HIGH-RESOLUTION IMAGING OF AROMATIC-MOLECULES ADSORBED ON RH(111) ANDPT(111) IN HYDROFLUORIC-ACID SOLUTION - IN-SITU STM STUDY

In situ scanning tunneling microscopy (STM) was employed to study adla yer structures of naphthalene, naphthoquinones, and anthracene on well -defined Rh(111) and Pt(111) electrodes in aqueous HF solutions. All m olecules were adsorbed with the flat-lying orientation on both electro des. Highly ordered adlayers of naphthalene and naphthoquinones were f ound to form on Rh(111) with the (3 root 3 x 3 root 3)R30 degrees stru cture, while disordered structures were found on Pt(111). Anthracene f ormed almost close-packed adlayers without long-range ordering. In sit u STM disclosed not only the adlayer structure and packing arrangement but also the internal structure of each aromatic molecule. Two- and t hree-ring structures were clearly discerned for naphthalene and anthra cene, respectively. An additional spot was observed for 1,2-naphthoqui none, which was attributed to the oxygen atom at the 2-position.