Charge transfer vibronic excitons and excitonic-type polaron states: photoluminescence in SBN

Autor(en): Vikhnin, VS
Kislova, I
Kutsenko, AB
Kapphan, SE
Stichwörter: ferroelectric oxides; luminescence; MICRODOMAINS; MULLER PHASE; optical properties; ORIGIN; PEROVSKITE-LIKE FERROELECTRICS; Physics; Physics, Condensed Matter; recombination and trapping; vibronic excitons
Erscheinungsdatum: 2002
Volumen: 121
Ausgabe: 2-3
Startseite: 83
Seitenende: 88
A theoretical model for two characteristic photoluminescence (PL) bands in SBN, `green luminescence' (GL-band), and `red luminescence' (RL-band) is proposed on the basis of the extended photoluminescence experiments in SBN/Cr, and also in SBN/Cc and in nominally pure SRN Systems Under different conditions. While the RL-band is suggested to be connected with charge transfer vibronic exciton (CTVE) clusters induced by Cr3+ impurities in the Nb-sites, the GL-band is connected with Nb4+ electronic polarons in a new excited state. Here Nb4+ centers are the cores of the CTVE clusters induced by these charged cores. The PL mechanism is the in-cluster CTVE recombination for both bands under discussion. But the CTVE states are quasi-resonantly mixed here with T-4(2) states of the Cr3+ core in the RL-band case, and with 5s-states of the Nb4+ Core in the G-band case. The CTVE-clusters induced by Cr3+ ions produce strong lattice distortion which can be the origin of the uncommonly high red shift of the fundamental absorption band edge detected for the SBN/Cr case. (C) 2002 Elsevier Science Ltd. All rights reserved.
ISSN: 00381098
DOI: 10.1016/S0038-1098(01)00469-0

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