Effects of postdeposition annealing in air or in vacuum on properties of W-doped In2O3 films of 10nm thickness or less

First, amorphous W-doped In 2 O 3 films with thicknesses ranging from 3 to 10 nm were deposited on glass substrates at room temperature by ion plating with direct current arc discharge. Second, they were then annealed in vacuum at 5 × 10 −4 Pa or in air at atmospheric pressure for 30 min at 250 °C. Out-of-plane grazing incidence and in-plane X-ray diffraction measurements revealed that the postdeposition annealing in vacuum at 5 × 10 −4 Pa process produced polycrystalline IWO films with thicknesses of 5, 7, and 10 nm, whereas the postdeposition annealing in air at atmospheric pressure produced 7- and 10-nm-thick polycrystalline IWO films. Atomic force microscopy measurements showed that the annealing in vacuum at 5 × 10 −4 Pa tended to produce spiky surfaces, whereas bumpy surfaces were formed through the annealing in air at atmospheric pressure. For polycrystalline IWO films, the Urbach energy, calculated using the optical absorption coefficient data, decreased with increasing thickness regardless of the postdeposition annealing conditions. Hall effect measurements at room temperature showed that, at any given thickness, the carrier concentration and Hall mobility of the polycrystalline IWO films postdeposition-annealed in vacuum at 5 × 10 −4 Pa were higher than those of the polycrystalline IWO films postdeposition-annealed in air at atmospheric pressure. • Amorphous W-doped In 2 O 3 films of thicknesses of 10 nm or less were prepared. • Postdeposition annealing in vacuum or in air for solid-phase crystallization. • In-vacuum treatment led to polycrstallized films with enhanced carrier transport. • Band tails strongly depend on postdeposition-annealing conditions. • Improvement of disorder enlarges Hall mobility and carrier concentration.