Fabrication of Superconducting Nanowires Using MgB₂ Thin Films

In this paper, we report on the fabrication and characterization of MgB2ultrathin films, which would be useful for hot electron bolometer mixers and superconducting single photon detectors. MgB2thin films were fabricated using a carousel sputtering system in which 6-nm-thick MgB2thin films showed a critical temperature of 7 K. We succeeded in fabricating hot electron detectors; these showed a high current density of 7.7 × 106A/cm2at 4.2 K in the 400-nm bridge with an MgB2thickness of 30 nm. Furthermore, we succeeded in fabricating detectors with a 250-nm-wide meander line, 10 nm thickness, and critical temperature of 12 K. These results indicate that the fabrication process for these devices is a promising technique for future experiments.