Femtosecond and Ultraviolet Laser Irradiation of Graphite-Like Hexagonal Boron Nitride

TL;DR

This study investigates how femtosecond and nanosecond UV laser irradiation affects graphite-like hexagonal boron nitride, revealing different surface modifications, recovery behaviors, and an ablation threshold of 78 mJ/cm2.

Contribution

It provides new insights into the effects of femtosecond and nanosecond UV laser irradiation on hBN, including surface enrichment and reversible fluorescence changes.

Findings

Nanosecond irradiation enriches surface with boron.

Femtosecond irradiation causes reversible fluorescence changes.

Ablation threshold is 78 mJ/cm2 for femtosecond laser.

Abstract

Effect of the femtosecond and nanosecond UV laser irradiation (below the ablation threshold) of graphite-like hexagonal boron nitride (hBN) has been studied. Experiments were carried out with the compacted powder under high vacuum at room temperature using excimer KrF laser (248 nm). In the nanosecond operation mode, the laser-induced fluorescence spectra are found strongly modified depending on the integrated doze, which is attributed to a progressive enrichment of the surface layer by elemental boron. A slow sample recovery after the laser irradiation has been observed. On the other hand, in the femtosecond mode the fluorescence spectra depend on the laser fluence, and the changes are reversible: low energy fluorescence spectra are restored immediately when the laser energy decreases. This effect can be explained by a material bleaching, which favors a bulk centers emission. The ablation threshold has been determined as 78 mJ/cm2 in the femtosecond laser operational mode.