Structural Investigation of 1,1′-Biphenyl-4-thiol Self-Assembled Monolayers on Au(111) by Scanning Tunneling Microscopy and Low-Energy Electron Diffraction

Abstract

Self-assembled monolayers (SAMs) of 1,1'-biphenyl-4-thiol (H-(C(6)H(4))(2)-SH) on Au(111) were prepared from solution or via vapor deposition in ultrahigh vacuum and characterized by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and X-ray photoelectron spectroscopy (XPS). In contrast to the typically observed for densely packed alkane-thiol SAMs on Au(111) (√3 × √3)R30° structure, the densely packed aromatic biphenylthiol SAMs prepared by both methods exhibit an unusual hexagonal (2 × 2) structure. Upon annealing at 100 °C, this structure evolves into the (2 × 7√3) structure resulting in the formation of highly ordered pinstripes oriented along the [1 -1 0] directions. Lower density SAMs, prepared by vapor deposition in vacuum, show mixed structures comprising the hexagonal (2 × 2) structure and two rectangular arrangements with the unit cells of (3√3 × 9) and (2√3 × 8). An extinction of the (3√3 × 9) structure in the favor of the (2√3 × 8) structure is observed upon annealing at temperatures of ~100 °C.

Classical molecular dynamics investigations of biphenyl-based carbon nanomembranes

“…This has two reasons: BPT molecules self-assemble in various structures (hexagonal 2 × 2, herringbone, ) depending for instance on the metallic support [18–21]. But, maybe even more importantly, they rearrange in the process of irradiation in an uncontrolled manner (as they also do at elevated temperatures) [22–23]. Therefore, we investigated the initial arrangements on quadratic, triangular (corresponds to hexagonal 2 × 2), and herringbone lattices.…”

Nanoscale Chemical Imaging of Interfacial Monolayers by Tip‐Enhanced Raman Spectroscopy

“…[2] Despite extensive investigations of interfacial MLs, [1b] quantitative and nondestructive characterization of molecular orientations and intermolecular interactions at the nanoscale is still challenging because of the very small thickness. However,these approaches are limited by optical diffraction, so that they only reveal average molecular information recorded from an area af ew hundred nanometers to am illimeter in size.A lternatively,n anoscale,e ven atomic resolution analysis of MLs can be reached by microscopic methods,s uch as low-energy electron diffraction (LEED), [9] grazing incidence X-ray diffraction (GIXD), [10] and scanning probe microscopy (SPM). However,these approaches are limited by optical diffraction, so that they only reveal average molecular information recorded from an area af ew hundred nanometers to am illimeter in size.A lternatively,n anoscale,e ven atomic resolution analysis of MLs can be reached by microscopic methods,s uch as low-energy electron diffraction (LEED), [9] grazing incidence X-ray diffraction (GIXD), [10] and scanning probe microscopy (SPM).…”

Vibrational modes of ultrathin carbon nanomembrane mechanical resonators

“…34 When the SAM is exposed to electrons, the irradiation would lead to a reduction of 5%-10% in the carbon density. 21 This is associated with the presence of isolated, non-linked molecules in the SAM as a consequence of steric hindrances.…”