Optical properties of amorphous Na2O-WO3-B2O3 thin films deposited by electron beam evaporation

Thickness dependencies of the optical properties of as-deposited amorphous 30Na2O-10WO3-60B2O3 prepared by electron beam evaporation on glass substrates at a base pressure of 9 × 10−7 Torr have been studied. Glancing angle X-ray diffraction studies were performed to confirm the amorphous nature of the prepared films. The absorption coefficient α, therefore extinction coefficient k, have been determined from the reflectance and transmission spectra at the strong absorption region. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple – DiDomenico model. The optical constants such as optical band gap, Urbach energy, the average excitation energy Eo and Ed the dispersion energy of thin films were determined. The optical data revealed the existence of allowed indirect transitions.