  The crystallographic orientation of SrIrO3 surfaces is decisive for the
occurrence of topological surface states. We show from DFT computations that
(001) and (110) free surfaces have comparable energies, and, correspondingly,
we experimentally observe that single micro-crystals exhibit both facet
orientations. These surfaces are found to relax over typically the length of
one oxygen octahedron, defining a structural critical thickness for thin films.
A reconstruction of the electronic density associated to tilts of the oxygen
octahedra is observed. On the other hand, thin films have invariably been
reported to grow along the (110) direction. We show that the interfacial energy
associated to the oxygen octahedra distortion for epitaxy is likely at the
origin of this specific feature, and propose leads to induce (001) SrIrO3
growth.
