Ordered Domain Structures of Self-Assembled Monolayers on Au(111) Formed by Endo-Cylic Thiols

Abstract

The spontaneous adsorption of organosulfur compounds on metal surfaces serves as a simple method for achieving a variety of modifications of the metal surfaces, resulting in the formation of organic self-assembled monolayers (SAMs). It has been demonstrated that the resulting SAMs can be used as molecular templates for various technical applications such as wetting, corrosion inhibition, molecular sensors, and nanopatterning. Especially, SAMs prepared from n-alkanethiols and -functionalized alkanethiols have been extensively studied to date, and these SAM systems are now relatively well characterized. To our knowledge, however, there have been very few studies on the formation of cyclic thiol SAMs on gold surfaces. In order to extend the application of SAMs, it is essential to develop and characterize a new SAM system. It is also very important to understand the nature of the self-assembly process and the SAM structure. In this study, we have characterized SAM samples formed on Au(111) by several endo-cyclic thiols using scanning tunneling microscopy and X-ray photoelectron spectroscopy. It was found that surface structures these SAMs such as molecular packing structure and distribution of vacancy islands were strongly influenced by the size of cyclic ring containing the sulfur atom. This result means that the control of ring size is one of crucial factors to tune SAM characteristics.