Dipole-induced structure in aromatic-terminated self-assembled monolayers: A study by near edge x-ray absorption fine structure spectroscopy

Near edge x-ray absorption fine structure spectroscopy (NEXAFS) was used to study the structure of self-assembled monolayers presenting aromatic rings at a surface. It was observed that the fluorine substitution at asymmetric positions in the aromatic rings was used to generate a layer of dipoles at the surface of the monolayer. It was observed that the fluorine substituted aromatic rings were more ordered than unsubstituted aromatic rings by a factor of two based on the polarization dependence of the lowest C 1s to π ^* transition. It was found that this result was consistent with the influence of dipole-dipole interactions and quadrupolar interactions between the aromatic groups due to the substitution of fluorine atoms.