Control of thin NbN film superconducting properties by ScN buffer layer

TL;DR

This study demonstrates that incorporating a scandium nitride buffer layer enhances the superconducting properties of niobium nitride thin films by improving crystal quality and increasing critical temperature.

Contribution

It introduces the use of a ScN buffer layer to significantly improve NbN thin film superconducting characteristics, supported by structural analysis.

Findings

Critical temperature increased from 9 K to 12.5 K

Resistivity at 20 K decreased from 330 to 210 mkOhm*cm

Enhanced lattice matching improves film quality

Abstract

This work investigates the effect of a scandium nitride buffer layer on the superconducting properties of niobium nitride thin films. The use of a ScN buffer layer significantly improves the characteristics of 29 nm thick NbN films: the critical temperature Tc increases from 9 K to 12.5 K, while the resistivity at 20 K decreases from 330 mkOhm*cm to 210 mkOhm*cm compared to films without a buffer layer. These enhancements are attributed to the better lattice matching between NbN and ScN, which results in a higher quality crystal lattice of the NbN film, as confirmed by transmission electron microscopy and X-ray diffraction data.