High pressure photoluminescence and Raman studies of ZnxCd1-xSe quantum dots

Raman and photoluminescence (PL) studies of wurtzite alloy ZnxCd1-xSe (x = 0.2) quantum dots (QDs) with size ∼4.7 nm were carried out under hydrostatic pressure up to 130 kbar using the diamond anvil cell technique. The structural phase transition from wurtzite to rock-salt was observed at 71 kbar, indicated by the disappearance of both PL and Raman peaks. In addition, the abrupt change of PL pressure coefficient and Raman peak splitting were observed at about 25.8 kbar, which may indicate a new unidentified structural phase transition of the alloy QDs. This new unidentified phase transition was discussed and possible explanations were proposed. The results of alloyed ZnCdSe QDs differ greatly from that of bare CdSe or ZnSe QDs as well as the corresponding bulk materials, implying that the quantum size effect plays an important role in the structural stability of the alloy QDs