In-situ Measurements of Reconstructed Anatase TiO₂(001) Surface by Variable-Temperature STM

The catalytic performance of metal oxide surface mainly depends on its atomic surface structure, which usually changes under various treatment conditions and during catalytic reactions. Therefore, it is quite important to acquire the atomic geometries of the surfaces under different treatments for further understanding the catalytic mechanisms in the surfaces with complicated reconstructions. Here, we report the investigation on the evolution of surface geometries of the Ar⁺-ion-sputtered anatase TiO _2 (001) films followed by heating treatments at various temperatures, characterized using variable-temperature scanning tunneling microscopy. Our experimental results reveal the different surface morphologies at different heating temperatures. During the heating treatment, the migrations of O atoms from the bulk to the surface of TiO _2 (001) play an important role in the reoxidation of the Ti ^2+ and Ti ^3+ states for the formation of (1×4) reconstruction. The atomic-resolution images of the ridges show asymmetric features, which well support the fully oxidized structural model of the reconstructed TiO _2 (001)-(1×4) surface.