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Luminescence‐detected EPR of oxygen‐fluorine vacancy complexes in CaF 2
Author(s) -
Rogulis Uldis,
Baetzold Roger C.,
Spaeth JohannMartin
Publication year - 2009
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200844373
Subject(s) - excited state , electron paramagnetic resonance , luminescence , metastability , impurity , vacancy defect , chemistry , shallow donor , atomic physics , doping , crystallography , materials science , nuclear magnetic resonance , condensed matter physics , physics , optoelectronics , organic chemistry
In several CaF 2 single crystals grown by the Bridgman method and doped with CaO or in addition with SrF 2 or NaF a luminescence band between 470 nm and 600 nm could be excited at 212 nm, its peak wavelength depending on the doping. With photo‐luminescence (PL) detected EPR five spin triplet centres were identified. Their axial fine structure constants D varied from 87 mT to 690 mT whereby the most intense spectra had the smallest D value. Theoretical calculations of the fine structure tensors and superhyperfine interactions show that the most intense and probable triplet centre consists of a pair of an O F – on a F – site next to a nearest neighbour F – vacancy which, compared to the well‐known F centre, is occupied by an excited electron in a shallow orbital and coupled to the 2p hole at the oxygen to form a S = 1 excited state. This centre can be excited optically at low temperature to a metastable new configuration where the F centre jumps into a 〈111〉 position opposite the O F – . The other triplet centres have probably also an O – –F centre nearest neighbour configuration but have in addition a cation impurity or vacancy nearby. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)