Structural and optical properties of Nb2O5 films prepared by dual ion assisted deposition

Nb2O5 films were deposited with dual ion assisted deposition (DIAD) on silicon and corning 7980 quartz substrates, to investigate the effects of ion bombardment on the structural and optical properties of the films deposited in large coating chamber. The structure and chemical composition studies have been carried out using XRD, AFM, and XPS technologies. When the annealing temperature of the films is between 773 K and 873 K, the crystallization starts and some of the hexagonal phase peaks appear. The surface roughness increases along with the increase of the anode current. XPS spectra suggested that the films were all Nb2O5 films. The optical properties such as transmittance, refractive index and optical band gap energy have been estimated for Nb2O5 films. The refractive index and surface roughness of the films deposited with DIAD increased as the anode current of the ion source increased. The estimated indirect optical band gap energy was found to be somewhere between 3.42 eV and 3.43 eV for all the amorphous microstructure films. The dispersion energy parameters for different thin films are obtained by Lorentzian oscillator model as well as a single term Sellmeier oscillator model, in the normal dispersion range. The calculated values of the lattice dielectric constant, N/m* and ωp were found to increase with the rising anode current of the ion source.