Molybdenum-Rhenium superconducting suspended nanostructures

TL;DR

This paper reports on the fabrication and characterization of suspended MoRe superconducting nanostructures, demonstrating how annealing improves their superconducting properties and enabling potential electromechanical device applications.

Contribution

It introduces a fabrication process for suspended MoRe nanostructures and shows how annealing enhances their superconducting performance through contaminant desorption.

Findings

Critical temperature increases by 0.5K after annealing.

Superconducting channels as narrow as 50 nm were achieved.

Superconducting properties depend on annealing and channel width.

Abstract

Suspended superconducting nanostructures of MoRe $50\%/50\%$ by weight are fabricated employing commonly used fabrication steps in micro- and nano-meter scale devices followed by wet-etching with Hydro-fluoric acid of a SiO$_2$ sacrificial layer. Suspended superconducting channels as narrow as $50\,\rm{nm}$ and length $3\,\rm{\mu m}$ have a critical temperature of $\approx 6.5\,\rm{K}$, which can increase by $0.5\rm{K}$ upon annealing at $400\,^{\circ}\mathrm{C}$. A detailed study of the dependence of the superconducting critical current and critical temperature upon annealing and in devices with different channel width reveals that desorption of contaminants is responsible for the improved superconducting properties. These findings pave the way for the development of superconducting electromechanical devices using standard fabrication techniques.