Electron Irradiation-Induced Local Surface Reconstruction to the (1 × 1) Domain on the Anatase TiO₂(001)-(1 × 4)...

In this study, we use low-energy electron diffraction, X-ray photoelectron spectroscopy, temperature-programmed desorption, and density functional theory calculations to unveil that low-energy electron irradiation (140.8 eV) induces local reconstruction of the irradiated area on the anatase TiO₂(001)-(1 × 4) surface to the (1 × 1) domain, accompanied by the formation of Ti³⁺ species in the subsurface region and subsurface oxygen vacancies/surface hydroxyl groups, whereas the unirradiated regions retain the (1 × 4) periodicity. The low-energy electrons locally stimulate desorption of oxygen from the anatase TiO₂(001)-(1 × 4) surface probably via interatomic Auger processes, creating surface oxygen vacancies with associated Ti³⁺ species that consequently trigger the local (1 × 4) → (1 × 1) surface reconstruction. Such a local surface reconstruction process is facilitated by surface hydroxyl groups. The created surface oxygen vacancies and Ti³⁺ species tend to migrate into the bulk, leading to a recovery of the (1 × 4) surface structure. The anatase TiO₂(001)-(1 × 1) domain provides reactive Ti_5c surface sites with a much larger density than the reactive Ti_4c surface sites on the corresponding anatase TiO₂(001)-(1 × 4) surface. These results demonstrate the sensitivity of TiO₂ surface structures to the surface reduction, which commonly occurs for TiO₂-involved (photo/electro)catalysts.