FORMATION OF NANOCRYSTALS IN A-SI THIN-FILMS INDUCED BY PULSED-LASER ULTRAVIOLET-IRRADIATION

We extend the theoretical model of recrystallization of a-Si films ind uced by pulsed laser irradiation and determine c-Si cluster distributi on in the solid phase and we discuss the possibility of nanocluster fo rmation in the a-Si thin layer. Our theory is based on the description of nucleation and growth of the crystalline phase in molten Si during fast heating and cooling processes. We are able to describe nonequili brium solidification, including the distribution of nanocrystals as a function of laser pulse energy. Calculations of temperature distributi on during recrystallization processes and the kinetics of crystalline phase formation show that nucleation of c-Si in l-Si must be taken int o account in simulations of recrystallization of a-Si induced by high energy density pulsed laser irradiation (>200mJ/cm(2)). The presence o f nanoclusters in the Si layer is possible if recrystallization starts from the strong supercooled l-Si, e.g., if a-Si is melted immediately . (C) 1997 American Vacuum Society.