Fabrication of Superconducting Nanowires Using $\hbox {MgB}_{2}$ Thin Films

In this paper, we report on the fabrication and characterization of MgB₂ ultrathin films, which would be useful for hot electron bolometer mixers and superconducting single photon detectors. MgB₂ thin films were fabricated using a carousel sputtering system in which 6-nm-thick MgB₂ thin films showed a critical temperature of 7 K. We succeeded in fabricating hot electron detectors; these showed a high current density of 7.7 × 10⁶ A/cm² at 4.2 K in the 400-nm bridge with an MgB₂ thickness 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.