Superconducting vacancy-ordered rock-salt NbO films

TL;DR

This paper reports the successful molecular beam epitaxy synthesis of vacancy-ordered NbO thin films that exhibit superconductivity with critical temperatures up to 1.37 K, expanding the potential for high-temperature epitaxy of complex oxides.

Contribution

It demonstrates the growth of high-quality, superconducting NbO films via molecular beam epitaxy, addressing challenges in epitaxial synthesis of compounds with unusual oxidation states.

Findings

Superconductivity observed with $T_c$ up to 1.37 K.

Al$_2$O$_3$ (0001) is identified as the optimal substrate.

High-temperature growth (>1000°C) yields high-quality, single-phase films.

Abstract

We report molecular beam epitaxy synthesis of vacancy-ordered rocksalt NbO thin films which display superconductivity. A comparative study of substrates identifies Al$_2$O$_3$ (0001) as the optimal platform for realizing high-quality, single-phase films when growing at temperatures exceeding 1000 $^\circ$C. The controlled NbO films exhibit superconductivity with critical temperatures up to $T_\mathrm{c}$ = 1.37 K, comparable to bulk single crystals. This work addresses the fundamental bottlenecks encountered in the high-temperature epitaxy of compounds with uncommon oxidation states, while expanding the scope of available thin-film superconductors.