Atomic scale evidence for faceting stabilization of a polar oxide surface

By highest-resolution dynamic scanning force microscopy operated in the non-contact mode, we reveal the complex stabilization mechanism of polar zinc-terminated ZnO(0001). The nanoscopic and atomic structures unveiled corroborate a model of stabilization via triangular structures. High-temperature preparation (T > 1300 K) yields a phase with an additional stabilization by faceting in the form of highly ordered step arrays. The terraces between steps are partly covered with triangular reconstructions exhibiting exclusively {10 (1) over bar0} nanofacets on step edges. Both mechanisms together allow a complete stabilization of the surface without the involvement of adsorbates.