High-Tc thin films prepared by laser ablation: material distribution and droplet problem

The lateral material distribution of laser-deposited YBa2Cu3O7¿¿ films and the density of droplets coming from the target were studied by varying the laser pulse energy, the laser spot size and the target-to-substrate distance. Silicon wafers at ambient temperature were used as substrates to guarantee a large sticking coefficient of the particles. The deposition rate is found to depend linearly on the laser energy density E and quadratically on the spot size S at the target, whereas the droplet density is slightly dependent on E and increases linearly with 1/S, yielding a threshold energy of 0.9 J cm¿2. With a laser spot size of 7.15 mm2 and a laser energy density of 1.2 J cm¿2, we were able to reduce the number of droplets to one to two per 500 ¿m2 for a high quality high Tc film with a typical thickness of 100 nm

Droplets and outgrowths on high-Tc laser ablated thin films

YBa2Cu30x 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

Droplets and outgrowths on high-Tc laser ablated thin films

YBa2Cu30x 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