Orientation and self-assembly of hydrophobic fluoroalkylsilanes

Fluoroalkylsilanes (FAS) prove to be an interesting water-repellent coating for the recently discussed "superhydrophobic surfaces". The FAS investigated here form a self-assembled monolayer when brought into contact with a surface. They arrange at a high degree of orientation with their molecular axis perpendicular to the substrate surface. The film stability and the film thickness were observed using X-ray photoelectron spectroscopy. The orientation of the FAS molecules was investigated with polarization-dependent X-ray absorption near edge spectroscopy (XANES). Furthermore using density functional theory the molecular structure was calculated in order to aid in the interpretation of the polarization dependence of the XANES spectrum at F K-edge.