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 25x25 nm(2). At room and 313 K of temperatures, the oblique (root 3x root 3)R30 degrees structure was observed, whereas, at 333 K the superstructure (4 root 3x2 root 3)R30 degrees 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 angstrom x 8.6 angstrom 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).