1
|
Gutiérrez Y, Dicorato S, Dilonardo E, Palumbo F, Giangregorio MM, Losurdo M. Stability of Nanometer-Thick Layered Gallium Chalcogenides and Improvements via Hydrogen Passivation. ACS APPLIED NANO MATERIALS 2023; 6:20161-20172. [PMID: 37969785 PMCID: PMC10644295 DOI: 10.1021/acsanm.3c03899] [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: 08/23/2023] [Revised: 10/06/2023] [Accepted: 10/06/2023] [Indexed: 11/17/2023]
Abstract
The gallium monochalcogenides family, comprising gallium sulfide (GaS), gallium selenide (GaSe), and gallium telluride (GaTe), is capturing attention for its applications in energy storage and production, catalysis, photonics, and optoelectronics. This interest originates from their properties, which include an optical bandgap larger than those of most common transition metal dichalcogenides, efficient light absorption, and significant carrier mobility. For any application, stability to air exposure is a fundamental requirement. Here, we perform a comparative study of the stability of layered GaS, GaSe, and GaTe nanometer-thick films down to a few layers with the goal of identifying the most suitable Ga chalcogenide for future integration in photonic and optoelectronic devices. Our study unveils a trend of decreasing air stability from sulfide to selenide and finally to telluride. Furthermore, we demonstrate a hydrogen passivation process to prevent the oxidation of GaSe with a higher feasibility and durability than other state-of-the-art passivation methods proposed in the literature.
Collapse
Affiliation(s)
- Yael Gutiérrez
- Istituto
di Chimica della Materia Condensata e delle Tecnologie per l’Energia,
ICMATE, CNR, C.so Stati
Uniti 4, 35127 Padova, Italy
- Physics
Department, University of Oviedo, 33007 Oviedo, Spain
| | - Stefano Dicorato
- Institute
of Nanotechnology, CNR-NANOTEC, via Orabona 4, 70126 Bari, Italy
| | - Elena Dilonardo
- Institute
of Nanotechnology, CNR-NANOTEC, via Orabona 4, 70126 Bari, Italy
| | - Fabio Palumbo
- Institute
of Nanotechnology, CNR-NANOTEC, via Orabona 4, 70126 Bari, Italy
| | | | - Maria Losurdo
- Istituto
di Chimica della Materia Condensata e delle Tecnologie per l’Energia,
ICMATE, CNR, C.so Stati
Uniti 4, 35127 Padova, Italy
| |
Collapse
|
2
|
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.
Collapse
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
| |
Collapse
|
3
|
Heymann L, Weber ML, Wohlgemuth M, Risch M, Dittmann R, Baeumer C, Gunkel F. Separating the Effects of Band Bending and Covalency in Hybrid Perovskite Oxide Electrocatalyst Bilayers for Water Electrolysis. ACS APPLIED MATERIALS & INTERFACES 2022; 14:14129-14136. [PMID: 35293734 PMCID: PMC8972245 DOI: 10.1021/acsami.1c20337] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 03/02/2022] [Indexed: 06/14/2023]
Abstract
The Co-O covalency in perovskite oxide cobaltites such as La1-xSrxCoO3 is believed to impact the electrocatalytic activity during electrochemical water splitting at the anode where the oxygen evolution reaction (OER) takes place. Additionally, space charge layers through band bending at the interface to the electrolyte may affect the electron transfer into the electrode, complicating the analysis and identification of true OER activity descriptors. Here, we separate the influence of covalency and band bending in hybrid epitaxial bilayer structures of highly OER-active La0.6Sr0.4CoO3 and undoped and less-active LaCoO3. Ultrathin LaCoO3 capping layers of 2-8 unit cells on La0.6Sr0.4CoO3 show intermediate OER activity between La0.6Sr0.4CoO3 and LaCoO3 evidently caused by the increased surface Co-O covalency compared to single LaCoO3 as detected by X-ray photoelectron spectroscopy. A Mott-Schottkyanalysis revealed low flat band potentials for different LaCoO3 capping layer thicknesses, indicating that no limiting extended space charge layer exists under OER conditions as all catalyst bilayer films exhibited hole accumulation at the surface. The combined X-ray photoelectron spectroscopy and Mott-Schottky analysis thus enables us to differentiate between the influence of the covalency and intrinsic space charge layers, which are indistinguishable in a single physical or electrochemical characterization. Our results emphasize the prominent role of transition metal oxygen covalency in perovskite electrocatalysts and introduce a bilayer approach to fine-tune the surface electronic structure.
Collapse
Affiliation(s)
- Lisa Heymann
- Peter
Gruenberg Institute 7, Forschungszentrum
Juelich GmbH, 52425 Juelich, Germany
- JARA-FIT, RWTH Aachen University, 52056 Aachen, Germany
| | - Moritz L. Weber
- Peter
Gruenberg Institute 7, Forschungszentrum
Juelich GmbH, 52425 Juelich, Germany
- JARA-FIT, RWTH Aachen University, 52056 Aachen, Germany
| | - Marcus Wohlgemuth
- Peter
Gruenberg Institute 7, Forschungszentrum
Juelich GmbH, 52425 Juelich, Germany
- JARA-FIT, RWTH Aachen University, 52056 Aachen, Germany
| | - Marcel Risch
- Nachwuchsgruppe
Gestaltung des Sauerstoffentwicklungsmechanismus, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 14109 Berlin, Germany
| | - Regina Dittmann
- Peter
Gruenberg Institute 7, Forschungszentrum
Juelich GmbH, 52425 Juelich, Germany
- JARA-FIT, RWTH Aachen University, 52056 Aachen, Germany
| | - Christoph Baeumer
- Peter
Gruenberg Institute 7, Forschungszentrum
Juelich GmbH, 52425 Juelich, Germany
- JARA-FIT, RWTH Aachen University, 52056 Aachen, Germany
- MESA+
Institute for Nanotechnology, Faculty of Science and Technology, University of Twente, 7522 NB Enschede, Netherlands
| | - Felix Gunkel
- Peter
Gruenberg Institute 7, Forschungszentrum
Juelich GmbH, 52425 Juelich, Germany
- JARA-FIT, RWTH Aachen University, 52056 Aachen, Germany
| |
Collapse
|
4
|
Kim J, Kendall O, Ren J, Murdoch BJ, McConville CF, van Embden J, Della Gaspera E. Highly Conductive and Visibly Transparent p-Type CuCrO 2 Films by Ultrasonic Spray Pyrolysis. ACS APPLIED MATERIALS & INTERFACES 2022; 14:11768-11778. [PMID: 35213125 DOI: 10.1021/acsami.1c24023] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The development of high-performing p-type transparent conducting oxides will enable immense progress in the fabrication of optoelectronic devices including invisible electronics and all-oxide power electronics. While n-type transparent electrodes have already reached widespread industrial production, the lack of p-type counterparts with comparable transparency and conductivity has created a bottleneck for the development of next-generation optoelectronic devices. In this work, we present the fabrication of delafossite copper chromium oxide p-type transparent electrodes with outstanding optical and electrical properties. These layers were deposited using ultrasonic spray pyrolysis, a wet chemical method that is fast, simple, and scalable. Through careful screening of the deposition conditions, highly crystalline, dense, and smooth CuCrO2 coatings were obtained. A detailed investigation of the role played by the deposition temperature and the cation ratio enabled the properties of the prepared layers to be reliably tuned, as verified using X-ray diffraction, X-ray photoelectron spectroscopy, optical spectroscopy, Hall effect measurements, and electron and atomic force microscopies. We demonstrate record conductivities for solution-processed CuCrO2, exceeding 100 S cm-1, and we also obtained the highest value for two separate figures of merit for p-type transparent conducting oxides. These performances position solution-deposited CuCrO2 as the leading p-type transparent-conducting oxide currently available.
Collapse
Affiliation(s)
- Jaewon Kim
- School of Science, RMIT University, Melbourne VIC 3001, Australia
| | - Owen Kendall
- School of Science, RMIT University, Melbourne VIC 3001, Australia
| | - Jiawen Ren
- School of Science, RMIT University, Melbourne VIC 3001, Australia
| | - Billy J Murdoch
- RMIT Microscopy and Microanalysis Facility, College of Science, Engineering and Health, RMIT University, Melbourne, VIC 3000, Australia
| | | | - Joel van Embden
- School of Science, RMIT University, Melbourne VIC 3001, Australia
| | | |
Collapse
|
5
|
Opto-Electronic Characterization of Photocatalysts Based on p,n-Junction Ternary and Quaternary Mixed Oxides Semiconductors (Cu2O-In2O3 and Cu2O-In2O3-TiO2). Catalysts 2022. [DOI: 10.3390/catal12020153] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Semiconductor materials are the basis of electronic devices employed in the communication and media industry. In the present work, we report the synthesis and characterization of mixed metal oxides (MOs) as p,n-junction photocatalysts, and demonstrate the correlation between the preparation technique and the properties of the materials. Solid-state UV-visible diffuse reflectance spectroscopy (UV-VIS DRS) allowed for the determination of the light absorption properties and the optical energy gap. X-ray photoelectron spectroscopy (XPS) allowed for the determination of the surface speciation and composition and for the determination of the valence band edge. The opto-electronic behavior was evaluated measuring the photocurrent generated after absorption of chopped visible light in a 3-electrode cell. Scanning electron microscopy (SEM) measurements allowed for auxiliary characterization of size and morphology, showing the formation of composites for the ternary Cu2O-In2O3 p,n-mixed oxide, and even more for the quaternary Cu2O-In2O3-TiO2 MO. Light absorption spectra and photocurrent-time curves mainly depend upon the composition of MOs, while the optical energy gap and defective absorption tail are closely related to the preparation methodology, time and thermal treatment. Qualitative electronic band structures of semiconductors are also presented.
Collapse
|
6
|
Janowitz C, Mahmoodinezhad A, Kot M, Morales C, Naumann F, Plate P, Zoellner MH, Bärwolf F, Stolarek D, Wenger C, Henkel K, Flege JI. Toward controlling the Al 2O 3/ZnO interface properties by in situ ALD preparation. Dalton Trans 2022; 51:9291-9301. [DOI: 10.1039/d1dt04008a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The electronic band alignment of an alumina/zinc oxide thin-film heterostructure solely grown by atomic layer deposition has been determined by XPS/UPS depth profiling, correlating the electronic properties with the interface chemical composition.
Collapse
Affiliation(s)
- Christoph Janowitz
- Applied Physics and Semiconductor Spectroscopy, Brandenburg University of Technology Cottbus–Senftenberg, K.-Zuse-Str. 1, 03046 Cottbus, Germany
| | - Ali Mahmoodinezhad
- Applied Physics and Semiconductor Spectroscopy, Brandenburg University of Technology Cottbus–Senftenberg, K.-Zuse-Str. 1, 03046 Cottbus, Germany
| | - Małgorzata Kot
- Applied Physics and Semiconductor Spectroscopy, Brandenburg University of Technology Cottbus–Senftenberg, K.-Zuse-Str. 1, 03046 Cottbus, Germany
| | - Carlos Morales
- Applied Physics and Semiconductor Spectroscopy, Brandenburg University of Technology Cottbus–Senftenberg, K.-Zuse-Str. 1, 03046 Cottbus, Germany
| | - Franziska Naumann
- SENTECH Instruments GmbH, Schwarzschildstraße 2, 12489 Berlin, Germany
| | - Paul Plate
- SENTECH Instruments GmbH, Schwarzschildstraße 2, 12489 Berlin, Germany
| | - Marvin Hartwig Zoellner
- IHP – Leibniz-Institut für innovative Mikroelektronik, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - Florian Bärwolf
- IHP – Leibniz-Institut für innovative Mikroelektronik, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - David Stolarek
- IHP – Leibniz-Institut für innovative Mikroelektronik, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - Christian Wenger
- IHP – Leibniz-Institut für innovative Mikroelektronik, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
| | - Karsten Henkel
- Applied Physics and Semiconductor Spectroscopy, Brandenburg University of Technology Cottbus–Senftenberg, K.-Zuse-Str. 1, 03046 Cottbus, Germany
| | - Jan Ingo Flege
- Applied Physics and Semiconductor Spectroscopy, Brandenburg University of Technology Cottbus–Senftenberg, K.-Zuse-Str. 1, 03046 Cottbus, Germany
| |
Collapse
|
7
|
Fernández-Catalá J, Navlani-García M, Berenguer-Murcia Á, Cazorla-Amorós D. Exploring CuxO-doped TiO2 modified with carbon nanotubes for CO2 photoreduction in a 2D-flow reactor. J CO2 UTIL 2021. [DOI: 10.1016/j.jcou.2021.101796] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
8
|
Olivieri G, Kladnik G, Cvetko D, Brown MA. Determination of the valence band edge of Fe oxide nanoparticles dispersed in aqueous solution through resonant photoelectron spectroscopy from a liquid microjet. NANOSCALE ADVANCES 2021; 3:4513-4518. [PMID: 36133461 PMCID: PMC9419094 DOI: 10.1039/d1na00275a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 05/30/2021] [Indexed: 06/01/2023]
Abstract
We use X-ray photoemission and a near ambient pressure with a liquid microjet setup to investigate the electronic structure of FeOOH nanoparticles dispersed in aqueous solution. In particular, we show that by using X-ray resonant photoemission in dilute solutions, we can overcome the limits of conventional photoemission such as low nanoparticle-to-solvent signal ratio, and local nanoparticle charging and measure the valence band structure of FeOOH nanoparticles in aqueous solution with chemical specificity. The resonant photoemission signal across the Fe 2p3/2 absorption edge is measured for 2 wt% aqueous solutions of FeOOH nanoparticles (NPs) and the valence band maximum (VBM) of the hydrated FeOOH nanoparticles is determined. We compare the obtained VBM value in aqueous solution to that of FeOOH NPs in the dry phase. We show that the valence band edge position of NPs in the liquid phase can be accurately predicted from the values obtained in the dry phase provided that a simple potential shift due to solution chemistry is applied. Our results demonstrate the suitability of resonant photoemission in measuring the electronic structure of strongly diluted nanosystems where the conventional non-resonant photoemission technique fails.
Collapse
Affiliation(s)
- Giorgia Olivieri
- Laboratory for Surface Science and Technology, Department of Materials ETH Zürich, Vladimir-Prelog-Weg 5 CH-8093 Zürich Switzerland
| | - Gregor Kladnik
- Faculty for Mathematics and Physics, University of Ljubljana Jadranska 19 Ljubljana SI-1000 Slovenia
- IOM-CNR, Laboratorio TASC Basovizza SS-14, km 163.5 Trieste 34149 Italy
| | - Dean Cvetko
- Faculty for Mathematics and Physics, University of Ljubljana Jadranska 19 Ljubljana SI-1000 Slovenia
- IOM-CNR, Laboratorio TASC Basovizza SS-14, km 163.5 Trieste 34149 Italy
- Jožef Stefan Institute Jamova 39 Ljubljana SI-1000 Slovenia
| | - Matthew A Brown
- Laboratory for Surface Science and Technology, Department of Materials ETH Zürich, Vladimir-Prelog-Weg 5 CH-8093 Zürich Switzerland
- Metrology Research Centre, National Research Council of Canada Ottawa Ontario Canada
| |
Collapse
|
9
|
Goel N, Kumar R, Kumar M. Visualization of band offsets at few-layer MoS 2/Ge heterojunction. NANOTECHNOLOGY 2021; 32:375711. [PMID: 34102621 DOI: 10.1088/1361-6528/ac0932] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 06/08/2021] [Indexed: 06/12/2023]
Abstract
The visualization of band alignment for designing heterostructures between transition metal dichalcogenides and germanium plays a vital role in a deeper understanding of carrier dynamics at the heterointerface. Here, to study the band alignment across the MoS2/Ge heterojunction, we have deposited a wafer-scale highly crystalline few atomic layers MoS2film via a highly controllable and scalable sputtering technique coupled with a post sulfurization process in a sulfur-rich environment. The Raman and XRD spectra of as-fabricated MoS2/Ge heterojunction expose the presence of highly crystalline few atomic layer MoS2on top of Ge substrate. Interestingly, we found a type-II band alignment at the MoS2/Ge heterointerface having valence band, and conduction band offset values of 0.88 and 0.21 eV, which can provide very efficient recombination through spatially confining charge carriers. The calculation of band offset parameters offers a promising way for device engineering across the MoS2/Ge heterojunction interface. Moreover, to demonstrate the practicability of the fabricated heterostructure, we explored the suitability of our device for broadband photodetection applications.
Collapse
Affiliation(s)
- Neeraj Goel
- Department of Electrical Engineering, Indian Institute of Technology Jodhpur, Jodhpur 342011, India
- Department of Electrical Engineering, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Rahul Kumar
- Department of Electrical Engineering, Indian Institute of Technology Jodhpur, Jodhpur 342011, India
- Centre for Nanoscience and Engineering, Indian Institute of Science, Bangalore 560012, India
| | - Mahesh Kumar
- Department of Electrical Engineering, Indian Institute of Technology Jodhpur, Jodhpur 342011, India
| |
Collapse
|
10
|
Zhang L, Jiang J, Cai Y, Yao S, Azhar B, Chen Z, Hu Y, Pendse S, Guo Y, Jia R, Tian Z, Sun C, Liao P, Shi J. Doping-Enabled Reconfigurable Strongly Correlated Phase in a Quasi-2D Perovskite. J Phys Chem Lett 2021; 12:5091-5098. [PMID: 34028281 DOI: 10.1021/acs.jpclett.1c00353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Highlighted by the discovery of high-temperature superconductivity, strongly correlated oxides with highly distorted perovskite structures serve as intriguing model systems for pursuing emerging materials physics and testing technological concepts. While 3d correlated oxides with a distorted perovskite structure are not uncommon, their 4d counterparts are unfortunately rare. In this work, we report the tuning of the electrical and optical properties of a quasi-2D perovskite niobate CsBiNb2O7 via hydrogenation. It is observed that hydrogenation induces drastic changes of lattice dynamics, optical transmission, and conductance. It is suggested that changing the orbital occupancy of Nb d orbitals could trigger the on-site Coulomb interaction in the NbO6 octahedron. The observed hydrogen doping-induced electrical plasticity is implemented for simulating neural synaptic activity. Our finding sheds light on the role of hydrogen in 4d transition metal oxides and suggests a new avenue for the design and development of novel electronic phases.
Collapse
Affiliation(s)
- Lifu Zhang
- Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Jie Jiang
- Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Yao Cai
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, PR China
| | - Shukai Yao
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Bilal Azhar
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14850, United States
| | - Zhizhong Chen
- Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Yang Hu
- Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Saloni Pendse
- Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Yuwei Guo
- Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Ru Jia
- Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Zhiting Tian
- Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York 14850, United States
| | - Chengliang Sun
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, PR China
| | - Peilin Liao
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Jian Shi
- Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| |
Collapse
|
11
|
McNeill AR, Martinez-Gazoni R, Reeves RJ, Allen MW, Downard AJ. Electroreduction of Aryldiazonium Ion at the Polar and Non-Polar Faces of ZnO: Characterisation of the Grafted Films and Their Influence on Near-Surface Band Bending. Chemphyschem 2021; 22:1344-1351. [PMID: 33942472 DOI: 10.1002/cphc.202100240] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 05/02/2021] [Indexed: 01/02/2023]
Abstract
ZnO is a strong candidate for transparent electronic devices due to its wide band gap and earth-abundance, yet its practical use is limited by its surface metallicity arising from a surface electron accumulation layer (SEAL). The SEAL forms by hydroxylation of the surface under normal atmospheric conditions, and is present at all crystal faces of ZnO, although with differing hydroxyl structures. Multilayer aryl films grafted from aryldiazonium salts have previously been shown to decrease the downward bending at O-polar ZnO thin films, with Zn-O-C bonds anchoring the aryl films to the substrate. Herein we show that the Zn-polar (0001), O-polar (000 1 ‾ ), and non-polar m-plane (10 1 ‾ 0) faces of ZnO single crystals, can also be successfully electrografted with nitrophenyl (NP) films. In all cases, X-ray photoelectron spectroscopy (XPS) measurements reveal that the downward surface band bending decreases after modification. XPS provides strong evidence for Zn-O-C bonding at each face. Electrochemical reduction of NP films on O-polar ZnO single crystals converts the film to a mainly aminophenyl layer, although with negligible further change in band bending. This contrasts with the large upward shifts in band bending caused by X-ray induced reduction.
Collapse
Affiliation(s)
- Alexandra R McNeill
- School of Physical and Chemical Sciences, University of Canterbury, Private Bag 4800, 4180, Christchurch, New Zealand.,Syft Technologies, 3 Craft Place, 8024, Christchurch, New Zealand
| | - Rodrigo Martinez-Gazoni
- School of Physical and Chemical Sciences, University of Canterbury, Private Bag 4800, 4180, Christchurch, New Zealand
| | - Roger J Reeves
- School of Physical and Chemical Sciences, University of Canterbury, Private Bag 4800, 4180, Christchurch, New Zealand
| | - Martin W Allen
- Department of Electrical and Computer Engineering, University of Canterbury, Private Bag 4800, 4180, Christchurch, New Zealand
| | - Alison J Downard
- School of Physical and Chemical Sciences, University of Canterbury, Private Bag 4800, 4180, Christchurch, New Zealand
| |
Collapse
|
12
|
The effect of nanostructure dimensionality on the photoelectrochemical properties of derived TiO2 films. Electrochim Acta 2021. [DOI: 10.1016/j.electacta.2021.137900] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
13
|
Schuwalow S, Schröter NBM, Gukelberger J, Thomas C, Strocov V, Gamble J, Chikina A, Caputo M, Krieger J, Gardner GC, Troyer M, Aeppli G, Manfra MJ, Krogstrup P. Band Structure Extraction at Hybrid Narrow-Gap Semiconductor-Metal Interfaces. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:2003087. [PMID: 33643798 PMCID: PMC7887586 DOI: 10.1002/advs.202003087] [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: 08/12/2020] [Revised: 10/07/2020] [Indexed: 06/12/2023]
Abstract
The design of epitaxial semiconductor-superconductor and semiconductor-metal quantum devices requires a detailed understanding of the interfacial electronic band structure. However, the band alignment of buried interfaces is difficult to predict theoretically and to measure experimentally. This work presents a procedure that allows to reliably determine critical parameters for engineering quantum devices; band offset, band bending profile, and number of occupied quantum well subbands of interfacial accumulation layers at semiconductor-metal interfaces. Soft X-ray angle-resolved photoemission is used to directly measure the quantum well states as well as valence bands and core levels for the InAs(100)/Al interface, an important platform for Majorana-zero-mode based topological qubits, and demonstrate that the fabrication process strongly influences the band offset, which in turn controls the topological phase diagrams. Since the method is transferable to other narrow gap semiconductors, it can be used more generally for engineering semiconductor-metal and semiconductor-superconductor interfaces in gate-tunable superconducting devices.
Collapse
Affiliation(s)
- Sergej Schuwalow
- Center for Quantum DevicesNiels Bohr InstituteUniversity of Copenhagen and Microsoft Quantum Materials Lab CopenhagenLyngbyDenmark
| | | | | | - Candice Thomas
- Microsoft Station Q PurdueBirck Nanotechnology CenterPurdue UniversityWest LafayetteIN47907USA
- Department of Physics and AstronomyPurdue UniversityWest LafayetteIN47907USA
| | - Vladimir Strocov
- Paul Scherrer InstitutSwiss Light SourcePSIVilligenCH‐5232Switzerland
| | - John Gamble
- Microsoft QuantumOne Microsoft WayRedmondWA98052USA
| | - Alla Chikina
- Paul Scherrer InstitutSwiss Light SourcePSIVilligenCH‐5232Switzerland
| | - Marco Caputo
- Paul Scherrer InstitutSwiss Light SourcePSIVilligenCH‐5232Switzerland
| | - Jonas Krieger
- Paul Scherrer InstitutSwiss Light SourcePSIVilligenCH‐5232Switzerland
| | - Geoffrey C. Gardner
- Microsoft Station Q PurdueBirck Nanotechnology CenterPurdue UniversityWest LafayetteIN47907USA
| | | | - Gabriel Aeppli
- Paul Scherrer InstitutSwiss Light SourcePSIVilligenCH‐5232Switzerland
- Physics DepartmentETHZurichCH‐8093Switzerland
- Institut de PhysiqueEPFLLausanneCH‐1015Switzerland
| | - Michael J. Manfra
- Microsoft Station Q PurdueBirck Nanotechnology CenterPurdue UniversityWest LafayetteIN47907USA
- Department of Physics and AstronomyPurdue UniversityWest LafayetteIN47907USA
- School of Electrical and Computer Engineering and School of Materials EngineeringPurdue UniversityWest LafayetteIN47907USA
| | - Peter Krogstrup
- Center for Quantum DevicesNiels Bohr InstituteUniversity of Copenhagen and Microsoft Quantum Materials Lab CopenhagenLyngbyDenmark
| |
Collapse
|
14
|
Zhu T, Chan GKL. All-Electron Gaussian-Based G0W0 for Valence and Core Excitation Energies of Periodic Systems. J Chem Theory Comput 2021; 17:727-741. [DOI: 10.1021/acs.jctc.0c00704] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Tianyu Zhu
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Garnet Kin-Lic Chan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| |
Collapse
|
15
|
Yang X, Pristovsek M, Nitta S, Liu Y, Honda Y, Koide Y, Kawarada H, Amano H. Epitaxial Combination of Two-Dimensional Hexagonal Boron Nitride with Single-Crystalline Diamond Substrate. ACS APPLIED MATERIALS & INTERFACES 2020; 12:46466-46475. [PMID: 32940029 DOI: 10.1021/acsami.0c11883] [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
Hexagonal boron nitride (hBN) and diamond are promising materials for next-generation electronics and optoelectronics. However, their combination is rarely reported. In this study, we for the first time demonstrate the success to direct growth of two-dimensional (2D) hBN crystal layers on diamond substrates by metalorganic vapor phase epitaxy. Compared with the disordered growth we found on diamond (100), atomic force microscopy, X-ray diffraction, and transmission electron microscopy results all support 2D hBN with highly oriented lattice formation on diamond (111). Also, the epitaxial relationship between hBN and diamond (111) substrate is revealed to be [0 0 0 1]hBN // [1 1 1]diamond and [1 0 1̅ 0]hBN // [1 1 2̅]diamond. The valence band offset at hBN/diamond (111) heterointerface determined by X-ray photoelectron spectroscopy is 1.4 ± 0.2 eV, thus yielding a conduction band offset of 1.0 ± 0.2 eV and type II staggered band alignment with a bandgap of 5.9 eV assumed for hBN. Furthermore, prior thermal cleaning of diamond in a pure H2 atmosphere smoothens the surface for well-ordered layered hBN epitaxy, while thermal cleaning in a mixed H2 and NH3 atmosphere etches the diamond surface, creating many small faceted pits that destroy the following epitaxy of hBN.
Collapse
Affiliation(s)
- Xu Yang
- Venture Business Laboratory, Nagoya University, Nagoya 464-8603, Japan
| | - Markus Pristovsek
- Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8601, Japan
| | - Shugo Nitta
- Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8601, Japan
| | - Yuhuai Liu
- Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8601, Japan
- National Center for International Joint Research of Electronic Materials and Systems, School of Information Engineering, Zhengzhou University, Zhengzhou 450001, China
| | - Yoshio Honda
- Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8601, Japan
| | - Yasuo Koide
- National Institute for Materials Science, Tsukuba 305-0044, Japan
| | | | - Hiroshi Amano
- Venture Business Laboratory, Nagoya University, Nagoya 464-8603, Japan
- Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8601, Japan
- Akasaki Research Center, Nagoya University, Nagoya 464-8603, Japan
| |
Collapse
|
16
|
Synthesis and Characterization of p-n Junction Ternary Mixed Oxides for Photocatalytic Coprocessing of CO2 and H2O. Catalysts 2020. [DOI: 10.3390/catal10090980] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
In the present paper, we report the synthesis and characterization of both binary (Cu2O, Fe2O3, and In2O3) and ternary (Cu2O-Fe2O3 and Cu2O-In2O3) transition metal mixed-oxides that may find application as photocatalysts for solar driven CO2 conversion into energy rich species. Two different preparation techniques (High Energy Milling (HEM) and Co-Precipitation (CP)) are compared and materials properties are studied by means of a variety of characterization and analytical techniques UV-Visible Diffuse Reflectance Spectroscopy (UV-VIS DRS), X-ray Photoelectron Spectroscopy (XPS), X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Energy Dispersive X-Ray spectrometry (EDX). Appropriate data elaboration methods are used to extract materials bandgap for Cu2O@Fe2O3 and Cu2O@In2O3 prepared by HEM and CP, and foresee whether the newly prepared semiconductor mixed oxides pairs are useful for application in CO2-H2O coprocessing. The experimental results show that the synthetic technique influences the photoactivity of the materials that can correctly be foreseen on the basis of bandgap experimentally derived. Of the mixed oxides prepared and described in this work, only Cu2O@In2O3 shows positive results in CO2-H2O photo-co-processing. Preliminary results show that the composition and synthetic methodologies of mixed-oxides, the reactor geometry, the way of dispersing the photocatalyst sample, play a key role in the light driven reaction of CO2–H2O. This work is a rare case of full characterization of photo-materials, using UV-Visible DRS, XPS, XRD, TEM, EDX for the surface and bulk analytical characterization. Surface composition may not be the same of the bulk composition and plays a key role in photocatalysts behavior. We show that a full material knowledge is necessary for the correct forecast of their photocatalytic behavior, inferred from experimentally determined bandgaps.
Collapse
|
17
|
Spatial defects nanoengineering for bipolar conductivity in MoS 2. Nat Commun 2020; 11:3463. [PMID: 32651374 PMCID: PMC7351723 DOI: 10.1038/s41467-020-17241-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2018] [Accepted: 06/17/2020] [Indexed: 01/26/2023] Open
Abstract
Understanding the atomistic origin of defects in two-dimensional transition metal dichalcogenides, their impact on the electronic properties, and how to control them is critical for future electronics and optoelectronics. Here, we demonstrate the integration of thermochemical scanning probe lithography (tc-SPL) with a flow-through reactive gas cell to achieve nanoscale control of defects in monolayer MoS2. The tc-SPL produced defects can present either p- or n-type doping on demand, depending on the used gasses, allowing the realization of field effect transistors, and p-n junctions with precise sub-μm spatial control, and a rectification ratio of over 104. Doping and defects formation are elucidated by means of X-Ray photoelectron spectroscopy, scanning transmission electron microscopy, and density functional theory. We find that p-type doping in HCl/H2O atmosphere is related to the rearrangement of sulfur atoms, and the formation of protruding covalent S-S bonds on the surface. Alternatively, local heating MoS2 in N2 produces n-character. Bipolar conductivity is fundamental for electronic devices based on two-dimensional semiconductors. Here, the authors report on-demand p- and n-doping of monolayer MoS2 via defects engineering using thermochemical scanning probe lithography, and achieve a p-n junction with rectification ratio over 104.
Collapse
|
18
|
K Markose K, Shaji M, Bhatia S, Nair PR, Saji KJ, Antony A, Jayaraj MK. Novel Boron-Doped p-Type Cu 2O Thin Films as a Hole-Selective Contact in c-Si Solar Cells. ACS APPLIED MATERIALS & INTERFACES 2020; 12:12972-12981. [PMID: 32083458 DOI: 10.1021/acsami.9b22581] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
p-type Cu2O thin films doped with trivalent cation boron are demonstrated for the first time as an efficient hole-selective layer for c-Si heterojunction solar cells. Cu2O and Cu2O:B films were deposited by rf magnetron sputtering, and the optical and electrical properties of the doped and undoped films were investigated. Boron doping enhanced the carrier concentration and the electrical conductivity of the Cu2O film. The band alignment of the Cu2O:B/Si heterojunction was investigated using XPS and UPS measurements. The Cu2O:B/Si interface has a valance band offset of 0.08 eV, which facilitates hole transport, and a conduction band offset of 1.35 eV, which blocks the electrons. A thin SiOx tunnel oxide interlayer was also explored as the passivation layer. The initial trials of incorporating this Cu2O:B layer as a hole transporting layer in a single heterojunction solar cell with the structure, ITO/Cu2O:B/n-Si/Ag, and a cell area of 1 cm2 yielded an open-circuit voltage of 370 mV, a short-circuit current density of 36.5 mA/cm2, and an efficiency of 5.4%. This p-type material could find potential applications in various optoelectronic applications like organic solar cells, TFTs, and LEDs.
Collapse
Affiliation(s)
- Kurias K Markose
- Department of Physics, Cochin University of Science and Technology, Kochi 682022, India
| | - Manu Shaji
- Department of Physics, Cochin University of Science and Technology, Kochi 682022, India
| | - Swasti Bhatia
- Department of Electrical Engineering, Indian Institute of Technology, Bombay, Powai, Mumbai 400076, India
| | - Pradeep R Nair
- Department of Electrical Engineering, Indian Institute of Technology, Bombay, Powai, Mumbai 400076, India
| | - Kachirayil J Saji
- International School of Photonics, Cochin University of Science and Technology, Kochi 682022, India
- Centre of Excellence in Advanced Technology, Cochin University of Science and Technology, Kochi 682022, India
- Inter University Centre for Nanomaterials and Devices, Cochin University of Science and Technology, Kochi 682022, India
| | - Aldrin Antony
- Department of Physics, Cochin University of Science and Technology, Kochi 682022, India
- Department of Electrical Engineering, Indian Institute of Technology, Bombay, Powai, Mumbai 400076, India
- NCPRE, Department of Electrical Engineering, Indian Institute of Technology, Bombay, Powai, Mumbai 400076, India
| | - Madambi K Jayaraj
- Department of Physics, Cochin University of Science and Technology, Kochi 682022, India
- Centre of Excellence in Advanced Technology, Cochin University of Science and Technology, Kochi 682022, India
- Inter University Centre for Nanomaterials and Devices, Cochin University of Science and Technology, Kochi 682022, India
| |
Collapse
|
19
|
Huan YW, Xu K, Liu WJ, Zhang H, Golosov DA, Xia CT, Yu HY, Wu XH, Sun QQ, Ding SJ. Investigation of Band Alignment for Hybrid 2D-MoS 2/3D-β-Ga 2O 3 Heterojunctions with Nitridation. NANOSCALE RESEARCH LETTERS 2019; 14:360. [PMID: 31792627 PMCID: PMC6889261 DOI: 10.1186/s11671-019-3181-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2019] [Accepted: 10/10/2019] [Indexed: 05/14/2023]
Abstract
Hybrid heterojunctions based on two-dimensional (2D) and conventional three-dimensional (3D) materials provide a promising way toward nanoelectronic devices with engineered features. In this work, we investigated the band alignment of a mixed-dimensional heterojunction composed of transferred MoS2 on β-Ga2O3([Formula: see text]01) with and without nitridation. The conduction and valence band offsets for unnitrided 2D-MoS2/3D-β-Ga2O3 heterojunction were determined to be respectively 0.43 ± 0.1 and 2.87 ± 0.1 eV. For the nitrided heterojunction, the conduction and valence band offsets were deduced to 0.68 ± 0.1 and 2.62 ± 0.1 eV, respectively. The modified band alignment could result from the dipole formed by charge transfer across the heterojunction interface. The effect of nitridation on the band alignments between group III oxides and transition metal dichalcogenides will supply feasible technical routes for designing their heterojunction-based electronic and optoelectronic devices.
Collapse
Affiliation(s)
- Ya-Wei Huan
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai, 200433 China
| | - Ke Xu
- Key Laboratory of Micro and Nano Photonic Structures, Department of Optical Science and Engineering, Fudan University, Shanghai, 200433 China
| | - Wen-Jun Liu
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai, 200433 China
| | - Hao Zhang
- Key Laboratory of Micro and Nano Photonic Structures, Department of Optical Science and Engineering, Fudan University, Shanghai, 200433 China
| | | | - Chang-Tai Xia
- Key Laboratory of Materials for High Power Laser, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800 China
| | - Hong-Yu Yu
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen, 518055 China
| | - Xiao-Han Wu
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai, 200433 China
| | - Qing-Qing Sun
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai, 200433 China
| | - Shi-Jin Ding
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai, 200433 China
| |
Collapse
|
20
|
Hatayama S, Shuang Y, Fons P, Saito Y, Kolobov AV, Kobayashi K, Shindo S, Ando D, Sutou Y. Cr-Triggered Local Structural Change in Cr 2Ge 2Te 6 Phase Change Material. ACS APPLIED MATERIALS & INTERFACES 2019; 11:43320-43329. [PMID: 31647631 DOI: 10.1021/acsami.9b11535] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Cr2Ge2Te6 (CrGT) is a phase change material with higher resistivity in the crystalline phase than in the amorphous phase. CrGT exhibits an ultralow operation energy for amorphization. In this study, the origin of the increased resistance in crystalline CrGT compared to amorphous CrGT and the underlying phase change mechanism were investigated in terms of both local structural change and associated change in electronic state. The density of states at the Fermi level in crystalline CrGT decreased with increasing annealing temperature and became negligible upon annealing at 380 °C. Simultaneously, the Fermi level shifted from the vicinity of the valence band to the band gap center, leading to an increase in resistance. The phase change from amorphous to crystalline CrGT occurred through a metastable crystalline phase with a local structure similar to that of the amorphous phase. Cr nanoclusters were confirmed to exist in both the amorphous and crystalline phases. The presence of Cr nanoclusters induced Cr vacancies in the crystalline phase. These Cr vacancies generated hole carriers, leading to p-type conduction. Photoelectron spectroscopy of the Cr 2s core level clearly indicated a decrease in the fraction of Cr-Cr bonds and an increase in the fraction of Cr-Te bonds in crystalline CrGT upon annealing. Meanwhile, the coordination number of the Cr nanoclusters decreased as the number of Cr-Cr bonds was reduced. Together, these results imply that the origin of the increased resistance in crystalline CrGT is the filling of Cr vacancies by Cr atoms diffusing from Cr nanoclusters.
Collapse
Affiliation(s)
- Shogo Hatayama
- Department of Materials Science, Graduate School of Engineering , Tohoku University , 6-6-11, Aoba-yama , Aoba-ku, Sendai 980-8579 , Japan
| | - Yi Shuang
- Department of Materials Science, Graduate School of Engineering , Tohoku University , 6-6-11, Aoba-yama , Aoba-ku, Sendai 980-8579 , Japan
| | - Paul Fons
- Nanoelectronics Research Institute , National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba Central 5, 1-1-1 Higashi , Tsukuba 305-8565 , Japan
- Japan Synchrotron Radiation Research Institute (SPring-8) , 1-1-1 Kouto , Sayo-cho , Hyogo 679-5198 , Japan
| | - Yuta Saito
- Nanoelectronics Research Institute , National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba Central 5, 1-1-1 Higashi , Tsukuba 305-8565 , Japan
| | - Alexander V Kolobov
- Nanoelectronics Research Institute , National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba Central 5, 1-1-1 Higashi , Tsukuba 305-8565 , Japan
- Department of Physical Electronics, Faculty of Physics , Herzen State Pedagogical University , 48 Moika Embankment , St. Petersburg 191186 , Russia
| | - Keisuke Kobayashi
- Materials Sciences Research Center , Japan Atomic Energy Agency , 1-1-1 Kouto , Sayo-cho , Hyogo 679-5148 , Japan
- Research Institute of Kochi University of Technology , Tosa yamada, Kami City , Kochi 782-8502 , Japan
| | - Satoshi Shindo
- Department of Materials Science, Graduate School of Engineering , Tohoku University , 6-6-11, Aoba-yama , Aoba-ku, Sendai 980-8579 , Japan
| | - Daisuke Ando
- Department of Materials Science, Graduate School of Engineering , Tohoku University , 6-6-11, Aoba-yama , Aoba-ku, Sendai 980-8579 , Japan
| | - Yuji Sutou
- Department of Materials Science, Graduate School of Engineering , Tohoku University , 6-6-11, Aoba-yama , Aoba-ku, Sendai 980-8579 , Japan
| |
Collapse
|
21
|
Huan YW, Liu WJ, Tang XB, Xue XY, Wang XL, Sun QQ, Ding SJ. Investigation of Nitridation on the Band Alignment at MoS 2/HfO 2 Interfaces. NANOSCALE RESEARCH LETTERS 2019; 14:181. [PMID: 31144185 PMCID: PMC6541675 DOI: 10.1186/s11671-019-3020-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Accepted: 05/20/2019] [Indexed: 05/17/2023]
Abstract
The effect of nitridation treatment on the band alignment between few-layer MoS2 and HfO2 has been investigated by X-ray photoelectron spectroscopy. The valence (conduction) band offsets of MoS2/HfO2 with and without nitridation treatment were determined to be 2.09 ± 0.1 (2.41 ± 0.1) and 2.34 ± 0.1 (2.16 ± 0.1) eV, respectively. The tunable band alignment could be attributed to the Mo-N bonding formation and surface band bending for HfO2 triggered by nitridation. This study on the energy band engineering of MoS2/HfO2 heterojunctions may also be extended to other high-k dielectrics for integrating with two-dimensional materials to design and optimize their electronic devices.
Collapse
Affiliation(s)
- Ya-Wei Huan
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai, 200433 China
| | - Wen-Jun Liu
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai, 200433 China
| | - Xiao-Bing Tang
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai, 200433 China
| | - Xiao-Yong Xue
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai, 200433 China
| | - Xiao-Lei Wang
- Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing, 100029 China
| | - Qing-Qing Sun
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai, 200433 China
| | - Shi-Jin Ding
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai, 200433 China
| |
Collapse
|
22
|
Baeumer C, Funck C, Locatelli A, Menteş TO, Genuzio F, Heisig T, Hensling F, Raab N, Schneider CM, Menzel S, Waser R, Dittmann R. In-Gap States and Band-Like Transport in Memristive Devices. NANO LETTERS 2019; 19:54-60. [PMID: 30241437 DOI: 10.1021/acs.nanolett.8b03023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Point defects such as oxygen vacancies cause emergent phenomena such as resistive switching in transition-metal oxides, but their influence on the electron-transport properties is far from being understood. Here, we employ direct mapping of the electronic structure of a memristive device by spectromicroscopy. We find that oxygen vacancies result in in-gap states that we use as input for single-band transport simulations. Because the in-gap states are situated below the Fermi level, they do not contribute to the current directly but impact the shape of the conduction band. Accordingly, we can describe our devices with band-like transport and tunneling across the Schottky barrier at the interface.
Collapse
Affiliation(s)
- Christoph Baeumer
- Peter Gruenberg Institute , Forschungszentrum Juelich GmbH and JARA-FIT , 52425 Juelich , Germany
| | - Carsten Funck
- Institute for Electronic Materials, IWE2 , RWTH Aachen University , 52074 Aachen , Germany
| | - Andrea Locatelli
- Elettra - Sincrotrone Trieste S.C.p.A., S.S. 14 km - 163,5 in AREA Science Park , I-34149 Basovizza , Trieste , Italy
| | - Tevfik Onur Menteş
- Elettra - Sincrotrone Trieste S.C.p.A., S.S. 14 km - 163,5 in AREA Science Park , I-34149 Basovizza , Trieste , Italy
| | - Francesca Genuzio
- Elettra - Sincrotrone Trieste S.C.p.A., S.S. 14 km - 163,5 in AREA Science Park , I-34149 Basovizza , Trieste , Italy
| | - Thomas Heisig
- Peter Gruenberg Institute , Forschungszentrum Juelich GmbH and JARA-FIT , 52425 Juelich , Germany
| | - Felix Hensling
- Peter Gruenberg Institute , Forschungszentrum Juelich GmbH and JARA-FIT , 52425 Juelich , Germany
| | - Nicolas Raab
- Peter Gruenberg Institute , Forschungszentrum Juelich GmbH and JARA-FIT , 52425 Juelich , Germany
| | - Claus M Schneider
- Peter Gruenberg Institute , Forschungszentrum Juelich GmbH and JARA-FIT , 52425 Juelich , Germany
| | - Stephan Menzel
- Peter Gruenberg Institute , Forschungszentrum Juelich GmbH and JARA-FIT , 52425 Juelich , Germany
| | - Rainer Waser
- Peter Gruenberg Institute , Forschungszentrum Juelich GmbH and JARA-FIT , 52425 Juelich , Germany
- Institute for Electronic Materials, IWE2 , RWTH Aachen University , 52074 Aachen , Germany
| | - Regina Dittmann
- Peter Gruenberg Institute , Forschungszentrum Juelich GmbH and JARA-FIT , 52425 Juelich , Germany
| |
Collapse
|
23
|
Schuurman JC, McNeill AR, Martinez-Gazoni RF, Scott JI, Reeves RJ, Allen MW, Downard AJ. The effect of covalently bonded aryl layers on the band bending and electron density of SnO2 surfaces probed by synchrotron X-ray photoelectron spectroscopy. Phys Chem Chem Phys 2019; 21:17913-17922. [DOI: 10.1039/c9cp03040a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A downward to upward surface band bending change can be induced by grafted 4-(trifluoromethyl)phenyl groups on SnO2.
Collapse
Affiliation(s)
- Joel C. Schuurman
- School of Physical and Chemical Sciences
- University of Canterbury
- Christchurch 8140
- New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology
| | - Alexandra R. McNeill
- School of Physical and Chemical Sciences
- University of Canterbury
- Christchurch 8140
- New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology
| | - Rodrigo F. Martinez-Gazoni
- School of Physical and Chemical Sciences
- University of Canterbury
- Christchurch 8140
- New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology
| | - Jonty I. Scott
- School of Physical and Chemical Sciences
- University of Canterbury
- Christchurch 8140
- New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology
| | - Roger J. Reeves
- School of Physical and Chemical Sciences
- University of Canterbury
- Christchurch 8140
- New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology
| | - Martin W. Allen
- MacDiarmid Institute for Advanced Materials and Nanotechnology
- Wellington 6012
- New Zealand
- Department of Electrical and Computer Engineering
- University of Canterbury
| | - Alison J. Downard
- School of Physical and Chemical Sciences
- University of Canterbury
- Christchurch 8140
- New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology
| |
Collapse
|
24
|
Tan HL, Abdi FF, Ng YH. Heterogeneous photocatalysts: an overview of classic and modern approaches for optical, electronic, and charge dynamics evaluation. Chem Soc Rev 2019; 48:1255-1271. [DOI: 10.1039/c8cs00882e] [Citation(s) in RCA: 148] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
This review summarizes current experimental techniques, including the conventional and the state-of-the-art tools, to examine the key aspects of photocatalysts.
Collapse
Affiliation(s)
- Hui Ling Tan
- Particles and Catalysis Research Group
- School of Chemical Engineering
- The University of New South Wales
- Sydney
- Australia
| | - Fatwa F. Abdi
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Institute for Solar Fuels
- Berlin 14109
- Germany
| | - Yun Hau Ng
- Particles and Catalysis Research Group
- School of Chemical Engineering
- The University of New South Wales
- Sydney
- Australia
| |
Collapse
|
25
|
Skaja K, Andrä M, Rana V, Waser R, Dittmann R, Baeumer C. Reduction of the forming voltage through tailored oxygen non-stoichiometry in tantalum oxide ReRAM devices. Sci Rep 2018; 8:10861. [PMID: 30022129 PMCID: PMC6052165 DOI: 10.1038/s41598-018-28992-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 07/03/2018] [Indexed: 11/08/2022] Open
Abstract
In this study, we investigated the influence of oxygen non-stoichiometry on the resistive switching performance of tantalum oxide based memristive devices. Thin-films of tantalum oxide were deposited with varying sputter power and oxygen partial pressure. The electroforming voltage was found to decrease with increasing power density or decreased oxygen partial pressure, while the endurance remained stable and the resistance window ROFF/RON was found to increase. In-depth XPS analysis connects these observations to a controllable oxygen sub-stoichiometry in the sputter-deposited films. Our analysis shows that the decrease of the forming voltage results from an increase in carrier density in the as-prepared thin-films, which is induced by the presence of oxygen vacancies.
Collapse
Affiliation(s)
- Katharina Skaja
- Peter Grünberg Institute and JARA-FIT, FZ Jülich, D-52425, Jülich, Germany
| | - Michael Andrä
- Peter Grünberg Institute and JARA-FIT, FZ Jülich, D-52425, Jülich, Germany
| | - Vikas Rana
- Peter Grünberg Institute and JARA-FIT, FZ Jülich, D-52425, Jülich, Germany
| | - Rainer Waser
- Peter Grünberg Institute and JARA-FIT, FZ Jülich, D-52425, Jülich, Germany
- Institute for Electronic Materials, IWE2, RWTH Aachen University, D-52074, Aachen, Germany
| | - Regina Dittmann
- Peter Grünberg Institute and JARA-FIT, FZ Jülich, D-52425, Jülich, Germany
| | - Christoph Baeumer
- Peter Grünberg Institute and JARA-FIT, FZ Jülich, D-52425, Jülich, Germany.
| |
Collapse
|
26
|
Madapu KK, Sivadasan AK, Baral M, Dhara S. Observation of surface plasmon polaritons in 2D electron gas of surface electron accumulation in InN nanostructures. NANOTECHNOLOGY 2018; 29:275707. [PMID: 29658895 DOI: 10.1088/1361-6528/aabe60] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Recently, heavily doped semiconductors have been emerging as an alternative to low-loss plasmonic materials. InN, belonging to the group III nitrides, possesses the unique property of surface electron accumulation (SEA), which provides a 2D electron gas (2DEG) system. In this report, we demonstrated the surface plasmon properties of InN nanoparticles originating from SEA using the real-space mapping of the surface plasmon fields for the first time. The SEA is confirmed by Raman studies, which are further corroborated by photoluminescence and photoemission spectroscopic studies. The frequency of 2DEG corresponding to SEA is found to be in the THz region. The periodic fringes are observed in the near-field scanning optical microscopic images of InN nanostructures. The observed fringes are attributed to the interference of propagated and back-reflected surface plasmon polaritons (SPPs). The observation of SPPs is solely attributed to the 2DEG corresponding to the SEA of InN. In addition, a resonance kind of behavior with the enhancement of the near-field intensity is observed in the near-field images of InN nanostructures. Observation of SPPs indicates that InN with SEA can be a promising THz plasmonic material for light confinement.
Collapse
Affiliation(s)
- Kishore K Madapu
- Nanomaterials Characterization and Sensors Section, Surface and Nanoscience Division, Indira Gandhi Centre for Atomic Research, Homi Bhabha National Institute, Kalpakkam-603102, India
| | | | | | | |
Collapse
|
27
|
Mukherjee S, Sarkar K, Wiederrecht GP, Schaller RD, Gosztola DJ, Stroscio MA, Dutta M. Defect induced structural inhomogeneity, ultraviolet light emission and near-band-edge photoluminescence broadening in degenerate In 2O 3 nanowires. NANOTECHNOLOGY 2018; 29:175201. [PMID: 29443008 DOI: 10.1088/1361-6528/aaaf34] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We demonstrate here defect induced changes on the morphology and surface properties of indium oxide (In2O3) nanowires and further study their effects on the near-band-edge (NBE) emission, thereby showing the significant influence of surface states on In2O3 nanostructure based device characteristics for potential optoelectronic applications. In2O3 nanowires with cubic crystal structure (c-In2O3) were synthesized via carbothermal reduction technique using a gold-catalyst-assisted vapor-liquid-solid method. Onset of strong optical absorption could be observed at energies greater than 3.5 eV consistent with highly n-type characteristics due to unintentional doping from oxygen vacancy [Formula: see text] defects as confirmed using Raman spectroscopy. A combination of high resolution transmission electron microscopy, x-ray photoelectron spectroscopy and valence band analysis on the nanowire morphology and stoichiometry reveals presence of high-density of [Formula: see text] defects on the surface of the nanowires. As a result, chemisorbed oxygen species can be observed leading to upward band bending at the surface which corresponds to a smaller valence band offset of 2.15 eV. Temperature dependent photoluminescence (PL) spectroscopy was used to study the nature of the defect states and the influence of the surface states on the electronic band structure and NBE emission has been discussed. Our data reveals significant broadening of the NBE PL peak consistent with impurity band broadening leading to band-tailing effect from heavy doping.
Collapse
Affiliation(s)
- Souvik Mukherjee
- Department of Electrical and Computer Engineering, University of Illinois at Chicago, 851 South Morgan Street, M/C 154, Chicago, IL 60607, United States of America
| | | | | | | | | | | | | |
Collapse
|
28
|
Yang YL. Tuning thermal stability and electronic properties of germanium oxide on Ge(001) surface with the incorporation of nitrogen. SURF INTERFACE ANAL 2018. [DOI: 10.1002/sia.6377] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Yu Lin Yang
- School of Opto-Electronic and Communication Engineering; Xiamen University of Technology; Xiamen 361024 China
- Fujian Key Laboratory of Optoelectronic Technology and Devices; Xiamen University of Technology; Xiamen 361024 China
- Fujian Key Laboratory of Communication Network and Information Processing; Xiamen University of Technology; Xiamen 361024 China
- Xiamen LED Lighting Engineering Research Center; Xiamen University of Technology; Xiamen 361024 China
| |
Collapse
|
29
|
Maheu C, Cardenas L, Puzenat E, Afanasiev P, Geantet C. UPS and UV spectroscopies combined to position the energy levels of TiO2 anatase and rutile nanopowders. Phys Chem Chem Phys 2018; 20:25629-25637. [DOI: 10.1039/c8cp04614j] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Positioning of absolute energy levels and the quantitative description of occupied levels obtained for TiO2 nanopowders, combining UPS and UV-Vis spectroscopies.
Collapse
Affiliation(s)
- Clément Maheu
- Université de Lyon
- Institut de Recherches sur la Catalyse et l'Environnement de Lyon – IRCELYON – UMR 5256
- CNRS-UCB Lyon 1
- 69626 Villeurbanne cedex
- France
| | - Luis Cardenas
- Université de Lyon
- Institut de Recherches sur la Catalyse et l'Environnement de Lyon – IRCELYON – UMR 5256
- CNRS-UCB Lyon 1
- 69626 Villeurbanne cedex
- France
| | - Eric Puzenat
- Université de Lyon
- Institut de Recherches sur la Catalyse et l'Environnement de Lyon – IRCELYON – UMR 5256
- CNRS-UCB Lyon 1
- 69626 Villeurbanne cedex
- France
| | - Pavel Afanasiev
- Université de Lyon
- Institut de Recherches sur la Catalyse et l'Environnement de Lyon – IRCELYON – UMR 5256
- CNRS-UCB Lyon 1
- 69626 Villeurbanne cedex
- France
| | - Christophe Geantet
- Université de Lyon
- Institut de Recherches sur la Catalyse et l'Environnement de Lyon – IRCELYON – UMR 5256
- CNRS-UCB Lyon 1
- 69626 Villeurbanne cedex
- France
| |
Collapse
|
30
|
Yan B, Liu S, Heng Y, Yang Y, Yu Y, Wen K. Band Offset Measurements in Atomic-Layer-Deposited Al 2O 3/Zn 0.8Al 0.2O Heterojunction Studied by X-ray Photoelectron Spectroscopy. NANOSCALE RESEARCH LETTERS 2017; 12:363. [PMID: 28532128 PMCID: PMC5438334 DOI: 10.1186/s11671-017-2131-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/24/2016] [Accepted: 05/08/2017] [Indexed: 06/07/2023]
Abstract
Pure aluminum oxide (Al2O3) and zinc aluminum oxide (Zn x Al1-x O) thin films were deposited by atomic layer deposition (ALD). The microstructure and optical band gaps (E g ) of the Zn x Al1-x O (0.2 ≤ x ≤ 1) films were studied by X-ray diffractometer and Tauc method. The band offsets and alignment of atomic-layer-deposited Al2O3/Zn0.8Al0.2O heterojunction were investigated in detail using charge-corrected X-ray photoelectron spectroscopy. In this work, different methodologies were adopted to recover the actual position of the core levels in insulator materials which were easily affected by differential charging phenomena. Valence band offset (ΔE V) and conduction band offset (ΔE C) for the interface of the Al2O3/Zn0.8Al0.2O heterojunction have been constructed. An accurate value of ΔE V = 0.82 ± 0.12 eV was obtained from various combinations of core levels of heterojunction with varied Al2O3 thickness. Given the experimental E g of 6.8 eV for Al2O3 and 5.29 eV for Zn0.8Al0.2O, a type-I heterojunction with a ΔE C of 0.69 ± 0.12 eV was found. The precise determination of the band alignment of Al2O3/Zn0.8Al0.2O heterojunction is of particular importance for gaining insight to the design of various electronic devices based on such heterointerface.
Collapse
Affiliation(s)
- Baojun Yan
- State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China.
| | - Shulin Liu
- State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Yuekun Heng
- State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Yuzhen Yang
- State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
- Department of Physics, Nanjing University, Nanjing, 210093, People's Republic of China
| | - Yang Yu
- State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
- School of Science, Xi'an University of Technology, Xi'an, 710048, People's Republic of China
| | - Kaile Wen
- State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
- University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| |
Collapse
|
31
|
Cui W, Li J, Dong F, Sun Y, Jiang G, Cen W, Lee SC, Wu Z. Highly Efficient Performance and Conversion Pathway of Photocatalytic NO Oxidation on SrO-Clusters@Amorphous Carbon Nitride. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:10682-10690. [PMID: 28817265 DOI: 10.1021/acs.est.7b00974] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
This work demonstrates the first molecular-level conversion pathway of NO oxidation over a novel SrO-clusters@amorphous carbon nitride (SCO-ACN) photocatalyst, which is synthesized via copyrolysis of urea and SrCO3. The inclusion of SrCO3 is crucial in the formation of the amorphous carbon nitride (ACN) and SrO clusters by attacking the intralayer hydrogen bonds at the edge sites of graphitic carbon nitride (CN). The amorphous nature of ACN can promote the transportation, migration, and transformation of charge carriers on SCO-ACN. And the SrO clusters are identified as the newly formed active centers to facilitate the activation of NO via the formation of Sr-NOδ(+), which essentially promotes the conversion of NO to the final products. The combined effects of the amorphous structure and SrO clusters impart outstanding photocatalytic NO removal efficiency to the SCO-ACN under visible-light irradiation. To reveal the photocatalytic mechanism, the adsorption and photocatalytic oxidation of NO over CN and SCO-ACN are analyzed by in situ DRIFTS, and the intermediates and conversion pathways are elucidated and compared. This work presents a novel in situ DRIFTS-based strategy to explore the photocatalytic reaction pathway of NO oxidation, which is quite beneficial to understand the mechanism underlying the photocatalytic reaction and advance the development of photocatalytic technology for environmental remediation.
Collapse
Affiliation(s)
- Wen Cui
- Chongqing Key Laboratory of Catalysis and New Environmental Materials, College of Environment and Resources, Chongqing Technology and Business University , Chongqing 400067, China
| | - Jieyuan Li
- College of Architecture and Environment, Institute of New Energy and Low Carbon Technology, Sichuan University , Sichuan 610065, China
| | - Fan Dong
- Chongqing Key Laboratory of Catalysis and New Environmental Materials, College of Environment and Resources, Chongqing Technology and Business University , Chongqing 400067, China
| | - Yanjuan Sun
- Chongqing Key Laboratory of Catalysis and New Environmental Materials, College of Environment and Resources, Chongqing Technology and Business University , Chongqing 400067, China
| | - Guangming Jiang
- Chongqing Key Laboratory of Catalysis and New Environmental Materials, College of Environment and Resources, Chongqing Technology and Business University , Chongqing 400067, China
| | - Wanglai Cen
- College of Architecture and Environment, Institute of New Energy and Low Carbon Technology, Sichuan University , Sichuan 610065, China
| | - S C Lee
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University , Hong Kong, China
| | - Zhongbiao Wu
- Department of Environmental Engineering, Zhejiang University , Hangzhou 310027, China
| |
Collapse
|
32
|
Zhang KHL, Wu R, Tang F, Li W, Oropeza FE, Qiao L, Lazarov VK, Du Y, Payne DJ, MacManus-Driscoll JL, Blamire MG. Electronic Structure and Band Alignment at the NiO and SrTiO 3 p-n Heterojunctions. ACS APPLIED MATERIALS & INTERFACES 2017; 9:26549-26555. [PMID: 28695740 DOI: 10.1021/acsami.7b06025] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Understanding the energetics at the interface, including the alignment of valence and conduction bands, built-in potentials, and ionic and electronic reconstructions, is an important challenge in designing oxide interfaces that have controllable multifunctionalities for novel (opto-)electronic devices. In this work, we report detailed investigations on the heterointerface of wide-band-gap p-type NiO and n-type SrTiO3 (STO). We show that despite a large lattice mismatch (∼7%) and dissimilar crystal structure, high-quality NiO and Li-doped NiO (LNO) thin films can be epitaxially grown on STO(001) substrates through a domain-matching epitaxy mechanism. X-ray photoelectron spectroscopy studies indicate that NiO/STO heterojunctions form a type II "staggered" band alignment. In addition, a large built-in potential of up to 0.97 eV was observed at the interface of LNO and Nb-doped STO (NbSTO). The LNO/NbSTO p-n heterojunctions exhibit not only a large rectification ratio of 2 × 103 but also a large ideality factor of 4.3. The NiO/STO p-n heterojunctions have important implications for applications in photocatalysis and photodetectors as the interface provides favorable energetics for facile separation and transport of photogenerated electrons and holes.
Collapse
Affiliation(s)
- Kelvin H L Zhang
- Department of Materials Science & Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, U.K
| | - Rui Wu
- Department of Materials Science & Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, U.K
| | - Fengzai Tang
- Department of Materials Science & Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, U.K
| | - Weiwei Li
- Department of Materials Science & Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, U.K
| | - Freddy E Oropeza
- Department of Materials, Imperial College London , Exhibition Road, London SW7 2AZ, U.K
| | - Liang Qiao
- School of Materials, The University of Manchester , Manchester M13 9PL, U.K
| | - Vlado K Lazarov
- Department of Physics, University of York , Heslington, York YO10 5DD, U.K
| | - Yingge Du
- Physical Sciences Division, Physical & Computational Sciences Directorate, Pacific Northwest National Laboratory , Richland, Washington 99352, United States
| | - David J Payne
- Department of Materials, Imperial College London , Exhibition Road, London SW7 2AZ, U.K
| | - Judith L MacManus-Driscoll
- Department of Materials Science & Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, U.K
| | - Mark G Blamire
- Department of Materials Science & Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, U.K
| |
Collapse
|
33
|
Žerjav G, Arshad MS, Djinović P, Junkar I, Kovač J, Zavašnik J, Pintar A. Improved electron-hole separation and migration in anatase TiO 2 nanorod/reduced graphene oxide composites and their influence on photocatalytic performance. NANOSCALE 2017; 9:4578-4592. [PMID: 28321442 DOI: 10.1039/c7nr00704c] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The as-synthesized TiO2 nanorods a-TNR (amorphous TiO2 layer covering the crystalline anatase TiO2 core) and TNR (fully crystalline anatase TiO2) were decorated with reduced graphene oxide (rGO) to synthesize two series of TiO2 + rGO composites with different nominal loadings of GO (from 4 to 20 wt%). The structural, surface and electronic properties of the obtained TiO2 + rGO composites were analyzed and correlated to their performance in the photocatalytic oxidation of aqueous bisphenol A solution. X-ray photoelectron spectroscopy (XPS) analyses revealed that charge separation in TiO2 + rGO composites is improved due to the perfect matching of TiO2 and rGO valence band maxima (VBM). Cyclic voltammetry (CV) experiments revealed that the peak-to-peak separations (ΔEp) are the lowest and the oxidation current densities are the highest for composites with a nominal 10 wt% GO content, meaning that it is much easier for the charge carriers to percolate through the solid, resulting in improved charge migration. Due to the high charge carrier mobility in rGO and perfect VBM matching between TiO2 and rGO, the electron-hole recombination in composites was suppressed, resulting in more electrons and holes being able to participate in the photocatalytic reaction. rGO amounts above 10 wt% decreased the photocatalytic activity; thus, it is critical to optimize its amount in the TiO2 + rGO composites for achieving the highest photocatalytic activity. BPA degradation rates correlated completely with the results of the CV measurements, which directly evidenced improved charge separation and migration as the crucial parameters governing photocatalysis.
Collapse
Affiliation(s)
- Gregor Žerjav
- Department for Environmental Sciences and Engineering, National Institute of Chemistry, Hajdrihova 19, SI-1001 Ljubljana, Slovenia.
| | - Muhammad Shahid Arshad
- Department for Environmental Sciences and Engineering, National Institute of Chemistry, Hajdrihova 19, SI-1001 Ljubljana, Slovenia.
| | - Petar Djinović
- Department for Environmental Sciences and Engineering, National Institute of Chemistry, Hajdrihova 19, SI-1001 Ljubljana, Slovenia.
| | - Ita Junkar
- Department of Surface Engineering and Optoelectronics, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
| | - Janez Kovač
- Department of Surface Engineering and Optoelectronics, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
| | - Janez Zavašnik
- Centre for Electron Microscopy and Microanalysis, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
| | - Albin Pintar
- Department for Environmental Sciences and Engineering, National Institute of Chemistry, Hajdrihova 19, SI-1001 Ljubljana, Slovenia.
| |
Collapse
|
34
|
Comes R, Chambers S. Interface Structure, Band Alignment, and Built-In Potentials at LaFeO_{3}/n-SrTiO_{3} Heterojunctions. PHYSICAL REVIEW LETTERS 2016; 117:226802. [PMID: 27925724 DOI: 10.1103/physrevlett.117.226802] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Indexed: 06/06/2023]
Abstract
Interface structure at polar-nonpolar interfaces has been shown to be a key factor in controlling emergent behavior in oxide heterostructures, including the LaFeO_{3}/n-SrTiO_{3} system. We demonstrate via high-energy-resolution x-ray photoemission that epitaxial LaFeO_{3}/n-SrTiO_{3}(001) heterojunctions engineered to have opposite interface polarities exhibit very similar band offsets and potential gradients within the LaFeO_{3} films. However, differences in the potential gradient within the SrTiO_{3} layer depending on polarity may promote hole diffusion into LaFeO_{3} for applications in photocatalysis.
Collapse
Affiliation(s)
- Ryan Comes
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
- Department of Physics, Auburn University, Auburn, Alabama 36849, USA
| | - Scott Chambers
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
| |
Collapse
|
35
|
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.
Collapse
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
| |
Collapse
|
36
|
Yang Y, Hoffmann MR. Synthesis and Stabilization of Blue-Black TiO 2 Nanotube Arrays for Electrochemical Oxidant Generation and Wastewater Treatment. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:11888-11894. [PMID: 27648479 DOI: 10.1021/acs.est.6b03540] [Citation(s) in RCA: 100] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Efficient, inexpensive, and stable electrode materials are key components of commercially viable electrochemical wastewater treatment system. In this study, blue-black TiO2 nanotube array (BNTA) electrodes are prepared by electrochemical self-doping. The 1-D structure, donor state density, and Fermi energy level position are critical for maintaining the semimetallic functionality of the BNTA. The structural strength of the BNTA is enhanced by surface crack minimization, reinforcement of the BNTA-Ti metal interface, and stabilized by a protective overcoating with nanoparticulate TiO2 (Ti/EBNTA). Ti/EBNTA electrodes are employed as both anodes and cathodes with polarity switching at a set frequency. Oxidants are generated at the anode, while the doping levels are regenerated along with byproduct reduction at the cathode. The estimated maximum electrode lifetime is 16 895 h. Ti/EBNTA has comparable hydroxyl radical production activity (6.6 × 10-14 M) with boron-doped diamond (BDD, 7.4 × 10-14 M) electrodes. The chlorine production rate follows a trend with respective to electrode type of Ti/EBNTA > BDD > IrO2. Ti/EBNTA electrodes operated in a bipolar mode have a minimum energy consumption of 62 kWh/kg COD, reduced foam formation due to less gas bubble production, minimum scale formation, and lower chlorate production levels (6 mM vs 18 mM for BDD) during electrolytic wastewater treatment.
Collapse
Affiliation(s)
- Yang Yang
- Linde + Robinson Laboratories California Institute of Technology 1200 E. California Blvd. MC 131-24 Pasadena, California 91125, United States
| | - Michael R Hoffmann
- Linde + Robinson Laboratories California Institute of Technology 1200 E. California Blvd. MC 131-24 Pasadena, California 91125, United States
| |
Collapse
|
37
|
Superconductor to Mott insulator transition in YBa2Cu3O7/LaCaMnO3 heterostructures. Sci Rep 2016; 6:33184. [PMID: 27627855 PMCID: PMC5024130 DOI: 10.1038/srep33184] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 08/15/2016] [Indexed: 11/08/2022] Open
Abstract
The superconductor-to-insulator transition (SIT) induced by means such as external magnetic fields, disorder or spatial confinement is a vivid illustration of a quantum phase transition dramatically affecting the superconducting order parameter. In pursuit of a new realization of the SIT by interfacial charge transfer, we developed extremely thin superlattices composed of high Tc superconductor YBa2Cu3O7 (YBCO) and colossal magnetoresistance ferromagnet La0.67Ca0.33MnO3 (LCMO). By using linearly polarized resonant X-ray absorption spectroscopy and magnetic circular dichroism, combined with hard X-ray photoelectron spectroscopy, we derived a complete picture of the interfacial carrier doping in cuprate and manganite atomic layers, leading to the transition from superconducting to an unusual Mott insulating state emerging with the increase of LCMO layer thickness. In addition, contrary to the common perception that only transition metal ions may respond to the charge transfer process, we found that charge is also actively compensated by rare-earth and alkaline-earth metal ions of the interface. Such deterministic control of Tc by pure electronic doping without any hindering effects of chemical substitution is another promising route to disentangle the role of disorder on the pseudo-gap and charge density wave phases of underdoped cuprates.
Collapse
|
38
|
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.
Collapse
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
| |
Collapse
|
39
|
Zhu H, Qin X, Cheng L, Azcatl A, Kim J, Wallace RM. Remote Plasma Oxidation and Atomic Layer Etching of MoS2. ACS APPLIED MATERIALS & INTERFACES 2016; 8:19119-26. [PMID: 27386734 DOI: 10.1021/acsami.6b04719] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Exfoliated molybdenum disulfide (MoS2) is shown to chemically oxidize in a layered manner upon exposure to a remote O2 plasma. X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED), and atomic force microscopy (AFM) are employed to characterize the surface chemistry, structure, and topography of the oxidation process and indicate that the oxidation mainly occurs on the topmost layer without altering the chemical composition of underlying layer. The formation of S-O bonds upon short, remote plasma exposure pins the surface Fermi level to the conduction band edge, while the MoOx formation at high temperature modulates the Fermi level toward the valence band through band alignment. A uniform coverage of monolayer amorphous MoO3 is obtained after 5 min or longer remote O2 plasma exposure at 200 °C, and the MoO3 can be completely removed by annealing at 500 °C, leaving a clean ordered MoS2 lattice structure as verified by XPS, LEED, AFM, and scanning tunneling microscopy. This work shows that a remote O2 plasma can be useful for both surface functionalization and a controlled thinning method for MoS2 device fabrication processes.
Collapse
Affiliation(s)
- Hui Zhu
- Department of Materials Science and Engineering, University of Texas at Dallas , Richardson, Texas 75080, United States
| | - Xiaoye Qin
- Department of Materials Science and Engineering, University of Texas at Dallas , Richardson, Texas 75080, United States
| | - Lanxia Cheng
- Department of Materials Science and Engineering, University of Texas at Dallas , Richardson, Texas 75080, United States
| | - Angelica Azcatl
- Department of Materials Science and Engineering, University of Texas at Dallas , Richardson, Texas 75080, United States
| | - Jiyoung Kim
- Department of Materials Science and Engineering, University of Texas at Dallas , Richardson, Texas 75080, United States
| | - Robert M Wallace
- Department of Materials Science and Engineering, University of Texas at Dallas , Richardson, Texas 75080, United States
| |
Collapse
|
40
|
Hong S, Nakhmanson SM, Fong DD. Screening mechanisms at polar oxide heterointerfaces. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2016; 79:076501. [PMID: 27308889 DOI: 10.1088/0034-4885/79/7/076501] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The interfaces of polar oxide heterostructures can display electronic properties unique from the oxides they border, as they require screening from either internal or external sources of charge. The screening mechanism depends on a variety of factors, including the band structure at the interface, the presence of point defects or adsorbates, whether or not the oxide is ferroelectric, and whether or not an external field is applied. In this review, we discuss both theoretical and experimental aspects of different screening mechanisms, giving special emphasis to ways in which the mechanism can be altered to provide novel or tunable functionalities. We begin with a theoretical introduction to the problem and highlight recent progress in understanding the impact of point defects on polar interfaces. Different case studies are then discussed, for both the high thickness regime, where interfaces must be screened and each interface can be considered separately, and the low thickness regime, where the degree and nature of screening can be manipulated and the interfaces are close enough to interact. We end with a brief outlook toward new developments in this rapidly progressing field.
Collapse
Affiliation(s)
- Seungbum Hong
- Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA. Department of Materials Science & Engineering, KAIST, Daejeon 305-701, Korea
| | | | | |
Collapse
|
41
|
|
42
|
Ohtsubo Y, Kishi JI, Hagiwara K, Le Fèvre P, Bertran F, Taleb-Ibrahimi A, Yamane H, Ideta SI, Matsunami M, Tanaka K, Kimura SI. Surface Tomonaga-Luttinger-Liquid State on Bi/InSb(001). PHYSICAL REVIEW LETTERS 2015; 115:256404. [PMID: 26722934 DOI: 10.1103/physrevlett.115.256404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Indexed: 06/05/2023]
Abstract
A 1D metallic surface state was created on an anisotropic InSb(001) surface covered with Bi. Angle-resolved photoelectron spectroscopy (ARPES) showed a 1D Fermi contour with almost no 2D distortion. Close to the Fermi level (E_{F}), the angle-integrated photoelectron spectra showed power-law scaling with the binding energy and temperature. The ARPES plot above E_{F}, obtained thanks to a thermally broadened Fermi edge at room temperature, showed a 1D state with continuous metallic dispersion across E_{F} and power-law intensity suppression around E_{F}. These results strongly suggest a Tomonaga-Luttinger liquid on the Bi/InSb(001) surface.
Collapse
Affiliation(s)
- Yoshiyuki Ohtsubo
- Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
- Department of Physics, Graduate School of Science, Osaka Unviersity, Toyonaka 560-0043, Japan
- Synchrotron SOLEIL, Saint-Aubin-BP 48, F-91192 Gif sur Yvette, France
| | - Jun-Ichiro Kishi
- Department of Physics, Graduate School of Science, Osaka Unviersity, Toyonaka 560-0043, Japan
| | - Kenta Hagiwara
- Department of Physics, Graduate School of Science, Osaka Unviersity, Toyonaka 560-0043, Japan
| | - Patrick Le Fèvre
- Synchrotron SOLEIL, Saint-Aubin-BP 48, F-91192 Gif sur Yvette, France
| | - François Bertran
- Synchrotron SOLEIL, Saint-Aubin-BP 48, F-91192 Gif sur Yvette, France
| | - Amina Taleb-Ibrahimi
- Synchrotron SOLEIL, Saint-Aubin-BP 48, F-91192 Gif sur Yvette, France
- UR1/CNRS Synchrotron SOLEIL, Saint-Aubin, F-91192 Gif sur Yvette, France
| | | | | | | | | | - Shin-Ichi Kimura
- Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
- Department of Physics, Graduate School of Science, Osaka Unviersity, Toyonaka 560-0043, Japan
| |
Collapse
|
43
|
Beinik I, Hellström M, Jensen TN, Broqvist P, Lauritsen JV. Enhanced wetting of Cu on ZnO by migration of subsurface oxygen vacancies. Nat Commun 2015; 6:8845. [PMID: 26567989 PMCID: PMC4660204 DOI: 10.1038/ncomms9845] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2015] [Accepted: 10/06/2015] [Indexed: 12/02/2022] Open
Abstract
Metal adhesion on metal oxides is strongly controlled by the oxide surface structure and composition, but lack of control over the surface conditions often limits the possibilities to exploit this in opto- and micro-electronics applications and heterogeneous catalysis where nanostructural control is of utmost importance. The Cu/ZnO system is among the most investigated of such systems in model studies, but the presence of subsurface ZnO defects and their important role for adhesion on ZnO have been unappreciated so far. Here we reveal that the surface-directed migration of subsurface defects affects the Cu adhesion on polar ZnO(0001) in the technologically interesting temperature range up to 550 K. This leads to enhanced adhesion and ultimately complete wetting of ZnO(0001) by a Cu overlayer. On the basis of our experimental and computational results we demonstrate a mechanism which implies that defect concentrations in the bulk are an important, and possibly controllable, parameter for the metal-on-oxide growth. Comprehensive elucidation of metal-support interactions is important for controlling and improving their performances in a range of pertinent technologies. Here, the authors reveal how subsurface defects influence the adhesion and wetting of a metal on the surface of a metal oxide.
Collapse
Affiliation(s)
- Igor Beinik
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus DK-8000, Denmark
| | - Matti Hellström
- Department of Chemistry-Ångström, Uppsala University, Box 538, Uppsala SE-75121, Sweden
| | - Thomas N Jensen
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus DK-8000, Denmark
| | - Peter Broqvist
- Department of Chemistry-Ångström, Uppsala University, Box 538, Uppsala SE-75121, Sweden
| | - Jeppe V Lauritsen
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus DK-8000, Denmark
| |
Collapse
|
44
|
Choi H, Kim TH, Chae J, Baeck J, Kee CS, Jeong KH, Jeong HS, Kang C, Cho MH. Evolution of the surface state in Bi2Se2Te thin films during phase transition. NANOSCALE 2015; 7:14924-14936. [PMID: 26300223 DOI: 10.1039/c5nr04354a] [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
Topological insulators, a new quantum state of matter, have created exciting opportunities for studies in topological quantum physics and for exploring spintronics applications due to their gapless helical metallic surface states. In this study, thin films composed of alternate layers of Bi and Se (Te) ({Bi(3 Å)Te(9 Å)}n/{Bi(3 Å)Se(9 Å)}n) were fabricated by controlling the layer thickness within the atomic scale using thermal evaporation techniques. The high-purity growth of uniform Bi2Se2Te1 thin films has not yet been achieved using a thermal evaporation method. However, as a result of a self-ordering process during annealing, an as-grown amorphous film with p-type polarity could transform into single crystalline Bi2Se2Te1 with n-type polarity. Using THz-time domain spectroscopy (THz-TDS) and ultraviolet photoemission spectroscopy (UPS), we concluded that the conductivity is dominated by the Drude contribution, suggesting the presence of a quantum well state and surface states. Moreover we demonstrated that the emission of terahertz waves from the (001) surface of the single crystalline Bi2Se2Te1 thin film would be possible under the excitation of 790 nm femtosecond optical pulses, indicating the presence of a Dirac-fermion, a photo-Dember effect at the surface state and the transient current within the surface depletion region. The results reported herein provide useful information regarding a valuable deposition method that can be useful in studies of the evolution of surface state electrons in topological insulators.
Collapse
Affiliation(s)
- Hyejin Choi
- Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, Korea.
| | | | | | | | | | | | | | | | | |
Collapse
|
45
|
Tong J, Wang X, Ouyang Z, Lennon A. Ultra-thin Tunnel Oxides Formed by Field-induced Anodisation for Carrier-selective Contacts. ACTA ACUST UNITED AC 2015. [DOI: 10.1016/j.egypro.2015.07.119] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
46
|
Visible light-driven efficient overall water splitting using p-type metal-nitride nanowire arrays. Nat Commun 2015; 6:6797. [DOI: 10.1038/ncomms7797] [Citation(s) in RCA: 268] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 02/27/2015] [Indexed: 02/06/2023] Open
|
47
|
Hudait MK, Clavel M, Zhu Y, Goley PS, Kundu S, Maurya D, Priya S. Integration of SrTiO3 on crystallographically oriented epitaxial germanium for low-power device applications. ACS APPLIED MATERIALS & INTERFACES 2015; 7:5471-5479. [PMID: 25695205 DOI: 10.1021/am5091726] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
SrTiO3 integration on crystallographic oriented (100), (110), and (111) epitaxial germanium (Ge) exhibits a potential for a new class of nanoscale transistors. Germanium is attractive due to its superior transport properties while SrTiO3 (STO) is promising due to its high relative permittivity, both being critical parameters for next-generation low-voltage and low-leakage metal-oxide semiconductor field-effect transistors. The sharp heterointerface between STO and each crystallographically oriented Ge layer, studied by cross-sectional transmission electron microscopy, as well as band offset parameters at each heterojunction offers a significant advancement for designing a new generation of ferroelectric-germanium based multifunctional devices. Moreover, STO, when used as an interlayer between metal and n-type (4 × 10(18) cm(-3)) epitaxial Ge in metal-insulator-semiconductor (MIS) structures, showed a 1000 times increase in current density as well as a decrease in specific contact resistance. Furthermore, the inclusion of STO on n-Ge demonstrated the first experimental findings of the MIS behavior of STO on n-Ge.
Collapse
Affiliation(s)
- Mantu K Hudait
- Advanced Devices & Sustainable Energy Laboratory (ADSEL), Bradley Department of Electrical and Computer Engineering, Virginia Tech , Blacksburg, Virginia 24061, United States
| | | | | | | | | | | | | |
Collapse
|
48
|
Integration of lead-free ferroelectric on HfO2/Si (100) for high performance non-volatile memory applications. Sci Rep 2015; 5:8494. [PMID: 25683062 PMCID: PMC4329549 DOI: 10.1038/srep08494] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 01/20/2015] [Indexed: 11/08/2022] Open
Abstract
We introduce a novel lead-free ferroelectric thin film (1-x)BaTiO3-xBa(Cu1/3Nb2/3)O3 (x = 0.025) (BT-BCN) integrated on to HfO2 buffered Si for non-volatile memory (NVM) applications. Piezoelectric force microscopy (PFM), x-ray diffraction, and high resolution transmission electron microscopy were employed to establish the ferroelectricity in BT-BCN thin films. PFM study reveals that the domains reversal occurs with 180° phase change by applying external voltage, demonstrating its effectiveness for NVM device applications. X-ray photoelectron microscopy was used to investigate the band alignments between atomic layer deposited HfO2 and pulsed laser deposited BT-BCN films. Programming and erasing operations were explained on the basis of band-alignments. The structure offers large memory window, low leakage current, and high and low capacitance values that were easily distinguishable even after ~106 s, indicating strong charge storage potential. This study explains a new approach towards the realization of ferroelectric based memory devices integrated on Si platform and also opens up a new possibility to embed the system within current complementary metal-oxide-semiconductor processing technology.
Collapse
|
49
|
Structure, morphology and electrochemical properties of zinc–cobalt oxide films on AISI 304 type steel. J APPL ELECTROCHEM 2015. [DOI: 10.1007/s10800-015-0802-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
|
50
|
Salvinelli G, Drera G, Baratto C, Braga A, Sangaletti L. Stoichiometry gradient, cation interdiffusion, and band alignment between a nanosized TiO2 blocking layer and a transparent conductive oxide in dye-sensitized solar cell front contacts. ACS APPLIED MATERIALS & INTERFACES 2015; 7:765-773. [PMID: 25469853 DOI: 10.1021/am5072018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
An angle-resolved photoemission spectroscopy study allowed us to identify cation interdiffusion and stoichiometry gradients at the interface between a nanosized TiO2 blocking layer and a transparent conductive Cd-Sn oxide substrate. A stoichiometry gradient for the Sn cations is already found in the bare Cd-Sn oxide layer. When TiO2 ultrathin layers are deposited by RF sputtering on the Cd-Sn oxide layer, Ti is found to partially replace Sn, resulting in a Cd-Sn-Ti mixed oxide layer with a thickness ranging from 0.85 to 3.3 nm. The band gap profile across the junction has been reconstructed for three TiO2 layers, resulting in a valence band offset decrease (and a conduction band offset increase) with the blocking layer thickness. The results are related to the cell efficiencies in terms of charge injection and recombination processes.
Collapse
Affiliation(s)
- Gabriele Salvinelli
- Interdisciplinary Laboratories for Advanced Materials Physics (I-LAMP) and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore , I-25121 Brescia, Italy
| | | | | | | | | |
Collapse
|