LASER ABLATION STUDIES OF MAGNESIUM-OXIDE

The ablation of single crystal magnesium oxide using a UV-excimer KrF laser at 248 nm has been studied using a variety of diagnostic techniques. Ablation depth rate measurements indicate a threshold fluence for significant material removal of approximately 3 J cm-2 although surface damage in the form of micro-cracks is observed below this value. The effective absorption coefficient at 248 nm of 4 X 10(4) cm-1, found from the ablation rate, was much greater than observed from small signal transmission measurements. Scanning electron microscopy reveals evidence of thermal removal in the ablation regime probably mediated by a breakdown plasma, and a degree of exfoliation below the ablation threshold. The velocity of selected ablation species has been determined from time-resolved emission spectroscopy and a charge collector probe used to measure the angular distribution of ions in the ablation plume.