Self-Assembled Monolayers Formed by Adsorption of Unsymmetric Dialkyl Monosulfides and Dialkyl Disulfides on Au(111)

Abstract

The surface structures and adsorption conditions of self-assembled monolayers (SAMs) formed by the spontaneous adsorption of unsymmetric dodecyl octyl sulfides (DDOS) and dialkyl disulfides (DADS) were examined by means of scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) measurements. STM imaging showed that DDOS SAMs have completely different surface characteristics in ordered structures and formation of vacancy islands compared with those of DADS SAMs. The remarkable differences in surface structures of both SAMs can be attributed to the differences in self-assembly mechanism during the adsorption of molecules. DDOS SAMs have a p 3 structure with a low molecular density, whereas DDOS SAMs have a hexagonally packed ( 3 3)R30º structure.