Superconducting Transition of Quench-Condensed Ultrathin Films

Abstract

The condition of the onset of superconductivity in highly homogeneous ultrathin Bi and Pb films has been investigated by measuring the temperature dependence of the sheet resistance R□. The experimental results suggest that highly homogeneous metal films with R□ lower than ∼6 k Ω could be superconducting, while those with R□ greater than ∼6 k Ω are insulating at zero temperature, in agreement with the condition of the onset of global superconductivity in granular films. The superconducting transition temperature Tc shows a remarkable decrease with increasing the normal-state sheet resistance, unlike the results of granular films.