7 research outputs found
Surface quality studies of high T superconductors of the Hg , Tl and HgTl-families: RBS and resonant C and O backscattering studies
The composition, crystallinity, uniformity, purity, and thermal stability of cuprate superconductors have been studied by Rutherford backscattering and channeling spectrometry, and 3.045 MeV He oxygen non-Rutherford resonant scattering. Further experiments have been performed with 1.75 MeV Hcarbon non-Rutherford resonant scattering. Three sets of samples were studied : HgBaCuO (Hg1201), HgT1BaCaCuO (Hg,T1-1223) and T1BaCuO/LaA10 (T1-2201), either in bulk or as an epitaxial thin film. It was observed that the superconductors exhibit a metal deficiency near the surface, which is largely compensated by excess oxygen. Moreover, the samples are significantly contaminated with carbon within the probing region of the H beam. The thermal stability and surface degradation were studied in both oxidizing ambient and vacuum. As a general trend, the heavy metal deficiency — and consequently the compensating oxygen excess — is enhanced as the temperature increases