Head Group and Solvent Effects on the Formation of Tolane Self-Assmbled Monolayers on Au(111)

Abstract

Self-assembled monlayers (SAMs) prepared by oligo(phenylene ethylene)s (OPE) molecules with -conjugated, rigid, rod-like molecular systems have been often used for the fabrication of electronic device applications due to their electronic properties [1,2]. Thioacetyl-terminated conjugated molecules were used for SAM fabrication because aromatic thiols can easily undergo oxidation to form disulfide or other oxidized products in the presence of a small amount of oxygen. In this study, structures and binding conditions of SAMs formed by tolane compounds on Au(111) were characterized by scanning tunneling microscopy (STM) and x-ray photoelectron spectroscopy (XPS). It was found that the formation of tolane thioacetate (TTA) SAMs was strongly influenced by the property of solvent. Among various solvents, polar protic solvents such as methanol and ethanol markedly contribute to form two-dimensional ordered monolayers. In addition, using TMS, tolanedisulfide (TDS), and tolane methyl sulfide (TMS). we have investigated the effect of sulfur headgroup having different chemical groups for SAM formation.