Fabrication of Nb/A1 Superconducting Tunnel Junction

Abstract

We report the successful fabrication and I--V curve superconductivity test results of the Nb/Al-based superconducting tunnel junctions. STJs with side-lengths of 20, 40, 60 and 80 μm were fabricated by deposition of polycrystalline Nb/Al/AlOx/Al/Nb 5-layer thin films incorporated on a 3-inch Si wafer. STJ was designed by TannerTM L-Edit 8.3 program, and fabricated in SQUID fabrication facility, KRISS. 5-layer STJ thin-films were fabricated using UV photolithography, DC magnetron sputtering, Reactive ion etching, and CVD(Chemical Vapor Deposition) techniques. Superconducting state test for STJ was succeeded in 4K with liquid helium cooling system. Their performance indicators such as energy gap, normal resistance, normal resistivity, dynamic resistance, dynamic resistivity, and quality factor were measured from I--V curve. Fabricated Nb/Al STJ shows 11% higher FWHM energy resolution than genuine Nb STJ.

Keywords

• astronomical detector
• superconducting tunnel junction