Atomic Structural Transformations on Clean Metal Surfaces

Abstract

Two types of structural transformations which occur on clean, single-crystal surfaces have been investigated in atomic detail at Sandia National Laboratories. The restructuring of surfaces from ''bulk-terminated'' to ''reconstructed'' structures and the configuring of cluster nuclei between two-dimensional islands and one-dimensional chains have been examined by field ion microscopy, a technique which provides direct images of individual surface atoms. Observations of the bulk-terminated (unreconstructed) Pt (110) surface with the field ion microscope surface indicate that atoms in the topmost layer are aligned in rows adjacent to each other. The unreconstructed surface is produced by a process known as field evaporation (i.e. the removal of atoms by a high electric field at temperatures of 77K), which typically leaves a surface with the bulk-terminated structure. This metastable surface is found to transform to the equilibrium, reconstructed surface at temperatures above 300K.