High Tc superconducting quantum interference devices made by ion irradiation

The authors describe a method to make superconducting quantum interference devices (SQUIDs) formed in a single layer of high T-c superconducting materials. The superconducting loop is patterned using ion beam irradiation through an in situ suitable gold mask. Josephson junctions are defined by a lower fluence irradiation through narrow slits opened in a polymethyl methacrylate resist. The critical current and the resistance of the SQUIDs at a given temperature can be adjusted precisely by choosing the fluence of irradiation to make the device operational at temperatures between 4.2 K and the T-c of the superconducting material. (c) 2006 American Institute of Physics.