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TT: Tiefe Temperaturen

TT 17: Superconductivity: Thin Film Preparation

TT 17.1: Vortrag

Dienstag, 28. März 2006, 14:00–14:15, HSZ 02

Growth of superconducting Na_0.3CoO₂·1.3D₂O thin films — •Y. Krockenberger^1,2, I. Fritsch¹, G. Cristiani¹, C. Bernhard³, L. Alff², and H-U. Habermeier¹ — ¹Max Planck Institut for Solid State Research, 70569 Stuttgart, Germany — ²Technische Universitaet Darmstadt, 64287 Darmstadt, Germany — ³Universite de Fribourg, Ch. du Musée 3, CH-1700 Fribourg

Layered cobaltates attracted much interest since superconductivity was found in hydrated samples [1]. The electronic and structural analogies between Na_0.3CoO₂·1.3H₂O and high T_c copper oxides suggests that their superconductivity may have a similar origin based on strong electron correlation. Furthermore, Terasaki et al. [2] reported large thermoelectric power values for Na_xCoO₂ with metallic resistivity behavior suggesting a promising material for thermoelectrical applications. Here, we report, that Na_xCoO₂ can be stabilized as a thin film by pulsed laser deposition technique in the doping range from x=0.25 up to x=1.0. In order to achieve superconducting thin films (with T_c≈ 4.4 K) a new process involving slow waterizing in a constant humidity is required. The sodium content has been decreased after depositing a Na_0.6CoO₂ thin film by soft chemical methods. These thin films have been characterized by x-ray diffraction, and resisitivity measurements. Additionally, the surface quality enabled us to perform far infrared spectroscopy in the range of λ =100 to 1000 cm⁻¹ for various doping levels. (1) K. Takada et al., Nature 422, 53 (2003). (2) I. Terasaki et al., Phys. Rev. B 56, R12685 (1997). (3) Y. Krockenberger et al., APL 86, 191913 (2005).