ANALYSIS OF THE EXPANSION OF HYDROXYAPATITE LASER-ABLATION PLUMES

Fast intensified CCD imaging has been used to analyze the expansion of hydroxyapatite laser ablation plumes after KrF excimer laser irradiat ion. images as obtained have shown the presence of three different glo w regions. A plume-like plasma followed by a smaller and slower plasma cloud freely expand from the first instants of time after the laser p ulse. A third glow region, the expansion of which begins over 50 mu s after the laser impingement, is formed by hot particles leaving the ta rget. The same experiment has been repeated under the same conditions by changing the laser wavelength to that of ArF. Only the first two pl asma clouds have been identified in this case. Finally, in order to re late the detection of hot particles with the presence of droplets in H A pulsed laser deposited films, scanning electron micrographs of the d eposited coatings have been obtained showing a much lower density of d roplets in the case of ArF irradiation than in that of KrF.