SCANNING TUNNELING MICROSCOPIC INVESTIGATION OF IODINE-COVERED PT SINGLE-CRYSTAL ELECTRODES

Using a home-built scanning tunnelling microscope (STM), the structure of iodine adlayers in air and in electrolyte has been investigated, I n air, the occurrence of tip-adatom interactions was demonstrated and an antiphase domain boundary was resolved atomically. The adlayer stru cture on the Pt(100) surface in 10(-4) mol dm-3 I- Solution (pH 4) is potential dependent. At 0.75 V vs. RHE the Pt(100) (square-root 2 x 5 square-root 2)R45-degrees-I adlattice is found. At 0.5 V, domains of t his structure and of a Pt(100) (square-root 2 x 5 square-root 2)R45-de grees-I adlattice exist. Desorption of iodine (at 0.25 V) leads to a h exagonally reconstructed surface. During deposition of small amounts o f copper onto the iodine-covered surface, islands with diameters betwe en 10 and 30 angstrom, which are one to three atomic layers high, are formed first and then coalesce to a hill-like structure.