Atomic Arrangement of Au(100) and Related Metal Overlayer Surface Structures. I

Abstract

It has been shown, through analysis of simple overlayer structures consisting of a monolayer of Au or Ag on Cu(100) and Pd(100) surfaces, that Au atoms have an abnormal tendency to contract when positioned in a surface environment. This strong tendency for reduced interatomic spacing of Au surface layers is related to the atomically rearranged Au(100) surface, which consists of a hexagonal layer of Au atoms superimposed on a square array of substrate atoms. The driving force for rearrangement is interpreted in terms of the extreme sensitivity of the effective valency of Au to its atomistic environment. It is concluded that this interpretation of surface rearrangement is consistent with other unique properties of gold reported for binding energies of molecules in the vapor, and features of the band structure. In addition to providing information regarding the Au(100) surface structure, examination of metal overlayer structures has shown that pseudomorphism occurs during early growth stages of Ag and Au on the Pd(100) surface. Surface alloying of Au and Cu on the Cu(100) and on the Au (100) surfaces are also discussed.