Superconducting MgB2 thin films nano-bridges for cryo-electronic application

TL;DR

This paper reports the fabrication of smooth MgB2 superconducting thin films on sapphire, optimized annealing processes, and the creation of nano-bridges with high critical current density for cryo-electronic applications.

Contribution

It introduces an optimized annealing process for MgB2 films and demonstrates the fabrication of nano-bridges with high critical current density using lithography.

Findings

Smooth MgB2 films with roughness below 10 nm achieved

Critical temperature Tcon = 31 K maintained

Critical current density jc (4.2 K) = 7.3x10^6 A/cm2

Abstract

Precursor MgB2 thin films were prepared on sapphire substrates by magnetron sputtering. Influence of ex-situ annealing process on superconducting MgB2 thin films roughness is discussed. Optimized annealing process of MgB precursor thin films in vacuum results in smooth superconducting MgB2 thin films with roughness below 10 nm, critical temperature Tcon = 31 K and transition width DTc less than 1 K. Nano-bridges based on the superconducting MgB2 thin films using optical and Focused Ion Beam lithography were prepared. Critical current density jc (4.2 K) measured on 50 nm wide strip was 7.3x106 A/cm2 and no significant loss of superconducting properties was detected. Resistance vs. temperature and critical current vs. temperature characteristics were measured on these structures using standard DC four probe measurements.