Superconducting T_c's of Sputter-Deposited Nb-Ge Films and T_c Nonuniformity within Films

概要

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The superconducting transition temperature T_c and nonuniformity of Nb-Ge films prepared on sapphire substraies from compound targets by dc sputtering have been studied. The relationships between the transition temperature, the electrical resistivity ratio and the film thickness have been studied using targets with different compositions, and the conditions for preparing high-T_c. Nb-Ge films below 〜2000 Å in thickness have been determined. The T_c values for Nb-Ge films are appreciably improved in films thinner than 〜1000 Å with a Ge-richer target (Nb/Ge=2.8) and onset T_c's greater than 20 K are obtained in films with thicknesses of 〜500 Å. The nonuniformity of T_c in the films has been measured. The high T_c arises from the film surface layer and the T_c variation along the film thickness is greatly affected by changes in the substrate temperature during deposition.
社団法人応用物理学会の論文
1982-06-20