Large grain growth by annealing of Ag-covered Bi2Sr2CaCu2O8+δ thin films and its application in the fabrication of intrinsic Josephson junctions

Thin films of Bi2Sr2CaCu2O8+delta (Bi-2212) covered by layers of Ag in selected regions were grown by pulsed-laser deposition with subsequent annealing. The grain size at the Ag-covered region was as large as 60-90 mu m. These grains were about three times as large as those in conventional films lacking the covering layer of silver, and the optimal annealing temperature for the silver-covered films was 15 degrees C lower than that for the uncovered films. The technique was adopted for use in the fabrication of intrinsic Josephson junctions (IJJs). The mesa structure for IJJs was fabricated on a Bi-2212 film with a 60 nm thick layer of silver annealed at 876 degrees C, and the resulting IJJs exhibited current-voltage characteristics that showed clear multiple branches.