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GaAs 1-xBi x growth on Ge: anti-phase domains, ordering, and exciton localization. Sci Rep 2020; 10:2002. [PMID: 32029827 PMCID: PMC7005183 DOI: 10.1038/s41598-020-58812-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 01/20/2020] [Indexed: 11/17/2022] Open
Abstract
The dilute bismide alloy GaAs1-xBix has drawn significant attention from researchers interested in its fundamental properties and the potential for infrared optoelectronics applications. To extend the study of bismides, molecular-beam heteroepitaxy of nominally 1.0 eV bandgap bismide on Ge substrates is comprehensively investigated. Analysis of atomic-resolution anti-phase domain (APD) images in the direct-epitaxy revealed a high-density of Ga vacancies and a reduced Bi content at their boundaries. This likely played a key role in the preferential dissolution of Bi atoms from the APD interiors and Bi spiking in Ge during thermal annealing. Introduction of GaAs buffer on offcut Ge largely suppressed the formation of APDs, producing high-quality bismide with single-variant CuPtB-type ordered domains as large as 200 nm. Atomic-resolution X-ray imaging showed that 2-dimensional Bi-rich (111) planes contain up to x = 9% Bi. The anomalously early onset of localization found in the temperature-dependent photoluminescence suggests enhanced interactions among Bi states, as compared to non-ordered samples. Growth of large-domain single-variant ordered GaAs1-xBix films provides new prospects for detailed analysis of the structural modulation effects and may allow to further tailor properties of this alloy for optoelectronic applications.
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Chen YZ, Trier F, Wijnands T, Green RJ, Gauquelin N, Egoavil R, Christensen DV, Koster G, Huijben M, Bovet N, Macke S, He F, Sutarto R, Andersen NH, Sulpizio JA, Honig M, Prawiroatmodjo GEDK, Jespersen TS, Linderoth S, Ilani S, Verbeeck J, Van Tendeloo G, Rijnders G, Sawatzky GA, Pryds N. Extreme mobility enhancement of two-dimensional electron gases at oxide interfaces by charge-transfer-induced modulation doping. NATURE MATERIALS 2015; 14:801-806. [PMID: 26030303 DOI: 10.1038/nmat4303] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Accepted: 04/22/2015] [Indexed: 06/04/2023]
Abstract
Two-dimensional electron gases (2DEGs) formed at the interface of insulating complex oxides promise the development of all-oxide electronic devices. These 2DEGs involve many-body interactions that give rise to a variety of physical phenomena such as superconductivity, magnetism, tunable metal-insulator transitions and phase separation. Increasing the mobility of the 2DEG, however, remains a major challenge. Here, we show that the electron mobility is enhanced by more than two orders of magnitude by inserting a single-unit-cell insulating layer of polar La(1-x)Sr(x)MnO3 (x = 0, 1/8, and 1/3) at the interface between disordered LaAlO3 and crystalline SrTiO3 produced at room temperature. Resonant X-ray spectroscopy and transmission electron microscopy show that the manganite layer undergoes unambiguous electronic reconstruction, leading to modulation doping of such atomically engineered complex oxide heterointerfaces. At low temperatures, the modulation-doped 2DEG exhibits Shubnikov-de Haas oscillations and fingerprints of the quantum Hall effect, demonstrating unprecedented high mobility and low electron density.
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Affiliation(s)
- Y Z Chen
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, 4000 Roskilde, Denmark
| | - F Trier
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, 4000 Roskilde, Denmark
| | - T Wijnands
- Faculty of Science and Technology and MESA + Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
| | - R J Green
- 1] Quantum Matter Institute, Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada [2] Max Planck Institute for Chemical Physics of Solids, Nöthnitzerstraße 40, 01187 Dresden, Germany
| | - N Gauquelin
- EMAT, University of Antwerp, Groenenborgerlaan 171 2020 Antwerp, Belgium
| | - R Egoavil
- EMAT, University of Antwerp, Groenenborgerlaan 171 2020 Antwerp, Belgium
| | - D V Christensen
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, 4000 Roskilde, Denmark
| | - G Koster
- Faculty of Science and Technology and MESA + Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
| | - M Huijben
- Faculty of Science and Technology and MESA + Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
| | - N Bovet
- Nano-Science Center, Department of Chemistry, University of Copenhagen, 2100 Copenhagen, Denmark
| | - S Macke
- 1] Quantum Matter Institute, Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada [2] Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - F He
- Canadian Light Source, Saskatoon, Saskatchewan S7N 2V3, Canada
| | - R Sutarto
- Canadian Light Source, Saskatoon, Saskatchewan S7N 2V3, Canada
| | - N H Andersen
- Department of Physics, Technical University of Denmark, 2800 Lyngby, Denmark
| | - J A Sulpizio
- Department of Condensed Matter Physics, Weizmann Institute of Science, 76100 Rehovot, Israel
| | - M Honig
- Department of Condensed Matter Physics, Weizmann Institute of Science, 76100 Rehovot, Israel
| | - G E D K Prawiroatmodjo
- Center for Quantum devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - T S Jespersen
- Center for Quantum devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - S Linderoth
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, 4000 Roskilde, Denmark
| | - S Ilani
- Department of Condensed Matter Physics, Weizmann Institute of Science, 76100 Rehovot, Israel
| | - J Verbeeck
- EMAT, University of Antwerp, Groenenborgerlaan 171 2020 Antwerp, Belgium
| | - G Van Tendeloo
- EMAT, University of Antwerp, Groenenborgerlaan 171 2020 Antwerp, Belgium
| | - G Rijnders
- Faculty of Science and Technology and MESA + Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
| | - G A Sawatzky
- Quantum Matter Institute, Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - N Pryds
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, 4000 Roskilde, Denmark
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De Backer A, Van Aert S, Van Dyck D. High precision measurements of atom column positions using model-based exit wave reconstruction. Ultramicroscopy 2011; 111:1475-82. [PMID: 21930019 DOI: 10.1016/j.ultramic.2011.07.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2011] [Revised: 07/06/2011] [Accepted: 07/14/2011] [Indexed: 11/29/2022]
Abstract
In this paper, it has been investigated how to measure atom column positions as accurately and precisely as possible using a focal series of images. In theory, it is expected that the precision would considerably improve using a maximum likelihood estimator based on the full series of focal images. As such, the theoretical lower bound on the variances of the unknown atom column positions can be attained. However, this approach is numerically demanding. Therefore, maximum likelihood estimation has been compared with the results obtained by fitting a model to a reconstructed exit wave rather than to the full series of focal images. Hence, a real space model-based exit wave reconstruction technique based on the channelling theory is introduced. Simulations show that the reconstructed complex exit wave contains the same amount of information concerning the atom column positions as the full series of focal images. Only for thin samples, which act as weak phase objects, this information can be retrieved from the phase of the reconstructed complex exit wave.
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Affiliation(s)
- A De Backer
- Electron Microscopy for Materials Science (EMAT), University of Antwerp, Belgium.
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