Fabrication of stacked intrinsic Josephson junctions from Bi₂Sr₂CaCu₂O_8+x thin films

Abstract

Stacked series arrays of intrinsic Josephson junctions were fabricated from Bi2Sr2CaCu2O8+x thin films, deposited by high-oxygen-pressure dc sputtering. Stacks with areas between 2 × 2 µm2 and 50 × 50 µm2, and thicknesses of 80 - 200 nm, were fabricated by photolithography and ion beam etching. We obtained RCSJ-like I - V curves with a critical current density of about 2 × 104 A cm-2 at 4.2 K. At high bias currents, we observed in some I - V curves many branches with gaps of about 10 mV corresponding to individual junctions. In addition, synchronized switching of more than 10 junctions was observed.