11677, Taiwan
| | - Tsu-Yi Fu
- Department of Physics, National Taiwan Normal University, Taipei 11677, Taiwan
| | - Pushpa Selvarasu
- Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 10607, Taiwan.
| | | | - Raman Sankar
- Institute of Physics, Academia Sinica, Taipei 115201, Taiwan
| | - Ruei-San Chen
- Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 10607, Taiwan.
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3
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Wang R, Schultz T, Papadogianni A, Longhi E, Gatsios C, Zu F, Zhai T, Barlow S, Marder SR, Bierwagen O, Amsalem P, Koch N. Tuning the Surface Electron Accumulation Layer of In 2 O 3 by Adsorption of Molecular Electron Donors and Acceptors. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2300730. [PMID: 37078833 DOI: 10.1002/smll.202300730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 03/23/2023] [Indexed: 05/03/2023]
Abstract
In2 O3 , an n-type semiconducting transparent transition metal oxide, possesses a surface electron accumulation layer (SEAL) resulting from downward surface band bending due to the presence of ubiquitous oxygen vacancies. Upon annealing In2 O3 in ultrahigh vacuum or in the presence of oxygen, the SEAL can be enhanced or depleted, as governed by the resulting density of oxygen vacancies at the surface. In this work, an alternative route to tune the SEAL by adsorption of strong molecular electron donors (specifically here ruthenium pentamethylcyclopentadienyl mesitylene dimer, [RuCp*mes]2 ) and acceptors (here 2,2'-(1,3,4,5,7,8-hexafluoro-2,6-naphthalene-diylidene)bis-propanedinitrile, F6 TCNNQ) is demonstrated. Starting from an electron-depleted In2 O3 surface after annealing in oxygen, the deposition of [RuCp*mes]2 restores the accumulation layer as a result of electron transfer from the donor molecules to In2 O3 , as evidenced by the observation of (partially) filled conduction sub-bands near the Fermi level via angle-resolved photoemission spectroscopy, indicating the formation of a 2D electron gas due to the SEAL. In contrast, when F6 TCNNQ is deposited on a surface annealed without oxygen, the electron accumulation layer vanishes and an upward band bending is generated at the In2 O3 surface due to electron depletion by the acceptor molecules. Hence, further opportunities to expand the application of In2 O3 in electronic devices are revealed.
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Affiliation(s)
- Rongbin Wang
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, 12489, Berlin, Germany
| | - Thorsten Schultz
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, 12489, Berlin, Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 12489, Berlin, Germany
| | - Alexandra Papadogianni
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V, 10117, Berlin, Germany
| | - Elena Longhi
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332-0400, USA
| | - Christos Gatsios
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, 12489, Berlin, Germany
| | - Fengshuo Zu
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, 12489, Berlin, Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 12489, Berlin, Germany
| | - Tianshu Zhai
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, 12489, Berlin, Germany
| | - Stephen Barlow
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332-0400, USA
- Renewable and Sustainable Energy Institute, University of Colorado Boulder, Boulder, CO, 80303, USA
| | - Seth R Marder
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332-0400, USA
- Renewable and Sustainable Energy Institute, University of Colorado Boulder, Boulder, CO, 80303, USA
- Department of Chemical and Biological Engineering and Department of Chemistry, University of Colorado Boulder, Boulder, CO, 80303, USA
| | - Oliver Bierwagen
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V, 10117, Berlin, Germany
| | - Patrick Amsalem
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, 12489, Berlin, Germany
| | - Norbert Koch
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, 12489, Berlin, Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 12489, Berlin, Germany
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4
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Scott JI, Adams RL, Martinez-Gazoni RF, Carroll LR, Downard AJ, Veal TD, Reeves RJ, Allen MW. Looking Outside the Square: The Growth, Structure, and Resilient Two-Dimensional Surface Electron Gas of Square SnO 2 Nanotubes. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023:e2300520. [PMID: 37191281 DOI: 10.1002/smll.202300520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 03/31/2023] [Indexed: 05/17/2023]
Abstract
Nanotechnology has delivered an amazing range of new materials such as nanowires, tubes, ribbons, belts, cages, flowers, and sheets. However, these are usually circular, cylindrical, or hexagonal in nature, while nanostructures with square geometries are comparatively rare. Here, a highly scalable method is reported for producing vertically aligned Sb-doped SnO2 nanotubes with perfectly-square geometries on Au nanoparticle covered m-plane sapphire using mist chemical vapor deposition. Their inclination can be varied using r- and a-plane sapphire, while unaligned square nanotubes of the same high structural quality can be grown on silicon and quartz. X-ray diffraction measurements and transmission electron microscopy show that they adopt the rutile structure growing in the [001] direction with (110) sidewalls, while synchrotron X-ray photoelectron spectroscopy reveals the presence of an unusually strong and thermally resilient 2D surface electron gas. This is created by donor-like states produced by the hydroxylation of the surface and is sustained at temperatures above 400 °C by the formation of in-plane oxygen vacancies. This persistent high surface electron density is expected to prove useful in gas sensing and catalytic applications of these remarkable structures. To illustrate their device potential, square SnO2 nanotube Schottky diodes and field effect transistors with excellent performance characteristics are fabricated.
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Affiliation(s)
- Jonty I Scott
- School of Physical and Chemical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Ryan L Adams
- Department of Electrical and Computer Engineering and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Rodrigo F Martinez-Gazoni
- School of Physical and Chemical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Liam R Carroll
- School of Physical and Chemical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Alison J Downard
- School of Physical and Chemical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Tim D Veal
- Stephenson Institute for Renewable Energy and Department of Physics, University of Liverpool, Liverpool, L69 7ZF, UK
| | - Roger J Reeves
- School of Physical and Chemical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Martin W Allen
- Department of Electrical and Computer Engineering and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
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5
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Zha C, Luo W, Zhang X, Yan X, Ren X. Low-Consumption Synaptic Devices Based on Gate-All-Around InAs Nanowire Field-Effect Transistors. NANOSCALE RESEARCH LETTERS 2022; 17:101. [PMID: 36301382 PMCID: PMC9613821 DOI: 10.1186/s11671-022-03740-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 10/17/2022] [Indexed: 06/16/2023]
Abstract
In this work, an artificial electronic synaptic device based on gate-all-around InAs nanowire field-effect transistor is proposed and analyzed. The deposited oxide layer (In2O3) on the InAs nanowire surface serves as a charge trapping layer for information storage. The gate voltage pulse serves as stimuli of the presynaptic membrane, and the drain current and channel conductance are treated as post-synaptic current and weights of the postsynaptic membrane, respectively. At low gate voltages, the device simulates synaptic behaviors including short-term depression and long-term depression. By increasing the amplitude and quantity of gate voltage pulses, the transition from short-term depression to long-term potentiation can be achieved. The device exhibits a large memory window of over 1 V and a minimal energy consumption of 12.5 pJ per synaptic event. This work may pave the way for the development of miniaturized low-consumption synaptic devices and related neuromorphic systems.
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Affiliation(s)
- Chaofei Zha
- State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing, 100876, China
| | - Wei Luo
- State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing, 100876, China
| | - Xia Zhang
- State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing, 100876, China.
| | - Xin Yan
- State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing, 100876, China.
| | - Xiaomin Ren
- State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing, 100876, China
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6
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Shi J, Zhang J, Yang L, Qu M, Qi DC, Zhang KHL. Wide Bandgap Oxide Semiconductors: from Materials Physics to Optoelectronic Devices. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2006230. [PMID: 33797084 DOI: 10.1002/adma.202006230] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2020] [Revised: 12/30/2020] [Indexed: 06/12/2023]
Abstract
Wide bandgap oxide semiconductors constitute a unique class of materials that combine properties of electrical conductivity and optical transparency. They are being widely used as key materials in optoelectronic device applications, including flat-panel displays, solar cells, OLED, and emerging flexible and transparent electronics. In this article, an up-to-date review on both the fundamental understanding of materials physics of oxide semiconductors, and recent research progress on design of new materials and high-performing thin film transistor (TFT) devices in the context of fundamental understanding is presented. In particular, an in depth overview is first provided on current understanding of the electronic structures, defect and doping chemistry, optical and transport properties of oxide semiconductors, which provide essential guiding principles for new material design and device optimization. With these principles, recent advances in design of p-type oxide semiconductors, new approaches for achieving cost-effective transparent (flexible) electrodes, and the creation of high mobility 2D electron gas (2DEG) at oxide surfaces and interfaces with a wealth of fascinating physical properties of great potential for novel device design are then reviewed. Finally, recent progress and perspective of oxide TFT based on new oxide semiconductors, 2DEG, and low-temperature solution processed oxide semiconductor for flexible electronics will be reviewed.
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Affiliation(s)
- Jueli Shi
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
| | - Jiaye Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
| | - Lu Yang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
| | - Mei Qu
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
| | - Dong-Chen Qi
- Centre for Materials Science, School of Chemistry and Physics, Queensland University of Technology, Brisbane, Queensland, 4001, Australia
| | - Kelvin H L Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
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7
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Blackman C. Do We Need "Ionosorbed" Oxygen Species? (Or, "A Surface Conductivity Model of Gas Sensitivity in Metal Oxides Based on Variable Surface Oxygen Vacancy Concentration"). ACS Sens 2021; 6:3509-3516. [PMID: 34570973 DOI: 10.1021/acssensors.1c01727] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The author provides an opinion on direct experimental evidence available to support the "ionosorption theory" often employed to interpret "electrophysical" measurements made during a gas sensing experiment. This article then aims to provide an alternative framework of a "surface conductivity" model based on recent advances in theoretical and experimental investigations in solid state physics, and to use this framework as a guide toward design rules for future improvement of gas sensor performance.
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Affiliation(s)
- Christopher Blackman
- Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, United Kingdom
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8
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Liu CP, Li ZH, Egbo KO, Kwok CK, Lv XH, Ho CY, Wang Y, Yu KM. Effects of oxygen flow ratio and thermal annealing on defect evolution of aluminum doped zinc oxide thin films by reactive DC magnetron sputtering. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:465703. [PMID: 34412043 DOI: 10.1088/1361-648x/ac1f50] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Accepted: 08/19/2021] [Indexed: 06/13/2023]
Abstract
Al doped ZnO (AZO) is a promising transparent conducting oxide to replace the expensive Sn doped In2O3(ITO). Understanding the formation and evolution of defects in AZO is essential for its further improvement. Here, we synthesize transparent conducting AZO thin films by reactive DC magnetron sputtering. The effects of oxygen flow ratio as well as the rapid thermal annealing (RTA) in different conditions on their structural and optoelectrical properties were investigated by a variety of analytical techniques. We find that AZO thin films grown in O-rich conditions exhibit inferior optoelectrical performance as compared with those grown in Zn-rich conditions, possibly due to the formation of excessive native acceptor defects and/or secondary phases (e.g. Al2O3). Temperature-dependent Hall measurements indicate that mobilities of these highly degenerate AZO films withN> 1020 cm-3are primarily limited by ionized and neutral impurities, while films with relatively lowN∼ 1019 cm-3exhibit a temperature-activated mobility owing to the grain-barrier scattering. AsNincreases, the optical band gap of AZO thin film increases as a result of Burstein-Moss shift and band gap narrowing. RTA treatments under appropriate conditions (i.e. at 500 °C for 60 s in Ar) can further improve the electrical properties of AZO thin film, with low resistivity of ∼6.2 × 10-4Ω cm achieved, while RTA at high temperature with longer time can lead to the formation of substantial sub-gap defect states and thus lowers the electron mobility. X-ray photoelectron spectroscopy provides further evidence on the variation of Al (Zn) content at the surface of AZO thin films with different processing conditions.
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Affiliation(s)
- Chao Ping Liu
- Research Center for Advanced Optics and Photoelectronics, Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, People's Republic of China
| | - Zhan Hua Li
- Research Center for Advanced Optics and Photoelectronics, Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, People's Republic of China
| | - Kingsley O Egbo
- Department of Physics, City University of Hong Kong, 83 Tat Chee Ave., Kowloon, Hong Kong Special Administrative Region of China
| | - Cheuk Kai Kwok
- Department of Physics, City University of Hong Kong, 83 Tat Chee Ave., Kowloon, Hong Kong Special Administrative Region of China
| | - Xiao Hu Lv
- Research Center for Advanced Optics and Photoelectronics, Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, People's Republic of China
| | - Chun Yuen Ho
- Department of Physics, City University of Hong Kong, 83 Tat Chee Ave., Kowloon, Hong Kong Special Administrative Region of China
| | - Ying Wang
- Department of Physics, City University of Hong Kong, 83 Tat Chee Ave., Kowloon, Hong Kong Special Administrative Region of China
| | - Kin Man Yu
- Department of Physics, City University of Hong Kong, 83 Tat Chee Ave., Kowloon, Hong Kong Special Administrative Region of China
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9
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Swallow JEN, Palgrave RG, Murgatroyd PAE, Regoutz A, Lorenz M, Hassa A, Grundmann M, von Wenckstern H, Varley JB, Veal TD. Indium Gallium Oxide Alloys: Electronic Structure, Optical Gap, Surface Space Charge, and Chemical Trends within Common-Cation Semiconductors. ACS APPLIED MATERIALS & INTERFACES 2021; 13:2807-2819. [PMID: 33426870 DOI: 10.1021/acsami.0c16021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The electronic and optical properties of (InxGa1-x)2O3 alloys are highly tunable, giving rise to a myriad of applications including transparent conductors, transparent electronics, and solar-blind ultraviolet photodetectors. Here, we investigate these properties for a high quality pulsed laser deposited film which possesses a lateral cation composition gradient (0.01 ≤ x ≤ 0.82) and three crystallographic phases (monoclinic, hexagonal, and bixbyite). The optical gaps over this composition range are determined, and only a weak optical gap bowing is found (b = 0.36 eV). The valence band edge evolution along with the change in the fundamental band gap over the composition gradient enables the surface space-charge properties to be probed. This is an important property when considering metal contact formation and heterojunctions for devices. A transition from surface electron accumulation to depletion occurs at x ∼ 0.35 as the film goes from the bixbyite In2O3 phase to the monoclinic β-Ga2O3 phase. The electronic structure of the different phases is investigated by using density functional theory calculations and compared to the valence band X-ray photoemission spectra. Finally, the properties of these alloys, such as the n-type dopability of In2O3 and use of Ga2O3 as a solar-blind UV detector, are understood with respect to other common-cation compound semiconductors in terms of simple chemical trends of the band edge positions and the hydrostatic volume deformation potential.
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Affiliation(s)
- Jack E N Swallow
- Stephenson Institute for Renewable Energy and Department of Physics, University of Liverpool, Liverpool L69 7ZF, U.K
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, U.K
| | - Robert G Palgrave
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Philip A E Murgatroyd
- Stephenson Institute for Renewable Energy and Department of Physics, University of Liverpool, Liverpool L69 7ZF, U.K
| | - Anna Regoutz
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Michael Lorenz
- Felix Bloch Institute for Solid State Physics, Universität Leipzig, Leipzig, Germany
| | - Anna Hassa
- Felix Bloch Institute for Solid State Physics, Universität Leipzig, Leipzig, Germany
| | - Marius Grundmann
- Felix Bloch Institute for Solid State Physics, Universität Leipzig, Leipzig, Germany
| | - Holger von Wenckstern
- Felix Bloch Institute for Solid State Physics, Universität Leipzig, Leipzig, Germany
| | - Joel B Varley
- Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Tim D Veal
- Stephenson Institute for Renewable Energy and Department of Physics, University of Liverpool, Liverpool L69 7ZF, U.K
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10
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Si M, Hu Y, Lin Z, Sun X, Charnas A, Zheng D, Lyu X, Wang H, Cho K, Ye PD. Why In 2O 3 Can Make 0.7 nm Atomic Layer Thin Transistors. NANO LETTERS 2021; 21:500-506. [PMID: 33372788 DOI: 10.1021/acs.nanolett.0c03967] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
In this work, we demonstrate enhancement-mode field-effect transistors by an atomic-layer-deposited (ALD) amorphous In2O3 channel with thickness down to 0.7 nm. Thickness is found to be critical on the materials and electron transport of In2O3. Controllable thickness of In2O3 at atomic scale enables the design of sufficient 2D carrier density in the In2O3 channel integrated with the conventional dielectric. The threshold voltage and channel carrier density are found to be considerably tuned by channel thickness. Such a phenomenon is understood by the trap neutral level (TNL) model, where the Fermi-level tends to align deeply inside the conduction band of In2O3 and can be modulated to the bandgap in atomic layer thin In2O3 due to the quantum confinement effect, which is confirmed by density function theory (DFT) calculation. The demonstration of enhancement-mode amorphous In2O3 transistors suggests In2O3 is a competitive channel material for back-end-of-line (BEOL) compatible transistors and monolithic 3D integration applications.
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Affiliation(s)
- Mengwei Si
- School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Yaoqiao Hu
- Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Zehao Lin
- School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Xing Sun
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Adam Charnas
- School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Dongqi Zheng
- School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Xiao Lyu
- School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Haiyan Wang
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Kyeongjae Cho
- Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Peide D Ye
- School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
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11
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Gong Y, Yang Z, Lari L, Azaceta I, Lazarov VK, Zhang J, Xu X, Cheng Q, Zhang KHL. Optimizing the Electronic Structure of In 2O 3 through Mg Doping for NiO/In 2O 3 p-n Heterojunction Diodes. ACS APPLIED MATERIALS & INTERFACES 2020; 12:53446-53453. [PMID: 33191725 DOI: 10.1021/acsami.0c14348] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In2O3 is a wide bandgap oxide semiconductor, which has the potential to be used as an active material for transparent flexible electronics and UV photodetectors. However, the high concentration of unintentional background electrons existing in In2O3 makes it hard to be modulated by the electric field or form p-n heterojunctions with a sufficient band-bending width at the interface. In this work, we report the reduction of the background electrons in In2O3 by Mg doping (Mg-In2O3) and thereby improve the device performance of p-n diodes based on the NiO/Mg-In2O3 heterojunction. In particular, Mg doping compensates the free electrons in In2O3 and reduces the electron concentration from 1.7 × 1019 cm-3 without doping to 1.8 × 1017 cm-3 with 5% Mg doping. Transparent p-n heterojunction diodes were fabricated based on p-type NiO and n-type Mg-In2O3. The device performance was considerably enhanced by Mg doping with a high rectification ratio of 3 × 104 and a remarkable high breakdown voltage of >20 V. High-resolution X-ray photoelectron spectroscopy was used to investigate the interfacial electronic structure between NiO and Mg-In2O3, revealing a type II band alignment with a valence band offset of 1.35 eV and a conduction band offset of 2.15 eV. A large built-in potential of 0.98 eV was found for the undoped In2O3 but decreased to 0.51 eV for 5% Mg doping of In2O3. The NiO/Mg-In2O3 diodes with an improved rectification ratio and wider depletion region provide the possibility of achieving photodetectors with rapid photoresponse.
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Affiliation(s)
| | | | - Leonardo Lari
- Department of Physics, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Irene Azaceta
- Department of Physics, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Vlado K Lazarov
- Department of Physics, University of York, Heslington, York YO10 5DD, United Kingdom
| | | | | | - Qijin Cheng
- Shenzhen Research Institute of Xiamen University, Shenzhen 518000, P. R. China
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12
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Loh JYY, Kherani NP. Relating surface defect energetics with reactant gas adsorption during the photo-catalytic reduction of CO 2 by partially hydrolyzed In 2O 3 nanorods. Phys Chem Chem Phys 2020; 22:23686-23698. [PMID: 33057489 DOI: 10.1039/d0cp03217d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Photo-Induced Transient Current Spectroscopy (PICTS) is a versatile technique for measurements of defect state energies and densities in photo-active materials. It is suitable for investigating the surface-gas adsorbate behavior and the defect characteristics of defect laden In2O3-x(OH)y nanorods, having oxygen vacancies and hydroxide surface groups, under in situ reactor conditions of dark ambient temperature, dark 150 °C and photo-illuminated 150 °C, for the photo-assisted Reverse Water Gas Shift reaction. From glovebox-protected X-ray Photoelectron Spectroscopy and in situ PICTS measurements we determined that the reduction of CO2 is associated with heterolytic dissociation of H2 into In-H§- and HO-H§+ centres accompanied by an increase in average carrier trap energies; increased carbonate formation in a photo/thermal reactor state of H2 + CO2, and an average trap energy decrease of 0.11 eV from H2 to a CO2 + H2 mixture, which correlates with binding energy shifts of the OH shoulder of the O1s spectra. These results show the reactivity link between the various OH groups, oxygen vacancies and trap energies of In2O3-x(OH)y in the reactant gas atmosphere components.
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Affiliation(s)
- Joel Y Y Loh
- Department of Electrical and Computing Engineering, University of Toronto, Toronto, Ontario M5S 3G4, Canada
| | - Nazir P Kherani
- Department of Electrical and Computing Engineering, University of Toronto, Toronto, Ontario M5S 3G4, Canada and Department of Material Science and Engineering, University of Toronto, Toronto, Ontario M5S 3E4, Canada.
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13
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Borgersen J, Vines L, Frodason YK, Kuznetsov A, von Wenckstern H, Grundmann M, Allen M, Zúñiga-Pérez J, Johansen KM. Experimental exploration of the amphoteric defect model by cryogenic ion irradiation of a range of wide band gap oxide materials. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:415704. [PMID: 32756022 DOI: 10.1088/1361-648x/abac8b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 08/05/2020] [Indexed: 06/11/2023]
Abstract
The evolution of electrical resistance as function of defect concentration is examined for the unipolarn-conducting oxides CdO,β-Ga2O3, In2O3, SnO2and ZnO in order to explore the predictions of the amphoteric defect model. Intrinsic defects are introduced by ion irradiation at cryogenic temperatures, and the resistance is measured in-situ by current-voltage sweeps as a function of irradiation dose. Temperature dependent Hall effect measurements are performed to determine the carrier concentration and mobility of the samples before and after irradiation. After the ultimate irradiation step, the Ga2O3and SnO2samples have both turned highly resistive. In contrast, the In2O3and ZnO samples are ultimately found to be less resistive than prior to irradiation, however, they both show an increased resistance at intermediate doses. Based on thermodynamic defect charge state transitions computed by hybrid density functional theory, a model expanding on the current amphoteric defect model is proposed.
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Affiliation(s)
- J Borgersen
- Department of Physics, University of Oslo, Norway
- Centre for Materials Science and Nanotechnology, University of Oslo, Norway
| | - L Vines
- Department of Physics, University of Oslo, Norway
- Centre for Materials Science and Nanotechnology, University of Oslo, Norway
| | - Y K Frodason
- Department of Physics, University of Oslo, Norway
- Centre for Materials Science and Nanotechnology, University of Oslo, Norway
| | - A Kuznetsov
- Department of Physics, University of Oslo, Norway
- Centre for Materials Science and Nanotechnology, University of Oslo, Norway
| | - H von Wenckstern
- Felix Bloch institute for Solid State Physics, Fakultät für Physik und Geowissenschaften, Universität Leipzig, Germany
| | - M Grundmann
- Felix Bloch institute for Solid State Physics, Fakultät für Physik und Geowissenschaften, Universität Leipzig, Germany
| | - M Allen
- Department of Electrical and Computer Engineering, University of Canterbury, New Zealand
| | - J Zúñiga-Pérez
- Centre de Recherche sur l'Hétéro-Epitaxie et ses Applications (CRHEA), CNRS, Université Côte d'Azur, France
| | - K M Johansen
- Department of Physics, University of Oslo, Norway
- Centre for Materials Science and Nanotechnology, University of Oslo, Norway
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14
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Tokarev S, Rumyantseva M, Nasriddinov A, Gaskov A, Moiseeva A, Fedorov Y, Fedorova O, Jonusauskas G. Electron injection effect in In 2O 3 and SnO 2 nanocrystals modified by ruthenium heteroleptic complexes. Phys Chem Chem Phys 2020; 22:8146-8156. [PMID: 32249864 DOI: 10.1039/c9cp07016h] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In this work, the optical characteristics and conductivity under photoactivation with visible light of hybrids based on nanocrystalline SnO2 or In2O3 semiconductor matrixes and heteroleptic Ru(ii) complexes were studied. The heteroleptic Ru(ii) complexes were prepared based on 1H-imidazo[4,5-f][1,10]phenanthroline and 2,2'-bipyridine ligands. Nanocrystalline semiconductor oxides were obtained by chemical precipitation with subsequent thermal annealing and characterized by XRD, SEM and single-point BET methods. The heteroleptic Ru(ii) complexes as well as hybrid materials were characterized by time-resolved luminescence and X-ray photoelectron spectroscopy. The results showed that the surface modification of SnO2 nanoparticles with heteroleptic ruthenium complexes led to an increase in conductivity upon irradiation with light appropriate for absorption by organometallic complexes. In the case of In2O3, the deposition of Ru(ii) complexes resulted in a decrease in conductivity, apparently due to the special structure of the surface layer of the semiconductor.
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Affiliation(s)
- Sergey Tokarev
- A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Vavilova str., 119991, Moscow, Russia. and Chemistry Department, M. V. Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Marina Rumyantseva
- Chemistry Department, M. V. Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Abulkosim Nasriddinov
- Chemistry Department, M. V. Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Alexander Gaskov
- Chemistry Department, M. V. Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Anna Moiseeva
- Chemistry Department, M. V. Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Yuri Fedorov
- A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Vavilova str., 119991, Moscow, Russia.
| | - Olga Fedorova
- A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Vavilova str., 119991, Moscow, Russia. and Chemistry Department, M. V. Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Gediminas Jonusauskas
- Laboratoire Ondes et Matière d'Aquitaine - UMR CNRS 5798, University of Bordeaux, 351 cours de la Libération, 33405 Talence, France.
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15
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Jovic V, Moser S, Papadogianni A, Koch RJ, Rossi A, Jozwiak C, Bostwick A, Rotenberg E, Kennedy JV, Bierwagen O, Smith KE. The Itinerant 2D Electron Gas of the Indium Oxide (111) Surface: Implications for Carbon- and Energy-Conversion Applications. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e1903321. [PMID: 31489781 DOI: 10.1002/smll.201903321] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 08/09/2019] [Indexed: 06/10/2023]
Abstract
Transparent conducting oxides (TCO) have integral and emerging roles in photovoltaic, thermoelectric energy conversion, and more recently, photocatalytic systems. The functional properties of TCOs, and thus their role in these applications, are often mediated by the bulk electronic band structure but are also strongly influenced by the electronic structure of the native surface 2D electron gas (2DEG), particularly under operating conditions. This study investigates the 2DEG, and its response to changes in chemistry, at the (111) surface of the model TCO In2 O3 , through angle resolved and core level X-ray photoemission spectroscopy. It is found that the itinerant charge carriers of the 2DEG reside in two quantum well subbands penetrating up to 65 Å below the surface. The charge carrier concentration of this 2DEG, and thus the high surface n-type conductivity, emerges from donor-type oxygen vacancies of surface character and proves to be remarkably robust against surface absorbents and contamination. The optical transparency, however, may rely on the presence of ubiquitous surface adsorbed oxygen groups and hydrogen defect states that passivate localized oxygen vacancy states in the bandgap of In2 O3 .
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Affiliation(s)
- Vedran Jovic
- National Isotope Center, GNS Science, MacDiarmid Institute for Advanced Materials and Nanotechnology, Lower Hutt, Wellington, 5010, New Zealand
- School of Chemical Sciences, The University of Auckland, Auckland, 1010, New Zealand
| | - Simon Moser
- Physikalisches Institut, Universität Würzburg, Würzburg, D-97074, Germany
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Alexandra Papadogianni
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., Hausvogteiplatz 5-7, Berlin, 10117, Germany
| | - Roland J Koch
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Antonio Rossi
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Department of Physics, University of California, Davis, CA, 95616, USA
| | - Chris Jozwiak
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Aaron Bostwick
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Eli Rotenberg
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - John V Kennedy
- National Isotope Center, GNS Science, MacDiarmid Institute for Advanced Materials and Nanotechnology, Lower Hutt, Wellington, 5010, New Zealand
| | - Oliver Bierwagen
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., Hausvogteiplatz 5-7, Berlin, 10117, Germany
| | - Kevin E Smith
- Department of Physics, Boston University, Boston, MA, 02215, USA
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16
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Michel J, Splith D, Rombach J, Papadogianni A, Berthold T, Krischok S, Grundmann M, Bierwagen O, von Wenckstern H, Himmerlich M. Processing Strategies for High-Performance Schottky Contacts on n-Type Oxide Semiconductors: Insights from In 2O 3. ACS APPLIED MATERIALS & INTERFACES 2019; 11:27073-27087. [PMID: 31269791 DOI: 10.1021/acsami.9b06455] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Preparation of rectifying Schottky contacts on n-type oxide semiconductors, such as indium oxide (In2O3), is often challenged by the presence of a distinct surface electron accumulation layer. We investigated the material properties and electrical transport characteristics of platinum contact/indium oxide heterojunctions to define routines for the preparation of high-performance Schottky diodes on n-type oxide semiconductors. Combining the evaluation of different Pt deposition methods, such as electron-beam evaporation and (reactive) sputtering in an (O and) Ar atmosphere, with oxygen plasma interface treatments, we identify key parameters to obtain Schottky-type contacts with high electronic barrier height and high rectification ratio. Different photoelectron spectroscopy approaches are compared to characterize the chemical properties of the contact layers and the interface region toward In2O3, to analyze charge transfer and plasma oxidation processes as well as to evaluate the precision and limits of different methodologies to determine heterointerface energy barriers. An oxygen-plasma-induced passivation of the semiconductor surface, which induces electron depletion and generates an intrinsic interface energy barrier, is found to be not sufficient to generate rectifying platinum contacts. The dissolution of the functional interface oxide layer within the Pt film results in an energy barrier of ∼0.5 eV, which is too low for an In2O3 electron concentration of ∼1018 cm-3. A reactive sputter process in an Ar and O atmosphere is required to fabricate rectifying contacts that are composed of platinum oxide (PtOx). Combining oxygen plasma interface oxidation of the semiconductor surface with reactive sputtering of PtOx layers results in the generation of a high Schottky barrier of ∼0.9 eV and a rectification ratio of up to 106. An additional oxygen plasma treatment after contact deposition further reduced the reverse leakage current, likely by eliminating a surface conduction path between the coplanar Ohmic and Schottky contacts. We conclude that processes that allow us to increase the oxygen content in the interface and contact region are essential for fabrication of device-quality-rectifying contacts on various oxide semiconductors.
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Affiliation(s)
- Jonas Michel
- Institut für Physik and Institut für Mikro- und Nanotechnologien , Technische Universität Ilmenau , PF 100565, 98684 Ilmenau , Germany
| | - Daniel Splith
- Felix Bloch Institute for Solid State Physics , Universität Leipzig , Linnéstr. 5 , 04103 Leipzig , Germany
| | - Julius Rombach
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V. , Hausvogteiplatz 5-7 , 10117 Berlin , Germany
| | - Alexandra Papadogianni
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V. , Hausvogteiplatz 5-7 , 10117 Berlin , Germany
| | - Theresa Berthold
- Institut für Physik and Institut für Mikro- und Nanotechnologien , Technische Universität Ilmenau , PF 100565, 98684 Ilmenau , Germany
| | - Stefan Krischok
- Institut für Physik and Institut für Mikro- und Nanotechnologien , Technische Universität Ilmenau , PF 100565, 98684 Ilmenau , Germany
| | - Marius Grundmann
- Felix Bloch Institute for Solid State Physics , Universität Leipzig , Linnéstr. 5 , 04103 Leipzig , Germany
| | - Oliver Bierwagen
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V. , Hausvogteiplatz 5-7 , 10117 Berlin , Germany
| | - Holger von Wenckstern
- Felix Bloch Institute for Solid State Physics , Universität Leipzig , Linnéstr. 5 , 04103 Leipzig , Germany
| | - Marcel Himmerlich
- Institut für Physik and Institut für Mikro- und Nanotechnologien , Technische Universität Ilmenau , PF 100565, 98684 Ilmenau , Germany
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17
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Deyu GK, Hunka J, Roussel H, Brötz J, Bellet D, Klein A. Electrical Properties of Low-Temperature Processed Sn-Doped In 2O 3 Thin Films: The Role of Microstructure and Oxygen Content and the Potential of Defect Modulation Doping. MATERIALS 2019; 12:ma12142232. [PMID: 31373290 PMCID: PMC6678076 DOI: 10.3390/ma12142232] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 07/02/2019] [Accepted: 07/08/2019] [Indexed: 11/16/2022]
Abstract
Low-temperature-processed ITO thin films offer the potential of overcoming the doping limit by suppressing the equilibrium of compensating oxygen interstitial defects. To elucidate this potential, electrical properties of Sn-doped In2O3 (ITO) thin films are studied in dependence on film thickness. In-operando conductivity and Hall effect measurements during annealing of room-temperature-deposited films, together with different film thickness in different environments, allow to discriminate between the effects of crystallization, grain growth, donor activation and oxygen diffusion on carrier concentrations and mobilities. At 200∘C, a control of carrier concentration by oxygen incorporation or extraction is only dominant for very thin films. The electrical properties of thicker films deposited at room temperature are mostly affected by the grain size. The remaining diffusivity of compensating oxygen defects at 200∘C is sufficient to screen the high Fermi level induced by deposition of Al2O3 using atomic layer deposition (ALD), which disables the use of defect modulation doping at this temperature. The results indicate that achieving higher carrier concentrations in ITO thin films requires a control of the oxygen pressure during deposition in combination with seed layers to enhance crystallinity or the use of near room temperature ALD.
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Affiliation(s)
- Getnet Kacha Deyu
- Electronic Structure of Materials, Department of Materials and Earth Sciences, Technische Universität Darmstadt, Otto-Berndt-Straße 3, 64287 Darmstadt, Germany
- Univ. Grenoble Alpes, CNRS, Grenoble INP, LMGP, 38 000 Grenoble, France
| | - Jonas Hunka
- Electronic Structure of Materials, Department of Materials and Earth Sciences, Technische Universität Darmstadt, Otto-Berndt-Straße 3, 64287 Darmstadt, Germany
| | - Hervé Roussel
- Univ. Grenoble Alpes, CNRS, Grenoble INP, LMGP, 38 000 Grenoble, France
| | - Joachim Brötz
- Structural Research, Department of Materials and Earth Sciences, Technische Universität Darmstadt, Otto-Berndt-Straße 3, 64287 Darmstadt, Germany
| | - Daniel Bellet
- Univ. Grenoble Alpes, CNRS, Grenoble INP, LMGP, 38 000 Grenoble, France
| | - Andreas Klein
- Electronic Structure of Materials, Department of Materials and Earth Sciences, Technische Universität Darmstadt, Otto-Berndt-Straße 3, 64287 Darmstadt, Germany.
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18
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Relevance of the Preparation of the Target for PLD on the Magnetic Properties of Films of Iron-Doped Indium Oxide. COATINGS 2019. [DOI: 10.3390/coatings9060381] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
This paper concerns the importance of the preparation of the targets that may be used for pulsed laser deposition of iron-doped indium oxide films. Targets with a fixed concentration of iron are fabricated from indium oxide and iron metal or one of the oxides of iron, FeO, Fe3O4 and Fe2O3. Films from each target were ablated onto sapphire substrates at the same temperature under different oxygen pressures such that the thickness of the films was kept approximately constant. The films were studied using X-ray diffraction, X-ray absorption (both XANES and EXAFS), optical absorption and magnetic circular dichroism. The magnetic properties were measured with a SQUID magnetometer. At the lowest oxygen pressure, there was evidence that some of the iron ions in the films were in the state Fe2+, rather than Fe3+, and there was also a little metallic iron; these properties were accompanied by a substantial magnetisation. As the amount of the oxygen was increased, the number of defect phases and the saturation magnetisation was reduced and the band gap increased. In each case, we found that the amount of the oxygen that had been included in the target from the precursor added to the effect of adding oxygen in the deposition chamber. It was concluded that the amount of oxygen in the target due to the precursor was an important consideration but not a defining factor in the quality of the films.
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Three-dimensional band structure and surface electron accumulation of rs-Cd xZn 1-xO studied by angle-resolved photoemission spectroscopy. Sci Rep 2019; 9:8026. [PMID: 31142755 PMCID: PMC6541624 DOI: 10.1038/s41598-019-44423-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 05/16/2019] [Indexed: 11/27/2022] Open
Abstract
Three-dimensional band structure of rock-salt (rs) CdxZn1−xO (x = 1.0, 0.83, and 0.60) have been determined by angle-resolved photoemission spectroscopy (ARPES) using synchrotron radiation. Valence-band features shift to higher binding energy with Zn content, while the conduction band position does not depend strongly on Zn content. An increase of the indirect band gap with Zn-doping is larger than that of the direct band gap, reflecting a weaker hybridization between Zn 3d and O 2p than that between Cd 4d and O 2p. Two-dimensional electronic states due to the quantization along surface normal direction are formed in the surface accumulation layer and show non-parabolic dispersions. Binding energy of the quantized two-dimensional state is well reproduced using an accumulation potential with the observed surface band bending and the characteristic width of about 30 Å.
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Park DS, Rees GJ, Wang H, Rata D, Morris AJ, Maznichenko IV, Ostanin S, Bhatnagar A, Choi CJ, Jónsson RDB, Kaufmann K, Kashtiban R, Walker M, Chiang CT, Thorsteinsson EB, Luo Z, Park IS, Hanna JV, Mertig I, Dörr K, Gíslason HP, McConville CF. Electromagnetic Functionalization of Wide-Bandgap Dielectric Oxides by Boron Interstitial Doping. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1802025. [PMID: 30133008 DOI: 10.1002/adma.201802025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 07/05/2018] [Indexed: 06/08/2023]
Abstract
A surge in interest of oxide-based materials is testimony for their potential utility in a wide array of device applications and offers a fascinating landscape for tuning the functional properties through a variety of physical and chemical parameters. In particular, selective electronic/defect doping has been demonstrated to be vital in tailoring novel functionalities, not existing in the bulk host oxides. Here, an extraordinary interstitial doping effect is demonstrated centered around a light element, boron (B). The host matrix is a novel composite system, made from discrete bulk LaAlO3 :LaBO3 compounds. The findings show a spontaneous ordering of the interstitial B cations within the host LaAlO3 lattices, and subsequent spin-polarized charge injection into the neighboring cations. This leads to a series of remarkable cation-dominated electrical switching and high-temperature ferromagnetism. Hence, the induced interstitial doping serves to transform a nonmagnetic insulating bulk oxide into a ferromagnetic ionic-electronic conductor. This unique interstitial B doping effect upon its control is proposed to be as a general route for extracting/modifying multifunctional properties in bulk oxides utilized in energy and spin-based applications.
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Affiliation(s)
- Dae-Sung Park
- Zentrum für Innovationskompetenz SiLi-nano, 06120, Halle, Germany
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120, Halle, Germany
| | - Gregory J Rees
- Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
| | - Haiyuan Wang
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195, Berlin, Germany
| | - Diana Rata
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120, Halle, Germany
| | - Andrew J Morris
- School of Metallurgy and Materials, University of Birmingham, B15 2TT, Birmingham, UK
| | - Igor V Maznichenko
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120, Halle, Germany
| | - Sergey Ostanin
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120, Halle, Germany
- Max-Planck-Institut für Mikrostrukturphysik, 06120, Halle, Germany
| | - Akash Bhatnagar
- Zentrum für Innovationskompetenz SiLi-nano, 06120, Halle, Germany
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120, Halle, Germany
| | - Chel-Jong Choi
- School of Semiconductor and Chemical Engineering, Chonbuk National University, Jeonju, 54596, Republic of Korea
| | | | - Kai Kaufmann
- Fraunhofer Center for Silicon Photovoltaics CSP, Halle, 06120, Germany
| | - Reza Kashtiban
- Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
| | - Marc Walker
- Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
| | - Cheng-Tien Chiang
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120, Halle, Germany
- Max-Planck-Institut für Mikrostrukturphysik, 06120, Halle, Germany
| | | | - Zhengdong Luo
- Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
| | - In-Sung Park
- Institute of Nano Science and Technology, Hanyang University, Seoul, 04763, Republic of Korea
| | - John V Hanna
- Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
| | - Ingrid Mertig
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120, Halle, Germany
- Max-Planck-Institut für Mikrostrukturphysik, 06120, Halle, Germany
| | - Kathrin Dörr
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120, Halle, Germany
| | | | - Chris F McConville
- Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
- College of Science, Engineering & Health, RMIT University, Melbourne, VIC, 3000, Australia
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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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Garlapati SK, Divya M, Breitung B, Kruk R, Hahn H, Dasgupta S. Printed Electronics Based on Inorganic Semiconductors: From Processes and Materials to Devices. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1707600. [PMID: 29952112 DOI: 10.1002/adma.201707600] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Revised: 03/20/2018] [Indexed: 06/08/2023]
Abstract
Following the ever-expanding technological demands, printed electronics has shown palpable potential to create new and commercially viable technologies that will benefit from its unique characteristics, such as, large-area and wide range of substrate compatibility, conformability and low-cost. Through the last few decades, printed/solution-processed field-effect transistors (FETs) and circuits have witnessed immense research efforts, technological growth and increased commercial interests. Although printing of functional inks comprising organic semiconductors has already been initiated in early 1990s, gradually the attention, at least partially, has been shifted to various forms of inorganic semiconductors, starting from metal chalcogenides, oxides, carbon nanotubes and very recently to graphene and other 2D semiconductors. In this review, the entire domain of printable inorganic semiconductors is considered. In fact, thanks to the continuous development of materials/functional inks and novel design/printing strategies, the inorganic printed semiconductor-based circuits today have reached an operation frequency up to several hundreds of kilohertz with only a few nanosecond time delays at the individual FET/inverter levels; in this regard, often circuits based on hybrid material systems have been found to be advantageous. At the end, a comparison of relative successes of various printable inorganic semiconductor materials, the remaining challenges and the available future opportunities are summarized.
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Affiliation(s)
- Suresh Kumar Garlapati
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), D-76344, Eggenstein-Leopoldshafen, Germany
| | - Mitta Divya
- Department of Materials Engineering, Indian Institute of Science, Bangalore, 560012, India
| | - Ben Breitung
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), D-76344, Eggenstein-Leopoldshafen, Germany
| | - Robert Kruk
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), D-76344, Eggenstein-Leopoldshafen, Germany
| | - Horst Hahn
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), D-76344, Eggenstein-Leopoldshafen, Germany
- KIT-TUD Joint Research Laboratory Nanomaterials, Technische Universität Darmstadt (TUD), Institute of Materials Science, Jovanka-Bontschits-Str. 2, ,64287, Darmstadt, Germany
| | - Subho Dasgupta
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), D-76344, Eggenstein-Leopoldshafen, Germany
- Department of Materials Engineering, Indian Institute of Science, Bangalore, 560012, India
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23
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Two-dimensional electronic transport and surface electron accumulation in MoS 2. Nat Commun 2018; 9:1442. [PMID: 29650960 PMCID: PMC5897365 DOI: 10.1038/s41467-018-03824-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2016] [Accepted: 03/15/2018] [Indexed: 12/02/2022] Open
Abstract
Because the surface-to-volume ratio of quasi-two-dimensional materials is extremely high, understanding their surface characteristics is crucial for practically controlling their intrinsic properties and fabricating p-type and n-type layered semiconductors. Van der Waals crystals are expected to have an inert surface because of the absence of dangling bonds. However, here we show that the surface of high-quality synthesized molybdenum disulfide (MoS2) is a major n-doping source. The surface electron concentration of MoS2 is nearly four orders of magnitude higher than that of its inner bulk. Substantial thickness-dependent conductivity in MoS2 nanoflakes was observed. The transfer length method suggested the current transport in MoS2 following a two-dimensional behavior rather than the conventional three-dimensional mode. Scanning tunneling microscopy and angle-resolved photoemission spectroscopy measurements confirmed the presence of surface electron accumulation in this layered material. Notably, the in situ-cleaved surface exhibited a nearly intrinsic state without electron accumulation. In absence of dangling bonds, van der Waals layered crystals are expected to have inert surfaces. In contrast, here the authors show presence of surface electron accumulation in MoS2, with a surface electron concentration nearly four orders of magnitude higher than that of MoS2 inner bulk.
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24
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Vines L, Bhoodoo C, von Wenckstern H, Grundmann M. Electrical conductivity of In 2O 3 and Ga 2O 3 after low temperature ion irradiation; implications for instrinsic defect formation and charge neutrality level. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:025502. [PMID: 29235447 DOI: 10.1088/1361-648x/aa9e2a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The evolution of sheet resistance of n-type In2O3 and Ga2O3 exposed to bombardment with MeV 12C and 28Si ions at 35 K is studied in situ. While the sheet resistance of Ga2O3 increased by more than eight orders of magnitude as a result of ion irradiation, In2O3 showed a more complex defect evolution and became more conductive when irradiated at the highest doses. Heating up to room temperature reduced the sheet resistivity somewhat, but Ga2O3 remained highly resistive, while In2O3 showed a lower resistance than as deposited samples. Thermal admittance spectroscopy and deep level transient spectroscopy did not reveal new defect levels for irradiation up to [Formula: see text] cm-2. A model where larger defect complexes preferentially produce donor like defects in In2O3 is proposed, and may reveal a microscopic view of a charge neutrality level within the conduction band, as previously proposed.
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Affiliation(s)
- L Vines
- Department of Physics/Centre for Materials Science and Nanotechnology, University of Oslo, PO Box 1048 Blindern, N-0316 Oslo, Norway
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25
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Wagner M, Lackner P, Seiler S, Brunsch A, Bliem R, Gerhold S, Wang Z, Osiecki J, Schulte K, Boatner LA, Schmid M, Meyer B, Diebold U. Resolving the Structure of a Well-Ordered Hydroxyl Overlayer on In 2O 3(111): Nanomanipulation and Theory. ACS NANO 2017; 11:11531-11541. [PMID: 29091395 PMCID: PMC5707633 DOI: 10.1021/acsnano.7b06387] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Changes in chemical and physical properties resulting from water adsorption play an important role in the characterization and performance of device-relevant materials. Studies of model oxides with well-characterized surfaces can provide detailed information that is vital for a general understanding of water-oxide interactions. In this work, we study single crystals of indium oxide, the prototypical transparent contact material that is heavily used in a wide range of applications and most prominently in optoelectronic technologies. Water adsorbs dissociatively already at temperatures as low as 100 K, as confirmed by scanning tunneling microscopy (STM), photoelectron spectroscopy, and density functional theory. This dissociation takes place on lattice sites of the defect-free surface. While the In2O3(111)-(1 × 1) surface offers four types of surface oxygen atoms (12 atoms per unit cell in total), water dissociation happens exclusively at one of them together with a neighboring pair of 5-fold coordinated In atoms. These O-In groups are symmetrically arranged around the 6-fold coordinated In atoms at the surface. At room temperature, the In2O3(111) surface thus saturates at three dissociated water molecules per unit cell, leading to a well-ordered hydroxylated surface with (1 × 1) symmetry, where the three water OWH groups plus the surface OSH groups are imaged together as one bright triangle in STM. Manipulations with the STM tip by means of voltage pulses preferentially remove the H atom of one surface OSH group per triangle. The change in contrast due to strong local band bending provides insights into the internal structure of these bright triangles. The experimental results are further confirmed by quantitative simulations of the STM image corrugation.
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Affiliation(s)
- Margareta Wagner
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
- E-mail:
| | - Peter Lackner
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
| | - Steffen Seiler
- Interdisciplinary
Center for Molecular Materials and Computer-Chemistry-Center, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nägelsbachstraße 25, 91052 Erlangen, Germany
| | - Achim Brunsch
- Interdisciplinary
Center for Molecular Materials and Computer-Chemistry-Center, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nägelsbachstraße 25, 91052 Erlangen, Germany
| | - Roland Bliem
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
| | - Stefan Gerhold
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
| | - Zhiming Wang
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
| | - Jacek Osiecki
- MAX
IV Laboratory, Lund University, Ole Römers väg 1, 223 63 Lund, Sweden
| | - Karina Schulte
- MAX
IV Laboratory, Lund University, Ole Römers väg 1, 223 63 Lund, Sweden
| | - Lynn A. Boatner
- Materials
Science and Technology Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Michael Schmid
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
| | - Bernd Meyer
- Interdisciplinary
Center for Molecular Materials and Computer-Chemistry-Center, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nägelsbachstraße 25, 91052 Erlangen, Germany
| | - Ulrike Diebold
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
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26
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Lord AM, Evans JE, Barnett CJ, Allen MW, Barron AR, Wilks SP. Surface sensitivity of four-probe STM resistivity measurements of bulk ZnO correlated to XPS. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:384001. [PMID: 28678024 DOI: 10.1088/1361-648x/aa7dc8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Multi-probe instruments based on scanning tunnelling microscopy (STM) are becoming increasingly common for their ability to perform nano- to atomic-scale investigations of nanostructures, surfaces and in situ reactions. A common configuration is the four-probe STM often coupled with in situ scanning electron microscopy (SEM) that allows precise positioning of the probes onto surfaces and nanostructures enabling electrical and scanning experiments to be performed on highly localised regions of the sample. In this paper, we assess the sensitivity of four-probe STM for in-line resistivity measurements of the bulk ZnO surface. The measurements allow comparisons to established models that are used to relate light plasma treatments (O and H) of the surfaces to the resistivity measurements. The results are correlated to x-ray photoelectron spectroscopy (XPS) and show that four-probe STM can detect changes in surface and bulk conduction mechanisms that are beyond conventional monochromatic XPS.
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Affiliation(s)
- Alex M Lord
- Centre for NanoHealth, College of Engineering, University of Swansea, Singleton Park, SA2 8PP, United Kingdom
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27
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Das A, Gautam SK, Shukla DK, Singh F. Correlations of charge neutrality level with electronic structure and p-d hybridization. Sci Rep 2017; 7:40843. [PMID: 28102312 PMCID: PMC5244377 DOI: 10.1038/srep40843] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 12/09/2016] [Indexed: 11/18/2022] Open
Abstract
The formation of charge neutrality level (CNL) in highly conducting Cadmium oxide (CdO) thin films is demonstarted by the observed variation in the band gap upon annealing and doping. It may be explained by the observation that Tin (Sn) doping breaks the perfect periodicity of CdO cubic crystal structure and creates virtual gap states (ViGS). The level of local CNL resides at the branch point of ViGS, making the energy at which native defect’s character changes from predominantly donor-like below CNL to predominantly acceptor-like above the CNL and a schematic band diagram is developed to substantiate the same. Further investigations using soft x-ray absorption spectroscopy (SXAS) at Oxygen and Cadmium edges show the reduction of Sn4+ to Sn2+. The analysis of the spectral features has revealed an evidence of p-d interaction between O 2p and Cd 4d orbitals that pushes the valence band minima at higher energies which is symmetry forbidden at г point and causing a positive valance band dispersion away from the zone centre in the г ~ L, K direction. Thus, origin of the CNL is attributed to the high density of the Oxygen vacancies as confirmed by the change in the local electronic structure and p-d hybridization of orbitals.
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Affiliation(s)
- Arkaprava Das
- Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Subodh K Gautam
- Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - D K Shukla
- UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452017, India
| | - Fouran Singh
- Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi-110067, India
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28
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McNeill AR, Hyndman AR, Reeves RJ, Downard AJ, Allen MW. Tuning the Band Bending and Controlling the Surface Reactivity at Polar and Nonpolar Surfaces of ZnO through Phosphonic Acid Binding. ACS APPLIED MATERIALS & INTERFACES 2016; 8:31392-31402. [PMID: 27768292 DOI: 10.1021/acsami.6b10309] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
ZnO is a prime candidate for future use in transparent electronics; however, development of practical materials requires attention to factors including control of its unusual surface band bending and surface reactivity. In this work, we have modified the O-polar (0001̅), Zn-polar (0001), and m-plane (101̅0) surfaces of ZnO with phosphonic acid (PA) derivatives and measured the effect on the surface band bending and surface sensitivity to atmospheric oxygen. Core level and valence band synchrotron X-ray photoemission spectroscopy was used to measure the surface band bending introduced by PA modifiers with substituents of opposite polarity dipole moment: octadecylphosphonic acid (ODPA) and 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctylphosphonic acid (F13OPA). Both PAs act as surface electron donors, increasing the downward band bending and the strength of the two-dimensional surface electron accumulation layer on all of the ZnO surfaces investigated. On the O-polar (0001̅) and m-plane (101̅0) surfaces, the ODPA modifier produced the largest increase in downward band bending relative to the hydroxyl-terminated unmodified surface of 0.55 and 0.35 eV, respectively. On the Zn-polar (0001) face, the F13OPA modifier gave the largest increase (by 0.50 eV) producing a total downward band bending of 1.00 eV, representing ∼30% of the ZnO band gap. Ultraviolet (UV) photoinduced surface wettability and photoconductivity measurements demonstrated that the PA modifiers are effective at decreasing the sensitivity of the surface toward atmospheric oxygen. Modification with PA derivatives produced a large increase in the persistence of UV-induced photoconductivity and a large reduction in UV-induced changes in surface wettability.
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Affiliation(s)
- Alexandra R McNeill
- MacDiarmid Institute for Advanced Materials and Nanotechnology , Wellington 6140, New Zealand
| | - Adam R Hyndman
- MacDiarmid Institute for Advanced Materials and Nanotechnology , Wellington 6140, New Zealand
| | - Roger J Reeves
- MacDiarmid Institute for Advanced Materials and Nanotechnology , Wellington 6140, New Zealand
| | - Alison J Downard
- MacDiarmid Institute for Advanced Materials and Nanotechnology , Wellington 6140, New Zealand
| | - Martin W Allen
- MacDiarmid Institute for Advanced Materials and Nanotechnology , Wellington 6140, New Zealand
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29
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Wagner M, Lackner P, Seiler S, Gerhold S, Osiecki J, Schulte K, Boatner LA, Schmid M, Meyer B, Diebold U. Well-Ordered In Adatoms at the In_{2}O_{3}(111) Surface Created by Fe Deposition. PHYSICAL REVIEW LETTERS 2016; 117:206101. [PMID: 27886498 DOI: 10.1103/physrevlett.117.206101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Indexed: 05/27/2023]
Abstract
Metal deposition on oxide surfaces usually results in adatoms, clusters, or islands of the deposited material, where defects in the surface often act as nucleation centers. Here an alternate configuration is reported. After the vapor deposition of Fe on the In_{2}O_{3}(111) surface at room temperature, ordered adatoms are observed with scanning tunneling microscopy. These are identical to the In adatoms that form when the sample is reduced by heating in ultrahigh vacuum. Density functional theory calculations confirm that Fe interchanges with In in the topmost layer, pushing the excess In atoms to the surface where they arrange as a well-ordered adatom array.
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Affiliation(s)
- Margareta Wagner
- Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
| | - Peter Lackner
- Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
| | - Steffen Seiler
- Interdisciplinary Center for Molecular Materials and Computer-Chemistry-Center, Friedrich-Alexander-University Erlangen-Nürnberg, Nägelsbachstraße 25, 91052 Erlangen, Germany
| | - Stefan Gerhold
- Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
| | - Jacek Osiecki
- MAX IV Laboratory, Lund University, Ole Römers väg 1, 223 63 Lund, Sweden
| | - Karina Schulte
- MAX IV Laboratory, Lund University, Ole Römers väg 1, 223 63 Lund, Sweden
| | - Lynn A Boatner
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Michael Schmid
- Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
| | - Bernd Meyer
- Interdisciplinary Center for Molecular Materials and Computer-Chemistry-Center, Friedrich-Alexander-University Erlangen-Nürnberg, Nägelsbachstraße 25, 91052 Erlangen, Germany
| | - Ulrike Diebold
- Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
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30
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Speckbacher M, Treu J, Whittles TJ, Linhart WM, Xu X, Saller K, Dhanak VR, Abstreiter G, Finley JJ, Veal TD, Koblmüller G. Direct Measurements of Fermi Level Pinning at the Surface of Intrinsically n-Type InGaAs Nanowires. NANO LETTERS 2016; 16:5135-42. [PMID: 27458736 DOI: 10.1021/acs.nanolett.6b02061] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Surface effects strongly dominate the intrinsic properties of semiconductor nanowires (NWs), an observation that is commonly attributed to the presence of surface states and their modification of the electronic band structure. Although the effects of the exposed, bare NW surface have been widely studied with respect to charge carrier transport and optical properties, the underlying electronic band structure, Fermi level pinning, and surface band bending profiles are not well explored. Here, we directly and quantitatively assess the Fermi level pinning at the surfaces of composition-tunable, intrinsically n-type InGaAs NWs, as one of the prominent, technologically most relevant NW systems, by using correlated photoluminescence (PL) and X-ray photoemission spectroscopy (XPS). From the PL spectral response, we reveal two dominant radiative recombination pathways, that is, direct near-band edge transitions and red-shifted, spatially indirect transitions induced by surface band bending. The separation of their relative transition energies changes with alloy composition by up to more than ∼40 meV and represent a direct measure for the amount of surface band bending. We further extract quantitatively the Fermi level to surface valence band maximum separation using XPS, and directly verify a composition-dependent transition from downward to upward band bending (surface electron accumulation to depletion) with increasing Ga-content x(Ga) at a crossover near x(Ga) ∼ 0.2. Core level spectra further demonstrate the nature of extrinsic surface states being caused by In-rich suboxides arising from the native oxide layer at the InGaAs NW surface.
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Affiliation(s)
- Maximilian Speckbacher
- Walter Schottky Institut, Physik Department, and Center of Nanotechnology and Nanomaterials, Technische Universität München , Am Coulombwall 4, Garching 85748, Germany
| | - Julian Treu
- Walter Schottky Institut, Physik Department, and Center of Nanotechnology and Nanomaterials, Technische Universität München , Am Coulombwall 4, Garching 85748, Germany
| | - Thomas J Whittles
- Stephenson Institute for Renewable Energy and Department of Physics, University of Liverpool , Liverpool L69 7ZF, United Kingdom
| | - Wojciech M Linhart
- Stephenson Institute for Renewable Energy and Department of Physics, University of Liverpool , Liverpool L69 7ZF, United Kingdom
| | - Xiaomo Xu
- Walter Schottky Institut, Physik Department, and Center of Nanotechnology and Nanomaterials, Technische Universität München , Am Coulombwall 4, Garching 85748, Germany
| | - Kai Saller
- Walter Schottky Institut, Physik Department, and Center of Nanotechnology and Nanomaterials, Technische Universität München , Am Coulombwall 4, Garching 85748, Germany
| | - Vinod R Dhanak
- Stephenson Institute for Renewable Energy and Department of Physics, University of Liverpool , Liverpool L69 7ZF, United Kingdom
| | - Gerhard Abstreiter
- Walter Schottky Institut, Physik Department, and Center of Nanotechnology and Nanomaterials, Technische Universität München , Am Coulombwall 4, Garching 85748, Germany
| | - Jonathan J Finley
- Walter Schottky Institut, Physik Department, and Center of Nanotechnology and Nanomaterials, Technische Universität München , Am Coulombwall 4, Garching 85748, Germany
| | - Tim D Veal
- Stephenson Institute for Renewable Energy and Department of Physics, University of Liverpool , Liverpool L69 7ZF, United Kingdom
| | - Gregor Koblmüller
- Walter Schottky Institut, Physik Department, and Center of Nanotechnology and Nanomaterials, Technische Universität München , Am Coulombwall 4, Garching 85748, Germany
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31
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Lim T, Han J, Seo K, Joo MK, Kim JS, Kim WY, Kim GT, Ju S. Fabrication of controllable and stable In₂O₃ nanowire transistors using an octadecylphosphonic acid self-assembled monolayer. NANOTECHNOLOGY 2015; 26:145203. [PMID: 25771996 DOI: 10.1088/0957-4484/26/14/145203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The controllability and stability of nanowire transistor characteristics are essential for the development of low-noise and fast-switching nano-electronic devices. In this study, the positive shift of threshold voltage and the improvement of interface quality on In2O3 nanowire transistors were simultaneously achieved by using octadecylphosphonic acid (OD-PA) self-assembly. Following the chemical bond of OD-PA molecules on the surface of In2O3 nanowires, the threshold voltage was positively shifted to 2.95 V, and the noise amplitude decreased to approximately 87.5%. The results suggest that an OD-PA self-assembled monolayer can be used to manipulate and stabilize the transistor characteristics of nanowire-based memory and display devices that require high-sensitivity, low-noise, and fast-response.
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Affiliation(s)
- Taekyung Lim
- Department of Physics, Kyonggi University, Suwon, Gyeonggi-Do 443-760, Korea
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32
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Dopant chemical potential modulation on oxygen vacancies formation in In2O3: A comparative density functional study. Chem Phys Lett 2015. [DOI: 10.1016/j.cplett.2015.01.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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33
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Liang D, Cabán-Acevedo M, Kaiser NS, Jin S. Gated Hall effect of nanoplate devices reveals surface-state-induced surface inversion in iron pyrite semiconductor. NANO LETTERS 2014; 14:6754-6760. [PMID: 25398133 DOI: 10.1021/nl501942w] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Understanding semiconductor surface states is critical for their applications, but fully characterizing surface electrical properties is challenging. Such a challenge is especially crippling for semiconducting iron pyrite (FeS2), whose potential for solar energy conversion has been suggested to be held back by rich surface states. Here, by taking advantage of the high surface-to-bulk ratio in nanostructures and effective electrolyte gating, we develop a general method to fully characterize both the surface inversion and bulk electrical transport properties for the first time through electrolyte-gated Hall measurements of pyrite nanoplate devices. Our study shows that pyrite is n-type in the bulk and p-type near the surface due to strong inversion and yields the concentrations and mobilities of both bulk electrons and surface holes. Further, solutions of the Poisson equation reveal a high-density of surface holes accumulated in a 1.3 nm thick strong inversion layer and an upward band bending of 0.9-1.0 eV. This work presents a general methodology for using transport measurements of nanostructures to study both bulk and surface transport properties of semiconductors. It also suggests that high-density of surface states are present on surface of pyrite, which partially explains the universal p-type conductivity and lack of photovoltage in polycrystalline pyrite.
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Affiliation(s)
- Dong Liang
- Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
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34
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Park DS, Vasheghani Farahani SK, Walker M, Mudd JJ, Wang H, Krupski A, Thorsteinsson EB, Seghier D, Choi CJ, Youn CJ, McConville CF. Recrystallization of highly-mismatched Be(x)Zn(1-x)O alloys: formation of a degenerate interface. ACS APPLIED MATERIALS & INTERFACES 2014; 6:18758-18768. [PMID: 25289707 DOI: 10.1021/am5043388] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We investigate the effect of thermally induced phase transformations on a metastable oxide alloy film, a multiphase Be(x)Zn(1-x)O (BZO), grown on Al2O3(0001) substrate for annealing temperatures in the range of 600-950 °C. A pronounced structural transition is shown together with strain relaxation and atomic redistribution in the annealed films. Increasing annealing temperature initiates out-diffusion and segregation of Be and subsequent nucleation of nanoparticles at the surface, corresponding to a monotonic decrease in the lattice phonon energies and band gap energy of the films. Infrared reflectance simulations identify a highly conductive ZnO interface layer (thicknesses in the range of ≈ 10-29 nm for annealing temperatures ≥ 800 °C). The highly degenerate interface layers with temperature-independent carrier concentration and mobility significantly influence the electronic and optical properties of the BZO films. A parallel conduction model is employed to determine the carrier concentration and conductivity of the bulk and interface regions. The density-of-states-averaged effective mass of the conduction electrons for the interfaces is calculated to be in the range of 0.31 m0 and 0.67 m0. A conductivity as high as 1.4 × 10(3) S · cm(-1) is attained, corresponding to the carrier concentration n(Int) = 2.16 × 10(20) cm(-3) at the interface layers, and comparable to the highest conductivities achieved in highly doped ZnO. The origin of such a nanoscale degenerate interface layer is attributed to the counter-diffusion of Be and Zn, rendering a high accumulation of Zn interstitials and a giant reduction of charge-compensating defects. These observations provide a broad understanding of the thermodynamics and phase transformations in Be(x)Zn(1-x)O alloys for the application of highly conductive and transparent oxide-based devices and fabrication of their alloy nanostructures.
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Affiliation(s)
- Dae-Sung Park
- Department of Physics, University of Warwick , Coventry CV4 7AL, United Kingdom
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35
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Luna E, Grandal J, Gallardo E, Calleja JM, Sánchez-García MÁ, Calleja E, Trampert A. Investigation of III-V nanowires by plan-view transmission electron microscopy: InN case study. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2014; 20:1471-1478. [PMID: 25156830 DOI: 10.1017/s1431927614013038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We discuss observations of InN nanowires (NWs) by plan-view high-resolution transmission electron microscopy (TEM). The main difficulties arise from suitable methods available for plan-view specimen preparation. We explore different approaches and find that the best results are obtained using a refined preparation method based on the conventional procedure for plan-view TEM of thin films, specifically modified for the NW morphology. The fundamental aspects of such a preparation are the initial mechanical stabilization of the NWs and the minimization of the ion-milling process after dimpling the samples until perforation. The combined analysis by plan-view and cross-sectional TEM of the NWs allows determination of the degree of strain relaxation and reveals the formation of an unintentional shell layer (2-3-nm thick) around the InN NWs. The shell layer is composed of bcc In2O3 nanocrystals with a preferred orientation with respect to the wurtzite InN: In2O3 [111] || InN [0001] and In2O3<110>||InN<1120>.
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Affiliation(s)
- Esperanza Luna
- 1Paul-Drude-Institut für Festkörperelektronik,Hausvogteiplatz 5-7,D-10117 Berlin,Germany
| | - Javier Grandal
- 1Paul-Drude-Institut für Festkörperelektronik,Hausvogteiplatz 5-7,D-10117 Berlin,Germany
| | - Eva Gallardo
- 1Paul-Drude-Institut für Festkörperelektronik,Hausvogteiplatz 5-7,D-10117 Berlin,Germany
| | - José M Calleja
- 2Departamento de Física de Materiales,Universidad Autónoma de Madrid,E-28049 Madrid,Spain
| | - Miguel Á Sánchez-García
- 3ISOM and Departamento Ingeniería Electrónica,ETSI Telecomunicación,Universidad Politécnica de Madrid,E-28040 Madrid,Spain
| | - Enrique Calleja
- 3ISOM and Departamento Ingeniería Electrónica,ETSI Telecomunicación,Universidad Politécnica de Madrid,E-28040 Madrid,Spain
| | - Achim Trampert
- 1Paul-Drude-Institut für Festkörperelektronik,Hausvogteiplatz 5-7,D-10117 Berlin,Germany
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36
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Lin JJ, Li ZQ. Electronic conduction properties of indium tin oxide: single-particle and many-body transport. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:343201. [PMID: 25105780 DOI: 10.1088/0953-8984/26/34/343201] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Indium tin oxide (Sn-doped In2O3-δ or ITO) is a very interesting and technologically important transparent conducting oxide. This class of material has been extensively investigated for decades, with research efforts mostly focusing on the application aspects. The fundamental issues of the electronic conduction properties of ITO from room temperature down to liquid-helium temperatures have rarely been addressed thus far. Studies of the electrical-transport properties over a wide range of temperature are essential to unravelling the underlying electronic dynamics and microscopic electronic parameters. In this topical review, we show that one can learn rich physics in ITO material, including the semi-classical Boltzmann transport, the quantum-interference electron transport, as well as the many-body Coulomb electron-electron interaction effects in the presence of disorder and inhomogeneity (granularity). To fully reveal the numerous avenues and unique opportunities that the ITO material has provided for fundamental condensed matter physics research, we demonstrate a variety of charge transport properties in different forms of ITO structures, including homogeneous polycrystalline thin and thick films, homogeneous single-crystalline nanowires and inhomogeneous ultrathin films. In this manner, we not only address new physics phenomena that can arise in ITO but also illustrate the versatility of the stable ITO material forms for potential technological applications. We emphasize that, microscopically, the novel and rich electronic conduction properties of ITO originate from the inherited robust free-electron-like energy bandstructure and low-carrier concentration (as compared with that in typical metals) characteristics of this class of material. Furthermore, a low carrier concentration leads to slow electron-phonon relaxation, which in turn causes the experimentally observed (i) a small residual resistance ratio, (ii) a linear electron diffusion thermoelectric power in a wide temperature range 1-300 K and (iii) a weak electron dephasing rate. We focus our discussion on the metallic-like ITO material.
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Affiliation(s)
- Juhn-Jong Lin
- NCTU-RIKEN Joint Research Laboratory, Institute of Physics and Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan
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37
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Park DS, Mudd JJ, Walker M, Krupski A, Seghier D, Saniee NF, Choi CJ, Youn CJ, McMitchell SRC, McConville CF. Pinning effect on the band gap modulation of crystalline BexZn1−xO alloy films grown on Al2O3(0001). CrystEngComm 2014. [DOI: 10.1039/c3ce42011f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Pinning effect on crystalline BexZn1−xO alloy films on Al2O3(0001).
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Affiliation(s)
- Dae-Sung Park
- Department of Physics
- University of Warwick
- Coventry CV4 7AL, UK
| | - James J. Mudd
- Department of Physics
- University of Warwick
- Coventry CV4 7AL, UK
| | - Marc Walker
- Department of Physics
- University of Warwick
- Coventry CV4 7AL, UK
| | | | | | | | - Chel-Jong Choi
- School of Semiconductor and Chemical Engineering
- Chonbuk National University
- Jeonju 561-756, South Korea
| | - Chang-Ju Youn
- School of Semiconductor and Chemical Engineering
- Chonbuk National University
- Jeonju 561-756, South Korea
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38
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Nashim A, Martha S, Parida KM. Gd2Ti2O7/In2O3: Efficient Visible-Light-Driven Heterojunction-Based Composite Photocatalysts for Hydrogen Production. ChemCatChem 2013. [DOI: 10.1002/cctc.201300037] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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39
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Zhang KHL, Egdell RG, Offi F, Iacobucci S, Petaccia L, Gorovikov S, King PDC. Microscopic origin of electron accumulation in In2O3. PHYSICAL REVIEW LETTERS 2013; 110:056803. [PMID: 23414041 DOI: 10.1103/physrevlett.110.056803] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Indexed: 06/01/2023]
Abstract
Angle-resolved photoemission spectroscopy reveals the presence of a two-dimensional electron gas at the surface of In(2)O(3)(111). Quantized subband states arise within a confining potential well associated with surface electron accumulation. Coupled Poisson-Schrödinger calculations suggest that downward band bending for the conduction band must be much bigger than band bending in the valence band. Surface oxygen vacancies acting as doubly ionized shallow donors are shown to provide the free electrons within this accumulation layer. Identification of the origin of electron accumulation in transparent conducting oxides has significant implications in the realization of devices based on these compounds.
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Affiliation(s)
- K H L Zhang
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR, United Kingdom
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40
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Prokscha T, Chow KH, Stilp E, Suter A, Luetkens H, Morenzoni E, Nieuwenhuys GJ, Salman Z, Scheuermann R. Photo-induced persistent inversion of germanium in a 200-nm-deep surface region. Sci Rep 2013; 3:2569. [PMID: 23995307 PMCID: PMC3759057 DOI: 10.1038/srep02569] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Accepted: 08/19/2013] [Indexed: 11/17/2022] Open
Abstract
The controlled manipulation of the charge carrier concentration in nanometer thin layers is the basis of current semiconductor technology and of fundamental importance for device applications. Here we show that it is possible to induce a persistent inversion from n- to p-type in a 200-nm-thick surface layer of a germanium wafer by illumination with white and blue light. We induce the inversion with a half-life of ~12 hours at a temperature of 220 K which disappears above 280 K. The photo-induced inversion is absent for a sample with a 20-nm-thick gold capping layer providing a Schottky barrier at the interface. This indicates that charge accumulation at the surface is essential to explain the observed inversion. The contactless change of carrier concentration is potentially interesting for device applications in opto-electronics where the gate electrode and gate oxide could be replaced by the semiconductor surface.
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Affiliation(s)
- T Prokscha
- Paul Scherrer Institute, Laboratory for Muon Spin Spectroscopy, Villigen PSI, Switzerland.
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41
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Bahramy M, King P, de la Torre A, Chang J, Shi M, Patthey L, Balakrishnan G, Hofmann P, Arita R, Nagaosa N, Baumberger F. Emergent quantum confinement at topological insulator surfaces. Nat Commun 2012; 3:1159. [DOI: 10.1038/ncomms2162] [Citation(s) in RCA: 211] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Accepted: 09/25/2012] [Indexed: 11/09/2022] Open
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Kim S, Carpenter PD, Jean RK, Chen H, Zhou C, Ju S, Janes DB. Role of self-assembled monolayer passivation in electrical transport properties and flicker noise of nanowire transistors. ACS NANO 2012; 6:7352-7361. [PMID: 22775468 DOI: 10.1021/nn302484c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Semiconductor nanowires have achieved great attention for integration in next-generation electronics. However, for nanowires with diameters comparable to the Debye length, which would generally be required for one-dimensional operation, surface states degrade the device performance and increase the low-frequency noise. In this study, single In(2)O(3) nanowire transistors were fabricated and characterized before and after surface passivation with a self-assembled monolayer of 1-octadecanethiol (ODT). Electrical characterization of the transistors shows that device performance can be enhanced upon ODT passivation, exhibiting steep subthreshold slope (~64 mV/dec), near zero threshold voltage (~0.6 V), high mobility (~624 cm(2)/V·s), and high on-currents (~40 μA). X-ray photoelectron spectroscopy studies of the ODT-passivated nanowires indicate that the molecules are bound to In(2)O(3) nanowires through the thiol linkages. Device simulations using a rectangular geometry to represent the nanowire indicate that the improvement in subthreshold slope and positive shift in threshold voltage can be explained in terms of reduced interface trap density and changes in fixed charge density. Flicker (low-frequency, 1/f) noise measurements show that the noise amplitude is reduced following passivation. The interface trap density before and after ODT passivation is profiled throughout the band gap energy using the subthreshold current-voltage characteristics and is compared to the values extracted from the low-frequency noise measurements. The results indicate that self-assembled monolayer passivation is a promising optimization technology for the realization of low-power, low-noise, and fast-switching applications such as logic, memory, and display circuitry.
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Affiliation(s)
- Seongmin Kim
- School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
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43
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Zhao S, Fathololoumi S, Bevan KH, Liu DP, Kibria MG, Li Q, Wang GT, Guo H, Mi Z. Tuning the surface charge properties of epitaxial InN nanowires. NANO LETTERS 2012; 12:2877-2882. [PMID: 22545811 DOI: 10.1021/nl300476d] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We have investigated the correlated surface electronic and optical properties of [0001]-oriented epitaxial InN nanowires grown directly on silicon. By dramatically improving the epitaxial growth process, we have achieved, for the first time, intrinsic InN both within the bulk and at nonpolar InN surfaces. The near-surface Fermi-level was measured to be ∼0.55 eV above the valence band maximum for undoped InN nanowires, suggesting the absence of surface electron accumulation and Fermi-level pinning. This result is in direct contrast to the problematic degenerate two-dimensional electron gas universally observed on grown surfaces of n-type degenerate InN. We have further demonstrated that the surface charge properties of InN nanowires, including the formation of two-dimensional electron gas and the optical emission characteristics can be precisely tuned through controlled n-type doping. At relatively high doping levels in this study, the near-surface Fermi-level was found to be pinned at ∼0.95-1.3 eV above the valence band maximum. Through these trends, well captured by the effective mass and ab initio materials modeling, we have unambiguously identified the definitive role of surface doping in tuning the surface charge properties of InN.
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Affiliation(s)
- S Zhao
- Department of Electrical and Computer Engineering, McGill University, 3480 University Street, Montreal, QC, H3A 2A7, Canada
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44
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King PDC, He RH, Eknapakul T, Buaphet P, Mo SK, Kaneko Y, Harashima S, Hikita Y, Bahramy MS, Bell C, Hussain Z, Tokura Y, Shen ZX, Hwang HY, Baumberger F, Meevasana W. Subband structure of a two-dimensional electron gas formed at the polar surface of the strong spin-orbit perovskite KTaO3. PHYSICAL REVIEW LETTERS 2012; 108:117602. [PMID: 22540511 DOI: 10.1103/physrevlett.108.117602] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Indexed: 05/31/2023]
Abstract
We demonstrate the formation of a two-dimensional electron gas (2DEG) at the (100) surface of the 5d transition-metal oxide KTaO3. From angle-resolved photoemission, we find that quantum confinement lifts the orbital degeneracy of the bulk band structure and leads to a 2DEG composed of ladders of subband states of both light and heavy carriers. Despite the strong spin-orbit coupling, our measurements provide a direct upper bound for the potential Rashba spin splitting of only Δk(parallel)}~0.02 Å(-1) at the Fermi level. The polar nature of the KTaO3(100) surface appears to help mediate the formation of the 2DEG as compared to nonpolar SrTiO3(100).
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Affiliation(s)
- P D C King
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife, United Kingdom
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45
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Shi K, Li DB, Song HP, Guo Y, Wang J, Xu XQ, Liu JM, Yang AL, Wei HY, Zhang B, Yang SY, Liu XL, Zhu QS, Wang ZG. Determination of InN/Diamond Heterojunction Band Offset by X-ray Photoelectron Spectroscopy. NANOSCALE RESEARCH LETTERS 2011; 6:50. [PMID: 27502672 PMCID: PMC3212014 DOI: 10.1007/s11671-010-9796-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Accepted: 09/10/2010] [Indexed: 05/30/2023]
Abstract
Diamond is not only a free standing highly transparent window but also a promising carrier confinement layer for InN based devices, yet little is known of the band offsets in InN/diamond system. X-ray photoelectron spectroscopy was used to measure the energy discontinuity in the valence band offset (VBO) of InN/diamond heterostructure. The value of VBO was determined to be 0.39 ± 0.08 eV and a type-I heterojunction with a conduction band offset (CBO) of 4.42 ± 0.08 eV was obtained. The accurate determination of VBO and CBO is important for the application of III-N alloys based electronic devices.
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Affiliation(s)
- K Shi
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, 100083, Beijing, People's Republic of China.
| | - D B Li
- Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16 Dong Nan Hu Road, 130033, Changchun, People's Republic of China.
| | - H P Song
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, 100083, Beijing, People's Republic of China
| | - Y Guo
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, 100083, Beijing, People's Republic of China
| | - J Wang
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, 100083, Beijing, People's Republic of China
| | - X Q Xu
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, 100083, Beijing, People's Republic of China
| | - J M Liu
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, 100083, Beijing, People's Republic of China
| | - A L Yang
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, 100083, Beijing, People's Republic of China
| | - H Y Wei
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, 100083, Beijing, People's Republic of China
| | - B Zhang
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, 100083, Beijing, People's Republic of China
| | - S Y Yang
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, 100083, Beijing, People's Republic of China
| | - X L Liu
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, 100083, Beijing, People's Republic of China.
| | - Q S Zhu
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, 100083, Beijing, People's Republic of China
| | - Z G Wang
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, 100083, Beijing, People's Republic of China
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46
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Burbano M, Scanlon DO, Watson GW. Sources of Conductivity and Doping Limits in CdO from Hybrid Density Functional Theory. J Am Chem Soc 2011; 133:15065-72. [DOI: 10.1021/ja204639y] [Citation(s) in RCA: 154] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mario Burbano
- School of Chemistry and CRANN, Trinity College Dublin, Dublin 2, Ireland
| | - David O. Scanlon
- School of Chemistry and CRANN, Trinity College Dublin, Dublin 2, Ireland
| | - Graeme W. Watson
- School of Chemistry and CRANN, Trinity College Dublin, Dublin 2, Ireland
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47
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De Vico L, Iversen L, Sørensen MH, Brandbyge M, Nygård J, Martinez KL, Jensen JH. Predicting and rationalizing the effect of surface charge distribution and orientation on nano-wire based FET bio-sensors. NANOSCALE 2011; 3:3635-3640. [PMID: 21811738 DOI: 10.1039/c1nr10316d] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A single charge screening model of surface charge sensors in liquids (De Vico et al., Nanoscale, 2011, 3, 706-717) is extended to multiple charges to model the effect of the charge distributions of analyte proteins on FET sensor response. With this model we show that counter-intuitive signal changes (e.g. a positive signal change due to a net positive protein binding to a p-type conductor) can occur for certain combinations of charge distributions and Debye lengths. The new method is applied to interpret published experimental data on Streptavidin (Ishikawa et al., ACS Nano, 2009, 3, 3969-3976) and Nucleocapsid protein (Ishikawa et al., ACS Nano, 2009, 3, 1219-1224).
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Affiliation(s)
- Luca De Vico
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100, Copenhagen, Denmark.
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48
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King PDC, Hatch RC, Bianchi M, Ovsyannikov R, Lupulescu C, Landolt G, Slomski B, Dil JH, Guan D, Mi JL, Rienks EDL, Fink J, Lindblad A, Svensson S, Bao S, Balakrishnan G, Iversen BB, Osterwalder J, Eberhardt W, Baumberger F, Hofmann P. Large tunable Rashba spin splitting of a two-dimensional electron gas in Bi2Se3. PHYSICAL REVIEW LETTERS 2011; 107:096802. [PMID: 21929260 DOI: 10.1103/physrevlett.107.096802] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Indexed: 05/13/2023]
Abstract
We report a Rashba spin splitting of a two-dimensional electron gas in the topological insulator Bi(2)Se(3) from angle-resolved photoemission spectroscopy. We further demonstrate its electrostatic control, and show that spin splittings can be achieved which are at least an order-of-magnitude larger than in other semiconductors. Together these results show promise for the miniaturization of spintronic devices to the nanoscale and their operation at room temperature.
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Affiliation(s)
- P D C King
- School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, United Kingdom
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49
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Walsh A, Da Silva JLF, Wei SH. Multi-component transparent conducting oxides: progress in materials modelling. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:334210. [PMID: 21813942 DOI: 10.1088/0953-8984/23/33/334210] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Transparent conducting oxides (TCOs) play an essential role in modern optoelectronic devices through their combination of electrical conductivity and optical transparency. We review recent progress in our understanding of multi-component TCOs formed from solid solutions of ZnO, In(2)O(3), Ga(2)O(3) and Al(2)O(3), with a particular emphasis on the contributions of materials modelling, primarily based on density functional theory. In particular, we highlight three major results from our work: (i) the fundamental principles governing the crystal structures of multi-component oxide structures including (In(2)O(3))(ZnO)(n) and (In(2)O(3))(m)(Ga(2)O(3))(l)(ZnO)(n); (ii) the relationship between elemental composition and optical and electrical behaviour, including valence band alignments; (iii) the high performance of amorphous oxide semiconductors. On the basis of these advances, the challenge of the rational design of novel electroceramic materials is discussed.
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Affiliation(s)
- Aron Walsh
- Kathleen Lonsdale Materials Chemistry, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK
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50
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Zhang KHL, Lazarov VK, Veal TD, Oropeza FE, McConville CF, Egdell RG, Walsh A. Thickness dependence of the strain, band gap and transport properties of epitaxial In2O3 thin films grown on Y-stabilised ZrO2(111). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:334211. [PMID: 21813945 DOI: 10.1088/0953-8984/23/33/334211] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Epitaxial films of In(2)O(3) have been grown on Y-stabilised ZrO(2)(111) substrates by molecular beam epitaxy over a range of thicknesses between 35 and 420 nm. The thinnest films are strained, but display a 'cross-hatch' morphology associated with a network of misfit dislocations which allow partial accommodation of the lattice mismatch. With increasing thickness a 'dewetting' process occurs and the films break up into micron sized mesas, which coalesce into continuous films at the highest coverages. The changes in morphology are accompanied by a progressive release of strain and an increase in carrier mobility to a maximum value of 73 cm(2) V(-1) s(-1). The optical band gap in strained ultrathin films is found to be smaller than for thicker films. Modelling of the system, using a combination of classical pair-wise potentials and ab initio density functional theory, provides a microscopic description of the elastic contributions to the strained epitaxial growth, as well as the electronic effects that give rise to the observed band gap changes. The band gap increase induced by the uniaxial compression is offset by the band gap reduction associated with the epitaxial tensile strain.
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Affiliation(s)
- K H L Zhang
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK
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