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Title: Defects, stoichiometry, and electronic transport in SrTiO{sub 3-δ} epilayers: A high pressure oxygen sputter deposition study

Abstract

SrTiO{sub 3} is not only of enduring interest due to its unique dielectric, structural, and lattice dynamical properties, but is also the archetypal perovskite oxide semiconductor and a foundational material in oxide heterostructures and electronics. This has naturally focused attention on growth, stoichiometry, and defects in SrTiO{sub 3}, one exciting recent development being such precisely stoichiometric defect-managed thin films that electron mobilities have finally exceeded bulk crystals. This has been achieved only by molecular beam epitaxy, however (and to a somewhat lesser extent pulsed laser deposition (PLD)), and numerous open questions remain. Here, we present a study of the stoichiometry, defects, and structure in SrTiO{sub 3} synthesized by a different method, high pressure oxygen sputtering, relating the results to electronic transport. We find that this form of sputter deposition is also capable of homoepitaxy of precisely stoichiometric SrTiO{sub 3}, but only provided that substrate and target preparation, temperature, pressure, and deposition rate are carefully controlled. Even under these conditions, oxygen-vacancy-doped heteroepitaxial SrTiO{sub 3} films are found to have carrier density, mobility, and conductivity significantly lower than bulk. While surface depletion plays a role, it is argued from particle-induced X-ray emission (PIXE) measurements of trace impurities in commercial sputtering targets thatmore » this is also due to deep acceptors such as Fe at 100's of parts-per-million levels. Comparisons of PIXE from SrTiO{sub 3} crystals and polycrystalline targets are shown to be of general interest, with clear implications for sputter and PLD deposition of this important material.« less

Authors:
; ; ; ; ; ;  [1];  [2]
  1. Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455 (United States)
  2. Characterization Facility, University of Minnesota, Minneapolis, Minnesota 55455 (United States)
Publication Date:
OSTI Identifier:
22597695
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 120; Journal Issue: 5; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CARRIER DENSITY; DEFECTS; DIELECTRIC MATERIALS; DOPED MATERIALS; ELECTRON MOBILITY; ENERGY BEAM DEPOSITION; LASER RADIATION; MOLECULAR BEAM EPITAXY; MOLECULAR BEAMS; OXIDES; OXYGEN; PEROVSKITE; PIXE ANALYSIS; POLYCRYSTALS; PULSED IRRADIATION; SPUTTERING; STOICHIOMETRY; STRONTIUM TITANATES; THIN FILMS

Citation Formats

Ambwani, P., Xu, P., Jeong, J. S., Deng, R., Mkhoyan, K. A., Jalan, B., Leighton, C., E-mail: leighton@umn.edu, and Haugstad, G. Defects, stoichiometry, and electronic transport in SrTiO{sub 3-δ} epilayers: A high pressure oxygen sputter deposition study. United States: N. p., 2016. Web. doi:10.1063/1.4960343.
Ambwani, P., Xu, P., Jeong, J. S., Deng, R., Mkhoyan, K. A., Jalan, B., Leighton, C., E-mail: leighton@umn.edu, & Haugstad, G. Defects, stoichiometry, and electronic transport in SrTiO{sub 3-δ} epilayers: A high pressure oxygen sputter deposition study. United States. doi:10.1063/1.4960343.
Ambwani, P., Xu, P., Jeong, J. S., Deng, R., Mkhoyan, K. A., Jalan, B., Leighton, C., E-mail: leighton@umn.edu, and Haugstad, G. Sun . "Defects, stoichiometry, and electronic transport in SrTiO{sub 3-δ} epilayers: A high pressure oxygen sputter deposition study". United States. doi:10.1063/1.4960343.
@article{osti_22597695,
title = {Defects, stoichiometry, and electronic transport in SrTiO{sub 3-δ} epilayers: A high pressure oxygen sputter deposition study},
author = {Ambwani, P. and Xu, P. and Jeong, J. S. and Deng, R. and Mkhoyan, K. A. and Jalan, B. and Leighton, C., E-mail: leighton@umn.edu and Haugstad, G.},
abstractNote = {SrTiO{sub 3} is not only of enduring interest due to its unique dielectric, structural, and lattice dynamical properties, but is also the archetypal perovskite oxide semiconductor and a foundational material in oxide heterostructures and electronics. This has naturally focused attention on growth, stoichiometry, and defects in SrTiO{sub 3}, one exciting recent development being such precisely stoichiometric defect-managed thin films that electron mobilities have finally exceeded bulk crystals. This has been achieved only by molecular beam epitaxy, however (and to a somewhat lesser extent pulsed laser deposition (PLD)), and numerous open questions remain. Here, we present a study of the stoichiometry, defects, and structure in SrTiO{sub 3} synthesized by a different method, high pressure oxygen sputtering, relating the results to electronic transport. We find that this form of sputter deposition is also capable of homoepitaxy of precisely stoichiometric SrTiO{sub 3}, but only provided that substrate and target preparation, temperature, pressure, and deposition rate are carefully controlled. Even under these conditions, oxygen-vacancy-doped heteroepitaxial SrTiO{sub 3} films are found to have carrier density, mobility, and conductivity significantly lower than bulk. While surface depletion plays a role, it is argued from particle-induced X-ray emission (PIXE) measurements of trace impurities in commercial sputtering targets that this is also due to deep acceptors such as Fe at 100's of parts-per-million levels. Comparisons of PIXE from SrTiO{sub 3} crystals and polycrystalline targets are shown to be of general interest, with clear implications for sputter and PLD deposition of this important material.},
doi = {10.1063/1.4960343},
journal = {Journal of Applied Physics},
number = 5,
volume = 120,
place = {United States},
year = {Sun Aug 07 00:00:00 EDT 2016},
month = {Sun Aug 07 00:00:00 EDT 2016}
}