High resistance of superconducting TiN thin films against environmental attacks

TL;DR

This study demonstrates that superconducting TiN thin films exhibit exceptional resistance to environmental attacks such as acids and alkalis, maintaining their structure and properties even after prolonged exposure, which is promising for durable applications.

Contribution

The paper reveals the unexpected environmental stability of superconducting TiN films against acids and alkalis, supported by experimental and theoretical analyses of corrosion mechanisms.

Findings

TiN films remain structurally stable after 7 days in acid and alkaline solutions

Corrosion mechanisms involve defect creation and film thinning due to specific chemical interactions

TiN's durability suggests potential for reliable superconducting applications in harsh environments

Abstract

Superconductors, an essential class of functional materials, hold a vital position in both fundamental science and practical applications. However, most superconductors, including MgB$_2$, Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, and FeSe, are highly sensitive to environmental attacks (such as water and moist air), hindering their wide applications. More importantly, the surface physical and chemical processes of most superconductors in various environments remain poorly understood. Here, we comprehensively investigate the high resistance of superconducting titanium nitride (TiN) epitaxial films against acid and alkali attacks. Unexpectedly, despite immersion in acid and alkaline solutions for over 7 days, the crystal structure and superconducting properties of TiN films remain stable, as demonstrated by high-resolution X-ray diffraction, electrical transport, atomic force microscopy, and scanning electron microscope. Furthermore, combining scanning transmission electron microscopy analysis with density functional theory calculations revealed the corrosion mechanisms: acid corrosions lead to the creation of numerous defects due to the substitution of Cl ions for N anions, whereas alkaline environments significantly reduce the film thickness through the stabilization of OH$^\ast$ adsorbates. Our results uncover the unexpected stability and durability of superconducting materials against environmental attacks, highlighting their potential for enhanced reliability and longevity in diverse applications.