Low-Coverage Decanethiolate Structure on Au(111):  Substrate Effects

Abstract

The effects that a reconstructed (herringbone) and stepped Au(111) surface have on the structure of submonolayers of decanethiolate were studied by variable-temperature scanning tunneling microscopy (VT-STM) between 25 and 60 °C. At 25 °C, formation of lattice gas (R) species at low coverages alters the herringbone structure by shortening the periodicity of the elbows from 25 to 15 nm. In addition, small β-phase islands nucleate and grow anisotropically in regions of fcc stacking. These domains grow by incorporating nearby lattice gas species, consuming herringbone ridges and altering the remnant ridges that surround them. In a given domain, the β-phase rows take one of the three 〈121〉 directions of the Au(111) surface. No β-phase is found in regions of hcp stacking or in the bridge atom regions separating the fcc and hcp stacked regions. Increasing the coverage increases the β-phase island size at the expense of herringbone ridges that bound the domains. For a coverage that saturates the β-phase (∼0.25 of the closest packing achievable), raising the temperature to 30 or 40 ο C increases the average size of the β-phase islands by condensation of neighboring islands with no evidence, at the selected coverage, for the presence of any other thiolate phase. At 60 °C, well above the thiolate melting point to form the -phase, small β-phase domains remain. These are stabilized by boundaries of two types remnant herringbone and step edges and for a given domain, fluctuations of the distribution between the -and β-phases were observed on a time scale of minutes.

Cooperative light-induced molecular movements of highly ordered azobenzene self-assembled monolayers

“…The high electron density at the Au-S bond has been shown to originate a high contrast in STM images, allowing the easy identification of the Au-thiols binding sites (33). Therefore, we attribute the brighter spot to the straight biphenyl- thiolated side of the aromatic chain (34).…”

Collision-induced annealing of octanethiol self-assembled monolayers by high-kinetic-energy xenon atoms

“…The various lattice structures of alkanethiol SAMs on metal surfaces, especially on Au͑111͒, have been studied extensively, and alkanethiol molecules are known to form multiple surface phases. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] Scanning tunneling microscopy ͑STM͒ is an important tool for investigating alkanethiol monolayers. STM investigations have probed the surface structure and, in some cases, the surface dynamics of SAMs at the scale of individual molecules.…”

“…STM investigations have probed the surface structure and, in some cases, the surface dynamics of SAMs at the scale of individual molecules. For alkanethiols on Au͑111͒, STM has been used to characterize a large number of complex lattice structures, [13][14][15][16]20,21,23,25,[27][28][29][30][31][32][33][34] to investigate phase transitions, 17,18,30,[35][36][37][38] and to elucidate mechanisms for monolayer formation and growth. 19 Sibener and co-workers [39][40][41][42] and Morris and co-workers [43][44][45][46] have published the results of beam-surface scattering experiments and have provided extensive detail about the properties of rare-gas/alkanethiol collisions.…”

Self‐organized nanotemplating on misfit dislocation networks investigated by scanning tunneling microscopy

“…10) (Nenchev et al, to be published). Pattern in methanethiol self-assembled monolayers (SAMs) (Fitts et al, 2002;Maksymovych et al, 2006;Poirier and Pylant, 1996) forms as a 2D imprint of ordered Co cluster-array grown on the herringbone pattern of Au(111). This cluster-array and dislocation pattern imprinting process can be applied to a wide variety of sulfur-containing molecular films.…”