THE SIZE DEPENDENCE OF THE HIGH-PRESSURE PHASE-STABILITY OF II-VI SEMICONDUCTOR NANOCRYSTALS

We report pressure-dependent optical studies for different sized CdSxSe1-x nanocrystals embedded in a glass matrix. The increase in the phase stability in going from wurtzite to rock salt structure is reversible and size dependent. Different possible sources such as strain from defects, semiconductor-to-glass-matrix thermal expansion mismatch, increase in the electronic energy due to confinement, and surface tension which may cause this effect are discussed. Results indicate that surface tension is the major contribution and a simple model is developed that produces estimates of the size distribution and difference between the surface tensions of the two phases.