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Herklotz A, Lee D, Guo EJ, Meyer TL, Petrie JR, Lee HN. Strain coupling of oxygen non-stoichiometry in perovskite thin films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:493001. [PMID: 29130456 DOI: 10.1088/1361-648x/aa949b] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The effects of strain and oxygen vacancies on perovskite thin films have been studied in great detail over the past decades and have been treated separately from each other. While epitaxial strain has been realized as a tuning knob to tailor the functional properties of correlated oxides, oxygen vacancies are usually regarded as undesirable and detrimental. In transition metal oxides, oxygen defects strongly modify the properties and functionalities via changes in oxidation states of the transition metals. However, such coupling is not well understood in epitaxial films, but rather deemed as cumbersome or experimental artifact. Only recently it has been recognized that lattice strain and oxygen non-stoichiometry are strongly correlated in a vast number of perovskite systems and that this coupling can be beneficial for information and energy technologies. Recent experimental and theoretical studies have focused on understanding the correlated phenomena between strain and oxygen vacancies for a wide range of perovskite systems. These correlations not only include the direct relationship between elastic strain and the formation energy of oxygen vacancies, but also comprise highly complex interactions such as strain-induced phase transitions due to oxygen vacancy ordering. Therefore, we aim in this review to give a comprehensive overview on the coupling between strain and oxygen vacancies in perovskite oxides and point out the potential applications of the emergent functionalities strongly coupled to oxygen vacancies.
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Affiliation(s)
- Andreas Herklotz
- Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States of America
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Dai W, Yang M, Lee H, Lee JW, Eom CB, Cen C. Tailoring the Doping Mechanisms at Oxide Interfaces in Nanoscale. NANO LETTERS 2017; 17:5620-5625. [PMID: 28806520 DOI: 10.1021/acs.nanolett.7b02508] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Here, we demonstrate the nanoscale manipulations of two types of charge transfer to the LaAlO3/SrTiO3 interfaces: one from surface adsorbates and another from oxygen vacancies inside LaAlO3 films. This method can be used to produce multiple insulating and metallic interface states with distinct carrier properties that are highly stable in air. By reconfiguring the patterning and comparing interface structures formed from different doping sources, effects of extrinsic and intrinsic material characters on the transport properties can be distinguished. In particular, a multisubband to single-subband transition controlled by the structural phases in SrTiO3 was revealed. In addition, the transient behaviors of nanostructures also provided a unique opportunity to study the nanoscale diffusions of adsorbates and oxygen vacancies in oxide heterostructures. Knowledge of such dynamic processes is important for nanodevice implementations.
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Affiliation(s)
- Weitao Dai
- Department of Physics and Astronomy, West Virginia University , Morgantown, West Virginia 26506, United States
| | - Ming Yang
- Department of Physics and Astronomy, West Virginia University , Morgantown, West Virginia 26506, United States
| | - Hyungwoo Lee
- Department of Material Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Jung-Woo Lee
- Department of Material Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Chang-Beom Eom
- Department of Material Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Cheng Cen
- Department of Physics and Astronomy, West Virginia University , Morgantown, West Virginia 26506, United States
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Coey JMD, Venkatesan M, Stamenov P. Surface magnetism of strontium titanate. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:485001. [PMID: 27666311 DOI: 10.1088/0953-8984/28/48/485001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
SrTiO3 plays a central role in oxide electronics. It is the substrate of choice for functional oxide heterostructures based on perovskite-structure thin-film stacks, and its surface or interface with a polar oxide such as LaAlO3 can become a 2D conductor because of electronic reconstruction or the presence of oxygen defects. Inconsistent reports of magnetic order in SrTiO3 abound in the literature. Here, we report a systematic experimental study aimed at establishing how and when SrTiO3 can develop a magnetic moment at room temperature. Polished (1 0 0), (1 1 0) or (1 1 1) crystal slices from four different suppliers are characterized before and after vacuum annealing at 750 °C, both in single-crystal and powdered form. Impurity content is analysed at the surface and in the bulk. Besides the underlying intrinsic diamagnetism of SrTiO3, magnetic signals are of three types-a Curie law susceptibility due to dilute magnetic impurities at the ppm level, a hysteretic temperature-dependent ferromagnetic impurity contribution, and a practically anhysteretic defect-related temperature-independent component that saturates in about 200 mT. The latter component is intrinsic. It is often the largest, reaching 10 μ B nm-2 of the surface area or more and dominating the magnetic response in low fields at room temperature. It is associated with defects near the surface, and can be destroyed by treatment with Tiron (C6H4Na2O8S2), an electron donor molecule that forms a strong complex with titanium at the surface. The origin of this unusual high-temperature ferromagnetic-like response is discussed.
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Affiliation(s)
- J M D Coey
- School of Physics, Trinity College, Dublin 2, Ireland
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Interfacial control of oxygen vacancy doping and electrical conduction in thin film oxide heterostructures. Nat Commun 2016; 7:11892. [PMID: 27283250 PMCID: PMC4906403 DOI: 10.1038/ncomms11892] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 05/10/2016] [Indexed: 11/26/2022] Open
Abstract
Oxygen vacancies in proximity to surfaces and heterointerfaces in oxide thin film heterostructures have major effects on properties, resulting, for example, in emergent conduction behaviour, large changes in metal-insulator transition temperatures or enhanced catalytic activity. Here we report the discovery of a means of reversibly controlling the oxygen vacancy concentration and distribution in oxide heterostructures consisting of electronically conducting In2O3 films grown on ionically conducting Y2O3-stabilized ZrO2 substrates. Oxygen ion redistribution across the heterointerface is induced using an applied electric field oriented in the plane of the interface, resulting in controlled oxygen vacancy (and hence electron) doping of the film and possible orders-of-magnitude enhancement of the film's electrical conduction. The reversible modified behaviour is dependent on interface properties and is attained without cation doping or changes in the gas environment. Oxygen vacancies near the interface in oxide heterostructures can lead to large changes in properties, including metal–insulator transition temperatures or catalytic activity. Here, the authors demonstrate a way to reversibly control the oxygen-vacancy concentration and distribution in oxide heterostructures.
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Han K, Palina N, Zeng SW, Huang Z, Li CJ, Zhou WX, Wan DY, Zhang LC, Chi X, Guo R, Chen JS, Venkatesan T, Rusydi A, Ariando A. Controlling Kondo-like Scattering at the SrTiO3-based Interfaces. Sci Rep 2016; 6:25455. [PMID: 27147407 PMCID: PMC4857089 DOI: 10.1038/srep25455] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 04/13/2016] [Indexed: 11/08/2022] Open
Abstract
The observation of magnetic interaction at the interface between nonmagnetic oxides has attracted much attention in recent years. In this report, we show that the Kondo-like scattering at the SrTiO3-based conducting interface is enhanced by increasing the lattice mismatch and growth oxygen pressure PO2. For the 26-unit-cell LaAlO3/SrTiO3 (LAO/STO) interface with lattice mismatch being 3.0%, the Kondo-like scattering is observed when PO2 is beyond 1 mTorr. By contrast, when the lattice mismatch is reduced to 1.0% at the (La0.3Sr0.7)(Al0.65Ta0.35)O3/SrTiO3 (LSAT/STO) interface, the metallic state is always preserved up to PO2 of 100 mTorr. The data from Hall measurement and X-ray absorption near edge structure (XANES) spectroscopy reveal that the larger amount of localized Ti(3+) ions are formed at the LAO/STO interface compared to LSAT/STO. Those localized Ti(3+) ions with unpaired electrons can be spin-polarized to scatter mobile electrons, responsible for the Kondo-like scattering observed at the LAO/STO interface.
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Affiliation(s)
- K. Han
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - N. Palina
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Singapore Synchrotron Light Source, National University of Singapore, Singapore 117603, Singapore
| | - S. W. Zeng
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Z. Huang
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
| | - C. J. Li
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
| | - W. X. Zhou
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - D.-Y. Wan
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - L. C. Zhang
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - X. Chi
- Singapore Synchrotron Light Source, National University of Singapore, Singapore 117603, Singapore
| | - R. Guo
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Material Science & Engineering, National University of Singapore, Singapore 117575, Singapore
| | - J. S. Chen
- Department of Material Science & Engineering, National University of Singapore, Singapore 117575, Singapore
| | - T. Venkatesan
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
- Department of Material Science & Engineering, National University of Singapore, Singapore 117575, Singapore
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576, Singapore
- National University of Singapore Graduate School for Integrative Sciences and Engineering (NGS), 28 Medical Drive, Singapore 117456, Singapore
| | - A. Rusydi
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
- Singapore Synchrotron Light Source, National University of Singapore, Singapore 117603, Singapore
| | - A Ariando
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
- National University of Singapore Graduate School for Integrative Sciences and Engineering (NGS), 28 Medical Drive, Singapore 117456, Singapore
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