Nucleation and Growth of Functionalized Aryl Films on Graphite Electrodes

This paper describes the nucleation and growth of functionalized aryl films on ordered graphite. The attachment of aryl groups to carbon surfaces is induced by the electrochemical reduction of the corresponding diazonium salt. This deposition procedure affords the ability to control film formation by potential cycling in a low concentration of precursor. Electrochemical and scanning probe microscopic techniques were utilized to track film formation. The blocking of Fe(CN)6 3-/4- electron transfer and scanning force microscopy images both indicate that initial nucleation of these films starts at cleavage steps. Continued deposition results in growth on the supposedly nonreactive basal plane. Scanning tunneling microscopy provides clear images of film nucleation on the basal plane, which likely occurs at atomic scale defect sites. The structure of the completed film consists of 3-dimensional features which form via a polymerization type reaction between the bound monolayer and the free radicals in solution.