Self-assembled monolayers (SAMs) formed from thiophenol, 1,1′-biphenyl-4-thiol, 1,1′;4′,1′′-terphenyl-4-thiol, and anthracene-2-thiol on polycrystalline Au and Ag were characterized by X-ray photoelectron spectroscopy and angle-resolved near-edge X-ray absorption fine structure spectroscopy. With the exception of the poorly defined thiophenol film on Au, all thioaromatic molecules were found to form highly oriented and densely packed SAMs on both substrates. The molecular orientation and orientational order of the adsorbed thioaromatic molecules depends on the number of aromatic rings, the substrate, and the rigidity of the aromatic system. The molecules, which on average are slightly inclined with respect to the surface normal, show a less tilted orientation with increasing length of the aromatic chain, and as observed for aliphatic SAMs, they exhibit smaller tilt angles on Ag than on Au. However, the difference in the tilt angles for aromatic SAMs on Au and Ag is smaller than that observed in the aliphatic films. A comparison of the monolayers formed from p-terphenylthiol and anthracenethiol films suggests that a higher molecular rigidity has only a slight effect on the final molecular orientation within the respective SAMs.

Articles you may be interested inElectron-beam-induced alteration of the dielectric properties of sandwiched self-assembled organic monolayers Modification of thiol-derived self-assembling monolayers by electron and x-ray irradiation: Scientific and lithographic aspects

Chemically defined surface patterning has been achieved via irradiation with low‐energy electrons. Irradiation of nitro‐arene‐thiol monolayers leads to the reduction of the nitro groups to amino groups, which can then be further chemically modified. The Figure shows such a monolayer that was irradiated through a copper grid followed by acylation with trifluoroacetic acid anhydride.

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Articles you may be interested inSelf-assembled monolayer cleaning methods: Towards fabrication of clean high-temperature superconductor nanostructures Appl. Phys. Lett. 86, 154104 (2005); 10.1063/1.1899753 Electrode modification by electron-induced patterning of self-assembled monolayersWe show the fabrication of gold nanostructures using self-assembled monolayers of aliphatic and aromatic thiols as positive and negative electron beam resists. We applied a simple and versatile proximity printing technique using focused ion beam structured stencil masks and low energy ͑300 eV͒ electrons. We also used conventional e-beam lithography with a beam energy of 2.5 keV and doses from 3500 to 80 000 C/cm 2 . Gold patterns were generated by wet etching in KCN/KOH and characterized by atomic force microscopy and scanning electron microscopy. The width of the finest lines is ϳ20 nm; their edge definition is limited by the isotropic etching process in the polycrystalline gold.