Microwave Dependence of $a$ -Axis Oriented ${\rm YBa}_{2}{\rm Cu}_{3}{\rm O}_{7}$ Thin Film

The a-axis oriented YBa₂Cu₃O₇ thin films were grown on SrLaGaO₄ (100) substrate with a buffer layer of 50 nm thick Gd₂CuO₄ using pulsed laser deposition technique. The thickness of Y-123 thin film was about 500 nm. Intrinsic Josephson junctions (CuO₂ planes) were aligned perpendicular to the substrate in the thin films. The bridge type pattern was fabricated using focused ion beam milling technique in such a way so that the current flow along the c -axis in thin film. The dimensions of bridge were 1 μm in length along the c-axis and 5 μm in width along the b-axis. The resistance vs. temperature characteristics showed transition temperature of about 89 K. The critical current density (J_c) of 2×10⁶ A/cm² was measured from current-voltage (I-V) characteristics at 10 K. The samples were irradiated with external microwave at 20 GHz and the J_c was suppressed with increase in power. This suppression in J_c indicates the formation of layered structure with strong coupling. The voltage steps were appeared with microwave irradiation in I-V characteristics. The values of voltage steps were irregular and change with increase in power. We have also studied all a-axis oriented multilayered thin films of YBa₂Cu₃O₇ (Y123) and PrBa₂Cu₃O₇ (Pr123). We fabricated a submicron stack in which Josephson junctions were forming by Y123 and Pr123. The submicron stack showed response with microwave irradiation of different frequency and power. The transport characteristics of these thin films are discussed in detail.