Droplets and outgrowths on high-T_c laser ablated thin films

YBa₂Cu₃0_x thin films have been grown on silicon, SrTi0₃ and Zr0₂ substrates using the pulsed laser deposition technique. Special attention has been paid to droplets and outgrowths which appear on the thin films during the growth process. The droplet density was studied as a function of the laser spot size, the laser energy and the target density. The number of droplets could be reduced to 1 per 100 μm² for a 100 nm thick film, by ta1cing a large laser spot size and low energy density. The droplet density does not depend on the target density in the range from 80 to 94 % . The number of outgrowths could be reduced to 1 per 100 μm² for a 100 nm thick film by reducing the deposition temperature or increasing the laser frequency. However, the critical temperature of these layers was reduced by 5 to 10 K. Using SAM no differences in composition between
an outgrowth and the rest of the film could be detected.