In situ scanning tunnelling microscopy of benzene, naphthalene, and anthracene adsorbed on Cu(111) in solution

In situ scanning tunneling microscopy (STM) was used to probe the adlayer structures of benzene, naphthalene, and anthracene on a well-defined Cu(lll) electrode surface in aqueous HClO4 solution. These molecules were found to form highly ordered adlayers on a clean Cu(lll) surface with a flat-lying orientation. The molecular orientation and packing arrangement were also determined. The ordered benzene adlayer was observed to form a (3 x 3) structure with a characteristic triangular shape for each benzene molecule. The naphthalene adlayer was observed with a (4 x 4) symmetry. The naphthalene molecules were preferentially aligned with their long Ct axes along the atom rows of the Cu(lll) substrate. A long range ordered structure was also found for the anthracene adlayer. Straight molecular chains formed along the atomic rows of Cu(lll) with a side-by-side configuration.