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HL: Fachverband Halbleiterphysik
HL 27: II-VI semiconductors
HL 27.3: Talk
Wednesday, March 28, 2007, 14:45–15:00, H13
Conductivity measurements on ZnO/YBaCuO — •Nilotpal Ghosh1, Heidemarie Schmidt1, Qingyu Xu1, Lars Hartmann1, Holger Hochmuth1, Michael Lorenz1, Gerald Wagner2, and Marius Grundmann1 — 1Universität Leipzig, Fakultät für Physik und Geowissenschaften, Institut für Experimentelle Physik II, Linnéstr. 5, 04103 Leipzig, Germany — 2Institut für Mineralogie, Kristallographie und Materialwissenschaft, Linnéstr. 5,04103 Leipzig, Germany
200 nm magnetic ZnO films were grown on Y1B2Cu3O7(YBCO) films on sapphire by pulsed laser deposition for future Andreev Reflection (AR) study and to compare with previous spin polarization results [1]. Initial critical current density of 6×106 A/cm2 of YBCO at 77K [2] slightly reduced after growth of granular ZnO film and critical temperature was above 77K. Four-point transport measurements across ZnO/YBCO junction (area ≫ 1 mm2) resulted in nonlinear I-V characteristics in 5-150 K. Noisy conductivity fluctuations noticed at lower T at 0 bias were probably due to large junction area lying in Maxwell range (where d ≫ l , d = contact radius, l = mean free path). Fitting of conductivity data after Blonder-Tinkham-Klapwijk theory showed that superconducting gap (Δ) of YBCO and interface dependent ZnO/YBCO barrier strength (Z) amount to Δ ≤ 20.4 (±1) meV and Z ≥ 0.74 (±0.23) respectively. Smaller junction area AR measurements and Point contact AR measurements are underway. [1] L. Hartmann,etal, J. Phys. D.: Appl. Phys. 39(2006)1. [2] M.Lorenz, etal,IEEE Transactions on Applied Superconductivity 11 (2001) 3209.