Fabrication and critical currents of thin-film-type Bi 2Sr 2CaCu 2O x intrinsic Josephson junctions

Abstract

We fabricated intrinsic Josephson junctions using Bi 2Sr 2CaCu 2O x thin films. High quality of the thin film is achieved by adjusting the composition of the thin films precisely using an atomic absorption spectroscopy system and by annealing the films at a high temperature. Current–voltage characteristics along the c-axis of the thin films show multiple branches of a series connection of Josephson junctions with large hystereses. Voltage jumps range from 24 to 36 mV and are comparable with those of bulk single crystals. The magnetic field dependence of critical currents was measured, and the results were compared with the numerical simulation using the Sakai–Bodin–Pedersen model. We found that 1 μm long intrinsic Josephson junctions with the current density of 1.2–3.0 kA/cm 2 exhibited critical currents smaller than those of the Fraunhofer type approximation because of the fluxon interaction among the junctions.