Large pressure effect on photoluminescence lines in 6 H SiC:Ti crystal

Abstract

The effect of hydrostatic pressure up to 7.5 kbar on the so-called ABC lines in the photoluminescence spectrum of hexagonal 6 H SiC crystals with traces of Ti atoms has been studied at 77 K. Linear pressure shifts of these lines were found to be rather large (1.08–1.25 meV kbar −1) considering low compressibility of the crystal and the expected very small pressure coefficient for the band gap in 6 H SiC. The recorded pressure shifts exceed by more than 10 times those of the well-known R luminescence lines in ruby, Al 2O 3:Cr 3+, which has roughly the same compressibility as SiC. Fairly high sensitivity of ABC lines to the applied pressure is interpreted in terms of a ligand field model for a quasimolecular impurity centre where Ti atom substitutes an about 20% smaller Si atom in SiC crystal.