ESTIMATION OF PLASMA ABSORPTION EFFECTS DURING PULSED-LASER ABLATION OF HIGH-CRITICAL-TEMPERATURE SUPERCONDUCTORS

During pulsed laser deposition of thin films, a significant amount of energy is coupled to the laser-generated plasma. The fraction of the energy absorbed in the plasma is a function of the incident laser wavelength, time-dependent plasma dimensions, and electron density. Due to time-varying parameters, a quantitative analysis of the plasma absorption is difficult. A method has been developed to estimate plasma absorption during deposition of thin films. In this model, the time-dependent plasma dimension is replaced by the time-dependent ablation depth, which can be easily determined. Using simulated absorption coefficient values, the ablation depth of the target as a function of energy density and laser wavelengths has been computed. These calculations have been compared with experimental results obtained from excimer laser deposition of high-T-c superconductors. Correlations between plasma absorption coefficient and incident laser photon energy have also been determined.