Optical and transport properties of NbN thin films revisited

Abstract

Highly disordered NbN thin films exhibit promising superconducting and optical properties. Despite extensive study, discrepancies in its basic electronic properties persist. Analysis of the optical conductivity of disordered ultra-thin NbN films, obtained from spectroscopic ellipsometry by standard Drude-Lorentz model, provides inconsistent parameters. We argue that this discrepancy arise from neglecting the presence of quantum corrections to conductivity in the IR range. To resolve this matter, we propose a modification to the Drude-Lorentz model, incorporating quantum corrections. The parameters obtained from the modified model are consistent not only with transport and superconducting measurements but also with ab initio calculations. The revisited values describing conduction electrons, which differ significantly from commonly adopted ones, are the electron relaxation rate $\Gamma \approx 1.8\text{eV}/\hslash$, the Fermi velocity $v_F\approx 0.7\times 10^6{\text{ms}}^{-1}$ and the electron density of states $N(E_F)=2$states of both spins/eV/$V_{\text{f.u.}}$.

10 pages, 6 figures

References in corpus (4)

• Superconducting properties and Hall Effect of epitaxial NbN thin films
• Displaced Drude peak and bad metal from the interaction with slow fluctuations
• Thermodynamic properties of the Dynes superconductors
• Momentum-resolved electronic band structure and offsets in an epitaxial NbN/GaN superconductor/semiconductor heterojunction

Cited by in corpus (2)

• Nernst effect and its thickness dependence in superconducting NbN films
• Photothermal resistivity alignment of optical fibers to SNSPD