  We report the fabrication of (111)-oriented superlattice structures with
alternating 2m-layers (m = 1, 2, and 3) of Ca0.5Sr0.5IrO3 perovskite and two
layers of SrTiO3 perovskite on SrTiO3(111) substrates. In the case of m = 1
bilayer films, the Ir sub-lattice is a buckled honeycomb, where a topological
state may be anticipated. The successful growth of superlattice structures on
an atomic level along the [111] direction was clearly demonstrated by
superlattice reflections in x-ray diffraction patterns and by
atomically-resolved transmission electron microscope images. The ground states
of the superlattice films were found to be magnetic insulators, which may
suggest the importance of electron correlations in Ir perovskites in addition
to the much discussed topological effects.
