Structure of the Cs-induced (1×3) reconstruction of Au(110)

Abstract

The clean Au(110) surface exhibits a (1×2) reconstruction with an atomic arrangement corresponding to a missing-row (MR) structure. By depositing Cs on this surface, we have formed two new structures with (1×5) and (1×3) low-energy electron diffraction (LEED) patterns, corresponding to Cs coverages of (3±2)% and ${(5\mathrm{}}_{\mathrm{-}2}^{+6\mathrm{}}$)% of a monolayer, respectively. The superstructures therefore correspond to further substrate reconstructions. We have used medium-energy ion scattering (MEIS) with channeling and blocking to study the structure of the (1×3) reconstruction. Our results show a clear indication of a missing-row-type structure which displays long and narrow (111) microfacets that go deep into the crystal. The most important surface distortions are an inwards relaxation of the first layer by 22%, and a large buckling in the third layer. Other subsurface rearrangements are such that they produce a slight smoothing of this highly corrugated structure. These results are discussed in the light of recent theoretical calculations of the total energy of the fcc (110) surfaces. In these calculations the relative stability of the different surface geometries is dominated by the s-p electrons at the surface. For the Cs/Au system, a charge transfer from the alkali to the Au substrate alters the energy distribution of these electrons and shifts the equilibrium geometry from the (1×2) MR to the observed (1×3) structure.