Effects of pressure on photo-induced formation of Se and Te clusters in II-VI compounds

The tendency for clusters of crystalline Se or Te to form in the zincblende (ZB) phases of ZnSe, ZnTe, and CdSe is investigated as a function of applied pressure and under exposure to laser light. We find that nanoclusters of these elements in the trigonal phase form at pressures of >4.8 GPa for ZnSe and 0–0.9 GPa for ZnTe under exposure to moderate fluxes of sub-bandgap light ∼102 W mm−2. The appearance of the A1 Raman peaks of Se or Te, clearly identified by their negative pressure shifts, provide definitive evidence of the cluster formation. Several mis-assignments of these peaks in the literature are noted. For CdSe, the phase transition at 2.5 GPa leads to ambiguity in our results. Some mechanisms for the formation of Se (Te) clusters in II–VI solids are briefly considered.