MESOSCOPIC STRUCTURAL TRANSFORMATIONS OF THE AU(111) SURFACE-INDUCED BY ALKALI-METAL ADSORPTION

The response of the Au(111) surface reconstruction on the adsorption o f Na and K atoms was studied by means of scanning tunneling microscopy . With increasing coverage the periodicity of the chevron structure de creases continuously from about 250 to 100 angstrom. For Na coverages exceeding theta almost-equal-to 0.20 the stacking fault lines become d istorted and eventually a poorly ordered domain structure with hexagon al symmetry and even higher density of Au atoms is formed at theta alm ost-equal-to 0.23. These effects are attributed to an adsorbate-induce d weakening of the coupling between the first two Au layers by which t he influence of the elastic stress within the topmost layer becomes mo re dominant.