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Münster 1997 – scientific programme

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DF: Dielektrische Festkörper

DF 5: Störstellen, Inhomogene Medien

DF 5.2: Talk

Tuesday, March 18, 1997, 16:50–17:10, R2

Light-induced charge transport in BaTiO3:Fe — •A. Mazur, R. Scharfschwerdt, and O. F. Schirmer — Fachbereich Physik, Universit"at Osnabr"uck, 49069 Osnabr"uck

Using EPR and optical absorption simultaneously, we have studied the absorption and the light-induced charge transport characteristics of BaTiO3:Fe at room and cryogenic temperatures. We have also investigated the effect of thermal annealing on iron as well as the charge transport changes after such treatments.

The conversion of Fe4+ to Fe3+ occurs with the highest efficiency with light of ∼ 2.8 eV whereas the absorption transforming Fe5+ to Fe4+ is peaked near 2.5 eV. Under these illuminations valence band holes are created, which at low temperatures are captured at shallow acceptors such as (Na+, K+, Ptx+)-O. The thermal levels Fe3+/Fe4+ and Fe4+/Fe5+ are closer to the valence band, ∼ 1 eV and below, indicating sizeable Franck-Condon shifts.

The role of Fe in reduced BaTiO3 will also be discussed.

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