Fabrication and characteristics of intrinsic Josephson junctions in Bi2Sr2CaCu2O8+x single crystals

Mesa-structured intrinsic Josephson junctionsare fabricated in Bi2Sr2CaCu2O8+x single crystals. Typicalcurrent-voltage characteristics of intrinsic Josephson junc-tions are observed, which include multiple quasi-particle branches, surface junction with critical current lower than those of inner junctions, and subgap structures on quasi-particle branches. The corresponding physical explanationsare also given. The energy gap voltage of the intrinsicJosephson junctions at 30 K is about 20 mV. Besides, themeasured Ic-T relationship agrees quite well with thetheoretical computations based on -22-wavexyd supercon-ductor. Our measured dI/dV-V relationship shows theV-shaped gap structure, obviously differing from theU-shaped gap structure of the s-wave superconductor.