A study of superimposed tin and silver films

Abstract

The effects of film structure on the contact depression of the superconducting transition temperature for superimposed Sn and Ag films has been studied before and after annealing. The films were composed of a layer of 550 ± 50 Å Sn and a layer of Ag which varied from 20 to 385 Å (±30 Å). Experimental evidence has shown that the superimposed Sn and Ag films as deposited result in an inberdispersion of Ag3Sn compound and Sn rather than a composite of single Sn and Ag films. The depression of transition temperature for such films is not due to a contact effect between two superimposed films but to a contact effect at the adjacent surface between the dispersed Ag3Sn crystallites and the Sn matrix. Upon annealing of the superimposed films, grain growth and preferred orientation of the crystallites of Ag3Sn and Sn were observed. The decrease in contact surface, due to the grain growth of Ag3Sn, thus increases the transition temperatures of the superimposed films after annealing. © 1964.