Tunnel junctions on as-grown superconducting MgB2 thin films

TL;DR

This paper reports the successful fabrication of superconductor/insulator/normal-metal tunnel junctions on as-grown MgB2 thin films, revealing a well-defined superconducting gap with implications for superconducting device applications.

Contribution

It introduces a method to create tunnel junctions on as-grown MgB2 films using an Mg overlayer as an insulator, which is a novel approach in this context.

Findings

Reproducible superconducting gap observed (~2.5 meV)

The gap ratio 2delta/kBTc is smaller than BCS prediction

Effective fabrication of tunnel junctions on as-grown MgB2 films

Abstract

We demonstrate that good superconductor/insulator/normal-metal tunnel junctions can be fabricated on as-grown superconducting MgB2 thin films. The as-grown films were prepared by coevaporation at low growth temperatures of around 280deg. The insulating barrier was formed by an Mg overlayer, which is subsequently oxidized in air. The tunneling spectra for Au/MgOx/MgB2 junctions showed a reproducible and well-defined superconducting gap (delta= ~ 2.5 meV). The resultant 2delta/ kBTc was significantly smaller than the predicted BCS value of 3.52.