Fabrication and characteristics of submicron tunneling junctions on high Tc superconducting c-axis thin films and single crystals

Abstract

We report successful fabrication and characteristics of submicron-size tunneling junctions using c-axis YBa2Cu3O7−y (YBCO) thin films of 800 nm thickness and Bi2Sr2CaCu2O8+δ(Bi-2212) single-crystal whiskers. The junctions were made using a three-dimensional focused-ion-beam etching method. First, a microbridge was patterned in a required junction width by normal direction etching. By tilting the sample stage up to 90°, two grooves on the bridge were etched from the lateral direction in order to create the required junction size. The 60 K YBCO junctions did not show any degradation of critical current density (Jc) down to an in-plane area of 0.5 μm2 and showed current–voltage (I–V) characteristics of the collective switching transition from the zero voltage state to the resistive state. For Bi-2212 stacks smaller than 1 μm2, we identified some of the features of charging effects on the I–V characteristics.