Two-dimensional ordering of pentafluorobenzenethiol self-assembled monolayers on Au(111) prepared by ambient-pressure vapor deposition.

Formation and surface structures of pentafluorobenzenethiol (PFBT) self-assembled monolayers (SAMs) on Au(111) prepared by ambient-vapor phase deposition were examined by means of scanning tunneling microscopy (STM) as a function of deposition temperature. PFBT SAMs formed at room temperature have disordered phases with bright aggregated domains, which are very similar to benzenethiol SAMs. As deposition temperature increases to 50 degrees C, partially ordered domains and large aggregated domains appeared. High-resolution STM clearly revealed that PFBT SAMs formed at 75 degrees C were composed of long-range, two-dimensional (2D) ordered domains, which can be described as a c(2x radical3) structure. The results of this study clearly demonstrate that deposition temperature is a crucial factor for obtaining PFBT SAMs on Au(111) with a high degree of structural order.