Low-temperature studies of the photoluminescence in CdS under hydrostatic pressure

Abstract

We report the first study of the effect of pressure on the photoluminescence and Raman spectra of CdS at 6 K using a diamond-anvil cell. The shifts of the free and bound excitons and their phonon replicas are followed up to ∼25 kbar when CdS undergoes a phase transition from a direct-gap wurtzite to an indirect-gap rocksalt structure. In the latter structure, the luminescence is not present. The Raman spectra of the LO phonon and its overtones are also studied under pressure. Accurate low-temperature values of the pressure coefficients of the excitons, their LO replicas, and the Raman LO phonon are deduced.