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

Abstract

In this paper, we report on the fabrication and characterization of MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ultrathin films, which would be useful for hot electron bolometer mixers and superconducting single photon detectors. MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> thin films were fabricated using a carousel sputtering system in which 6-nm-thick MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 4.2 K in the 400-nm bridge with an MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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.