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DF: Fachverband Dielektrische Festkörper

DF 13: Electrical and mechanical properties

DF 13.3: Talk

Thursday, March 17, 2011, 10:55–11:15, MÜL Elch

Spectroscopic investigation of electro-coloration in Fe:SrTiO₃ — •Christian Lenser¹, Regina Dittmann¹, Kristof Szot¹, Aleksandr Kalinko², Alexei Kuzmin², Juris Purans², and Rainer Waser^1,3 — ¹Peter Grünberg Institut (PGI-7), Forschungszentrum Jülich, Jülich, Germany — ²Institute of Solid State Physics, University of Latvia, Riga, Latvia — ³Institut für Werkstoffe der Elektrotechnik, RWTH Aachen, Aachen, Germany

Electro-coloration of single crystals can be used as a model for the electroforming process of valence-change non-volative memory materials such as SrTiO₃ and TiO₂, which is necessary to access the switching properties of the material. Fe-doped SrTiO₃ single crystals are electro-colored by applying a DC-voltage between two evaporated Au-electrodes and stepwise increasing the current until metallic conductivity is reached.

The regions near the anode and cathode of the single crystal are investigated by X-ray absorption fine structure (XAFS), electron paramagnetic resonance (EPR) and Raman spectroscopy. EPR data show the presence of Fe³⁺-oxygen vacancy complexes in the cathodic region, as well as their absence in the anodic region. The concentration gradient of oxygen vacancies created by the electro-coloration process is correlated to the local environment of Fe-centers as investigated by XAFS, and the effect of complexation and oxidation state on the pre-edge intensity and Fe-O bond length is discussed.