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 microbalance. The measured single-shot ablation rate is found to be at least two orders of magnitude higher than the numerical 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 microsecond 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 hydrodynamic 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 between the gold vapor evaporated from the surface and the hydrodynamic motion in the molten gold.