1
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Caputo M, Studniarek M, Guedes EB, Schio L, Baiseitov K, Daffé N, Bachellier N, Chikina A, Di Santo G, Verdini A, Goldoni A, Muntwiler M, Piamonteze C, Floreano L, Radovic M, Dreiser J. Charge Transfer and Orbital Reconstruction at an Organic-Oxide Interface. NANO LETTERS 2023. [PMID: 38029285 DOI: 10.1021/acs.nanolett.3c03713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2023]
Abstract
The two-dimensional electron system (2DES) located at the surface of strontium titanate (STO) and at several other STO-based interfaces has been an established platform for the study of novel physical phenomena since its discovery. Here we report how the interfacing of STO and tetracyanoquinodimethane (TCNQ) results in a charge transfer that depletes the number of free carriers at the STO surface, with a strong impact on its electronic structure. Our study paves the way for efficient tuning of the electronic properties, which promises novel applications in the framework of oxide/organic-based electronics.
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Affiliation(s)
- Marco Caputo
- Elettra Sincrotrone Trieste, s.s. 14 km 163.5 in Area Science Park, 34149 Trieste, Italy
- MAX IV Laboratory, Lund University, PO Box 118, 22100 Lund, Sweden
| | - Michał Studniarek
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Eduardo Bonini Guedes
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Luca Schio
- Laboratorio TASC, Istituto Officina dei Materiali (IOM)-CNR, Area Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Kassymkhan Baiseitov
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Niéli Daffé
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Nicolas Bachellier
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Alla Chikina
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Giovanni Di Santo
- Elettra Sincrotrone Trieste, s.s. 14 km 163.5 in Area Science Park, 34149 Trieste, Italy
| | - Alberto Verdini
- Laboratorio TASC, Istituto Officina dei Materiali (IOM)-CNR, Area Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Andrea Goldoni
- Elettra Sincrotrone Trieste, s.s. 14 km 163.5 in Area Science Park, 34149 Trieste, Italy
| | - Matthias Muntwiler
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Cinthia Piamonteze
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Luca Floreano
- Laboratorio TASC, Istituto Officina dei Materiali (IOM)-CNR, Area Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Milan Radovic
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Jan Dreiser
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
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2
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Hydrogen-Ti<sup>3+</sup> Complex as a Possible Origin of Localized Electron Behavior in Hydrogen-Irradiated SrTiO<sub>3</sub>. E-JOURNAL OF SURFACE SCIENCE AND NANOTECHNOLOGY 2022. [DOI: 10.1380/ejssnt.2022-021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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3
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Fu R, Wu Z, Pan Z, Gao Z, Li Z, Kong X, Li L. Fluorine-Induced Surface Metallization for Ammonia Synthesis under Photoexcitation up to 1550 nm. Angew Chem Int Ed Engl 2021; 60:11173-11179. [PMID: 33650282 DOI: 10.1002/anie.202100572] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 02/17/2021] [Indexed: 11/10/2022]
Abstract
The first observation of surface metallization of TiO2-x induced by fluoride ions is presented. The emerging metallic states are contributed by the 3d orbital of surface Ti and the 2p orbital of surface bridging F, which are intrinsically originated from the strong electron repulsion between F- and adjacent Ti3+ . The metalized TiO2-x with reduced work function and downward band bending possesses high electron-donating power to supported Ru species via atomic-scale ohmic contacts, exhibiting unprecedented photocatalytic performances for ammonia synthesis across the entire solar spectrum region (200-1550 nm) at room temperature. Mechanism and kinetic analysis revealed that the loaded Ru could behave as efficient electron sinks to accumulate photogenerated electrons and that the metallic surface markedly enhanced the dissociation of H2 and N2 by the hot electrons generated by the visible or even infrared light irradiation.
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Affiliation(s)
- Rong Fu
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Zewen Wu
- College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China.,Centre for the Physics of Materials and Department of Physics, McGill University, Montreal, QC, H3A 2T8, Canada
| | - Ziye Pan
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Zhuoyang Gao
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Zhen Li
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Xianghua Kong
- College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China.,Centre for the Physics of Materials and Department of Physics, McGill University, Montreal, QC, H3A 2T8, Canada
| | - Lu Li
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun, 130012, P. R. China.,Electron Microscopy Center, Jilin University, Changchun, 130012, P. R. China
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4
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Fluorine‐Induced Surface Metallization for Ammonia Synthesis under Photoexcitation up to 1550 nm. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202100572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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5
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Qiu R, Tang J, Chen J, Ao B. Metallic and anti-metallic properties of hydrogen adsorbed AnO 2 (An = Th, U, and Pu) surfaces. Phys Chem Chem Phys 2021; 23:878-885. [PMID: 33346754 DOI: 10.1039/d0cp04824k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The effect of atomic hydrogen adsorption on AnO2 (An = Th, U, and Pu) surfaces is studied in the framework of density functional theory and Hubbard-corrected density functional theory. Several adsorption coverages (1/3, 1/2, 2/3, and 1 monolayer) are considered. For the band insulator ThO2, surface metallicity induced by hydrogen adsorption is observed due to the electron donation of the hydrogen to the surface. But this effect is found to be strongly suppressed by electronic correlation for the Mott insulators UO2 and PuO2 because the electrons from the adsorbed hydrogen atoms occupy the localized 5f orbitals of the surface U/Pu atoms.
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Affiliation(s)
- Ruizhi Qiu
- Science and Technology on Surface Physics and Chemistry Laboratory, Mianyang 621908, Sichuan, China.
| | - Jun Tang
- Science and Technology on Surface Physics and Chemistry Laboratory, Mianyang 621908, Sichuan, China.
| | - Jinfan Chen
- Science and Technology on Surface Physics and Chemistry Laboratory, Mianyang 621908, Sichuan, China.
| | - Bingyun Ao
- Science and Technology on Surface Physics and Chemistry Laboratory, Mianyang 621908, Sichuan, China.
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6
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Abstract
Hydrogen is ubiquitous in catalysis. It is involved in many important reactions such as water splitting, N2 reduction, CO2 reduction, and alkane activation. In this Perspective, we focus on the hydrogen atom and follow its electron as it interacts with a catalyst or behaves as part of a catalyst from a computational point of view. We present recent examples in both nanocluster and solid catalysts to elucidate the parameters governing the strength of the hydrogen-surface interactions based on site geometry and electronic structure. We further show the interesting behavior of hydride in nanometal and oxides for catalysis. The key take-home messages are: (1) the in-the-middle electronegativity and small size of hydrogen give it great versatility in interacting with active sites on nanoparticles and solid surfaces; (2) the strength of hydrogen binding to an active site on a surface is an important descriptor of the chemical and catalytic properties of the surface; (3) the energetics of the hydrogen binding is closely related to the electronic structure of the catalyst; (4) hydrides in nanoclusters and oxides and on surfaces offer unique reactivity for reduction reactions.
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Affiliation(s)
- Victor Fung
- Department of Chemistry, University of California, Riverside, California 92521, United States
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Guoxiang Hu
- Department of Chemistry, University of California, Riverside, California 92521, United States
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Zili Wu
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - De-En Jiang
- Department of Chemistry, University of California, Riverside, California 92521, United States
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7
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Portugal GR, Arantes JT. Structural and electronic properties of NaTaO3 cubic nanowires. Phys Chem Chem Phys 2020; 22:7250-7258. [DOI: 10.1039/c9cp06769h] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Sodium tantalate 1-D nanostructures show novel properties due to their edge confinement region, which may be relevant for distinct applications.
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Affiliation(s)
- Guilherme Ribeiro Portugal
- Federal University of ABC (UFABC)
- Center for Engineering
- Modeling and Applied Social Science – CECS
- Santo André
- Brazil
| | - Jeverson Teodoro Arantes
- Federal University of ABC (UFABC)
- Center for Engineering
- Modeling and Applied Social Science – CECS
- Santo André
- Brazil
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8
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Segmented Undulator for Extensive Polarization Controls in ≤1 nm-rad Emittance Rings. E-JOURNAL OF SURFACE SCIENCE AND NANOTECHNOLOGY 2019. [DOI: 10.1380/ejssnt.2019.41] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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9
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Morimoto Y, Nishiyama J, Takeda H, Tsurumi T, Hoshina T. Transparent semiconducting SrTiO3 crystal fabricated by heating treatment with gaseous ammonia and CeO2 powder. Sci Rep 2018; 8:5031. [PMID: 29568047 PMCID: PMC5864887 DOI: 10.1038/s41598-018-23019-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 03/02/2018] [Indexed: 11/09/2022] Open
Abstract
A transparent semiconducting SrTiO3 single crystal with a resistivity of the order of 103 Ω·cm was fabricated by heating a SrTiO3 single crystal with gaseous ammonia and CeO2 powder. Conductive atomic force microscope (C-AFM) measurement revealed that micro-sized voids were formed and the high conductivity was exhibited only at around the voids. It is considered that the micro-sized voids were caused by the concentrated SrO planar defects, and TiO2-terminated structure with oxygen vacancies contributed to the two-dimensional conduction. In the heating process, the CeO2 powder acted as an oxygen source, and radicals such as NH2 and NH were generated by the reaction of oxygen and ammonia. The radicals may have contributed to the formation of three-dimensional network of the conductive paths consisting of SrO planar defects without the reduction of the bulk components. The electrons were localized on the TiO2-terminated structure, and the volume content of the conductive paths was small compared to the insulating bulk component. Therefore, the crystal was optically transparent and semiconducting.
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10
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First-principles Study of Rashba Spin Splitting at Strained SrTiO<sub>3</sub>(001) Surfaces. E-JOURNAL OF SURFACE SCIENCE AND NANOTECHNOLOGY 2018. [DOI: 10.1380/ejssnt.2018.360] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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11
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Thermooptical evidence of carrier-stabilized ferroelectricity in ultrathin electrodeless films. Sci Rep 2018; 8:8497. [PMID: 29855531 PMCID: PMC5981214 DOI: 10.1038/s41598-018-26933-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Accepted: 05/17/2018] [Indexed: 11/25/2022] Open
Abstract
Ferroelectric films may lose polarization as their thicknesses decrease to a few nanometers because of the depolarizing field that opposes the polarization therein. The depolarizing field is minimized when electrons or ions in the electrodes or the surface/interface layers screen the polarization charge or when peculiar domain configuration is formed. Here, we demonstrate ferroelectric phase transitions using thermooptical studies in ∼5-nm-thick epitaxial Pb0.5Sr0.5TiO3 films grown on different insulating substrates. By comparing theoretical modeling and experimental observations, we show that ferroelectricity is stabilized through redistribution of charge carriers (electrons or holes) inside ultrathin films. The related high-density of screening carriers is confined within a few-nanometers-thick layer in the vicinity of the insulator, thus resembling a two-dimensional carrier gas.
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12
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Plumb NC, Radović M. Angle-resolved photoemission spectroscopy studies of metallic surface and interface states of oxide insulators. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:433005. [PMID: 28961143 DOI: 10.1088/1361-648x/aa833f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Over the last decade, conducting states embedded in insulating transition metal oxides (TMOs) have served as gateways to discovering and probing surprising phenomena that can emerge in complex oxides, while also opening opportunities for engineering advanced devices. These states are commonly realized at thin film interfaces, such as the well-known case of LaAlO3 (LAO) grown on SrTiO3 (STO). In recent years, the use of angle-resolved photoemission spectroscopy (ARPES) to investigate the k-space electronic structure of such materials led to the discovery that metallic states can also be formed on the bare surfaces of certain TMOs. In this topical review, we report on recent studies of low-dimensional metallic states confined at insulating oxide surfaces and interfaces as seen from the perspective of ARPES, which provides a direct view of the occupied band structure. While offering a fairly broad survey of progress in the field, we draw particular attention to STO, whose surface is so far the best-studied, and whose electronic structure is probably of the most immediate interest, given the ubiquitous use of STO substrates as the basis for conducting oxide interfaces. The ARPES studies provide crucial insights into the electronic band structure, orbital character, dimensionality/confinement, spin structure, and collective excitations in STO surfaces and related oxide surface/interface systems. The obtained knowledge increases our understanding of these complex materials and gives new perspectives on how to manipulate their properties.
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Affiliation(s)
- Nicholas C Plumb
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
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13
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Fukutani K, Wilde M, Ogura S. Nuclear Dynamics and Electronic Effects of Hydrogen on Solid Surfaces. CHEM REC 2016; 17:233-249. [DOI: 10.1002/tcr.201600077] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2016] [Indexed: 11/06/2022]
Affiliation(s)
- K. Fukutani
- Institute of Industrial Science; The University of Tokyo, Komaba, Meguro-ku; Tokyo 153-8505 Japan
| | - M. Wilde
- Institute of Industrial Science; The University of Tokyo, Komaba, Meguro-ku; Tokyo 153-8505 Japan
| | - S. Ogura
- Institute of Industrial Science; The University of Tokyo, Komaba, Meguro-ku; Tokyo 153-8505 Japan
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14
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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.
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Affiliation(s)
- Seungbum Hong
- Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA. Department of Materials Science & Engineering, KAIST, Daejeon 305-701, Korea
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15
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Mechanical writing of n-type conductive layers on the SrTiO3 surface in nanoscale. Sci Rep 2015; 5:10841. [PMID: 26042679 PMCID: PMC4455303 DOI: 10.1038/srep10841] [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: 02/18/2015] [Accepted: 05/01/2015] [Indexed: 11/22/2022] Open
Abstract
The fabrication and control of the conductive surface and interface on insulating SrTiO3 bulk provide a pathway for oxide electronics. The controllable manipulation of local doping concentration in semiconductors is an important step for nano-electronics. Here we show that conductive patterns can be written on bare SrTiO3 surface by controllable doping in nanoscale using the mechanical interactions of atomic force microscopy tip without applying external electric field. The conductivity of the layer is n-type, oxygen sensitive, and can be effectively tuned by the gate voltage. Hence, our findings have potential applications in oxide nano-circuits and oxygen sensors.
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16
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Goniakowski J, Noguera C. Conditions for electronic reconstruction at stoichiometric polar/polar interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:485010. [PMID: 25374280 DOI: 10.1088/0953-8984/26/48/485010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Relying on first principles simulations of ZnO(0 0 0 1)/MgO(1 1 1), MgO(1 1 1)/CaO(1 1 1) and AlN(0 0 0 1)/GaN(0 0 0 1) interfaces and examples taken from the literature, we discuss under which conditions stoichiometric polar/polar interfaces may display an electronic reconstruction. We point out the role of the three contributions to the interfacial polarization discontinuity--structure, valence and electronic terms--of interfacial strains, and of finite size effects. Depending upon their relative values, the interfaces may be polar (compensated by an electron reconstruction), non-polar, or polar uncompensated at low thickness. We stress that, in superlattices or heterostructures made of thin layers, the prediction of the interface polarity character from the bulk properties of the two materials may be questionable.
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Affiliation(s)
- Jacek Goniakowski
- CNRS, UMR 7588, Institut des Nanosciences de Paris, F-75005 Paris, France. Sorbonne Universités, UPMC Université Paris 06, UMR 7588, INSP, F-75005 Paris, France
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17
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Wang Z, Hao X, Gerhold S, Mares P, Wagner M, Bliem R, Schulte K, Schmid M, Franchini C, Diebold U. Stabilizing Single Ni Adatoms on a Two-Dimensional Porous Titania Overlayer at the SrTiO 3(110) Surface. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2014; 118:19904-19909. [PMID: 25177410 PMCID: PMC4148460 DOI: 10.1021/jp506234r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 07/29/2014] [Indexed: 05/24/2023]
Abstract
Nickel vapor-deposited on the SrTiO3(110) surface was studied using scanning tunneling microscopy, photoemission spectroscopy (PES), and density functional theory calculations. This surface forms a (4 × 1) reconstruction, composed of a 2-D titania structure with periodic six- and ten-membered nanopores. Anchored at these nanopores, Ni single adatoms are stabilized at room temperature. PES measurements show that the Ni adatoms create an in-gap state located at 1.9 eV below the conduction band minimum and induce an upward band bending. Both experimental and theoretical results suggest that Ni adatoms are positively charged. Our study produces well-dispersed single-adatom arrays on a well-characterized oxide support, providing a model system to investigate single-adatom catalytic and magnetic properties.
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Affiliation(s)
- Zhiming Wang
- Institute
of Applied Physics, Vienna University of
Technology, Wiedner Hauptstraße
8-10, 1040 Vienna, Austria
| | - Xianfeng Hao
- Institute
of Applied Physics, Vienna University of
Technology, Wiedner Hauptstraße
8-10, 1040 Vienna, Austria
| | - Stefan Gerhold
- Institute
of Applied Physics, Vienna University of
Technology, Wiedner Hauptstraße
8-10, 1040 Vienna, Austria
| | - Petr Mares
- Institute
of Applied Physics, Vienna University of
Technology, Wiedner Hauptstraße
8-10, 1040 Vienna, Austria
- CEITEC BUT, Technicka 10, 61669 Brno, Czech Republic
| | - Margareta Wagner
- Institute
of Applied Physics, Vienna University of
Technology, Wiedner Hauptstraße
8-10, 1040 Vienna, Austria
| | - Roland Bliem
- Institute
of Applied Physics, Vienna University of
Technology, Wiedner Hauptstraße
8-10, 1040 Vienna, Austria
| | - Karina Schulte
- MAX IV Laboratory, Lund University, Ole
Römers väg 1, 223 63 Lund, Sweden
| | - Michael Schmid
- Institute
of Applied Physics, Vienna University of
Technology, Wiedner Hauptstraße
8-10, 1040 Vienna, Austria
| | - Cesare Franchini
- Faculty of Physics
and Center for Computational Materials Science, University of Vienna, Sensengasse 8/12, 1090 Vienna, Austria
| | - Ulrike Diebold
- Institute
of Applied Physics, Vienna University of
Technology, Wiedner Hauptstraße
8-10, 1040 Vienna, Austria
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18
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Visikovskiy A, Mitsuhara K, Hazama M, Kohyama M, Kido Y. The atomic and electronic structures of NiO(001)∕Au(001) interfaces. J Chem Phys 2014; 139:144705. [PMID: 24116639 DOI: 10.1063/1.4820823] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The atomic and electronic structures of NiO(001)∕Au(001) interfaces were analyzed by high-resolution medium energy ion scattering (MEIS) and photoelectron spectroscopy using synchrotron-radiation-light. The MEIS analysis clearly showed that O atoms were located above Au atoms at the interface and the inter-planar distance of NiO(001)∕Au(001) was derived to be 2.30 ± 0.05 Å, which was consistent with the calculations based on the density functional theory (DFT). We measured the valence band spectra and found metallic features for the NiO thickness up to 3 monolayer (ML). Relevant to the metallic features, electron energy loss analysis revealed that the bandgap for NiO(001)∕Au(001) reduced with decreasing the NiO thickness from 10 down to 5 ML. We also observed Au 4f lines consisting of surface, bulk, and interface components and found a significant electronic charge transfer from Au(001) to NiO(001). The present DFT calculations demonstrated the presence of an image charge beneath Ni atoms at the interface just like alkali-halide∕metal interface, which may be a key issue to explain the core level shift and band structure.
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Affiliation(s)
- A Visikovskiy
- Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Fukuoka 819-0395, Japan
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19
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Takeyasu K, Fukada K, Ogura S, Matsumoto M, Fukutani K. Two charged states of hydrogen on the SrTiO3(001) surface. J Chem Phys 2014; 140:084703. [DOI: 10.1063/1.4866645] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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20
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King PDC, McKeown Walker S, Tamai A, de la Torre A, Eknapakul T, Buaphet P, Mo SK, Meevasana W, Bahramy MS, Baumberger F. Quasiparticle dynamics and spin–orbital texture of the SrTiO3 two-dimensional electron gas. Nat Commun 2014; 5:3414. [DOI: 10.1038/ncomms4414] [Citation(s) in RCA: 126] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 02/07/2014] [Indexed: 11/10/2022] Open
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21
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Cai Y, Bai Z, Pan H, Feng YP, Yakobson BI, Zhang YW. Constructing metallic nanoroads on a MoS₂ monolayer via hydrogenation. NANOSCALE 2014; 6:1691-1697. [PMID: 24343306 DOI: 10.1039/c3nr05218d] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Monolayer transition metal dichalcogenides recently emerged as a new family of two-dimensional materials potentially suitable for numerous applications in electronic and optoelectronic devices due to the presence of a finite band gap. Many proposed applications require efficient transport of charge carriers within these semiconducting monolayers. However, constructing a stable conducting nanoroad on these atomically thin semiconductors is still a challenge. Here we demonstrate that hydrogenation on the surface of a MoS₂ monolayer induces a semiconductor-metal transition, and strip-patterned hydrogenation is able to generate a conducting nanoroad. The band-gap closing arises from the formation of in-gap hybridized states mainly consisting of Mo 4d orbitals, as well as the electron donation from hydrogen to the lattice host. Ballistic conductance calculations reveal that such a nanoroad on the MoS₂ surface exhibits an integer conductance, indicating small carrier scattering, and thus is ideal for serving as a conducting channel or an interconnect without compromising the mechanical and structural integrity of the monolayer.
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Affiliation(s)
- Yongqing Cai
- Institute of High Performance Computing, 1 Fusionopolis Way, Singapore, 138632, Singapore.
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22
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Wang Z, Hao X, Gerhold S, Novotny Z, Franchini C, McDermott E, Schulte K, Schmid M, Diebold U. Water Adsorption at the Tetrahedral Titania Surface Layer of SrTiO 3(110)-(4 × 1). THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2013; 117:26060-26069. [PMID: 24353755 PMCID: PMC3864247 DOI: 10.1021/jp407889h] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Revised: 11/22/2013] [Indexed: 05/24/2023]
Abstract
The interaction of water with oxide surfaces is of great interest for both fundamental science and applications. We present a combined theoretical (density functional theory (DFT)) and experimental (scanning tunneling microscopy (STM) and photoemission spectroscopy (PES)) study of water interaction with the two-dimensional titania overlayer that terminates the SrTiO3(110)-(4 × 1) surface and consists of TiO4 tetrahedra. STM and core-level and valence band PES show that H2O neither adsorbs nor dissociates on the stoichiometric surface at room temperature, whereas it does dissociate at oxygen vacancies. This is in agreement with DFT calculations, which show that the energy barriers for water dissociation on the stoichiometric and reduced surfaces are 1.7 and 0.9 eV, respectively. We propose that water weakly adsorbs on two-dimensional, tetrahedrally coordinated overlayers.
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Affiliation(s)
- Zhiming Wang
- Institute
of Applied Physics, Vienna University of
Technology, 1040 Vienna, Austria
| | - Xianfeng Hao
- Institute
of Applied Physics, Vienna University of
Technology, 1040 Vienna, Austria
| | - Stefan Gerhold
- Institute
of Applied Physics, Vienna University of
Technology, 1040 Vienna, Austria
| | - Zbynek Novotny
- Institute
of Applied Physics, Vienna University of
Technology, 1040 Vienna, Austria
| | - Cesare Franchini
- Faculty
of Physics & Center for Computational
Materials Science, University of Vienna, 1090 Vienna, Austria
| | - Eamon McDermott
- Institute
of Materials Chemistry, Vienna University
of Technology, 1060 Vienna, Austria
| | - Karina Schulte
- MAX
IV Laboratory, Lund University, SE-221 00 Lund, Sweden
| | - Michael Schmid
- Institute
of Applied Physics, Vienna University of
Technology, 1040 Vienna, Austria
| | - Ulrike Diebold
- Institute
of Applied Physics, Vienna University of
Technology, 1040 Vienna, Austria
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23
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Lin C, Demkov AA. Electron correlation in oxygen vacancy in SrTiO3. PHYSICAL REVIEW LETTERS 2013; 111:217601. [PMID: 24313525 DOI: 10.1103/physrevlett.111.217601] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Indexed: 06/02/2023]
Abstract
Oxygen vacancies are an important type of defect in transition metal oxides. In SrTiO3 they are believed to be the main donors in an otherwise intrinsic crystal. At the same time, a relatively deep gap state associated with the vacancy is widely reported. To explain this inconsistency we investigate the effect of electron correlation in an oxygen vacancy (OV) in SrTiO3. When taking correlation into account, we find that the OV-induced localized level can at most trap one electron, while the second electron occupies the conduction band. Our results offer a natural explanation of how the OV in SrTiO3 can produce a deep in-gap level (about 1 eV below the conduction band bottom) in photoemission, and at the same time be an electron donor. Our analysis implies that an OV in SrTiO3 should be fundamentally regarded as a magnetic impurity, whose deep level is always partially occupied due to the strong Coulomb repulsion. An OV-based Anderson impurity model is derived, and its implications are discussed.
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Affiliation(s)
- Chungwei Lin
- Department of Physics, University of Texas at Austin, Austin, Texas 78712, USA
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24
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Matsuda T, Yoshida Y, Mitsuhara K, Kido Y. The structure of SrTiO3(001)-2 × 1 surface analyzed by high-resolution medium energy ion scattering coupled with ab initio calculations. J Chem Phys 2013; 138:244705. [PMID: 23822262 DOI: 10.1063/1.4811485] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
High-resolution medium energy ion scattering (MEIS) spectrometry coupled with photoelectron spectroscopy revealed unambiguously that the initial SrTiO3(001) surface chemically etched in a buffered NH4F-HF solution was perfectly terminated with a single-layer (SL) of TiO2(001) and annealing the surface at 600-800 [ordinal indicator, masculine]C in ultrahigh vacuum (UHV) led to a (2 × 1)-reconstructed surface terminated with a double-layer (DL) of TiO2(001). After annealing in UHV, rock-salt SrO(001) clusters with two atomic layer height grew epitaxially on the DL-TiO2(001)-2 × 1 surface with a coverage of 20%-30%. High-resolution MEIS in connection with ab initio calculations demonstrated the structure of the DL-TiO2(001)-2 × 1 surface close to that proposed by Erdman et al. [Nature (London) 419, 55 (2002)] rather than that predicted by Herger et al. [Phys. Rev. Lett. 98, 076102 (2007)]. Based on the MEIS analysis combined with the ab initio calculations, we propose the most probable (2 × 1) surface structure.
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Affiliation(s)
- Taishi Matsuda
- Department of Physics, Ritsumeikan University, Kusatsu, Shiga-ken 525-8577, Japan
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25
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Takeyasu K, Fukada K, Matsumoto M, Fukutani K. Control of the surface electronic structure of SrTiO3(001) by modulation of the density of oxygen vacancies. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:162202. [PMID: 23503170 DOI: 10.1088/0953-8984/25/16/162202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The influence of electron irradiation and the subsequent oxygen adsorption on the electronic structure of an SrTiO3(001) surface was investigated by ultraviolet photoemission spectroscopy (UPS). Electron irradiation induced an in-gap state (IGS) as observed by UPS keeping the surface 1 × 1, which is considered to originate from oxygen vacancies on the topmost surface due to the electron-stimulated desorption (ESD) of oxygen. Electron irradiation also caused a downward shift of the valence band maximum, indicating downward band bending and the formation of a conductive layer on the surface. Adsorption of oxygen on the electron-irradiated surface, on the other hand, reduced the intensity of the IGS along with yielding upward band bending, which points to disappearance of the conductive layer. The results show that ESD and oxygen adsorption can be used to control the surface electronic structure switching between semiconducting and metallic regimes by changing the density of the oxygen vacancies.
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Affiliation(s)
- Kotaro Takeyasu
- Institute of Industrial Science, The University of Tokyo, Meguro-ku, Tokyo, Japan.
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26
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Affiliation(s)
- Claudine Noguera
- Institut des Nanosciences de Paris, UMR 7588, CNRS, and Université Pierre et Marie Curie, 4 Place Jussieu, 75005 Paris, France
| | - Jacek Goniakowski
- Institut des Nanosciences de Paris, UMR 7588, CNRS, and Université Pierre et Marie Curie, 4 Place Jussieu, 75005 Paris, France
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