Long‐Range Atomic Order on Double‐Stepped Al₂O₃(0001) Surfaces

The deterministic preparation of highly ordered single‐crystalline surfaces is a key step for studying and utilizing the physical properties of various advanced materials. This paper presents the fast and straightforward preparation of vicinal Al 2 O 3 (0001) surfaces with micrometer‐scale atomic order. Crisp electron‐diffraction spots up to at least 20 th order evidence atomic coherence on terraces with widths exceeding 1 μm. The unique combination of three properties of Al 2 O 3 (0001) underlie this remarkable coherence: its high‐temperature stability; the differences in the ionic bonding systems of the surface as compared to the bulk; and the fact that the terraces are non‐polar whereas the step edges have a polar character. The step edges are furthermore found to have alternating configurations, which drive a step‐doubling transition. On double‐stepped surfaces, the Al‐rich ° surface reconstruction attains a singular in‐plane orientation. These results set a benchmark for high‐quality surface preparation and thus expand the scope for both fundamental studies on and the technological utilization of exciting material systems.