Acta Phys. -Chim. Sin. ›› 1991, Vol. 7 ›› Issue (03): 305-310.doi: 10.3866/PKU.WHXB19910309

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Variations in the Elemental Concentration in Surface Region of the YBCO Films and Interactions of the Films with Substrate in Heating Process Studied by Angular Deprndent XPS

Zhao Liang-Zhong; Guo Zhong-Cheng; Liang Zhen-Hua; Hu Yu-Xiu; Liu Han-Fan   

  1. Institute of Chemistry, Academia Sinica, Beijing 100080
  • Received:1990-03-09 Revised:1990-09-19 Published:1991-06-15
  • Contact: Zhao Liang-Zhong

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