Abstract

The phase transition properties of CdSe microcrystals embedded in glass were studied by Raman scattering and photoluminescence under pressure in a diamond anvil pressure cell. From careful measurement of Raman intensity versus pressure, a complete phase transition from wurtzite to rocksalt phase of the CdSe particles in the glass composite was observed above 70 kbar in contrast to approximately 30 kbar in bulk CdSe. During the phase transition there was no observed sudden color change which shows that the phase transition in small crystallites does not induce a large number of defects. From photoluminescence measurements we conclude that in the small particle system, after the phase transition there is not a sudden absorption edge drop which was observed in bulk materials. We also suggest from photoluminescence measurements of CdSe in the rocksalt phase that the bandgap of CdSe is indirect and about 2.02 eV.

© 1990 Optical Society of America