Studies on structural and dielectric properties of NbO[formula omitted]-Nb[formula omitted]O[formula omitted] thin-film-based devices

Abstract

The thin-film composition of NbO2 and Nb2O5 with excellent homogeneity are deposited using reactive sputtering technique by controlling oxygen flow rate in the Ar/O2 plasma ranging between 4 to 8 sccm. All the deposited films have been characterized using x-ray reflectivity (XRR), x-ray photoelectron spectroscopy (XPS) and Field Emission Scanning Electron Microscopy (FE-SEM) technique. Further, cross-sectional transmission electron microscope (TEM) and Energy-dispersive X-ray spectroscopy (EDX) were performed on one sample. Dielectric properties of Niobium oxide thin-film-based metal–oxide–semiconductor (MOS) devices also have been studied at frequencies ranging from 1 to 106Hz. The studies indicate that NbO2 content in the NbO2-Nb2O5 film decreases with the oxygen content in the plasma. The real (ε′) and imaginary (ε′′) part of dielectric constant, dissipation factor (tanδ) and ac conductivity (σac) are found to be dependent on the oxygen content in the film. The distribution parameter (α), mean relaxation time (τ0) and molecular relaxation time (τ), derived from Cole–Cole plot also vary with the oxygen content. In brief, oxygen vacancy and grain boundaries play vital role in exhibiting different electrical properties of the devices.