Atomic structure of O/Ir(2Â 1Â 0) nanofacets

A study of faceting of the O/Ir(2 1 0) surface has been conducted using scanning tunneling microscopy (STM). Three-sided nanometer-scale pyramids with {3 1 1} and (1 1 0) facets are found to cover the surface uniformly in the entire range of facet formation and growth temperatures. The {3 1 1} facets are smooth and unreconstructed. The (1 1 0) facets consist of unreconstructed terraces and restructured areas that exhibit a complex faceting pattern on the atomic level. The tilt angles of pyramid facets and distances between surface atoms for the facets and for the (1 1 0) superstructure are consistent with predictions based on truncated bulk iridium crystal properties. STM image simulations, based on electronic band structure calculations, have been used to validate the proposed surface terminations for the complex (1 1 0) facet superstructure.