EFFECT OF PROCESSING GEOMETRY ON YBA2CU3O7-X PLASMA EMISSION DURING SUPERCONDUCTING THIN-FILM GROWTH BY PULSED LASER EVAPORATION TECHNIQUE

In situ processing of YBa2Cu3O7-x (YBCO) superconducting thin films by pulsed laser evaporation is a technique critically dependent on the processing conditions (substrate temperature, oxygen partial pressure, etc.), and on the deposition setup, including the oxygen nozzle geometry required for incorporation of oxygen. It has been found necessary to have the oxygen nozzle directed toward the substrate during deposition for growth of high-quality superconducting thin films without further annealing [R. Singh et al. Appl. Phys. Lett. 55, 2351 (1989)]. We have taken optical emission spectra of YBCO plasma during the following deposition conditions: (1) In vacuum, (2) in 200 mTorr oxygen ambient with the oxygen nozzle directed toward the substrate, (3) in 200 mTorr oxygen ambient with oxygen nozzle directed toward the target, and (4) with the +300 V biasing ring interposing the target and the substrate. Our results show that enhanced formation of YO and CuO might lead to the growth of thin film at a lower substrate temperature under the biasing condition. A strong dependence of the Cu I (324.75 nm) neutral peak intensity and of the appearance of the molecular peaks such as YO on different deposition geometry is seen. These results provide important insight into the characteristics of plasma transport and deposition by the pulsed laser evaporation technique.