Epitaxial growth of high <i>T</i> <i>c</i> superconducting Nb3Ge on Nb3Ir

Abstract

Nb3Ir polycrystalline films with the A15 structure deposited on sapphire were used as substrates for the epitaxial growth of Nb3Ge because of the favorable lattice parameter match. The experimental results clearly show that epitaxial growth indeed occurs and helps to extend the range of homogeneity of the A15 phase up to 26.3 at.% Ge as compared with the thermodynamic equilibrium boundary at 19 at.% Ge. Furthermore, epitaxy results in a considerable rise in the superconducting transition temperature for Ge-rich samples together with a reduction in the transition width.