  The availability of low-index rutile TiO2 single crystal substrates with
atomically flat surfaces is essential for enabling epitaxial growth of rutile
transition metal oxide films. The high surface energy of the rutile (001)
surface often leads to surface faceting, which precludes the sputter and
annealing treatment commonly used for the preparation of clean and atomically
flat TiO2(110) substrate surfaces. In this work, we reveal that stable and
atomically flat rutile TiO2(001) surfaces can be prepared with an atomically
ordered reconstructed surface already during a furnace annealing treatment in
air. We tentatively ascribe this result to the decrease in surface energy
associated with the surface reconstruction, which removes the driving force for
faceting. Despite the narrow temperature window where this morphology can
initially be formed, we demonstrate that it persists in homoepitaxial growth of
TiO2(001) thin films. The stabilization of surface reconstructions that prevent
faceting of high-surface-energy crystal faces may offer a promising avenue
towards the realization of a wider range of high quality epitaxial transition
metal oxide heterostructures.
