Development of structural and optical properties of WOx films upon increasing oxygen partial pressure during reactive sputtering

WOx films were prepared by reactive dc magnetron sputtering using tungsten target. Sputtering was carried out at a total pressure of 1.2 Pa using a mixture of argon plus oxygen in an effort to determine the influence of the oxygen partial pressure on structural and optical properties of the films. The deposition rate decreases significantly as the surface of the target is oxidized. X-Ray diffraction revealed the amorphous nature of all the films prepared at oxygen partial pressures higher than 1.71×10−3 Pa. For higher oxygen partial pressures, fully transparent films were deposited, which showed a slight increase in optical band gap with increasing oxygen partial pressure, while the refractive index was simultaneously decreased.

Research highlights
► There are only a few detailed studies on the formation process of WOx films by reactive sputtering.
► Examination of the properties of the substoichiometric tungsten oxides.
► Examination of the effect of oxygen partial pressure on properties of WOx.