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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 Löhneysen1,21Forschungszentrum 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 550C. The film properties, like Tc 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 Tc of 35 K, theoretically predicted fine structures could be resolved which were missing in our former tunnelling experiments using films with a lower Tc of 32 K. Better crystalline order within the MgB2 grains is evidently the key to the details of the electron-phonon coupling.

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