The evolution of CO adsorption on Cu(111) as studied with bare and CO-functionalized scanning tunneling tips

CO adlayers on Cu(111) are studied using scanning tunneling microscopy with special attention to the role of functionalized tips prepared by vertical manipulation. An attractive adsorbate–adsorbate interaction is found already at ultra-low coverage using lateral manipulation. Increasing the coverage leads to island formation facilitated by a lowering of the diffusion barrier. At 1/3 ML coverage the 3×3R30° phase can be visualized clearly with CO-functionalized tips. Images obtained at CO saturation exhibit a 4×4 supercell of the adlayer as the basis structural element.