Self-organization of thin metal films by irradiation with nanosecond laser pulses

Modifications in thin metal films under intensive laser irradiation were studied. Gold, silver, copper, chromium and aluminum films with the thickness of 100 nm were deposited on the glass substrate. Back-side irradiation through the substrate with a burst of nanosecond pulses tightly focused to a line was applied. The film removal threshold with a single pulse F_th was estimated for every material and laser fluence was kept above it in the range of 1.5-3 F_th during experiments. Diverse behavior of the films depending on the metal, the shift between pulses and laser fluence was observed. In chromium, the regular structures were developed in a quite wide range of processing parameters. In gold, three kinds of ripples were observed: transverse (similar to ripples in chromium), longitudinal and a structure of ripples oriented at 60° to each other. The combination of physical properties facilitated the regular assembly of the molten metal in chromium and to some extent in gold.