Thermoplastic deformation of silicon surfaces induced by ultrashort pulsed lasers in submelting conditions

TL;DR

This paper presents a hybrid 2D theoretical model to analyze thermoplastic deformation of silicon surfaces caused by ultrashort pulsed lasers in submelting conditions, revealing crater formation and ripple effects.

Contribution

It introduces a novel hybrid model combining thermoplastic deformation and laser-material interaction under submelting conditions, including analysis of single and multiple pulse effects.

Findings

Single pulse creates picometre-sized craters.

Multiple pulses induce nanometre-sized ripples.

Surface modifications may serve as precursors for incubation effects.

Abstract

A hybrid 2D theoretical model is presented to describe thermoplastic deformation effects on silicon surfaces induced by single and multiple ultrashort pulsed laser irradiation in submelting conditions. An approximation of the Boltzmann transport equation is adopted to describe the laser irradiation process. The evolution of the induced deformation field is described initially by adopting the differential equations of dynamic thermoelasticity while the onset of plastic yielding is described by the von Mise's stress. Details of the resulting picometre sized crater, produced by irradiation with a single pulse, are then discussed as a function of the imposed conditions and thresholds for the onset of plasticity are computed. Irradiation with multiple pulses leads to ripple formation of nanometre size that originates from the interference of the incident and a surface scattered wave. It is suggested that ultrafast laser induced surface modification in semiconductors is feasible in submelting conditions, and it may act as a precursor of the incubation effects observed at multiple pulse irradiation of materials surfaces.