Surface structure ofCu(100)−c(2×2)−Na: A LEED analysis

Abstract

The surface structure of the $\mathrm{Cu}(100)\ensuremath{-}c(2\ifmmode\times\else\texttimes\fi{}2)\ensuremath{-}\mathrm{Na}$ phase formed by adsorption of one-half monolayer Na on Cu(100) has been determined by quantitative analysis of low-energy electron diffraction (LEED) measurements. Na atoms occupy fourfold hollow sites on an essentially unperturbed substrate for adsorption at both 100 and 300 K. The vertical distance between the Na layer and the first Cu layer is determined to be $2.37\ifmmode\pm\else\textpm\fi{}0.04$ \AA{} at 100 K and $2.42\ifmmode\pm\else\textpm\fi{}0.04$ \AA{} at 300 K. An analysis of LEED intensities measured for the clean Cu(100) surface confirms previous reports of a small contraction of the first layer spacing, but does not show an expansion of the second-layer spacing as found in medium energy ion scattering studies and in a previous LEED study. Bulk Debye temperatures found in this study are in remarkably good agreement with previous x-ray studies.