Numerical simulation on the temperature field induced by a nanosecond pulsed excimer laser in the phase-change film

In the paper, a three-dimensional finite element model was developed to demonstrate the temperature field induced by a nanosecond pulsed excimer laser in the phase-change film. The numerical model was established with an assumed rectangular temporal profile, following the continuous medium heat conduction theory with semi-infinity heat conduction. It showed that the temperature variation followed the exponential relation in both the heating/cooling procedures, and the whole heating/cooling process was divided into four regions I-IV, namely rapid heating region I and equilibrium heating region II in the heating process as well as quick cooling region III and equilibrium cooling region IV in the cooling process. The heating/cooling rates were then fitted from the temperature variation curve. The calculated heating/cooling rates were in the scale of 10⁸-10¹¹ K/s for the nano-scale pulse radiance. Furthermore, the effects of laser fluence and pulse duration on the temperature field were investigated. It was noted that the effect of pulse duration was focused on regions II and III, while the heating rate in region I was mainly determined by laser fluence.