Ultrathin MgB2 films fabricated on Al2O3 substrate by hybrid physical-chemical vapor deposition with high Tc and Jc

TL;DR

This paper reports the successful fabrication of ultrathin MgB2 superconducting films on Al2O3 with high critical temperature and current density, demonstrating their excellent superconducting properties at nanometer scales.

Contribution

The study introduces a hybrid physical-chemical vapor deposition method to produce phase-pure, oxidation-free ultrathin MgB2 films with record-high Tc at 7.5 nm thickness.

Findings

Tc of 34 K at 7.5 nm thickness

Jc of approximately 10^6 A/cm^2 at 16 K for films below 10 nm

Successful epitaxial growth of continuous ultrathin MgB2 films

Abstract

Ultrathin MgB2 superconducting films with a thickness down to 7.5 nm are epitaxially grown on (0001) Al2O3 substrate by hybrid physical-chemical vapor deposition method. The films are phase-pure, oxidation-free and continuous. The 7.5 nm thin film shows a Tc(0) of 34 K, which is so far the highest Tc(0) reported in MgB2 with the same thickness. The critical current density of ultrathin MgB2 films below 10 nm is demonstrated for the first time as Jc ~ 10^6 A cm^{-2} for the above 7.5 nm sample at 16 K. Our results reveal the excellent superconducting properties of ultrathin MgB2 films with thicknesses between 7.5 and 40 nm on Al2O3 substrate.