Phase transitions in metastable phases of silicon

Phase transitions in indentation induced Si-III/XII phases were investigated using a diamond anvil cell and nanoindentation combined with micro-Raman spectroscopy. The in situ high pressure Raman results demonstrate that the Si-III and Si-XII phases have very similar Raman spectra, indicating their relative amount cannot be determined if they are both present in a sample. The Si-III and Si-XII phases coexist in the indentations produced by a nanoindenter on a single crystalline silicon wafer as a result of the local residual compressive stresses near 1 GPa. High power laser annealing on the indentations can initiate a rapid Si-III/XII -> Si-I phase transition. The newly formed polycrystalline Si-I phase initially has very small grain size, and the grains grow when the annealing time is extended. Si-IV phase was not observed in our experiment. (C) 2014 AIP Publishing LLC.