Abstract

The optimization of interrelated deposition parameters during deposition of in situ YBa₂Cu₃O₇ thin films on MgO (001) substrates by KrF laser ablation was systematically studied in a single experimental chamber.  The optimum condition was found to be a substrate temperature of 720^oC and a target-substrate distance of 5 cm in an oxygen partial pressure of 100 mtorr.  These conditions produced films with Tc = 87 K. The presence of YO in the plasma plume was found to be important in producing good quality films.  The films were characterized by resistance-temperature measurements, energy dispersive x-ray analyses, scanning electron microscopy, and x-ray-diffraction measurements, and the physical reasons underlying film quality degradation at parameter values away from optimal are discussed.

Abstract

YBaCuO films with (001) orientation have been deposited on MgO by laser ablation at 248nm and 193nm wavelengths.  Transitions to zero resistance at 87K and 90K 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 80K in a hydrogen exchange gas cryostat.  Characterization studies of device-related multilayer YBaCuO/PrBaCuO structures by XRD are presented.

Abstract

Y-Ba-Cu-O 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 spectroscopy studies of the plume show the importance of molecular species in the ablate if good superconducting films are to be formed.  The substrate position in the plume and the substrate temperature are important in determining film quality.  The influence of oxygen gas pressure can be significant.  Scanning electron microscopy 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 in the film surface.  Film orientation is determined by X-ray diffraction and R vs.  T is measured down to 80 K in a hydrogen exchange gas cryostat.