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The energy level of the Fe2+/3+-transition in BaTiO3 and SrTiO3 single crystals

Suzuki, Issei and Gura, Leonard and Klein, Andreas (2019):
The energy level of the Fe2+/3+-transition in BaTiO3 and SrTiO3 single crystals.
In: Physical Chemistry Chemical Physics, 21Royal Society of Chemistry, pp. 6238-6246, ISSN 1463-9076,
DOI: 10.1039/C8CP07872F,
[Online-Edition: https://doi.org/10.1039/C8CP07872F],
[Article]

Abstract

An approach to determine the defect energy levels of the Fe impurities in BaTiO3 and SrTiO3 single crystals using electrical conductance measurements is presented. The defect levels are obtained from the dependence of the activation energy of electrical transport on the oxygen vacancy concentration, which is varied by stepwise re-oxidation of a reduced sample. An energy level at 0.7–0.8 eV below the conduction band minimum ECB is identified for BaTiO3, which can be assigned to the Fe2+/3+-transition in good agreement with literature. In contrast, the conductivity of Fe-doped SrTiO3 does not show a defect energy level in the upper half of the band gap, indicating that the Fe2+/3+-transition in SrTiO3 is near the conduction band minimum. The often reported alignment of defect energy levels, which is fulfilled for the Fe3+/4+-transition in BaTiO3 and SrTiO3, does not hold for the Fe2+/3+-transition in these compounds. This limits the applicability of Fe-doped SrTiO3 as a model system for studying resistance degradation in acceptor-doped high-permittivity dielectrics.

Item Type: Article
Erschienen: 2019
Creators: Suzuki, Issei and Gura, Leonard and Klein, Andreas
Title: The energy level of the Fe2+/3+-transition in BaTiO3 and SrTiO3 single crystals
Language: English
Abstract:

An approach to determine the defect energy levels of the Fe impurities in BaTiO3 and SrTiO3 single crystals using electrical conductance measurements is presented. The defect levels are obtained from the dependence of the activation energy of electrical transport on the oxygen vacancy concentration, which is varied by stepwise re-oxidation of a reduced sample. An energy level at 0.7–0.8 eV below the conduction band minimum ECB is identified for BaTiO3, which can be assigned to the Fe2+/3+-transition in good agreement with literature. In contrast, the conductivity of Fe-doped SrTiO3 does not show a defect energy level in the upper half of the band gap, indicating that the Fe2+/3+-transition in SrTiO3 is near the conduction band minimum. The often reported alignment of defect energy levels, which is fulfilled for the Fe3+/4+-transition in BaTiO3 and SrTiO3, does not hold for the Fe2+/3+-transition in these compounds. This limits the applicability of Fe-doped SrTiO3 as a model system for studying resistance degradation in acceptor-doped high-permittivity dielectrics.

Journal or Publication Title: Physical Chemistry Chemical Physics
Volume: 21
Publisher: Royal Society of Chemistry
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Electronic Structure of Materials (ESM)
Date Deposited: 28 Feb 2019 09:22
DOI: 10.1039/C8CP07872F
Official URL: https://doi.org/10.1039/C8CP07872F
Funders: Issei Suzuki has been financially supported by an OverseasResearch Fellowship of the Japanese Society for the Promotionof Science (JSPS), ). Support from the U.S. Air Force Office ofScientific Research under contract number FA9550-14-1-0158 isgratefully acknowledged., We also like to thank Roger A. de Souzafor helpful discussions.
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