Metallic superconducting Si and Ge produced by vapor quenching on Cu

Abstract

Fine-grained Si and Ge overlays crystallized in a metastable fcc phase were obtained by vapor quenching at 4.2 K onto microcrystalline Cu films quench-condensed at the same temperature on glass substrates. Measurements of the electrical resistance show that in this abnormal form Si and Ge behave as metals and can become superconductors. On warming, the metallic state keeps up to a critical temperature at which the overlay breaks. The fracture may be attributed to the large increase in volume occurring when the fcc phase transforms to the normal diamond-type semiconducting structure.