Pulsed laser ablation of Ni in vacuum and N₂ atmosphere at various fluences

Mechanisms of Ni ablation in vacuum and N₂ atmosphere at various fluences ranging from 2.1 J cm^-2 to 3.4 J cm^-2 are studied by using a KrF excimer laser. The formation of various conical microstructures, ripples, large-sized irregular shaped cavities and pits is found. It is shown that no new phases are formed in the case of Ni ablation in vacuum, while new phases of nitrides and nitrooxides appear in the N₂ environment. The microhardness analysis of targets irradiated in vacuum shows a decreasing trend with increasing fluence, whereas in the case of the N₂ environment, a monotonic increase in hardness with increasing fluence is observed. (interaction of laser radiation with matter. laser plasma)