INSITU SCANNING TUNNELING MICROSCOPY STUDY OF IODINE AND BROMINE ADSORPTION ON AU(111) UNDER POTENTIAL CONTROL

We have studied the adsorption of iodine and bromine onto Au(111) from NaI and NaBr solutions as a function of surface potential-using scanning tunneling microscopy. We have found that at low potentials both iodine and bromine form a (square-root 3 x square-root 3)R30-degrees structure. At higher potentials a 3 X 3 adlattice was observed for iodine, and a hexagonal close-packed adlattice with a rotation angle of approximately 20-degrees was observed for bromine. Adlattice orientations are determined by comparing the adsorbate lattice images and the images of bare Au(111) and by simultaneously imaging the adlattice and the substrate lattice in the case of iodine.