Molecular-scale investigation of octanethiol self-assembled monolayers on Au(1 1 1) prepared by solution and vapor deposition at high temperature

Octanethiol (OT) self-assembled monolayers (SAMs) were prepared on Au(1 1 1) by solution and ambient-pressure vapor deposition methods at 75 °C. Surface structures were investigated with scanning tunneling microscopy (STM) to understand molecular-scale structural features of OT SAMs according to deposition method and temperature. OT SAMs prepared by solution deposition have large-ordered domains corresponding to ∼100 nm with a c(4 × 2) superlattice, but disordered phases and structural defects in the ordered domains also formed from desorption of adsorbed molecules from the surface. However, high-quality OT SAMs were obtained by vapor deposition and showed large well-ordered domains of 20–50 nm without formation of disordered phases. The formation of vacancy islands was markedly influenced by deposition method. This study demonstrated that the formation and structure of OT SAMs on Au(1 1 1) were influenced by deposition method and temperature.