In-situ Investigation of the Phase Formation and Superconductivity in V$_3$Si Thin Films at High Temperatures

TL;DR

This study investigates the phase formation and superconducting properties of V$_3$Si thin films at high temperatures, revealing how annealing conditions affect film quality and superconductivity through in-situ analysis and modeling.

Contribution

It introduces a combined experimental and modeling approach to understand phase transformations and superconductivity in V$_3$Si films during high-temperature annealing.

Findings

Optimal annealing improves film quality and superconducting properties.

Over-annealing depletes the SiO$_2$ barrier and causes undesirable phases.

The $T_c$ of the films reaches 13 K under optimal conditions.

Abstract

Vanadium silicide (V$_3$Si) is a promising superconductor for integration with silicon-based electronics, however the interfacial growth kinetics have a strong influence on the resulting superconducting properties and are not yet fully understood. In this study, we have used neutron reflectometry to reveal the phase transformation during thin film growth driven by different annealing strategies. We examined the silicide formation when a thin layer of vanadium undergoes reactive diffusion with a silicon dioxide film on silicon at temperatures from 650-800 {\deg}C. To further investigate the time evolution of different phases under various annealing temperatures, a chemical model was developed and subsequent simulations were performed. The results of this model were validated using X-ray diffraction and cross-sectional TEM analysis. Correlations were observed between the structure and superconducting properties. Over-annealing films leads to complete depletion of the SiO$_2$ barrier layer, forming diffuse interfaces and driving the formation of undesirable silicon-rich silicides. Avoiding this by controlling time and temperature, allows higher quality superconducting films to be achieved. The $T_c$ of the films was found to be 13 K, and the annealing conditions influenced the critical fields and the paramagnetic Meissner effect near $T_c$. For optimally-annealed films, superconducting order parameters were calculated. Ginzberg-Landau theory was applied to explain flux penetration.