In The Direction of Perfect Design of Self-Assembled Monolayers: Scanning Tunneling Microscopy Study of SAMs Made of Decanethiol on Au(111)

Self-assembled monolayers (SAMs) of decanethiol (C10) on Au(111) substrate, prepared at room and elevated temperatures, were studied using scanning tunneling microscopy (STM). Preparation at elevated temperature results in highly-ordered layers with large ordered domains spreading on gold surface with dimensions easily exceeding 25×25 nm2. At room and 313 K of temperatures, the oblique (√3×√3)R30° structure was observed, whereas, at 333 K the superstructure (4√3×2√3)R30° was covering the gold substrate with four molecules per unit cell. The high-quality of STM results enables us to resolve four symmetry-inequivalent C10 molecules per 10 Å× 8.6Å unit cell. The dissimilarity in topographic heights of C10 molecules on Au(111) was attributed to the binding of sulfur headgroup moiety of C10 molecules with different adsorption sites on Au(111).