SIZE-INDUCED PHASE-TRANSITION (ZINCBLENDE TO WURTZITE) IN CDSSE NANOCRYSTALLITES EMBEDDED IN GLASS

We report the observation of a size-induced phase transition (from Zin cblende to Wurtzite) occurring in CdSSe nanocrystallites (quantum dots ) of radius R > 4 nm. The preferential Zincblende phase seems to be a peculiar property of the ultra small dots. The observed results may be interpreted qualitatively as follows. When the surface energy of the nanocrystallites with the zincblende structure is less than that in th e case of wurtzite structure crystallites, then with increasing quantu m dot size the relative contribution of the surface energy to the tota l cluster energy decreases and a following subsequent transition from Zincblende structure to the bulk Wurtzite structural modification occu rs.