Berlin 2008 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 15: Superconductivity: Poster Session

TT 15.42: Poster

Tuesday, February 26, 2008, 14:00–18:00, Poster B

Fine structure in the tunneling characteristic of MgB₂ thin films — •Rudolf Schneider¹, Jochen Geerk¹, Alexander Zaitsev¹, and Hilbert von Löhneysen^1,2 — ¹Forschungszentrum Karlsruhe, Institut für Festkörperphysik, 76021 Karlsruhe — ²Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe

We report on a progress in the in situ preparation of superconducting MgB₂ thin films by thermal evaporation of Mg combined with B sputtering. By sputtering the boron from a red-hot sintered target we were able to increase the substrate temperature up to 550^∘C. The film properties, like T_c and the residual resistivity, significantly improved compared to films deposited at lower substrate temperatures. In the negative second derivative of the current-voltage characteristic measured on sandwich-type crossed-strip tunnel junctions on MgB₂ films with a T_c of 35 K, theoretically predicted fine structures could be resolved which were missing in our former tunnelling experiments using films with a lower T_c of 32 K. Better crystalline order within the MgB₂ grains is evidently the key to the details of the electron-phonon coupling.