Nucleation and coexistence of nanometer-scale facet domains on O/Ir(2Â 1Â 0)

A study of faceting phenomena exhibited by the O/Ir(2 1 0) system has been conducted using low energy electron microscopy (LEEM). The initial nucleation and growth of three-sided pyramidal facets with {3 1 1} and (1 1 0) faces, as well as the conversion of planar Ir(2 1 0) into a completely faceted surface, are found to occur uniformly over the entire sample area. Facet relaxation on the clean faceted surface to form a planar surface is also found to proceed uniformly. Individual coexisting domains of planar and faceted surface, although present, cannot be resolved in LEEM at any stage of these transformations.