Debris and particulates formation and deposition in UV pulsed laser ablation of Al{sub}2O{sub}3-TiC ceramics

摘要

In this work the mechanisms of particles formation and deposition in pulsed laser ablation of Al{sub}2O{sub}3-TiC ceramics were investigated using 193 and 248 nm laser radiation. The influence of the ambient gas in debris and particulates formation was investigated using He (M=4), Ne (M=20), N{sub}2 (M=28), air (M≈29), Ar (M=40) and Kr (M=83). Around the processed area one can identify two kinds of particles: debris of a few tens of nanometers typically forming a film and larger particulates of spherical to semi-spherical shape, with a diameter of 0.5 - 8μm. Debris behaviour confirms the blast wave theory predictions, indicating they result from condensation of clusters in the ablation plume. Particulates are formed above a laser fluence threshold which is increasingly lower with increasing weight and pressure of the ambient gas. Evidence suggests particulates result from ejection of liquid and solid material from growing cones and liquid ejection from the molten Irradiated surface, due to a high pressure recoil wave hitting the target.