A study on the control of the material properties of Bi 2Sr 2CaCu 2O x thin films for intrinsic Josephson junctions

Abstract

We investigated the annealing conditions to observe intrinsic Josephson effects using Bi-cuprate superconductor thin films. We fabricated a mesa structure using as-grown and annealed Bi 2Sr 2CaCu 2O x (Bi-2212) thin films and measured their electrical properties along the c-axis. Consequently, we succeeded in fabricating intrinsic Josephson junctions using Bi-2212 thin films by means of a two-step annealing procedure, which is a combination of a high-temperature annealing in O 2 and a low-temperature annealing in N 2. By this annealing method, the grain size changed over the range from 0.02 μm to more than 5 μm in diameter and the critical temperature T c could be controlled in the range of 72–85 K. The critical current density along the c-axis, J cc, was also controlled in the range of 10 4–10 1 A/cm 2. The temperature dependence of the resistivity of the mesa with reduced J cc was semiconductor-like above T c. The current–voltage ( I– V) characteristics exhibited clear hystereses and multiple branches, and the observed voltage jump was 3–20 mV.