Light-induced VIS-absorption and light-induced charge transfer in pure and doped SBN crystals
Autor(en): | Gao, M Kapphan, S Pankrath, R Feng, XQ Tang, YF Vikhnin, V |
Stichwörter: | CE; CERIUM; Chemistry; Chemistry, Multidisciplinary; defects; MULLER PHASE; NIR ABSORPTION; optical properties; ORIGIN; oxides; PEROVSKITE-LIKE FERROELECTRICS; PHOTOREFRACTIVE SR0.61BA0.39NB2O6-CE CRYSTALS; Physics; Physics, Condensed Matter; POLAR MICRODOMAINS; STRONTIUM-BARIUM NIOBATE; TRANSFER VIBRONIC EXCITONS | Erscheinungsdatum: | 2000 | Herausgeber: | PERGAMON-ELSEVIER SCIENCE LTD | Enthalten in: | JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS | Band: | 61 | Ausgabe: | 11 | Startseite: | 1775 | Seitenende: | 1787 | Zusammenfassung: | Under illumination with Ar+-, Kr+-laser or UV light, SrxBa1-xNb2O6 (SBN):Ce, SBN:Cr and pure SBN crystals show a light-induced absorption band around 2.1 eV (600 nm) with a considerable dichroism. This light-induced VIS-absorption exhibits nonlinear intensity dependence with saturation at high illumination strength. The temperature dependence of the light-induced absorption of the VIS-center for a specific illumination intensity shows for temperatures T < 200 K a nearly constant value, which however decreases rapidly at higher temperatures T > 200 K. The decay of the light-induced VIS-centers after the illumination is switched off is non-monoexponential and strongly depends on temperature. The decay rate of the VIS-centers is nearly zero at low temperatures T < 100 K, increasing rapidly above T > 140 K. The absorption and therefore the concentration of Ce3+- or Cr3+-centers in SBN crystals have been found to decrease with increasing illumination intensity at T = 2 K. At low temperatures T < 140 K under illumination (with Ar+-, Kr+-laser, UV light), in addition to the VIS-center absorption, a strong absorption band because of Nb4+ polarons [1], similar to absorption bands observed in reduced SBN crystals [2], appears in the NIR spectral legion (lambda(max) about 1.6 mu m). The bandshape of this Nb4+ polaron absorption extends with its tail into the visible region, overlapping with the absorption of the VIS centers. The Nb4+ polaron absorption decays rapidly even at low temperatures, and above T > 140 K no NIR absorption of these centers could be detected any more. A light-induced charge transfer model is proposed to explain the experimental results of the light-induced NIR and VIS absorption and the possible origin of the light-induced VIS-centers. (C) 2000 Elsevier Science Ltd. All rights reserved. |
ISSN: | 00223697 | DOI: | 10.1016/S0022-3697(00)00056-1 |
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geprüft am 09.06.2024