YBa2Cu3O7-δ superconducting quantum interference devices with metallic to insulating barriers written with a focused helium ion beam

Abstract

In this work, we demonstrate the ability to fabricate superconducting quantum interference devices (SQUIDs) by directly writing Josephson junctions into the plane of YBa2Cu3O7-δ thin films with a focused helium ion beam. This technique allows for the control of the Josephson barrier transport properties through the single parameter, ion dose. SQUIDs written with a dose of 4-×-1016-ions/cm2 had metallic barrier junctions that exhibited nearly ideal electrical transport characteristics at 50-K and a flux noise of 20-μΦ0/Hz at 10-Hz. At higher irradiation doses, the SQUIDs had insulating barrier Josephson junctions with a quasi particle energy gap edge at 20-meV.