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In‐Gap States in Wide‐Band‐Gap SrTiO 3 Analyzed by Cathodoluminescence
Author(s) -
Yang KaiHsun,
Chen TingYu,
Ho NewJin,
Lu HongYang
Publication year - 2011
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2010.04324.x
Subject(s) - cathodoluminescence , exciton , materials science , band gap , schottky diode , luminescence , doping , valence (chemistry) , atomic physics , analytical chemistry (journal) , chemistry , optoelectronics , condensed matter physics , physics , organic chemistry , chromatography , diode
The cathodoluminescence spectra between 300 and 900 nm were investigated for undoped and Nb 2 O 5 ‐doped SrTiO 3 sintered both in air and under low oxygen partial pressure (). Two broadened emission peaks observed experimentally were deconvoluted into five luminescences in the visible range of 2.9 eV (427 nm) to 2.4 eV (516 nm), and in the infrared range of 1.57 eV (790 nm), 1.55 eV (800 nm), and 1.44 (861 nm); each of which was assigned to interband transitions between in‐gap energy states correspondingly by considering the intrinsic and extrinsic defect reactions. It is suggested that the 2.4 eV emission originated from charge transfer between Ti 4+ and O 2− by a mechanism of charge‐transfer vibronic excitons. The 2.9 eV luminescence was due to electrons trapped in the donor states of extrinsic Nb Ti • generated by donor doping, and of extrinsic V O •• produced by low‐sintering, and of the Schottky intrinsic V O •• in undoped samples deexciting directly to the valence band. The triplet of (1.57+1.44) and 1.55 eV was from the emissions between the Schottky intrinsic defects in SrTiO 3 and in second‐phase TiO 2 , respectively.