Growth Behavior of Al-Doped TiO₂ Thin Films by Atomic Layer Deposition

Abstract

This study examined the effect of Al incorporation on the growth behavior of TiO2 thin films deposited by atomic layer deposition (ALD) using Al(CH3)3, and Ti(O-i-C3H7)4 as the precursors and O3 as the reactant. Al-doped TiO2 thin films were deposited at a growth temperature of 250 °C, which was within the ALD window for both precursors. Despite the discrete feeding of the Al precursor, Al ions easily diffused along the direction normal to the film surface forming a uniform Al-doped thin film, even during film growth. The Al concentration in the films increased with increasing Al precursor feeding ratio. However, the adsorption of the Ti precursor on the growing surface became less active after the incorporation of Al. Therefore, the growth rate of the Al-doped TiO2 films decreased with increasing Al precursor feeding ratio because of the retarded chemisorption of the Ti precursor onto the Al−O and Al containing Ti−O surface. In contrast to the retarded adsorption of the Ti precursor on the Al−O surface, the adsorption of the Al precursor on the Ti−O surface was enhanced by ∼60% compared with that on the Al−O surface.