YBa2Cu3O7 nano-constriction Josephson junctions and SQUIDs fabricated by focused helium-ion-beam irradiation
Abstract
By focused 30\,keV He ion beam irradiation, epitaxially grown YBa2Cu3O7 (YBCO) thin films can be driven from the superconducting to the insulating state with increasing irradiation dose. A properly chosen dose suppresses superconductivity down to 4\,K, while crystallinity is still preserved. With this approach we create areas of normal-conducting YBCO that can be used to define resistively shunted constriction-type Josephson junctions (cJJs) on the nanometer scale. We also demonstrate that the fabricated cJJs can be incorporated in direct current superconducting quantum interference devices and can be used as detector junctions in THz antennas.
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