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Erlandsen R, Dahm RT, Trier F, Scuderi M, Di Gennaro E, Sambri A, Reffeldt Kirchert CK, Pryds N, Granozio FM, Jespersen TS. A Two-Dimensional Superconducting Electron Gas in Freestanding LaAlO 3/SrTiO 3 Micromembranes. NANO LETTERS 2022; 22:4758-4764. [PMID: 35679577 DOI: 10.1021/acs.nanolett.2c00992] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Freestanding oxide membranes constitute an intriguing material platform for new functionalities and allow integration of oxide electronics with technologically important platforms such as silicon. Sambri et al. recently reported a method to fabricate freestanding LaAlO3/SrTiO3 (LAO/STO) membranes by spalling of strained heterostructures. Here, we first develop a scheme for the high-yield fabrication of membrane devices on silicon. Second, we show that the membranes exhibit metallic conductivity and a superconducting phase below ∼200 mK. Using anisotropic magnetotransport we extract the superconducting phase coherence length ξ ≈ 36-80 nm and establish an upper bound on the thickness of the superconducting electron gas d ≈ 17-33 nm, thus confirming its two-dimensional character. Finally, we show that the critical current can be modulated using a silicon-based backgate. The ability to form superconducting nanostructures of LAO/STO membranes, with electronic properties similar to those of the bulk counterpart, opens opportunities for integrating oxide nanoelectronics with silicon-based architectures.
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Affiliation(s)
- Ricci Erlandsen
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, 2800 Kgs. Lyngby, Denmark
| | - Rasmus Tindal Dahm
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, 2800 Kgs. Lyngby, Denmark
| | - Felix Trier
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, 2800 Kgs. Lyngby, Denmark
| | - Mario Scuderi
- Institute for Microelectronics and Microsystems (CNR-IMM), Strada VIII n.5 Zona Industriale, I-95121 Catania, Italy
| | - Emiliano Di Gennaro
- Dipartimento di Fisica "Ettore Pancini", Università degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cinthia, I-80126 Napoli, Italy
| | - Alessia Sambri
- CNR-SPIN, Complesso Universitario di Monte Sant'Angelo, Via Cinthia, I-80126 Napoli, Italy
| | | | - Nini Pryds
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, 2800 Kgs. Lyngby, Denmark
| | - Fabio Miletto Granozio
- CNR-SPIN, Complesso Universitario di Monte Sant'Angelo, Via Cinthia, I-80126 Napoli, Italy
| | - Thomas Sand Jespersen
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
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Pulikkotil JJ. A spin-orbit coupling-induced two-dimensional electron gas in BiAlO 3/SrTiO 3 heterostructures. Phys Chem Chem Phys 2020; 22:3122-3127. [PMID: 31967128 DOI: 10.1039/c9cp05737d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Both LaAlO3 and BiAlO3 are isostructural, isoelectronic and band insulators. Therefore, in analogy to the LaAlO3/SrTiO3 heterostructure, a quasi two dimensional electron gas (q-2DEG) could be anticipated in BiAlO3/SrTiO3 heterostructures. Our density functional theory based scalar relativistic calculations show that BiAlO3/SrTiO3 heterostructures remain insulating for a BiAlO3 film thickness up to 5 unit cells. However, with spin orbit coupling included in the crystal Hamiltonian, we find a thickness dependent insulator to metal transition for BiAlO3/SrTiO3 heterostructures. However, unlike the Ti3+/Ti4+ electronic reconstruction in LaAlO3/SrTiO3, the conductivity in BiAlO3/SrTiO3 is found to originate from the subsurface Bi 6p states. The results suggest that the properties of q-2DEG in BiAlO3/SrTiO3 can be controlled using an external electric field, leading to a wide range of solid state applications.
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Affiliation(s)
- J J Pulikkotil
- CSIR-National Physical Laboratory, Dr K. S. Krishnan Marg, New Delhi 110012, India.
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Yin C, Smink AEM, Leermakers I, Tang LMK, Lebedev N, Zeitler U, van der Wiel WG, Hilgenkamp H, Aarts J. Electron Trapping Mechanism in LaAlO_{3}/SrTiO_{3} Heterostructures. PHYSICAL REVIEW LETTERS 2020; 124:017702. [PMID: 31976734 DOI: 10.1103/physrevlett.124.017702] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2019] [Revised: 09/13/2019] [Indexed: 06/10/2023]
Abstract
In LaAlO_{3}/SrTiO_{3} heterostructures, a still poorly understood phenomenon is that of electron trapping in back-gating experiments. Here, by combining magnetotransport measurements and self-consistent Schrödinger-Poisson calculations, we obtain an empirical relation between the amount of trapped electrons and the gate voltage. The amount of trapped electrons decays exponentially away from the interface. However, contrary to earlier observations, we find that the Fermi level remains well within the quantum well. The enhanced trapping of electrons induced by the gate voltage can therefore not be explained by a thermal escape mechanism. Further gate sweeping experiments strengthen that conclusion. We propose a new mechanism which involves the electromigration and clustering of oxygen vacancies in SrTiO_{3} and argue that such electron trapping is a universal phenomenon in SrTiO_{3}-based two-dimensional electron systems.
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Affiliation(s)
- Chunhai Yin
- Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Alexander E M Smink
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Inge Leermakers
- High Field Magnet Laboratory (HFML-EMFL), Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Lucas M K Tang
- High Field Magnet Laboratory (HFML-EMFL), Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Nikita Lebedev
- Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Uli Zeitler
- High Field Magnet Laboratory (HFML-EMFL), Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Wilfred G van der Wiel
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Hans Hilgenkamp
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Jan Aarts
- Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
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