1
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Li Y, Huang Y, Liu X, Wang Y, Yuan L. Density functional theory study on the formation mechanism and electrical properties of two-dimensional electron gas in biaxial-strained LaGaO 3 /BaSnO 3 heterostructure. Sci Rep 2024; 14:10259. [PMID: 38704471 DOI: 10.1038/s41598-024-60893-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2024] [Accepted: 04/29/2024] [Indexed: 05/06/2024] Open
Abstract
The two-dimensional electron gas (2DEG) in BaSnO3 -based heterostructure (HS) has received tremendous attention in the electronic applications because of its excellent electron migration characteristic. We modeled the n-type (LaO)+ /(SnO2 )0 interface by depositing LaGaO3 film on the BaSnO3 substrate and explored strain effects on the critical thickness for forming 2DEG and electrical properties of LaGaO3 /BaSnO3 HS system using first-principles electronic structure calculations. The results indicate that to form 2DEG in the unstrained LaGaO3 /BaSnO3 HS system, a minimum thickness of approximately 4 unit cells of LaGaO3 film is necessary. An increased film thickness of LaGaO3 is required to form the 2DEG for -3%-biaxially-strained HS system and the critical thickness is 3 unit cells for 3%-baxially-strained HS system, which is caused by the strain-induced change of the electrostatic potential in LaGaO3 film. In addition, the biaxial strain plays an important role in tailoring the electrical properties of 2DEG in LaGaO3 /BaSnO3 HS syestem. The interfacial charge carrier density, electron mobility and electrical conductivity can be optimized when a moderate tensile strain is applied on the BaSnO3 substrate in the ab-plane.
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Affiliation(s)
- Yuling Li
- Key Laboratory of Fluid and Power Machinery, School of Material Science and Engineering, Xihua University, Chengdu, 610039, People's Republic of China
| | - Yuxi Huang
- Key Laboratory of Fluid and Power Machinery, School of Material Science and Engineering, Xihua University, Chengdu, 610039, People's Republic of China
| | - Xiaohua Liu
- Key Laboratory of Fluid and Power Machinery, School of Material Science and Engineering, Xihua University, Chengdu, 610039, People's Republic of China
| | - Yaqin Wang
- Key Laboratory of Fluid and Power Machinery, School of Material Science and Engineering, Xihua University, Chengdu, 610039, People's Republic of China.
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, People's Republic of China.
| | - Le Yuan
- Key Laboratory of Fluid and Power Machinery, School of Material Science and Engineering, Xihua University, Chengdu, 610039, People's Republic of China
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2
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Kwon D, Kwak Y, Lee D, Jo W, Cho BG, Koo TY, Song J. Strong Rashba parameter of two-dimensional electron gas at CaZrO 3/SrTiO 3 heterointerface. Sci Rep 2023; 13:15927. [PMID: 37741927 PMCID: PMC10517959 DOI: 10.1038/s41598-023-43247-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Accepted: 09/21/2023] [Indexed: 09/25/2023] Open
Abstract
We synthesized a CaZrO3/SrTiO3 oxide heterostructure, which can serve as an alternative to LaAlO3/SrTiO3, and confirmed the generation of 2-dimensional electron gas (2-DEG) at the heterointerface. We analyzed the electrical-transport properties of the 2-DEG to elucidate its intrinsic characteristics. Based on the magnetic field dependence of resistance at 2 K, which exhibited Weak Anti-localization (WAL) behaviors, the fitted Rashba parameter values were found to be about 12-15 × 10-12 eV*m. These values are stronger than the previous reported Rashba parameters obtained from the 2-DEGs in other heterostructure systems and several layered 2D materials. The observed strong spin-orbit coupling (SOC) is attributed to the strong internal electric field generated by the lattice mismatch between the CaZrO3 layer and SrTiO3 substrate. This pioneering strong SOC of the 2-DEG at the CaZrO3/SrTiO3 heterointerface may play a pivotal role in the developing future metal oxide-based quantum nanoelectronics devices.
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Affiliation(s)
- Duhyuk Kwon
- Department of Physics, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Yongsu Kwak
- Department of Physics, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Doopyo Lee
- Department of Physics, Pohang University of Science and Technology, Pohang, Gyeongbuk, 37673, Republic of Korea
| | - Wonkeun Jo
- The Division of Computer Convergence, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Byeong-Gwan Cho
- Pohang Accelerator Laboratory, Pohang, Gyeongbuk, 37673, Republic of Korea
| | - Tae-Yeong Koo
- Pohang Accelerator Laboratory, Pohang, Gyeongbuk, 37673, Republic of Korea
| | - Jonghyun Song
- Department of Physics, Chungnam National University, Daejeon, 34134, Republic of Korea.
- Institute of Quantum Systems (IQS), Chungnam National University, Daejeon, 34134, Republic of Korea.
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3
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Rose MA, Barnett J, Wendland D, Hensling FVE, Boergers JM, Moors M, Dittmann R, Taubner T, Gunkel F. Local inhomogeneities resolved by scanning probe techniques and their impact on local 2DEG formation in oxide heterostructures. NANOSCALE ADVANCES 2021; 3:4145-4155. [PMID: 36132831 PMCID: PMC9419657 DOI: 10.1039/d1na00190f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 06/02/2021] [Indexed: 06/16/2023]
Abstract
Lateral inhomogeneities in the formation of two-dimensional electron gases (2DEG) directly influence their electronic properties. Understanding their origin is an important factor for fundamental interpretations, as well as high quality devices. Here, we studied the local formation of the buried 2DEG at LaAlO3/SrTiO3 (LAO/STO) interfaces grown on STO (100) single crystals with partial TiO2 termination, utilizing in situ conductive atomic force microscopy (c-AFM) and scattering-type scanning near-field optical microscopy (s-SNOM). Using substrates with different degrees of chemical surface termination, we can link the resulting interface chemistry to an inhomogeneous 2DEG formation. In conductivity maps recorded by c-AFM, a significant lack of conductivity is observed at topographic features, indicative of a local SrO/AlO2 interface stacking order, while significant local conductivity can be probed in regions showing TiO2/LaO interface stacking order. These results could be corroborated by s-SNOM, showing a similar contrast distribution in the optical signal which can be linked to the local electronic properties of the material. The results are further complemented by low-temperature conductivity measurements, which show an increasing residual resistance at 5 K with increasing portion of insulating SrO-terminated areas. Therefore, we can correlate the macroscopic electrical behavior of our samples to their nanoscopic structure. Using proper parameters, 2DEG mapping can be carried out without any visible alteration of sample properties, proving c-AFM and s-SNOM to be viable and destruction-free techniques for the identification of local 2DEG formation. Furthermore, applying c-AFM and s-SNOM in this manner opens the exciting prospect to link macroscopic low-temperature transport to its nanoscopic origin.
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Affiliation(s)
- M-A Rose
- Institute of Electronic Materials (IWE II), RWTH Aachen University Aachen Germany
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
| | - J Barnett
- I. Institute of Physics (IA), RWTH Aachen University Aachen Germany
| | - D Wendland
- I. Institute of Physics (IA), RWTH Aachen University Aachen Germany
| | - F V E Hensling
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
| | - J M Boergers
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
| | - M Moors
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
| | - R Dittmann
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
| | - T Taubner
- I. Institute of Physics (IA), RWTH Aachen University Aachen Germany
| | - F Gunkel
- Institute of Electronic Materials (IWE II), RWTH Aachen University Aachen Germany
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
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4
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Ma HJH, Scott JF. Non-Ohmic Variable-Range Hopping and Resistive Switching in SrTiO_{3} Domain Walls. PHYSICAL REVIEW LETTERS 2020; 124:146601. [PMID: 32338966 DOI: 10.1103/physrevlett.124.146601] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 01/04/2020] [Accepted: 02/28/2020] [Indexed: 06/11/2023]
Abstract
We report observation of electric field driven conductivity with negative differential conductance and resistive switching in insulating SrTiO_{3} samples over a wide range of applied voltages at low temperatures. The observed current follows I=I_{0}exp[-(E^{*}/E)^{1/2}] at large applied electric field, corresponding to variable range hopping conduction with a Coulomb gap in domain walls. Our data are sufficient to discriminate unambiguously between Shklovskii and Mott hopping via their different electric field exponent. Under some conditions space-charge-limited currents are observed, and the charge mobility limit is determined to be in the range of 17 and 210 cm^{2}/Vs.
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Affiliation(s)
- H J Harsan Ma
- Low Dimensional Quantum Physics & Device Group, School of Microelectronics, Xidian University, 2 South Taibai Road, Xi'an 710071, China
- State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology, School of Microelectronics, Xidian University, 2 South Taibai Road, Xi'an 710071, China
| | - J F Scott
- Schools of Chemistry and Physics, St Andrews University, St. Andrews KY16 9SS, United Kingdom
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5
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Dai W, Liang Y, Yang M, Schrecongost D, Gajurel P, Lee H, Lee JW, Chen J, Eom CB, Cen C. Large and Reconfigurable Infrared Photothermoelectric Effect at Oxide Interfaces. NANO LETTERS 2019; 19:7149-7154. [PMID: 31525937 DOI: 10.1021/acs.nanolett.9b02712] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
To maximize the photovoltaic efficiency, it is highly desirable to enable the electricity conversion from low energy photons and to extract the excessive energy from hot carriers. Here we report a large photovoltage generation at the LaAlO3/SrTiO3 interfaces from infrared photons with energies far below the oxide bandgaps. This effect is a result of the photoexcitation of hot carriers in metasurface electrical contacts and the subsequent thermoelectric charge separations by the interfacial two-dimensional electron gas (2DEG). Reaching a room-temperature responsivity of 4.4 V/W, such light-to-charge conversion can be spatially controlled and reconfigured through the patterning of 2DEG using conducting atomic force microscope. Compatible for broadband applications, our results demonstrate a new path toward efficient and programmable light sensing using oxide-based low-dimensional electron systems.
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Affiliation(s)
- Weitao Dai
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26506 , United States
| | - Yi Liang
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26506 , United States
- Guangxi Key Lab for Relativistic Astrophysics, Center on Nanoenergy Research, School of Physical Science and Technology , Guangxi University, Nanning , Guangxi 530004 , China
| | - Ming Yang
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26506 , United States
| | - Dustin Schrecongost
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26506 , United States
| | - Prakash Gajurel
- 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
| | - Jun Chen
- Department of Electrical and Computer Engineering and Peterson Institute of NanoScience and Engineering , University of Pittsburgh , Pittsburgh , Pennsylvania 15261 , 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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6
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Ryu YK, Knoll AW. Oxidation and Thermal Scanning Probe Lithography for High-Resolution Nanopatterning and Nanodevices. ELECTRICAL ATOMIC FORCE MICROSCOPY FOR NANOELECTRONICS 2019. [DOI: 10.1007/978-3-030-15612-1_5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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7
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Falsetti E, Kalaboukhov A, Nucara A, Ortolani M, Corasaniti M, Baldassarre L, Roy P, Calvani P. High conductivity of ultrathin nanoribbons of SrRuO 3 on SrTiO 3 probed by infrared spectroscopy. Sci Rep 2018; 8:15217. [PMID: 30315227 PMCID: PMC6185982 DOI: 10.1038/s41598-018-33632-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 09/28/2018] [Indexed: 11/09/2022] Open
Abstract
SrRuO3 (SRO) is a perovskite increasingly used in oxide-based electronics both for its intrinsic metallicity, which remains unaltered in thin films and for the ease of deposition on dielectric perovskites like SrTiO3, (STO) to implement SRO/STO microcapacitors and other devices. In order to test the reliability of SRO/STO also as high-current on-chip conductor, when the SRO dimensions are pushed to the nanoscale, here we have measured the electrodynamic properties of arrays of nanoribbons, fabricated by lithography starting from an ultrathin film of SRO deposited on a STO substrate. The nanoribbons are 6 or 4 nm thick, 400, 200 and 100 nm wide and 5 mm long. The measurements have been performed by infrared spectroscopy, a non-contact weakly perturbing technique which also allows one to separately determine the carrier density and their scattering rate or mobility. Far-infrared reflectivity spectra have been analyzed by Rigorous Coupled-Wave Analysis (RCWA) and by an Effective Medium Theory, obtaining consistent results. With the radiation polarized along the nanoribbons, we obtain a carrier density similar to that of a flat film used as reference, which in turn is similar to that of bulk SRO. Moreover, in the nanoribbons the carrier scattering rate is even smaller than in the unpatterned film by about a factor of 2. This shows that the transport properties of SRO deposited on STO remain at least unaltered down to nanometric dimensions, with interesting perspectives for implementing on-chip nano-interconnects in an oxide-based electronics. When excited in the perpendicular direction, the nanoribbons appear instead virtually transparent to the radiation field, as predicted by RCWA.
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Affiliation(s)
- E Falsetti
- Dipartimento di Fisica, Università di Roma "La Sapienza", P.le A. Moro 2, I-00185, Roma, Italy
| | - A Kalaboukhov
- Department of Microtechnology & Nanoscience, Chalmers University, S-41296, Gothenburg, Sweden
| | - A Nucara
- CNR-SPIN and Dipartimento di Fisica, Università di Roma "La Sapienza", P.le A. Moro 2, I-00185, Roma, Italy.
| | - M Ortolani
- Dipartimento di Fisica, Università di Roma "La Sapienza", P.le A. Moro 2, I-00185, Roma, Italy
| | - M Corasaniti
- Dipartimento di Fisica, Università di Roma "La Sapienza", P.le A. Moro 2, I-00185, Roma, Italy
| | - L Baldassarre
- Dipartimento di Fisica, Università di Roma "La Sapienza", P.le A. Moro 2, I-00185, Roma, Italy
| | - P Roy
- Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin, BP 48, F-91192, Gif-sur-Yvette Cedex, France
| | - P Calvani
- CNR-SPIN and Dipartimento di Fisica, Università di Roma "La Sapienza", P.le A. Moro 2, I-00185, Roma, Italy
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8
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Annadi A, Cheng G, Lee H, Lee JW, Lu S, Tylan-Tyler A, Briggeman M, Tomczyk M, Huang M, Pekker D, Eom CB, Irvin P, Levy J. Quantized Ballistic Transport of Electrons and Electron Pairs in LaAlO 3/SrTiO 3 Nanowires. NANO LETTERS 2018; 18:4473-4481. [PMID: 29924620 DOI: 10.1021/acs.nanolett.8b01614] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
SrTiO3-based heterointerfaces support quasi-two-dimensional (2D) electron systems that are analogous to III-V semiconductor heterostructures, but also possess superconducting, magnetic, spintronic, ferroelectric, and ferroelastic degrees of freedom. Despite these rich properties, the relatively low mobilities of 2D complex-oxide interfaces appear to preclude ballistic transport in 1D. Here we show that the 2D LaAlO3/SrTiO3 interface can support quantized ballistic transport of electrons and (nonsuperconducting) electron pairs within quasi-1D structures that are created using a well-established conductive atomic-force microscope (c-AFM) lithography technique. The nature of transport ranges from truly single-mode (1D) to three-dimensional (3D), depending on the applied magnetic field and gate voltage. Quantization of the lowest e2/ h plateau indicate a ballistic mean-free path lMF ∼ 20 μm, more than 2 orders of magnitude larger than for 2D LaAlO3/SrTiO3 heterostructures. Nonsuperconducting electron pairs are found to be stable in magnetic fields as high as B = 11 T and propagate ballistically with conductance quantized at 2 e2/ h. Theories of one-dimensional (1D) transport of interacting electron systems depend crucially on the sign of the electron-electron interaction, which may help explain the highly ballistic transport behavior. The 1D geometry yields new insights into the electronic structure of the LaAlO3/SrTiO3 system and offers a new platform for the study of strongly interacting 1D electronic systems.
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Affiliation(s)
- Anil Annadi
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 United States
| | - Guanglei Cheng
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 United States
- CAS Key Laboratory of Microscale Magnetic Resonance and Department of Modern Physics , University of Science and Technology of China , Hefei 230026 , China
| | - Hyungwoo Lee
- Department of Materials Science and Engineering , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Jung-Woo Lee
- Department of Materials Science and Engineering , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Shicheng Lu
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 United States
| | - Anthony Tylan-Tyler
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 United States
| | - Megan Briggeman
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 United States
| | - Michelle Tomczyk
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 United States
| | - Mengchen Huang
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 United States
| | - David Pekker
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 United States
| | - Chang-Beom Eom
- Department of Materials Science and Engineering , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Patrick Irvin
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 United States
| | - Jeremy Levy
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 United States
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9
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Chen L, Li J, Tang Y, Pai YY, Chen Y, Pryds N, Irvin P, Levy J. Extreme Reconfigurable Nanoelectronics at the CaZrO 3 /SrTiO 3 Interface. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1801794. [PMID: 29962024 DOI: 10.1002/adma.201801794] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 05/10/2018] [Indexed: 06/08/2023]
Abstract
Complex oxide heterostructures have fascinating emergent properties that originate from the properties of the bulk constituents as well as from dimensional confinement. The conductive behavior of the polar/nonpolar LaAlO3 /SrTiO3 interface can be reversibly switched using conductive atomic force microscopy (c-AFM) lithography, enabling a wide range of devices and physics to be explored. Here, extreme nanoscale control over the CaZrO3 /SrTiO3 (CZO/STO) interface, which is formed from two materials that are both nonpolar, is reported. Nanowires with measured widths as narrow as 1.2 nm are realized at the CZO/STO interface at room temperature by c-AFM lithography. These ultrathin nanostructures have spatial dimensions at room temperature that are comparable to single-walled carbon nanotubes, and hold great promise for alternative oxide-based nanoelectronics, as well as offer new opportunities to investigate the electronic structure of the complex oxide interfaces. The cryogenic properties of devices constructed from quasi-1D channels, tunnel barriers, and planar gates exhibit gate-tunable superconductivity, quantum oscillations, electron pairing outside of the superconducting regime, and quasi-ballistic transport. This newly demonstrated ability to control the metal-insulator transition at nonpolar oxide interface greatly expands the class of materials whose behavior can be patterned and reconfigured at extreme nanoscale dimensions.
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Affiliation(s)
- Lu Chen
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Jianan Li
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Yuhe Tang
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Yun-Yi Pai
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Yunzhong Chen
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, Roskilde, 4000, Denmark
| | - Nini Pryds
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, Roskilde, 4000, Denmark
| | - Patrick Irvin
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Jeremy Levy
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
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10
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Tomczyk M, Cheng G, Lee H, Lu S, Annadi A, Veazey JP, Huang M, Irvin P, Ryu S, Eom CB, Levy J. Micrometer-Scale Ballistic Transport of Electron Pairs in LaAlO_{3}/SrTiO_{3} Nanowires. PHYSICAL REVIEW LETTERS 2016; 117:096801. [PMID: 27610871 DOI: 10.1103/physrevlett.117.096801] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Indexed: 06/06/2023]
Abstract
High-mobility complex-oxide heterostructures and nanostructures offer new opportunities for extending the paradigm of quantum transport beyond the realm of traditional III-V or carbon-based materials. Recent quantum transport investigations with LaAlO_{3}/SrTiO_{3}-based quantum dots reveal the existence of a strongly correlated phase in which electrons form spin-singlet pairs without becoming superconducting. Here, we report evidence for the micrometer-scale ballistic transport of electron pairs in quasi-1D LaAlO_{3}/SrTiO_{3} nanowire cavities. In the paired phase, Fabry-Perot-like quantum interference is observed, in sync with conductance oscillations observed in the superconducting regime (at a zero magnetic field). Above a critical magnetic field B_{p}, the electron pairs unbind and the conductance oscillations shift with the magnetic field. These experimental observations extend the regime of ballistic electronic transport to strongly correlated phases.
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Affiliation(s)
- Michelle Tomczyk
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Guanglei Cheng
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Hyungwoo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Shicheng Lu
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Anil Annadi
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Joshua P Veazey
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
| | - Mengchen Huang
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Patrick Irvin
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Sangwoo Ryu
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Jeremy Levy
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
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11
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Zhuang HL, Zhang L, Xu H, Kent PRC, Ganesh P, Cooper VR. Tunable one-dimensional electron gas carrier densities at nanostructured oxide interfaces. Sci Rep 2016; 6:25452. [PMID: 27151049 PMCID: PMC4858694 DOI: 10.1038/srep25452] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 04/15/2016] [Indexed: 11/29/2022] Open
Abstract
The emergence of two-dimensional metallic states at the LaAlO3/SrTiO3 (LAO/STO) heterostructure interface is known to occur at a critical thickness of four LAO layers. This insulator to-metal transition can be explained through the “polar catastrophe” mechanism arising from the divergence of the electrostatic potential at the LAO surface. Here, we demonstrate that nanostructuring can be effective in reducing or eliminating this critical thickness. Employing a modified “polar catastrophe” model, we demonstrate that the nanowire heterostructure electrostatic potential diverges more rapidly as a function of layer thickness than in a regular heterostructure. Our first-principles calculations indicate that for nanowire heterostructures a robust one-dimensional electron gas (1DEG) can be induced, consistent with recent experimental observations of 1D conductivity at LAO/STO steps. Similar to LAO/STO 2DEGs, we predict that the 1D charge density decays laterally within a few unit cells away from the nanowire; thus providing a mechanism for tuning the carrier dimensionality between 1D and 2D conductivity. Our work provides insight into the creation and manipulation of charge density at an oxide heterostructure interface and therefore may be beneficial for future nanoelectronic devices and for the engineering of novel quantum phases.
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Affiliation(s)
- Houlong L Zhuang
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Bethel Valley Road, Oak Ridge, Tennessee 37831, United States
| | - Lipeng Zhang
- Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Haixuan Xu
- Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996, United States
| | - P R C Kent
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Bethel Valley Road, Oak Ridge, Tennessee 37831, United States.,Computer Science and Mathematics Division, Oak Ridge National Laboratory, Bethel Valley Road, Oak Ridge, Tennessee 37831, United States
| | - P Ganesh
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Bethel Valley Road, Oak Ridge, Tennessee 37831, United States
| | - Valentino R Cooper
- Materials Science and Technology Division, Oak Ridge National Laboratory, Bethel Valley Road, Oak Ridge, Tennessee 37831, United States
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12
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Zeng S, Lü W, Huang Z, Liu Z, Han K, Gopinadhan K, Li C, Guo R, Zhou W, Ma HH, Jian L, Venkatesan T. Liquid-Gated High Mobility and Quantum Oscillation of the Two-Dimensional Electron Gas at an Oxide Interface. ACS NANO 2016; 10:4532-4537. [PMID: 26974812 DOI: 10.1021/acsnano.6b00409] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Electric field effect in electronic double layer transistor (EDLT) configuration with ionic liquids as the dielectric materials is a powerful means of exploring various properties in different materials. Here, we demonstrate the modulation of electrical transport properties and extremely high mobility of two-dimensional electron gas at LaAlO3/SrTiO3 (LAO/STO) interface through ionic liquid-assisted electric field effect. With a change of the gate voltages, the depletion of charge carrier and the resultant enhancement of electron mobility up to 19 380 cm(2)/(V s) are realized, leading to quantum oscillations of the conductivity at the LAO/STO interface. The present results suggest that high-mobility oxide interfaces, which exhibit quantum phenomena, could be obtained by ionic liquid-assisted field effect.
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Affiliation(s)
- Shengwei Zeng
- NUSNNI-NanoCore, National University of Singapore , Singapore 117411, Singapore
- Department of Physics, National University of Singapore , Singapore 117542, Singapore
| | - Weiming Lü
- NUSNNI-NanoCore, National University of Singapore , Singapore 117411, Singapore
| | - Zhen Huang
- NUSNNI-NanoCore, National University of Singapore , Singapore 117411, Singapore
| | - Zhiqi Liu
- NUSNNI-NanoCore, National University of Singapore , Singapore 117411, Singapore
| | - Kun Han
- NUSNNI-NanoCore, National University of Singapore , Singapore 117411, Singapore
- Department of Physics, National University of Singapore , Singapore 117542, Singapore
| | - Kalon Gopinadhan
- NUSNNI-NanoCore, National University of Singapore , Singapore 117411, Singapore
| | - Changjian Li
- NUSNNI-NanoCore, National University of Singapore , Singapore 117411, Singapore
- National University of Singapore Graduate School for Integrative Sciences and Engineering (NGS) , 28 Medical Drive, Singapore 117456, Singapore
| | - Rui Guo
- NUSNNI-NanoCore, National University of Singapore , Singapore 117411, Singapore
- Department of Materials Science and Engineering, National University of Singapore , Singapore 117575, Singapore
| | - Wenxiong Zhou
- NUSNNI-NanoCore, National University of Singapore , Singapore 117411, Singapore
- Department of Physics, National University of Singapore , Singapore 117542, Singapore
| | - Haijiao Harsan Ma
- NUSNNI-NanoCore, National University of Singapore , Singapore 117411, Singapore
- Department of Physics, National University of Singapore , Singapore 117542, Singapore
| | - Linke Jian
- NUSNNI-NanoCore, National University of Singapore , Singapore 117411, Singapore
| | - Thirumalai Venkatesan
- 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
- Department of Materials Science and Engineering, National University of Singapore , Singapore 117575, Singapore
- Department of Electrical and Computer Engineering, National University of Singapore , Singapore 117576, Singapore
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13
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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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14
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Chen Y, Trier F, Kasama T, Christensen DV, Bovet N, Balogh ZI, Li H, Thydén KTS, Zhang W, Yazdi S, Norby P, Pryds N, Linderoth S. Creation of high mobility two-dimensional electron gases via strain induced polarization at an otherwise nonpolar complex oxide interface. NANO LETTERS 2015; 15:1849-1854. [PMID: 25692804 DOI: 10.1021/nl504622w] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The discovery of two-dimensional electron gases (2DEGs) in SrTiO3-based heterostructures provides new opportunities for nanoelectronics. Herein, we create a new type of oxide 2DEG by the epitaxial-strain-induced polarization at an otherwise nonpolar perovskite-type interface of CaZrO3/SrTiO3. Remarkably, this heterointerface is atomically sharp and exhibits a high electron mobility exceeding 60,000 cm(2) V(-1) s(-1) at low temperatures. The 2DEG carrier density exhibits a critical dependence on the film thickness, in good agreement with the polarization induced 2DEG scheme.
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Affiliation(s)
- Yunzhong Chen
- Department of Energy Conversion and Storage, Technical University of Denmark , Risø Campus, 4000 Roskilde, Denmark
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15
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16
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Azimi S, Song J, Li CJ, Mathew S, Breese MBH, Venkatesan T. Nanoscale lithography of LaAlO₃/SrTiO₃ wires using silicon stencil masks. NANOTECHNOLOGY 2014; 25:445301. [PMID: 25302579 DOI: 10.1088/0957-4484/25/44/445301] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We have developed a process to fabricate low-stress, fully crystalline silicon nanostencils, based on ion irradiation and the electrochemical anodization of p-type silicon. These nanostencils can be patterned with arbitrary feature shapes with openings hundreds of micrometers wide connected to long channels of less than 100 nm in width. These nanostencils have been used to deposit (2.5 μm- to 150 nm-wide) lines of LaAlO3 (LAO) on a SrTiO3 (STO) substrate, forming a confined electron layer at the interface arising from oxygen vacancies on the STO surface. Electrical characterization of the transport properties of the resulting LAO/STO nanowires exhibited a large electric field effect through back-gating using the STO as the dielectric, demonstrating electron confinement. Stencil lithography incorporating multiple feature sizes in a single mask shows great potential for future development of oxide electronics.
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Affiliation(s)
- S Azimi
- Centre for Ion Beam Applications (CIBA), Department of Physics, National University of Singapore, Singapore 11754222. Singapore Synchrotron Light Source (SSLS), National University of Singapore, 5 Research Link, Singapore 117603
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17
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Levy A, Bi F, Huang M, Lu S, Tomczyk M, Cheng G, Irvin P, Levy J. Writing and low-temperature characterization of oxide nanostructures. J Vis Exp 2014. [PMID: 25080268 PMCID: PMC4220744 DOI: 10.3791/51886] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Oxide nanoelectronics is a rapidly growing field which seeks to develop novel materials with multifunctional behavior at nanoscale dimensions. Oxide interfaces exhibit a wide range of properties that can be controlled include conduction, piezoelectric behavior, ferromagnetism, superconductivity and nonlinear optical properties. Recently, methods for controlling these properties at extreme nanoscale dimensions have been discovered and developed. Here are described explicit step-by-step procedures for creating LaAlO3/SrTiO3 nanostructures using a reversible conductive atomic force microscopy technique. The processing steps for creating electrical contacts to the LaAlO3/SrTiO3 interface are first described. Conductive nanostructures are created by applying voltages to a conductive atomic force microscope tip and locally switching the LaAlO3/SrTiO3 interface to a conductive state. A versatile nanolithography toolkit has been developed expressly for the purpose of controlling the atomic force microscope (AFM) tip path and voltage. Then, these nanostructures are placed in a cryostat and transport measurements are performed. The procedures described here should be useful to others wishing to conduct research in oxide nanoelectronics.
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Affiliation(s)
- Akash Levy
- Department of Physics, University of Pittsburgh;
| | - Feng Bi
- Department of Physics, University of Pittsburgh
| | | | - Shicheng Lu
- Department of Physics, University of Pittsburgh
| | | | | | | | - Jeremy Levy
- Department of Physics, University of Pittsburgh
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18
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Ron A, Dagan Y. One-dimensional quantum wire formed at the boundary between two insulating LaAlO3/SrTiO3 interfaces. PHYSICAL REVIEW LETTERS 2014; 112:136801. [PMID: 24745447 DOI: 10.1103/physrevlett.112.136801] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Indexed: 06/03/2023]
Abstract
We grow a tiled structure of insulating two-dimensional LaAlO3/SrTiO3 interfaces composed of alternating one and three LaAlO3 unit cells. The boundary between two tiles is conducting. At low temperatures this conductance exhibits quantized steps as a function of gate voltage indicative of a one-dimensional channel. The step size of half the quantum of conductance is evidence for the absence of spin degeneracy.
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Affiliation(s)
- A Ron
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Y Dagan
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel Aviv 69978, Israel
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19
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Veazey JP, Cheng G, Irvin P, Cen C, Bogorin DF, Bi F, Huang M, Bark CW, Ryu S, Cho KH, Eom CB, Levy J. Oxide-based platform for reconfigurable superconducting nanoelectronics. NANOTECHNOLOGY 2013; 24:375201. [PMID: 23965953 DOI: 10.1088/0957-4484/24/37/375201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We report quasi-1D superconductivity at the interface of LaAlO3 and SrTiO3. The material system and nanostructure fabrication method supply a new platform for superconducting nanoelectronics. Nanostructures having line widths w ~ 10 nm are formed from the parent two-dimensional electron liquid using conductive atomic force microscope lithography. Nanowire cross-sections are small compared to the superconducting coherence length in LaAlO3/SrTiO3, placing them in the quasi-1D regime. Broad superconducting transitions versus temperature and finite resistances in the superconducting state well below Tc ≈ 200 mK are observed, suggesting the presence of fluctuation- and heating-induced resistance. The superconducting resistances and V-I characteristics are tunable through the use of a back gate. Four-terminal resistances in the superconducting state show an unusual dependence on the current path, varying by as much as an order of magnitude. This new technology, i.e., the ability to 'write' gate-tunable superconducting nanostructures on an insulating LaAlO3/SrTiO3 'canvas', opens possibilities for the development of new families of reconfigurable superconducting nanoelectronics.
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Affiliation(s)
- Joshua P Veazey
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA
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