Formation and Unique Structures of Tolane Disulfide Self-Assembled Monolayers on Au(111)

Abstract

Nanometer-scale surface structures and binding conditions of tolane disulfide (TDS) self-assembled monolayers (SAMs) on Au(111) were investigated by scanning tunneling microscopy (STM) and x-ray photoelectron spectroscopy (XPS). We found that the formation and structure of TDS SAMs on Au(111) strongly depend on experimental conditions such as immersion temperature and time. Molecular-scale STM imaging demonstrated that TDS molecules on Au(111) can form well-ordered SAMs in the 1 mM EtOH and DMF (9:1) solution. The STM images of TDS SAMs are similar to those of tolanethioacetate (TTA) SAMs containing an unique ordered phase. In addition, XPS measurements showed a strong S 2p peak at 162 eV for TDS SAMs on Au(111), implying that the SAMs were formed via chemical reactions between the sulfur atoms and gold surfaces.