Structure, Composition, and Morphology of Photoelectrochemically Active TiO₂₋xNx Thin Films Deposited by Reactive DC Magnetron Sputtering

Films of nitrogen-doped TiO 2 were made by reactive DC magnetron sputtering in a mixture of argon, oxygen, and nitrogen. The nitrogen gas ratio Φ was varied in the 0 < Φ < 0.025 range during the depositions, resulting in TiO 2 - x N x films with 0 ≤ x ≤ 0.022 as determined by X-ray photoelectron spectroscopy. Structural and morphological properties of the films were investigated by X-ray diffraction, atomic force microscopy, and scanning and transmission electron microscopy. Films prepared without nitrogen had a rutile structure, while the nitrogen-doped films were either rutile or anatase depending on Φ being below or above ∼0.007. Deposition rate, effective grain size, root-mean-square roughness, morphology, and optical absorption were also found to depend on Φ. The films were photoelectrochemically active, as reported in an earlier papers of ours [ J. Phys . Chem. B 2003, 107, 5709−5716 and J. Phys. Chem. B 2004, 108, 5995−6003].