Excimer laser ablation of thin gold films on a quartz crystal microbalance at various argon background pressures

Abstract

Excimer laser ablation of gold films deposited on a quartz crystal microbalance is investigated. The ablation rate is directly obtained from the frequency shift of the mi- crobalance. The measured single-shot ablation rate is found to be at least two orders of magnitude higher than the numeri- cal predictions based on a surface vaporization model. Surface morphology studies indicate that hydrodynamic ablation plays a leading role in excimer laser ablation of thin gold films. In situ reflectivity and scattering measurements of the gold-film surface during the transient heating and melting upon excimer laser irradiation show that the melting duration is of microsec- ond order, which is much longer than the nanosecond melting duration in the case of a bulk target. This longer duration of melting may promote liquid motion, which leads to hydrody- namic ablation at a much higher rate compared with that of atomic vaporization from the surface. Experiments show that the ablation rate is also a strong function of the background gas pressure, which may be the result of the interactions be- tween the gold vapor evaporated from the surface and the hydrodynamic motion in the molten gold.