Effects of alloying and deposition temperature on phase formation and superconducting properties of TiZrTaNb-based high entropy-alloy films

A variety of bulk high-entropy alloy superconductors have been recently discovered; however, for thin films, only the TaNbHfZrTi high-entropy alloy system has been investigated for its superconducting properties. Here, (TiZrNbTa)(1-x)W-x and (TiZrNbTa)(1-x)V-x superconducting films have been produced by DC magnetron sputtering at different growth temperatures. The phase formation and superconducting behavior of these films depend on the content of alloying x and deposition temperature. A single body-centered cubic (bcc) phase can be formed in the low x range with enough driving energy for crystallinity, but phase transition between amorphous or two bcc structures is observed when increasing x. The highest superconducting transition temperature T-c reaches 8.0 K for the TiZrNbTa film. The superconducting transition temperature T-c of these films deposited at the same temperature decreases monotonically as a function of x. Increasing deposition temperature to 400 & DEG;C can enhance T-c for these films while retaining nearly equivalent compositions. Our experimental observations suggest that T-c of superconducting high entropy alloys relate to the atomic radii difference and electronegativity difference of involved elements beyond the valence electron number. (C) 2022 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license & nbsp;