Superconducting properties of Nb$_{0.85}$Sc$_{0.15}$ film deposited by magnetron co-sputtering

Abstract

The technology has been developed for synthesizing Nb$_{1-x}$Sc$_x$ films using magnetron co-sputtering from Nb and Sc targets. The material synthesis was accompanied by structural characterization using X-ray diffraction and X-ray reflectometry methods, which enabled the determination of thickness, phase composition and crystal structure. We also analyzed the superconducting properties. The critical temperature $T_c$ was measured for samples with different concentarions of Sc and Nb. The maximum value of $T_c$ equal to 6.35 K was observed for sample with a scandium content of approximately 15 %, which was determined by Auger spectroscopy. Transport and magnetoresistive measurements were performed in microbridges with length of 50 $\mu$m, width of 2 $\mu$m, and thickness of 30 nm. The critical current density was as high as 2.5 $\text{ MA/cm}^{2}$. Magnetic measurements were performed with the field oriented perpendicular to the sample. The upper critical field $H_{c2}(0) = 3.2$ T, electron diffusion coefficient $D = 1.1$ $\text{cm}^{2}/s$, and coherence length $\xi_{GL} = 10.1$ nm. The synthesized Nb$_{1-x}$Sc$_x$ intermetallic compound shows promise for various functional cryogenic electronics devices. \keywords{NbSc; superconductor; microbridge}