Electrical characterization of a-axis oriented Y123 thin film grown using pulsed laser deposition

摘要

The thin film of a-axis oriented YBa_2Cu_3O_7 (Y123) were grown on SrLaGaO_4 (100) substrate with a buffer layer of 50 nm thick Gd_2CuO_4 using pulsed laser deposition technique. The thickness of Y123 thin film is about 400 nm CuO_2 planes are aligned perpendicular to the substrate in the thin films. A micron-bridge was fabricated using focused ion beam milling technique in such a way that the current was forced to flow along the c-axis in thin film. Intrinsic Josephson junctions are aligned along the c-axis. The dimensions of bridge are 1 μm in length along the c-axis and 5 μm in width along the b-axis. Transition temperature (T_(cON)) is about 84 K with single phase. The critical current density (J_c) of 2 × 10~6 A/cm ~2 was measured from current-voltage (I-V) characteristics at 10 K. The samples were irradiated with external microwave of 20 GHz at different power and the J_c was suppressed as we increased the power. This suppression in J_c indicates the formation of layered structure with strong coupling. The voltage steps are appeared in non-linear I-V characteristics with microwave irradiation. The voltage steps are collective response of intrinsic Josephson junctions of micron-bridge.