DYNAMICS OF INSITU YBA2CU3O7 SUPERCONDUCTING FILM FORMATION

The dynamics of in situ superconducting YBa2Cu3O7 thin film formation was investigated. Emphasis was placed on the temporal dependence of the tetragonal to orthorhombic phase transformation. Using X-ray and in situ resistivity measurements, it was confirmed that during deposition, the tetragonal phase was formed, which was quickly transformed to the superconducting orthorhombic phase by in situ post-deposition oxygenation. The transformation takes place in a very short time by the diffusion of oxygen into the film to fill the vacant O-sites along the Cu-O chains. A one-dimensional diffusion model can fit the data quite well, yielding a diffusivity of 10(-10) cm2/s at 640-degrees-C. It was also shown that complete oxygenation took place in two steps, an isothermal structural phase transformation and an isobaric oxygen uptake.