关键词: 角分布XPS法, YBCO膜, 表面化学

Abstract: Variations of the elemental concentration of the YBCO films prepared by MOD method, diffusion and interactions between the films and ZrO_2 substrate have been studied by means of angular dependent XPS technique. A drastic change in the stoichiometry of YBCO films in surface region at different heating steps have been observed. For example, Cu~(2+)-enrichment and Ba~(2+)-deficiency occur in surface region for both thin (～0.1 μm) and thick (1～1.5 μm) films after heating the samples at about 530°～720 ℃. However, above 800 ℃ Cu~(2+)-deficiency is observed clearly, and the higher the temperature, the more the Cu~(2+)-deficiency. In addition, the extent of interdiffusion and interaction also increases with increasing temperature. After heating at 800 ℃ diffusion of Ba~(2+) From the thin film into ZrO_2 substrate is detected, and the valence of copper is +2. Whereas, with a heating temperature of 950 ℃, a Ba~(2+)-rich layer on the substrate has been formed, and the valence of copper on the layer is mainly +1. The results also show that degradation of the superconducting property caused by the diffusion and interaction is more severe for the thin film than for thick film.

Key words: Angular dependent XPS, YBCO film, Surface chemistry