Fundamental absorption edge in bismuth-vanadate glasses

Abstract

Optical measurements of fundamental absorption edge of bismuth-vanadate glass films containing 70 to 95 mol% V₂O₅ are made in the wavelength range 200 to 700 nm. The absorption edge in these glasses obeys the relation α (hω - E_opt)²/hω. The optical band gap, (E_opt) is determined to be 2.30 to 2.15 eV, depending on compositions of the glass and is found to decrease with increase of V₂O₅ content in the glass. The absorption coefficient is found to depend exponentially on the photon energy, which is explained to be due to the exponential distribution of the localized states in the optical gap.