Nanoscopic Investigation of the Self-Assembly Processes of Dialkyl Disulfides and Dialkyl Sulfides on Au(111)

The formation of striped phases of dialkyl disulfides and dialkyl sulfides on Au(111) and graphite has been monitored by scanning tunneling microscopy (STM) to investigate differences in adsorption of the sulfide to the gold surface. Striped phases formed by C18H37S- moieties after S−S bond cleavage of dioctadecyl disulfide on the gold surface were observed. On the other hand, self-assembled monolayers (SAMs) of dioctadecyl disulfide and dioctadecyl sulfide adsorbed on a graphite surface displayed long-range, well-ordered monolayers with one striped pattern that shows uniform periodicity as a function of molecular length via nondissociative adsorption. In the case of dioctadecyl sulfide SAMs on gold, molecular ordering was identical in periodicity and pattern to the striped phase of SAMs formed by physisorption on the graphite surface. In addition, the striped phase of dioctadecyl sulfide SAMs formed upon a 22 × √3 surface reconstruction of Au(111) was clearly observed for the first time in the SAM system...