Morphology of MgO(111) surfaces: artifacts associated with the faceting of polar oxide surfaces into neutral surfaces

It is shown by optical, atomic force, scanning and transmission electron microscopies that the MgO(111) surface does not Facet into neutral(100) type planes upon annealing. The triangular pyramidal pits that Henrich [V.E. Henrich Surf. Sci., 57 (1976) 385] associates with the polar (111) surface faceting into (100) planes turn out to be artifacts of the acid etch used in the sample preparation process. It is shown that the pyramidal pits have facets sloped at 10.8+/-2.8 degrees with respect to the (111) surface, corresponding to sets of vicinal surfaces. The pit edges are confirmed by transmission electron microscopy to be along the three equivalent [110]-type directions. (C) 1998 Elsevier Science B.V. All rights reserved.