Nb3Al thin-film synthesis by electron-beam coevaporation

Abstract

Nb3Al thin films have been prepared and characterized with varying deposition parameters, including substrate temperature, deposition rate, gas doping, and epitaxial growth. Nb-Al samples made with the optimum substrate temperature have lattice constants following the prediction of Geller radii and a systematic Tc increment with Al composition, namely, a ΔTc/ΔC of 1.9 K/at% Al. Employment of the self-epitaxial method results in extending the A15 phase boundary by 1 at% Al and an enhancement of Tc by 2.4 K at a given substrate temperature. By extrapolating from Tc =16.7 K, the highest transition temperature observed in this work, stoichiometric Nb3Al is predicted to have an Tc onset of 20.7 K.