Raman scattering by thin film nanomosaic rutile TiO2

Thin TiO2 films with rutile short-range atomic order grown at room temperature have a nanostructure of rectangular domains based on a faulted rutile structure. Raman scattering by nanomosaic rutile in single layer TiO2 and TiO2–Al2O3 nanolaminate films is reported here. In all architectures, the Eg phonon mode frequency is similar to bulk but the A1g mode frequency is significantly blueshifted. These results are different from published Raman scattering spectra of other nanocrystalline rutile TiO2. A model for nanomosaic rutile is presented in which TiO6 octahedra in the faulted regions are severely distorted with a lengthened equatorial Ti–O bond and a shortened apical Ti–O bond. The observed A1g mode blueshift is a consequence of the shortened apical bond.