Superconducting properties of Nb thin films deposited on porous silicon templates

TL;DR

This study explores how Nb thin films grown on porous silicon templates exhibit unique superconducting behaviors influenced by their nanostructure, revealing new insights into vortex pinning and critical field characteristics.

Contribution

It demonstrates the effects of porous silicon nanostructures on the superconducting properties of Nb films, highlighting novel behaviors in critical fields and transition features.

Findings

Change in H_c2(T) curvature observed

Oscillations in resistive transition width at 1 Tesla

High matching field due to small interpore distance

Abstract

Porous silicon, obtained by electrochemical etching, has been used as a substrate for the growth of nanoperforated Nb thin films. The films, deposited by UHV magnetron sputtering on the porous Si substrates, inherited their structure made of holes of 5 or 10 nm diameter and of 10 to 40 nm spacing, which provide an artificial pinning structure. The superconducting properties were investigated by transport measurements performed in the presence of magnetic field for different film thickness and substrates with different interpore spacing. Perpendicular upper critical fields measurements present peculiar features such as a change in the H_c2(T) curvature and oscillations in the field dependence of the superconducting resistive transition width at H=1 Tesla. This field value is much higher than typical matching fields in perforated superconductors, as a consequence of the small interpore distance.