Hot spot formation in focused-ion-beam-fabricated YBa 2 Cu 3 O 7-x nanobridges with high critical current densities

We report on the fabrication and evaluation of nanoscale YBa Cu O (YBCO) constrictions using focused-ion-beam techniques for potential application as YBCO bolometers. A gold protective layer was found to be critical for supressing contamination from gallium ions in order to obtain high critical current densities. Further processing using a radio-frequency plasma to remove the gold protective layer has also been studied and was found to be effective in minimizing sample damage resulting from overheating. Current-voltage measurement indicate that the nanobridges go through the transition from superconducting to normal state with different dissipation mechanism including flux creep and hot spot formation.