Low-energy electron microscopy was used to image the reversible transformation of the TiO2(110) surface between a high-temperature 1 x 1 structure and a low-temperature 1 x 2 structure. The reconstruction dynamics were novel: 1 x 2 bands nucleated during cooling at the steps of the starting 1 x 1 surface and then grew laterally from the steps. The transformation kinetics were dominated by mass flow from the surface to the bulk, a process that facilitated converting the high-density 1 x 1 phase to the lower-density 1 x 2 phase. It was also shown how the 1 x 1 surface reconstructs to 1 x 2 phase after sufficient oxygen was removed from the crystal bulk during vacuum annealing. Also, 1 x 2 bands nucleated and grew laterally from the initial 1 x 1-surface steps. However, because this isothermal 1 x 1 → 1 x 2 transition occurred largely by mass redistribution on the surface, the steps of the initial 1 x 1 surface and final 1 x 2 surface were offset. Models of mass redistribution during the 1 x 1 → 1 x 2 phase transition were proposed in order to explain this effect. It was concluded that the phase transition was first-order because it always occurred via the nucleation and growth of discrete phases. It was shown that quenching could roughen the TiO2 surface by forming pits, and that changing temperature caused step motion on 1 x 2 surfaces.

Spatially Resolved Dynamics of the TiO2(110) Surface Reconstruction. McCarty, K.F., Bartelt, N.C.: Surface Science, 2003, 540[2-3], 157-71