Optical properties of hydrated tungsten trioxide 3WO₃·H₂O

Spectroscopic ellipsometry was used to determine the optical properties of plate-like hydrated tungsten trioxide (3WO₃·H₂O) films in the energy range 300–4000 cm⁻¹. Films with different thicknesses were deposited on glass substrates pre-coated with fluorine-doped tin oxide via an efficient and simple hydrothermal method. Parametric models were used to extract thicknesses and optical constants of the thin films. The WO₃ was found to be more hydrated for thicker films. Moreover, the nano-plates are larger in thicker films, which leads to a decrease of the transmission due to an increase of the scattering. Features in the obtained dielectric functions of the 3WO₃·H₂O thin films were compared with the earlier published optical spectra of WO₃ and its hydrates ½WO₃·H₂O and WO₃·H₂O. - Highlights: • 3WO₃·H₂O films with different thickness grown on FTO glass by hydrothermal deposition. • The optical properties in infrared were studied by spectroscopic ellipsometry. • The presence of ½WO₃·H₂O compounds in the films is observed. • Films retain a great amount of water. • Thicker films scatter more light due to the larger size of the nano-plates