PNNL

Abstract

We have prepared and investigated the structural, compositional, morphological and photochemical properties of N-doped TiO2(110), (100) and (001) epitaxial films grown by means of plasma-assisted molecular beam epitaxy. The N solid solubility is limited to ~ 1 at. % of the total anions in the lattice in films where excellent long-range structural order is maintained throughout growth. The photochemical activity of the resulting surfaces was evaluated using hole-mediated decomposition of adsorbed trimethyl acetate. Undoped surfaces of the three orientations exhibited comparable photochemical activities. However, the dependence of the photochemical activity on N concentration shows a marked crystallographic dependence. The results are rationalized in terms of the apparent crystallographic anisotropy of hole mobility as well as hole trapping and detrapping probabilities.