Formation of Gold-Methanethiyl Self-Assembled Monolayers

摘要

Self-assembled monolayers (SAMs) may be useful in next-generation electronic devices as ordered organic layers tailor surface properties. Thiol—gold SAMs, formed by exposing thiols or disulfides to Au(111), are the most studied systems, owing to their stability and highly ordered structures. However, surface pitting can occur, and the surface chemistry is clearly very complex. We consider the properties of the iconic shortest SAM that formed by chemisorbed methanethiyl radicals CH_3S .Scanning tunneling microscopy (STM) experiments indicate that the initial chemi-sorption of dimethyldisulfide (DMDS) on the (22 × 3~(1/2)) reconstructed Au(111)surface proceeds without surface pitting. At moderate coverage the surface reconstruction is lifted and surface pitting sets in, until a regular (l×l) hexagonal monolayer lattice appears. Since in the reconstructed surface 46 atoms occupy 44 bulklike positions, forming two rows of 23 atoms along the (110) direction (see Figure la), SAM production involves a significant surface transformation.