Superconductivity in ultrathin films I. Transition temperatures of amorphous Bi and Ga

Research paper by C. G. Granqvist, T. Claeson

Indexed on: 01 Jun '74Published on: 01 Jun '74Published in: Zeitschrift für Physik B Condensed Matter


Superconducting transition temperatures (Tc) and electron tunneling characteristics have been measured on amorphous, vapour quenched films of Ga and Bi in the thickness range 3 to 50 nm. TheTc's are depressed and the tunnel densities of states are smeared as compared to bulk superconductors. A model considering the proximity effect between an extremely thin non-superconducting sheath (presumably due to the decrease of electron concentration at the surfaces) and a remaining bulk superconducting part gives good agreement withTc measurements, while the predicted tunnel density of states is only in qualitative correspondence with experiments.