Nonequilibrium model of laser-induced phase change processes in amorphous silicon thin films

A mathematical model of nonequilibrium phase change processes in amorphous silicon induced by pulsed lasers, which includes explosive crystallization, melting, evaporation, and crystallization from the solid/liquid interface and takes into account the thermophysical properties of polycrystalline silicon in dependence on the grain size, is formulated in the paper. The computational implementation of the model is used to simulate phase changes in a typical case of XeCl excimer laser irradiation of 50 nm to 8 {μ}m thick amorphous silicon layers deposited on the quartz substrate, where characteristic thermal and optical effects accompanying the irradiation process are demonstrated. The experimental verification of the model is discussed, and a comparison of simulated data with experimental measurements of various groups is performed. The model is shown to achieve agreement with experimental data in a variety of experimental situations. It can also be employed to provide estimated values of thermophysical and optical parameters of polycrystalline silicon in dependence on the grain size.