Structural transformations and metastability in semiconductor nanocrystals

Pressure-induced structural phase transitions have been studied in CdSe, Cd S, InP and Si semiconductor nanocrystals. Nanocrystals transform via single nucleation of the phase transition with a kinetic barrier that increases i n increasing cluster size. The structural transition path causes a shape ch ange in the nanocrystals, which dictates the surface energy and thus the ki netic and thermodynamic stability of the transformed nanocrystal. These fin ite size effects can be used to tune the metastability of the nanocrystals versus pressure. Enhanced metastability allows structural and optical measu rements in a regime inaccessible to the bulk solid, as well as possible rec overy of the dense high pressure phase to atmospheric pressure.