The surface structure of anatase TiO2(001) was investigated using scanning tunnelling microscopy, X-ray photo-electron spectroscopy, reflection high-energy electron diffraction, and low-energy electron diffraction. A two-domain (1 x 4)/(4 x 1) reconstruction, similar to those previously reported in low-energy electron diffraction and ion scattering studies, was observed by scanning tunnelling microscopy and reflection high-energy electron diffraction. This reconstruction was found to be stable not only from room temperature to 850C in ultra-high vacuum and oxygen-rich environments, but also during the anatase film growth. High-resolution scanning tunnelling microscopic images obtained at positive sample biases revealed two types of atomic row within each surface unit cell, indicating different Ti-derived states at the surface. At the same time, X-ray photo-electron spectroscopy of the reconstructed surfaces showed no evidence of Ti3+. Based on the scanning tunnelling microscopy, X-ray photo-electron spectroscopy, reflection high-energy electron diffraction and low-energy electron diffraction results, an “added”-and-“missing”-row model was proposed to account for the (1 x 4) reconstruction. Atomic steps and their relationship to the population of (1 x 4) and (4 x 1) domains were also investigated. The results showed that for vicinal surfaces the domain population depended strongly on the overall surface step orientation. While populations of the (1 x 4) and the (4 x 1) domains were nearly equal on flat (001) surfaces, they became significantly lopsided on a surface with its normal 2° away from the (001) direction, demonstrating a strong correlation between surface steps and domain population on vicinal surfaces.

Surface Structure of Anatase TiO2(001) - Reconstruction, Atomic Steps and Domains. Liang, Y., Gan, S., Chambers, S.A., Altman, E.I.: Physical Review B, 2001, 63[23], 235402