用角分布XPS法研究热处理时YBCO膜的表面组成变化及膜与衬底的相互作用

用角分布XPS法研究了MOD法制得的YBCO膜在热处理过程中膜的表面元素浓度变化以及膜与村底ZrO_2之间的原子扩散和固态化学反应。结果表明无论是薄膜(约0.1 μm)和较厚的膜(约1～1.5 μm), 在大约530～720 ℃的温度范围内加热后都发生铜表面富集和钡表面浓度偏低。在800 ℃以上加热后铜的表面浓度显著降低, 温度愈高, 降低愈甚。膜与衬底之间的化学反应也随温度升高而加剧。例如薄膜在890 ℃加热后钡向ZrO_2衬底扩散, 膜中的铜仍以+2价为主; 在950 ℃加热后衬底表面生成了富钡层, 而铜则主要以+1价的形式存在于富钡层表面。与厚膜相比, 在800 ℃以上薄膜与衬底的原子扩散和固态化学反应对于膜超导电性的损害更显著。

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

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.