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 E-g phonon mode frequency is similar to bulk but the A(1g) 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 A(1g) mode blueshift is a consequence of the shortened apical bond. (c) 2007 American Institute of Physics.