YBACUO PRBACUO MULTILAYERS BY EXCIMER LASER ABLATION

YBaCuO films with (001) orientation have been deposited on MgO by laser ablation at 248 and 193 nm wavelengths. Transitions to zero resistance at 87 K and 90 K have been reproducibly achieved in the respective cases. Optical spectroscopic studies of the plume show the importance of molecular species in the ablation if good superconducting films are to be formed. The substrate position in the plume and substrate temperature are important in determining film quality. The influence of oxygen gas pressure can be significant. SEM studies show the occurrence of second-phase outcrops with a needle-like morphology aligned over the whole area of the film along two mutually perpendicular directions on the film surface. Film orientation is determined by XRD and R against T is measured down to 80 K in a hydrogen exchange gas cryostat. Characterization studies of device-related multilayer YBaCuO/PrBaCuO structures by XRD are presented.