Fast displacement and structural transition of cyclohexanethiol self-assembled monolayers by octanethiols on Au (111).

Displacement of cyclohexanethiols (CHTs) self-assembled monolayers (SAMs) by octanethiols on Au (111) (OTs) was examined by scanning tunneling microscopy (STM) and contact angle measurements. We revealed that the fast displacement of CHT by OT takes place within a few minutes, and then displacement proceeds slowly to form the closely packed OT SAMs. The main driving force for the unusual fast displacement is due to the large increase of chemical interactions between the sulfur and gold atoms, and the van der Waals interactions between alkyl chains after displacement of CHT by OT. STM imaging clearly demonstrated the structural transitions from the (5 x 2 square root 10)R48 degrees structure of CHT SAMs to the (square root 3 x square root 3)R30 degrees or c(4 x 2) structures of OT SAMs via an intermediate phase that were often observed during alkanethiol SAM growth on gold. In this study, we found that CHT SAMs can be used as a new transient layer for the fabrication of nanostructures on a surface.