Publication
Title
A photosensitive $Cr^{3+}$ center in photorefractive $Bi_{12}SiO_{20}$ crystals co-doped with chromium and phosphorus
Author
Abstract
 A trigonal Cr3+ (3d3) defect in sillenite type Bi12SiO20 crystals co-doped with chromium and phosphorus has been identified by means of multi-frequency X-band (9.4 GHz), Q-band (35 GHz) and W-band (94 GHz) electron paramagnetic resonance (EPR). A consistent analysis of the observed spectra and their angular dependence was reached using an S = 3/2 spin Hamiltonian with axial symmetry around a 〈111〉 crystallographic direction, an isotropic g-value g = 1.983, and a zero field splitting parameter B20 = 0.1950 cm−1. The spectra are attributed to a chromium ion in the unusual Cr3+ valence replacing a substitutional Si4+ in tetrahedral oxygen coordination. Evidence is found that the symmetry lowering from tetrahedral to trigonal is not spontaneous but induced by an associated defect, for which a P5+ ion in a nearest-neighbor Si4+ site is the most plausible candidate. Optical excitation results in a reversible charge transfer process directly correlated with a photochromic effect: near-UV light leads to a strong reduction of the Cr3+ EPR signals, and induces a broad band at 675 nm in the absorption spectrum, and both effects are reversed under red light excitation.
Language
English
Source (journal)
Journal of applied physics / American Institute of Physics. - New York, N.Y., 1937, currens
Publication
New York, N.Y. : American Institute of Physics, 2011
ISSN
0021-8979 [print]
1089-7550 [online]
Volume/pages
109:8(2011), p. 083506,1-083506,7
Article Reference
083506
ISI
000290047000030
Medium
E-only publicatie
Full text (Publisher's DOI)
UAntwerpen
 Faculty/Department Research group Publication type Subject Affiliation Publications with a UAntwerp address