Interplay between step anisotropy and surface phase transformation onTiO2(110)

The dynamic behavior of steps on the ${\mathrm{TiO}}_2\mathrm{}\mathrm{}\left(110\right)\mathrm{}$ surface was studied during the transformation from a $1\times 1$ structure to a $1\times 2$ structure. We found that two types of steps dominate the transformation process: (1) [001], defined as steps that run along the [001] direction; and (2) $\left[11¯0\right]$ defined as steps that run parallel to the $\left[11¯0\right]$ direction. The stoichiometric $1\times 1$ surface contained mostly [001] steps. Reducing this surface caused nearly half the [001] steps to be gradually converted to $\left[11¯0\right]$ steps. This evolution in step structure was accompanied by growth of reconstructed $1\times 2$ domains initiated mostly at the $\left[11¯0\right]$ step edges. On the $1\times 2$ domains, the lengths of the [001] and $\left[11¯0\right]$ steps were approximately equal. The results of this work shed light on the step structure and correlation between the step energetics and the surface phase transformations on the ${\mathrm{TiO}}_2\mathrm{}\mathrm{}\left(110\right)\mathrm{}$ surface.