Observation of an interplay between single-electron charging effects and superconductivity iC

Cryogenic scanning tunneling microscopy is employed in studies of (Formula presented)(Formula presented)C in the superconducting phase. Samples prepared with Ni deficiency exhibit a sharp superconducting transition, onset around 15 K, while the local scanning tunneling spectroscopy measurements reveal granular properties. We have also measured I-V characteristics that manifest an interplay between single electron charging effects and superconductivity. Some of these characteristics show features consistent with tunneling into a small superconducting particle. Others correspond to tunneling into isolated metallic particles weakly coupled to a superconducting environment.