Variation of superconducting transition temperatures of transition-metal thin films deposited with the noble gases

Abstract

Thin films of Cr, Mo, Ti, W, and Zr metals deposited by dc ion‐beam sputtering in noble‐gas atmospheres were found to be superconducting with transition temperatures substantially higher than those observed for the respective bulk metals. Mo films deposited with a Xe ion beam were found to be superconducting at a temperature of 7.2°K. A variation of T_c was observed for films deposited using different noble gases with highest transition temperatures obtained for deposition with Xe gas. Ion‐beam‐sputtered thin films of Nb, Ru, Ta, and V metals were similarly deposited with a resulting decrease in T_c as compared with their bulk metals. Film deposition with noble gases of higher mass produced higher T_c's than those obtained with lower‐mass noble gases. The mechanism responsible for the variation of the superconducting transition temperatures of these metal films is not known at this time but may be associated with the formation of a dilute solution/mixture of the noble gas and the transition metal, a change in the d electron density of states at the Fermi level and a change in the Debye temperature.