Molecular Self-Assembly of Dialkyl Sulfides on Au(111)

Abstract

Formation of self-assembled monolayers (SAMs) by the spontaneous adsorption of dialkyl sulfides (DAS) with a different alkyl chain length were examined by means of scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. STM imaging showed that DAS SAMs have completely different surface characteristics, such as ordered structures and density of vacancy island, compared with those of alkanethiol SAMs or dialkyl disulfide SAMs. These remarkable structural differences for DAS SAMs originated from the differences in self-assembly mechanism during the adsorption of molecules. DAS molecules do not form well-ordered SAMs regardless of alkyl chain length, implying that the formation of SAMs is mainly driven by the interactions between the sulfur headgroups and gold surfaces, not the interactions between alkyl chains.