Steps and the structure of the (0001) α-alumina surface

The initial stages of facet formation on the (0001) α-alumina surface are explored through annealing vicinal single crystals for different lengths of time and characterizing the surface with atomic force microscopy. Faceting of the (0001) surface begins with the formation of 0.2 nm or ∼c/6 high steps (c = 1.3 nm). These steps show a preference for existing as pairs; the pairs then bunch together and form facets which are typically multiples of c in height. In this fashion, single facets and faceted domains initially exist together on the same surface. A faceted terrace-and-step morphology develops as the facet domains coalesce with longer annealing times.