Application of a two-temperature model for the investigation of the periodic structure formation on Si surface in femtosecond laser interaction

TL;DR

This paper introduces a numerical two-temperature model to explain the formation of periodic surface ripples on silicon caused by femtosecond laser irradiation, highlighting interference effects and energy transfer processes.

Contribution

The study develops a novel numerical model incorporating interference, free carrier dynamics, and electron-phonon coupling to elucidate ripple formation mechanisms.

Findings

Simulation results match experimental ripple patterns

Interference with surface waves influences ripple orientation

Energy relaxation processes are key to pattern development

Abstract

We consider the case of surface irradiation by a small number of femtosecond laser shots leading to the formation of surface ripples. To explain this effect, we propose a numerical model that accounts for the following processes: (i) interference of the laser irradiation with an electromagnetic surface wave propagating on a silicon sample; (ii) free carrier formation and laser energy absorption; (iii) energy relaxation and electron-phonon coupling. We perform numerical calculations taking into account the interference of a surface wave with laser; and present the obtained simulation results in order to explain formation mechanisms of the experimentally observed patterns.