Surface morphology and straight crack generation of ultrafast laser irradiated -Ga2O3

Single crystal (010) -Ga2O3 was irradiated by a Ti:sapphire ultrafast laser (150fs pulse width) with varying fluences and a number of pulses in air ambient. Femtosecond laser-induced damage threshold of -Ga2O3 is reported. Single pulse exposure results in surface morphological changes above a threshold laser fluence of 1.11J/cm(2). Laser-induced straight cracks aligned to the [001] crystallographic direction are observed in the laser irradiated regions, which are believed to be caused by laser-induced thermal stress, due to the unique low thermal conductivity and anisotropy associated with -Ga2O3. Multiple pulse irradiation below the single pulse damage threshold fluence exhibited the formation of high spatial frequency laser-induced periodic surface structures. Electron backscattering diffraction and Raman spectroscopy suggested that there was no apparent phase transition of the irradiated -Ga2O3 material for either single pulse or multiple pulse irradiation. This work serves as a starting point to further understanding the material properties of -Ga2O3 and to unlock the potential for ultrafast laser material processing of -Ga2O3.