Exploration of the chemical bonding forms of alkoxy-type organic monolayers directly attached to silicon

Alkoxy-type organic monolayers on hydrogen-terminated silicon were prepared from 1-undecanol (UN), 1-nonanol (NO), 1-heptanol (HP), and 4-phenylphenenol (PP). These monolayers were characterized based on x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). XPS spectra showed that the lowest amount of SiO_x oxide on the sample of the UN monolayer. On the other hand, a SiO_x peak was clearly observed for the HP, NO, and PP monolayers. The generation of SiO_x in the PP monolayer may have been due to steric hindrance of the aromatic rings. The–CH₂–region in the FT-IR spectra showed that shorter alkyl chains promoted the formation of gauche conformers in the monolayer. This increase of gauche conformers was determined to have caused the generation of SiO_x in the alkyl monolayers. © 2004 American Vacuum Society.