Junction area dependence of critical current density in Bi-2212 stacked junction

Abstract

We report the characteristics of stacked junctions fabricated by the focused ion beam etching method on a Bi-2212 whisker with low carrier concentration. In order to achieve low carrier concentration, the whisker edges were etched and the sample was annealed in 1 atm of flowing Ar at 200 °C for 1 h. A drop of critical current density (Jc) occurred when junction area (S) was decreased to the submicron range, and then the charging energy of the stack (Ec) was comparable to Josephson coupling energy (EJ). The Ec/EJ–Jc curves of the samples were similar to the theoretical curves which explains a fall of Jc due to Coulomb blockade for low TC superconductor. Also, the annealed sample showed high junction resistance and low EJ, owing to a low carrier concentration by annealing.