Computational model of pulsed laser-induced melting, evaporation and solidification of CdZnTe

A model of melting, evaporation and solidification of CdZnTe pseudobinary alloy due to pulsed laser irradiation is formulated using the mass and internal energy balances in the liquid and solid phases, the vapor being assumed to be removed from the sample surface into vacuum instantaneously. The interface between the solid and liquid phases is modeled as a discontinuity surface where, in addition to balance conditions, an interface response function is formulated on the basis of the Wilson–Frenkel theory so that both melting and solidification are treated as nonequilibrium processes. The liquid/vapor interface is modeled in a similar way, with an interface response function defined on the basis of the kinetic theory of gases. The numerical solution of the mathematical model is done using the Galerkin finite element method combined with a front-fixing technique. In the numerical simulations of pulsed laser-induced phase change processes in CdZnTe, the temperature and concentration fields, the positions and velocities of the solid/liquid and liquid/vapor phase interfaces, and the time-resolved incident laser reflectivities are calculated as functions of the laser energy density for two types of lasers, namely the Nd:YAG laser and ruby laser. The results obtained for both the lasers are discussed and recommendations for the optimization of experimental setups are given.