Displacement of Cyclohexanethiol Self-Assembled Monolayers by Alkanethiols on Au(111)

Abstract

Molecular-scale exchange processes of cyclohexanethiol (CHT) self-assembled monolayers (SAMs) by alkanethiols were examined by scanning tunneling microscopy (STM). Contrary to alkanethiol SAMs with hexagonal (√3 × √3) R30˚ structure, it was revealed that CHT SAMs have (5 2 10)R48 superstructure with lower surface coverage. Therefore, it is expected that CHT molecules in SAMs can be easily exchanged by other incoming molecules. In this study, it was elucidated that CHT molecules in SAMs are easily displaced by octanethiols or decanethiols even though these thiols have shorter alkyl chains. Complete replacement of CHT SAMs by alkanethiols occurred within 1 h, resulting in the formation of close-packed (√3 × √3) R30˚ domains for alkanethiol SAMs. From these results, we demonstrated that these transient CHT SAMs can be used as temporal layers in soft lithography for protection of reactive surfaces.