Josephson effect through YBa2Cu3 O7-δ /Au-encapsulated nanogaps

Abstract

We successfully fabricated and studied planar superconductor-normal-superconductor (SNS) Josephson junctions made of YBa2Cu3O7-δ (YBCO) high-TC superconductor (S) and Au normal metal (N). The crucial step in fabrication was done by using a Pt/Au bilayer encapsulation of the patterned YBCO nanogap. This procedure preserves the YBCO nanogap from the degradation due to the contact with resists, water, and chemicals involved in further processing for hybrid devices. The junctions exhibit Fraunhofer-like modulation patterns and Shapiro steps when they are irradiated by a rf field. Furthermore, we analyzed the IC(T) characteristics of our hybrid junctions employing a SINI′S (superconductor-insulator-normal conductor-insulator-superconductor) model.