DIRECT IMAGING OF ADSORPTION SITES AND LOCAL ELECTRONIC-BOND EFFECTS ON A METAL-SURFACE - C/AL(111)

C atoms are adsorbed on an Al(lll) surface in h.c.p.-type threefold hollow sites and significantly modify the charge density distribution in the surrounding Al atoms, as becomes evident from scanning tunnelling microscopy (STM) images resolving individual atoms of both the substrate and the adsorbate. Apparent modifications of the vertical positions of the Al atoms surrounding an adsorbate are not due to structural changes, but rather reflect local variations of their electronic structure induced by the chemical bond to the adsorbate, which lead to a decrease of the tunnel current at nearest neighbours and an increase at next-nearest neighbours, respectively. © 1990 IOP Publishing Ltd.