ABSTRACT
This chapter focuses on the experimental quasiparticle characteristics from tunneling into the N side of such S/N bilayers, which have elucidated the proximity effect. Specifically, junctions of the type Nb/Al-Al2O3/C are reviewed, where C is a convenient counterelectrode such as In, which can be switched easily between superconducting and normal states via a small magnetic field with minimal effects on the Nb superconductivity. The chapter shows the issue of the Nb oxides and their deleterious effects on the quasiparticle tunneling conductance and shows some recent results. While the Al overlayer mitigates such problems in the Josephson junction, there are still free Nb surfaces in Josephson devices, example SQUID loops, which may be affected by the Nb oxides. It reports key results of extensive point contact tunneling (PCT) studies of SIN type junctions on Nb using the native oxide as the barrier and a gold tip.
