Pressure Effects on CdS Microcrystals Embedded in Germanate Glasses

Abstract

We measured the absorption edge, photo-luminescence and Raman scattering spectra of CdS microcrystals embedded in germanate glasses under high hydrostatic pressure. We found that the one L0 phonon frequency shifts to the higher energy side with the increase of the pressure. The Raman shift with pressure variation is rather insensitive to the size of the CdS microcrystal and the change of its value with pressure is approximately equal to that of the bulk material. This strongly suggests that the stress induced by the glass medium is small. We also found that the absorption edge energy increases with the increase of the pressure. The bulk CdS shows a phase transition at 2.7 GPa pressure, however, the microcrystals exhibit no drastic change in the measured pressure range. The dependence of the luminescence on the pressure was also measured. The surface emission, which is in the lower energy part of the edge emission luminescence spectra, shifts to the higher energy side and disappears gradually with the Increase of the pressure.