Formation of high-aspect-ratio protrusions on gold films by localized pulsed laser irradiation

We report on the formation of microbumps and high-aspect-ratio protrusions on gold films as a result of single-pulse localized laser irradiation. The laser source employed in this work is a Q-switched nanosecond-pulse laser, emitting at its fourth harmonic of 266 nm. Gold films with a thickness of several hundred nanometers were irradiated in ambient or under low-vacuum conditions, with circular laser spots, several micrometers in diameter. A mask projection technique was used to generate these spot patterns. The resulting structures were imaged via scanning electron microscopy. The formation mechanism of these structures is briefly discussed in view of our results and other, related published work.