Scanning tunneling microscopy and low energy electron diffraction have been used to study the $\alpha {-\mathrm{F}\mathrm{e}}_2{\mathrm{O}}_3\left(0001\right)$ surface in an ultrahigh vacuum. Our results show that this surface can be stabilized by coexisting $\alpha {-\mathrm{F}\mathrm{e}}_2{\mathrm{O}}_3\left(0001\right)$ and FeO(111) phases, with each phase existing in atomically well-ordered islands of mesoscopic dimensions. Furthermore, the islands themselves are arranged to form a superlattice. The formation of this superlattice can be explained in terms of the lattice mismatch between two types of oxygen sublattices.

• Received 7 April 1995

DOI:https://doi.org/10.1103/PhysRevLett.75.1961