| 1. |
- Andreasson, Björn Pererik, 1979-, et al.
(författare)
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Detecting oxygen vacancies in SrTiO3 by 3d transition-metal tracer ions
- 2009
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - College Park, MD : American Physical Society. - 1098-0121 .- 1550-235X. ; 80:21, s. Article number: 212103-
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Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption experiments on 3d transition-metal tracer ions in SrTiO3 are presented. The absorption spectra of the tracer-ion changed upon reduction in the SrTiO3. This change is due to an oxygen vacancy created at the tracer-ion site. This finding is supported by density-functional theory calculations, which prove that the oxygen vacancies preferentially are created at the tracer-ion sites. Using the chemical sensitivity of x-ray absorption spectroscopy, tracer ions can be used to detect oxygen vacancies in SrTiO3 and possibly in other oxide systems. © 2009 The American Physical Society.
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| 2. |
- Andreasson, Björn Pererik, 1979-, et al.
(författare)
-
Origin of oxygen vacancies in resistive switching memory devices
- 2009
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Ingår i: Journal of Physics, Conference Series. - Bristol : Institute of Physics Publishing (IOPP). - 1742-6588 .- 1742-6596. ; 190, s. Article number: 012074-
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Tidskriftsartikel (refereegranskat)abstract
- The resistive switching state in Cr-doped SrTiO3 was induced by applying an electric field. This was done in ambient air and in an atmosphere of H2/Ar. The distribution of the thereby introduced oxygen vacancies was studied by spatially resolved X-ray fluorescence images. It was concluded that the oxygen vacancies were introduced in the interface between the SrTiO3 and the positively biased electrode. © 2009 IOP Publishing Ltd.
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| 3. |
- Andreasson, Björn Pererik, 1979-, et al.
(författare)
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Resistive switching in Cr-doped SrTiO3 : An X-ray absorption spectroscopy study
- 2007
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Ingår i: Materials Science & Engineering. - Amsterdam : Elsevier. - 0921-5107 .- 1873-4944. ; 144:1-3, s. 60-63
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Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption spectroscopy was used to study the microscopic origin of conductance and resistive switching in chromium-doped strontium titanate (Cr:SrTiO3). Differences in the X-ray absorption near edge spectroscopy (XANES) at the Cr K-edge indicate that the valence of Cr changes from 3+ to 4+ underneath the anode of our sample device after the application of an electric field. Spatially resolved X-ray fluorescence microscopy (μ-XRF) maps show that the Cr4+ region retracts from the anode-Cr:SrTiO3 interface after a conducting state has been achieved. This interface region is studied with extended X-ray absorption fine structure (EXAFS) and the results are compared with structural parameters obtained from density functional theory (DFT) calculations. They confirm that oxygen vacancies which are localized at the octahedron with a Cr at its center are introduced at the interface. It is proposed that the switching state is not due to a valence change of chromium but caused by changes of oxygen vacancies at the interface. © 2007 Elsevier B.V. All rights reserved.
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| 4. |
- Andreasson, Björn Pererik, 1979-, et al.
(författare)
-
Spatial distribution of oxygen vacancies in Cr-doped SrTiO3 during an electric-field-driven insulator-to-metal transition
- 2009
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Ingår i: Applied Physics Letters. - College Park, MD : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 94:1, s. Article number: 013513-
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Tidskriftsartikel (refereegranskat)abstract
- Spatially resolved x-ray fluorescence maps are presented that show the introduction and the evolution of oxygen vacancies in chromium-doped strontium titanate during an electric-field-driven insulator-to-metal transition. The vacancies are introduced at the anode and diffuse through the crystal toward the cathode. The spatial distribution of vacancies is explained by a model describing the electrical breakdown as a percolation process. Strong differences in the vacancy distribution were found when the transition took place in air and in a hydrogen-enriched atmosphere. In air, the vacancies disappeared from the surface, whereas in the reducing hydrogen atmosphere, they remained at the surface. © 2009 American Institute of Physics.
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