Structure stability, fracture, and tuning mechanism of CdSe nanobelts

High pressure synchrotron x-ray diffraction studies have been conducted to explore the structural stability, phase transformation, and resulting mechanisms of CdSe nanobelts. 25-nm-thick wurtzite CdSe nanobelts transform to a rocksalt structure with in situ fracture at 4.0 GPa; this is greater than the transition pressure of 2.5 GPa in bulk and 25 nm nanoparticle. Decompression results in the formation of wurtzite and sphalerite at 1.2 GPa. Total Gibbs free energy calculations demonstrate that the low surface energy +/-{2 (1) over bar0} facets are fully responsible for the enhancement of structure stability. A strongest particle size for the rocksalt phase was determined similar to 12 nm, providing a significant constraint for the fracture of nanobelts and size-tuned enhancement of mechanical properties. (c) 2007 American Institute of Physics.