Preparation of intrinsic Josephson junctions using Bi-2212 thin films

We fabricated intrinsic Josephson junctions 10 /spl mu/m/spl times/10 /spl mu/m in area using Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/ (Bi-2212) thin films with large grains employing a two-step annealing procedure. The first annealing step at a high temperature in O/sub 2/ is for the growth of crystal grains and the second step at a lower temperature in N/sub 2/ is for the control of the oxygen content in the film. By this method, Bi-2212 thin films with the c-axis critical current density J/sub c/ of 10/sup 1/-10/sup 4/ A/cm/sup 2/ were obtained. A mesa structure was formed on the surface of the annealed film and we measured its electrical properties along the c-axis. The current-voltage characteristics with clear hystereses and multiple branches were observed for the samples with J/sub c/ of /spl sim/10/sup 3/ A/cm/sup 2/ or less. The gap structure was observed in the current-voltage characteristics for low mesas. J/sub c/ and the voltage jump decreased more rapidly with increasing temperature than those predicted by the BCS theory. We could obtain intrinsic Josephson junctions in Bi-2212 thin films with similar properties as in single crystal samples.