LASER ABLATION PROCESSES IMAGED BY HIGH-SPEED REFLECTION ELECTRON-MICROSCOPY

Laser pulse-induced evaporation and ablation were studied with an imaging high-speed reflection electron microscope (HSREM) with a time resolution of a few nanoseconds. Evaporation processes on Si and GaAs were initiated by a frequency-doubled Nd:YAG pulse laser. Explosive evaporation of Si and GaAs caused by superheating of the melt are visualized by a sequence of short exposure images. Due to the rapid escape of material from the surface, the remaining melt expands in radial direction with velocities in the range 60-110 m/s. Typical microcraters are formed and are described by a simple recoil model. A series of short exposure images show the ablation kinetics of a laser-treated thin gold film on Si. Due to evaporation of the Au covered Si, a liquid gold lamella is ejected.