Determining Optical Constants of Sol-Gel Vanadium Pentoxide Thin Films using Transmittance and Reflectance Spectra
Nehad M. Tashtoush, Afafsheiab, Salam Momani, Mousa Jafar

Abstract
Vanadium pentoxide (V2O5) thin films have been prepared by Sol-Gel technique. The fluid resin which was prepared by dissolving V2O5 powder (99.6%) in H2O2 was spin coated on a glass substrate at room temperature. The effect of preparation conditions, such as spin speed and acceleration, on the film thickness has been investigated. Speed was found to be the most affecting parameter on the film thickness. Transmittance and reflectance spectra were made at normal incidence on these films in the range of 350 - 900 nm. SCOUT program was used to find out the thickness of all samples. In the region of the fundamental absorption edge, the absorption coefficient was calculated directly from the experimental transmittance and reflectance data using a formula that is nearly valid for non- uniform inhomogeneous films. Moreover, the band-gap energy was found to be around 2.3 eV. The refractive index of the films was calculated using PUMA code which is based on a certain fitting procedure for transmittance spectra according to Swanepoel formula. All results were in good agreement with those found in literature.

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