The Improvement of Compositional Distribution in Depth and Surface Morphology of YBa_2Cu_3O_<7-δ>-SrTiO_x Multilayers (Special Section on Superconducting Devices)

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Almost stoichiometric YBa_2Cu_3O_<7-δ>(110) or (103) and SrTiO_x(110) films, and multilayer films consisting of them have successfully been grown epitaxially on hot SrTiO_3 substrates by 90°Off-axis rf magnetron sputtering with facing targets. Their whole composition, compositional distribution in depth, crystallinity and surface morphology were examined by inductively coupled plasma spectroscopy, Auger electron spectroscopy, reflection high-energy electron diffraction, and scanning tunneling microscopy or atomic force microscope, respectively. When any YBa_2Cu_3O_<7-δ> film was exposed to air after deposition, a Ba-rich layer was formed in a near surface region of the film. However, such a compositional distribution in depth of the film was improved by in situ deposition of a SrTiO_x film on it. Moreover, the surface roughness of the YBa_2Cu_3O_<7-δ> film was improved by predeposition of a SrTiO_x film under it. On the basis of these results, both YBa_2Cu_3O_<7-δ>/ SrTiO_x/YBa_2Cu_3O_<7-δ>/SrTiO_3(sub.) and YBa_2Cu_3O_<7-δ>/SrTiO_x/ YBa_2Cu_3O_<7-δ>/SrTiO_x/SrTiO_3(sub.) multilayer films with average surface roughness of 〜 3 nm were grown reproducibly, which had uniform compositional distribution throughout the depth of the film except a near surface region of the top YBa_2Cu_3O_<7-δ> layer. A new 2 × 2 × 2 structure described by Sr_8 Ti_8 O_20 (Sr_2Ti_2O_5) with a long range ordered arrangement of oxygen vacancies was formed in the SrTiO_x films deposited epitaxially on YBa_2Cu_3O_<7-δ> films.
社団法人電子情報通信学会の論文
1994-08-25

The Improvement of Compositional Distribution in Depth and Surface Morphology of YBa_2Cu_3O_<7-δ>-SrTiO_x Multilayers (Special Section on Superconducting Devices)

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