Study of photoinduced charge transfer in SrTiO3: luminescence, photoconductivity and photo-EPR

S. A. Basun; U. Bianchi; V. E. Bursian; Alexander A. Kaplyanskii; W. Kleemann; L. S. Sochava; V. S. Vikhnin

doi:10.1117/12.229167

3 January 1996 Study of photoinduced charge transfer in SrTiO₃: luminescence, photoconductivity and photo-EPR

S. A. Basun, U. Bianchi, V. E. Bursian, Alexander A. Kaplyanskii, W. Kleemann, L. S. Sochava, V. S. Vikhnin

Proceedings Volume 2706, Tenth Feofilov Symposium on Spectroscopy of Crystals Activated by Rare-Earth and Transitional-Metal Ions; (1996) https://doi.org/10.1117/12.229167
Event: Tenth Feofilov Symposium on Spectroscopy of Crystals Activated by Rare Earth and Transitional Ions, 1995, St. Petersburg, Russian Federation

Abstract

A study of photoluminescence, photo-EPR, and of photoconductivity was carried out on SrTiO₃ and Sr_1-xCa_xTiO₃ (x equals 0.007) crystals containing a small amount of Cr. As a result, the location of Cr electronic levels in the band gap was found, Cr³⁺ being a donor located at 1.85 eV below the CB bottom and Cr⁴⁺ being an acceptor at 1.4 eV above the VB top. In accordance with this scheme, it was shown that: (1) Photons with energies exceeding 1.85 eV excite Cr³⁺ R luminescence in the course of the events; h(nu) _exc + Cr³⁺ yields e + Cr⁴⁺ yields Cr³⁺(²E) + phonons yields Cr³⁺(⁴A₂) + h(nu) _R. (2) Excitation with photon energies above 1.4 eV converts Cr⁴⁺ to Cr$3+):h(nu) _exc + Cr⁴⁺ yields h + Cr³⁺. (3) A band with low energy threshold at 2.1 eV is observed both in excitation spectra of R luminescence and of photoconductivity. The specific character of photoluminescence excitation manifests itself in a number of interesting observations: (i) Strong increase of steady-state R luminescence intensity under IR irradiation additional to excitation in the visible. (ii) IR induced transient R luminescence caused by previous irradiation in the visible. (iii) Very long tails on the time scale of 1000s in R luminescence decay with weak dependence on temperature from 2 K to 78 K.

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S. A. Basun, U. Bianchi, V. E. Bursian, Alexander A. Kaplyanskii, W. Kleemann, L. S. Sochava, and V. S. Vikhnin "Study of photoinduced charge transfer in SrTiO₃: luminescence, photoconductivity and photo-EPR", Proc. SPIE 2706, Tenth Feofilov Symposium on Spectroscopy of Crystals Activated by Rare-Earth and Transitional-Metal Ions, (3 January 1996); https://doi.org/10.1117/12.229167

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