# Superconductivity behavior in epitaxial TiN films points at surface magnetic disorder

## TL;DR

This study investigates how surface magnetic disorder affects the superconducting properties of epitaxial TiN films, revealing that surface defects significantly suppress the critical temperature as film thickness decreases.

## Contribution

It provides evidence that surface magnetic disorder is a key factor influencing superconductivity in high-quality TiN films, especially at reduced thicknesses.

## Key findings

- Residual resistivity increases with decreasing film thickness.
- Superconducting critical temperature decreases as film becomes thinner.
- Surface magnetic disorder is identified as a major factor affecting superconductivity.

## Abstract

We analyze the evolution of the normal and superconducting electronic properties in epitaxial TiN films, characterized by high Ioffe-Regel parameter values, as a function of the film thickness. As the film thickness decreases, we observe an increase of in the residual resistivity, which becomes dominated by diffusive surface scattering for $d\leq20\,$nm. At the same time, a substantial thickness-dependent reduction of the superconducting critical temperature is observed compared to the bulk TiN value. In such a high quality material films, this effect can be explained by a weak magnetic disorder residing in the surface layer with a characteristic magnetic defect density of $\sim10^{12}\,\mathrm{cm}^{-2}$. Our results suggest that surface magnetic disorder is generally present in oxidized TiN films.