In-situ measurements of excimer laser irradiated zinc sulphide films on silicon

Time-resolved reflectivity at 675 nm of thin films of zinc sulphide on silicon during excimer laser irradiation is contrasted with theoretical calculations based on known data for the temperature dependence of the refractive index of both film and substrate and temperature profiles generated using an analytical solution of the heat diffusion equation for a two-layer system. The calculated rates of heating and cooling are found to be in excellent agreement with the experimental measurements and the maximum surface temperature at the ablation threshold is found to be 11508C. We conclude therefore that the zinc sulphide does not reach the melting point ;18008C.before the onset of ablation and that sublimation plays a significant part in the ablation process. q1999 Elsevier Science B.V. All rights reserved.