Crystal grain nucleation in amorphous silicon

The solid phase crystallization of chemical vapor deposited amorphous silicon films onto oxidized silicon wafers, induced either by thermal annealing or by ion beam irradiation at high substrate temperatures, has been extensively developed and it is reviewed here. We report and discuss a large variety of processing conditions. The structural and thermodynamical properties of the starting phase are emphasized. The morphological evolution of the amorphous towards the polycrystalline phase is investigated by transmission electron microscopy and it is interpreted in terms of a physical model containing few free parameters related to the thermodynamical properties of amorphous silicon and to the kinetical mechanisms of crystal grain growth. A direct extension of this model explains also the data concerning the ion-assisted crystal grain nucleation.