Laser-induced phase transformation in p-doped nanocrystalline silicon thin films

The results of a study of phase transformation in boron doped hydrogenated nanocrystalline silicon thin films prepared by PECVD and exposed to a powerful Ar+ laser light (100 kw/cm2) are presented. Through Raman spectroscopy, it was determined that the induced phase transformation is correlated with the boron concentration in the silane diluted with hydrogen used as reactive gases in the preparation of the films, on the grain size, and the crystalline volume fraction of them. Measurements of dark conductivity and atomic-force microscopy (AFM) have been made to corroborate the Raman measurements. The results show that the sequence of phase transformation in nanocrystalline thin films presents different characteristics from those, which are produced in silicon crystals. The occurrence of a Raman peak at 350 cm−1 is attributed to the formation of the Si-XII phase, which is attributed to the stress compression in the films. A model for hot-spot phase transformation in p-doped nanocrystalline silicon thin films is discussed.