Comparison of Si and InSb as the normal layer of S-N-S junctions

Superconductor-semiconductor-superconductor (S-N-S) weak-link junctions with a normal layer of Si or InSb thin films were prepared by using focused ion beam (FIB) methods. The electrical properties were measured. Whereas InSb thin films on single crystals did not have an intrinsic mobility, S-N-S junctions with InSb show the characteristics of a Josephson S-N-S junction. A 200-nm-thick film of InSb deposited on MgO has a mobility of 83 cm²/V-s and a carrier density of 6.5×10¹⁷ cm^-3 at 4.2 K. The coherence length ξ_n was computed to be 17 nm. A critical superconducting current I_c of 100 μA was obtained for the S-N-S junction which had a line width of 10 μm and a channel length of 20 nm