Comparison of heat-affected zones due to nanosecond and femtosecond laser pulses using transmission electronic microscopy

TLDR

The study introduces a method to quantify the dimensions of the heat‑affected zone generated by nanosecond and femtosecond laser–matter interactions. The method involves microdrilling 0.1 µm thick Al samples, creating holes at fluences above the ablation threshold (5 J cm⁻² for nanosecond and 2 J cm⁻² for femtosecond pulses) and examining them with transmission electron microscopy. The results show a 40 µm wide heat‑affected zone for nanosecond pulses, while femtosecond pulses produce a zone less than 2 µm, below the observation limit.

Abstract

This letter presents a method aimed at quantifying the dimensions of the heat-affected zone (HAZ), produced during nanosecond and femtosecond laser–matter interactions. According to this method, 0.1 μm thick Al samples were microdrilled and observed by a transmission electronic microscopy technique. The holes were produced at laser fluences above the ablation threshold in both nanosecond and femtosecond regimes (i.e., 5 and 2 J/cm2, respectively). The grain size in the samples was observed near the microholes. The main conclusion is that a 40 μm wide HAZ is induced by the nanosecond pulses, whereas the femtosecond regime does not produce any observable HAZ. It turns out that the width of the femtosecond HAZ is less than 2 μm, which is our observation limit.