Effects of postdeposition annealing under atmospheric conditions on the properties of amorphous conductive W-doped In2O3 deposited on glass substrates by reactive plasma deposition with direct current arc discharge

We deposited tungsten (W)-doped In 2 O 3 (IWO) films with thicknesses varying from 5 to 50 nm on alkali-free glass substrates without the intentional heating of the substrates by reactive plasma deposition with direct current arc discharge. A sintered In 2 O 3 pellet with a WO 3 content of 1.0 wt% (corresponding to 0.6 at. %) was used as the source for film growth. The analysis of the data obtained by X-ray diffraction (XRD) measurements showed that as-deposited IWO films with thicknesses of 20 nm or more were polycrystalline with a cubic bixbyite structure, whereas thinner as-deposited IWO films had an amorphous structure. After the deposition, we performed annealing at temperatures (T a ) of 200 and 250 °C in air for 30 min. Except for the 50-nm-thick polycrystalline IWO films postdeposition-annealed at 200 °C, we found that the carrier concentration ( n e ) of each film was lower than that of the as-deposited IWO films regardless of T a ; a substantial decrease in n e was found in postdeposition annealed IWO films with thicknesses of 10 nm or less. In-plane XRD measurement results showed that 5-nm-thick amorphous IWO films were noncrystallized regardless of T a , and 7- and 10-nm-thick IWO films transformed from the amorphous phase to the polycrystalline phase. The higher the T a , the stronger the (111) orientation. For IWO films with thicknesses of 10 nm or less, T a governed the film properties. We elucidated the factors governing the carrier transform based on the Fermi gas model combined with the analysis of optical absorption coefficients calculated using optical transmission and reflectance. We thereby proposed a model clarifying the effects of the oxygen-related species chemisorbed on the surfaces of as-deposited IWO films on the properties of postdeposition annealed IWO films. • Tungsten-doped In 2 O 3 films with various thicknesses were deposited by RPD. • We investigated the properties of as-deposited and postdeposition annealed films. • We propose a model of effects of post-annealing on the film properties. • Lattice disorder and carrier concentration limit the carrier transport.