Influence of ion bombardment on the superconducting transition temperature of evaporated vanadium layers

Abstract

The influence of ion irradiation and implantation on the superconducting transition temperature T c of evaporated vanadium layers has been investigated as a function of ion species and layer purity. Irradiations of pure layers with Ne + ions and fluences of typically 10 16 ions/cm 2 lead to small T c decreases ( ΔT c∼ 0.1–0.2 K). In oxygen contaminated layers however appreciable changes of T c(ΔT c ∼ 2–3 K ) are observed depending on oxygen content and ion fluence. Similarly, the direct implantation of chemically active impurities (N +, O +) leads to drastic changes of T c . Here T c decreases as a function of nitrogen concentration down to the detection limit of 1.2 K. From these results it is concluded that the T c changes are due to impurity stabilized disorder. Energy dependent chanelling analysis of nitrogen and neon implanted V and Mo single crystals has been performed to obtain additional information on the nature of this disorder.