Phase segregation in the mixed alkyl thiol self-assembled monolayers on a gold surface at a high incubation temperature in a sealed container

Self-assembled monolayers (SAMs) of mixed 1-octanethiol (OT) and 1-decanethiol (DT) that were formed on gold substrates at a high incubation temperature in a sealed container were characterized using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). In mixed-composition monolayerfilms, self-assembly of the mixture could induce phase separation into discretemolecular domains at higher incubation temperatures. Mixtures of the alkanethiol molecules affected the domain size, defect density, packing density, and binding features of the resultant SAMs prepared on gold substrates. Single-moleculeresolved STM images of mixed SAMs revealed both c(4 × 2) - ns (non-shifted) for DT and c(4 × 2) - s (shifted) for OT domains. For the mixed SAMs, the peak S2 (XPS) increased in intensity relative to the peak S1, reflecting significant modifications in the binding characteristics of the thiols and surface roughness upon mixing.