Fabrication of mesoscopic superconducting Nb wires using conventional electron-beam lithographic techniques

Conventional electron-beam lithography has been used to fabricate mesoscopic Nb wires. Nb was deposited in an ultrahigh vacuum evaporation chamber using electron gun heating. The typical linewidth and the thickness were 200 and 50 nm, respectively. The transition temperatures were above 7 K. They increased with thickness and linewidth. To demonstrate the feasibility of two angle evaporation techniques, we also fabricated Nb/(Al–)AlOx/Nb tunnel junctions showing superconducting single-electron transistor characteristics.