Non-Fourier Energy Transport in Silicon Thin Films during Femtosecond Laser Heating

A numerical model which is based on the hyperbolic two-step model is developed to investigate the microscopic energy transport in silicon thin films during ultra-fast laser heating. It is observed that, electrons dominate energy transport within a few picoseconds. The coupling processes between electrons and phonons are non-local due to the ballistic transport of electrons, and the coupling coefficient is found to be much more strongly dependent on electron temperature than lattice temperature. The speed of heat wave propagation is the same magnitude as that of the electron energy transport. Predictions from the numerical model agree with available experimental data during ultra-fast laser heating.