PRESSURE-INDUCED STRUCTURAL TRANSFORMATIONS IN SI NANOCRYSTALS - SURFACE AND SHAPE EFFECTS

The kinetics of solid-solid phase transitions are explored using press ure-induced structural transformations in Si nanocrystals. In agreemen t with the predictions of homogeneous deformation theories, large elev ations in phase transition pressure are observed in nanocrystals as co mpared to bulk Si, and high pressure x-ray diffraction peak widths ind icate an overall change in nanocrystal shape upon transformation. In a ddition, unlike the BC8 phase recovered in bulk Si, amorphous Si nanoc lusters are obtained upon release of pressure, providing an example of kinetic size control over solid phases.