Surface quality studies of high-T-c superconductors of the Hg-, Tl- and HgxTl1-x-families: RBS and resonant C and O backscattering studies
Vantomme, André × Alves, E Correia, JG Bryntse, I Johansson, LG Loureiro, SM Lefloch, S Toulemonde, P Bordet, P Bougerol-Chaillout, C #
Elsevier science bv
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms vol:190 pages:673-678
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 HI carbon non-Rutherford resonant scattering. Three sets of samples were studied: HgBa2CuO(4+delta) (Hg1201), HgxTl1-xBa2Ca2Cu3O(2n+delta) (Hg,Tl-1223) and Tl1.85Ba2CuO6/LaAlO3 (Tl-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. (C) 2002 Elsevier Science B.V. All rights reserved.