EXPERIMENTAL AND THEORETICAL INVESTIGATION OF CUMULATIVE LASER IRRADIATION EFFECTS IN YBCO THIN-FILM PULSED-LASER DEPOSITION

Compositional and morphological modifications of superconducting YBCO targets under prolonged laser irradiation were investigated by EDS and SEM. Rotated and fixed targets were ablated at different process para meters - laser fluence and oxygen environment. Optical emission spectr oscopy was employed for investigation of the evolution of the laser-in duced plasma plume. The deposited film thickness distribution over the substrate surface area was examined through the film absorbance. The results can be consistently explained by assuming the existence of an additional effective ablation threshold imposed by the modified surfac e relief. A one-dimensional theoretical model of the laser beam-target interaction was developed involving temperature-dependent thermophysi cal parameters and the laser-induced plasma absorption. Reasonable agr eement between the experimental and theoretical dependencies of the er oded depth per shot on the pulse energy is found. The model results sh ow a possible influence of the post-pulse evaporation on the target su rface stoichiometric deviation found in the experiments.