Electrical and optical properties of tantalum oxide thin films prepared by reactive magnetron sputtering

Tantalum oxide thin films were prepared by using reactive dc magnetron sputtering in the mixed atmosphere of Ar and O-2 with various flow ratios. The structure and O/Ta atom ratio of the thin films were analyzed by X-ray diffraction and X-ray photoelectron spectroscopy (XPS). The optical and dielectric properties of the Ta2O5 thin films were investigated by using ultraviolet-visible spectra, spectral ellipsometry and dielectric spectra. The results reveal that the structure of the samples changes from the amorphous phase to the beta-Ta2O5 phase after annealing at 900 degrees C. The XPS analysis showed that the atomic ratio of O and Ta atom is a stoichiometric ratio of 2.50 for the sample deposited at Ar:O-2 = 4:1. The refractive index of the thin films is 2.11 within the wavelength range 300-1000 nm. The dielectric constants and loss tangents of the Ta2O5 thin films decrease with the increase of measurement frequency. The leakage current density of the Ta2O5 thin films decreases and the breakdown strength increases with the increase of Ar:O-2 flow ratios during deposition. (C) 2011 Elsevier B.V. All rights reserved.