Preparation and Superconducting Properties of Niobium–Zirconium Thin Films

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Abstract
Nb–Zr thin films (3000–4000 Å thick) have been prepared by dc sputtering at 350 °C and 630 °C. Measurements of the Jc–H characteristics in transverse fields of up to 85 kOe and of Tc’s were carried out as a function of composition. We also investigated the effects of different substrate materials and deposition rates on the superconducting properties of Nb-66 at.% Zr thin films deposited at 630 °C. The results show a distinct dependence of Jc–H data on the substrate temperature: Maximum critical fields of up to 60 kOe at 103 A/cm2 are observed for films deposited at 350 °C, whereas some films deposited at 630 °C are still superconducting at 85 kOe with current densities of 105 A/cm2. The Tc vs composition curve has a maximum at approximately 30 at.% and appears to be insensitive to deposition temperature at higher Zr concentrations. Additional annealing after deposition seems to increase Tc. The lower deposition rates yielded films with higher Tc’s and better Jc–H characteristics.

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