Effect of annealing on the superconducting properties of a-Nb(x)Si(1-x) thin films

TL;DR

This study investigates how annealing affects the superconducting properties of a-Nb(x)Si(1-x) thin films near the superconductor-insulator transition, revealing that annealing and composition influence superconductivity differently than thickness.

Contribution

It provides new insights into the effects of annealing on superconductivity in a-NbSi films and challenges the use of sheet resistance as the sole parameter for SIT.

Findings

Annealed films remain homogeneous up to 500°C.

Annealing and composition have different impacts on superconductivity.

Sheet resistance may not fully describe the SIT.

Abstract

a-Nb(x)Si(1-x) thin films with thicknesses down to 25 {\AA} have been structurally characterized by TEM (Transmission Electron Microscopy) measurements. As-deposited or annealed films are shown to be continuous and homogeneous in composition and thickness, up to an annealing temperature of 500{\deg}C. We have carried out low temperature transport measurements on these films close to the superconductor-to-insulator transition (SIT), and shown a qualitative difference between the effect of annealing or composition, and a reduction of the film thickness on the superconducting properties of a-NbSi. These results question the pertinence of the sheet resistance R_square as the relevant parameter to describe the SIT.