High-T c superconductor/normal-metal/superconductor edge junctions and SQUIDs with integrated groundplanes

Abstract
Epitaxial, high‐Tc superconductor/normal‐metal/superconductor (SNS) edge‐geometry weak links and superconducting quantum interference devices (SQUIDs) have been fabricated with integrated YBa2Cu3O7 (YBCO) groundplanes and SrTiO3 insulators, using a process which incorporates six epitaxial layers. The SNS edge junctions were produced using off‐axis sputtered films and Co‐doped‐YBCO normal metal interlayers. These devices show excellent performance with typical critical current‐resistance (IcRn) products of 500–800 μV for 100–150 Å thick normal metal layers at 65 K, and 1‐σ critical current density ( Jc) spreads as small as 12%. SNS SQUIDs incorporating groundplanes exhibit voltage modulation of up to 130 μV at 65 K and 40 μV at 77 K. SQUID inductance measurements indicate microstrip inductance values of 1 pH per square at 65 K.

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