Impact of Gd doping on morphology and superconductivity of NbN sputtered thin films

TL;DR

This study investigates how Gd doping affects the morphology and superconducting properties of NbN thin films, revealing that Gd inclusion deteriorates superconductivity but provides detailed characterization of the films.

Contribution

It provides new insights into the effects of Gd doping on NbN thin films' structure and superconducting behavior using comprehensive experimental analysis.

Findings

Gd doping reduces the critical temperature (Tc) of NbN films.

Gd doping decreases the upper critical field Hc2(0).

Optimized films achieved Tc of 14.8K without Gd, lower with Gd.

Abstract

We report effect of Gd inclusion in the NbN superconductor thin films. The films are deposited on single crystalline Silicon (100) by DC reactive sputtering technique i.e., deposition of Nb and Gd in presence of reactive N2 gas. The fabricated relatively thick films (400 nm) are crystallized in cubic structure. These films are characterized for their morphology, elemental analysis and roughness by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDAX) and Atomic Force Microscopy (AFM) respectively. The optimized film (maximum Tc) is achieved with gas ratio of Ar:N2 (80:20) for both pristine and Gd doped films. The optimized NbN film possesses Tc (R=0) in zero and 140kOe fields are at 14.8K and 8.8K respectively. The Gd doped NbN film showed Tc (R=0) in zero and 130kOe fields at 11.2K and 6.8 K respectively. The upper critical field Hc2(0) of the studied superconducting films is calculated from the magneto-transport [R(T)H] measurements using GL equations. It is found that Gd doping deteriorated the superconducting performance of NbN.