Control of two-dimensional structure of tolanethioacetate self-assembled monolayers on Au(1 1 1)

Nanometer-scale structure and binding condition of tolanethioacetate (TTA) self-assembled monolayers (SAMs) formed in various solutions on Au(1 1 1) were investigated by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). STM imaging revealed that two-dimensional (2D) ordered TTA SAMs with an overlayer structure of ( 13 × 5 ) R24 ° on Au(1 1 1) were formed in a polar protic solvent, while TTA SAMs with disordered phases were formed in a polar aprotic solvent and a nonpolar solvent. In addition, XPS measurements showed that the XPS spectra for TTA SAMs formed in a nonpolar solvent were markedly different from those formed in a polar protic solvent, indicating that the binding condition of TTA SAMs was influenced by the solvent properties. In this study, we found that 2D ordered TTA SAMs on Au(1 1 1) can be obtained by controlling the properties of solvents, in particular, by using a polar protic solvent.