Ambient-pressure influence on droplet formation and thickness distribution in pulsed laser ablation

Droplet formation and inhomogeneous thickness distribution, both of which are severe drawbacks in the films deposited bypulsed laser ablation, were investigated in detail for metal-oxide films and Si films prepared in various ambient pressures. It was found that the shock front observed for the high-pressure ambient is one of the important factors of the surface roughening with clustered fragments, the shape of droplets and the increase in the thickness distribution. Oxidation of ejected materials from non-oxide target in the ambient containing a small amount of O2 is also enhanced with the formation of the shock front by adding the high-pressure He. The ambient pressure forming no shock front is suitable for preventing the surface roughening and the severe thickness distribution.