Target ablation characteristics of thin films during nanosecond pulsed laser deposition in the ablation process

Abstract

The whole ablation process of target during the pulsed laser preparation of thin films is studied in this paper. An ablation model of targets in which the vapo rization is taken account is present based on the superheated theory. Different heat flux equations for different stages are then established. Finally, as usin g Si as the target, a finite difference method is employed to simulate the space _ and time_dependence of temperature in the target. Vaporization velocity and va porization thickness evolutions with different laser fluence are investigated. T he dependence of solid_liquid interface location S(t) on time which takes in to account the melting relaxation time is derived too. The results show that th e vaporization strongly affects the surface temperature in the pulsed laser abla tion. When the laser intensity reaches near the phase explosion energy threshold , the vaporization velocity and ablation depth will evidently decrease because o f the gas dynamic effects. This result is more appropriate than that obtained in previous works.