Temperature dependence of the return current in Bi2Sr2CaCu2Ox stacks fabricated by self-planarizing process

We investigated the temperature variation of the return currents of stacked Bi2Sr2CaCu2Ox (Bi-2212) intrinsic Josephson junctions fabricated using self-planarizing process. In this process, the Bi-2212 crystal around the junction window was changed to an insulator by soaking it into the solution of dilute hydrochloric acid. The current-voltage characteristics of the stacks with areas as large as 30×40μm2 exhibited large hystereses and multiple branches at 4.2K, which can be explained by a series connection of highly capacitive Josephson junctions. At higher temperatures than 40K, we found that the return current Ir of the intrinsic junction depended strongly on the temperature, T. We analyzed the Ir-T characteristics using simple resistively and capacitively shunted junction model in view of the temperature dependence of the c-axis resistance of the stack.