CHANGES IN-DEPTH PROFILES OF OXYGEN AND COPPER IN Y-BA-CU-O FILM UNDER ANNEALING

Changes in element depth profiles in a YBaCuO superconducting film on a SrTiO3 substrate due to one year aging and annealing were investigat ed by the ion backscattering technique. Crystal perfection of the film was checked by the X-ray rocking curve method. It was found that the film was polycrystalline, with the preferred orientation of the c axis along the normal to the substrate surface with an angle dispersion of 2-degrees, and that the in-plane a and b axes were randomly orientate d. The aging experiments have shown that the oxygen content in the sur face region increases with the time constant tau = 20 days. Annealing in a vacuum at 100-degrees-C restores the initial oxygen content. Afte r 2 hours of annealing in an oxygen atmosphere at 400-degrees-C, an un expectedly strong change in oxygen and copper depth profiles is observ ed. Since a strong correlation exists between the profile changes, a h ypothesis has been advanced about the relationship between oxygen and copper transport in the process of annealing. Taking into account the polycrystalline structure of the film, one can conclude that intergrai n diffusion dominates in the oxygen and copper transport.