High-dose ion implantation in YBa2Cu3O7-δ-films

Oxygen and chlorine ions at energies of 40 keV and doses up to 2 x 1017 cm-2 have been implanted into epitaxial Y1Ba2Cu3O7-δ films with different Tc ≅ 90 K and ≅ 60 K, so that ion ranges are smaller than the sample thickness. As has been established by both resistivity and Hall-effect measurements the layer underlying the implanted near-surface layer still retains its superconducting properties, thus indicating a possibility to realize a two-layered structure by means of ion implantation. Depth profiles of Y, Ba, Cu and Cl concentrations obtained by step-by-step sputtering of the samples and recording the core-level electron spectra of these elements by means of XPS could be accounted for by T-DYN Monte-Carlo code simulation, besides the differences caused by diffusion processes. A striking inadequacy of chlorine and oxygen ion implantation has been observed. XPS-spectra of the Cu2p-core level reveal Cu to remain in a divalent oxidation state even after Ar-sputtering for O-implanted films whereas in Cl-implanted specimens Cu is totally converted to Cu+ by sputtering. (orig.)