Improved Fabrication Method for Nb/Al/AlO x /Al/Nb Superconducting Tunnel Junctions as X-Ray Detectors

• Published in: Japanese Journal of Applied Physics 2000-09, Vol.39 (9R), p.5090
• Main Authors: Hiromi Sato, Hiromi Sato, Yoshiyuki Takizawa, Yoshiyuki Takizawa, Wataru Ootani, Wataru Ootani, Tokihiro Ikeda, Tokihiro Ikeda, Takayuki Oku, Takayuki Oku, Chiko Otani, Chiko Otani, Hiroshi Watanabe, Hiroshi Watanabe, Kazuhiko Kawai, Kazuhiko Kawai, Hiromasa Miyasaka, Hiromasa Miyasaka, Hiroshi Kato, Hiroshi Kato, Hirohiko M. Shimizu, Hirohiko M. Shimizu, Hiroshi Nakagawa, Hiroshi Nakagawa, Hiroshi Akoh, Hiroshi Akoh, Masahiro Aoyagi, Masahiro Aoyagi, Tohru Taino, Tohru Taino
• Format: Article
• Language: English
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/JJAP.39.5090

Niobium-based superconducting tunnel junctions (STJs) with aluminum trapping layers as X-ray detectors were fabricated. We applied a fabrication technique for reducing the leakage current and improving the energy resolution for X-rays at around 6 keV. The edges of two Al layers sandwiching a tunneling barrier were oxidized by plasma discharge. The performance of these new STJs was compared with other types of STJs to which thermal oxidization in an O 2 atmosphere had been applied. The oxidization process in O 2 plasma significantly improved the energy resolution for X-rays, which reached values (FWHM) of 41 eV, 58 eV, 65 eV, and 129 eV for STJs with the size of 20×20 µm 2 , 100×100 µm 2 , 200×200 µm 2 , and 500×500 µm 2 , respectively.