Abstract
By immersion into octanethiol (CH3(CH2)7SH) and dodecanethiol (CH3(CH2)11SH) solutions, self-assembled monolayers (SAMs) of molecules are observed to form on both types of Au(111), single crystal and surface on flame-annealed gold ball, by scanning tunneling microscopy (STM). These ordered structures are consisted of dark pits, 2.5□ in depth, )R30o and c(4 2) superlattices, and dark mesh, 1.0□ in depth, between them. SAMs are also observed in the dark pits. Thus, the dark pits are confirmed to be craters of monatomic layer in depth. All these observations are consistent with the reports in literature. The density of dark pits are found to increase with immersion time on both types of Au(111) surfaces. The structures of SAMs can be well resolved by STM only when higher tunneling impedances or lower tunneling currents are applied.