Surface Structure of Clean Au (100) and Ag (100) Surfaces

The proposal that reconstructed phases may exist for the clean (100) surfaces of some fcc metals is considered in terms of results obtained from low-energy electron-diffraction studies of epitaxial single-crystal films of silver and gold grown in ultrahigh vacuum (1×${10}^{-10\mathrm{}}$ Torr). The purpose of this paper is to show that the experimentally observed (1×5) structure on the Au(100) surface and the (1×1) structure on the Ag (100) surface are characteristic of the clean surface, and to suggest a possible atomic structure for the reconstructed Au(100) surface. The evidence from the epitaxial film studies indicates the occurrence of a thin hexagonal layer of pure gold on the (100) substrate rather than an impurity-stabilized surface layer of hexagonal symmetry, of some unknown substance. It is suggested that the interfacial energy between a thin hexagonal layer and the nonreconstructed substrate may be the determining factor in the occurrence of reconstruction on the (100) surface of fcc metals.