Surface Characteristics of Dialkyl Sulfide Self-Assembled Monolayers on Au(111)

초록

Surface structures, electrochemical properties, and binding conditions of symmetrical and asymmetrical dialkyl sulfides (DAS) self-assembled monolayers (SAMs) with various alkyl chain lengths (CH3(CH2)nS(CH2)nCH3, n=0,3,7,9,11) were investigated by means of scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) measurements. STM imaging showed that the surface structures of DAS SAMs were markedly different from those of alkanethiol (AT) SAMs or dialkyl disulfide (DADS) SAMs. AT and DADS SAMs have well-ordered domains containing a c(4 × 2) structure and many vacancy islands (VIs), whereas DAS SAMs have large ordered domains showing a line structure and a few VIs. From this study, we have clearly demonstrated that the adsorption mechanism of DAS molecules on Au(111) differs from that of DADS molecules during molecular self-assembly.