Self-assembly process of alkanethiol monolayers

To reveal formation of self-assembled monolayers (SAM), we analyzed the mol ecular orientation of SAMs of alkanethiol and the molecular organization in the Lanemuir-Blodgett (LB) and vacuum deposited (VD) films by Fourier-tran sform infrared reflection absorption spectroscopy (FT-IR-RAS) and X-ray dif fraction (XRD). XRD of the LB films suggests that alkanethiol orients norma l to a gold substrate. Alkanethiol in the VD films tilts with a larger angl e on the gold than on the glass substrates. The FT-IR-RAS spectra revealed that the molecular organization in the SAM on the gold (111) surface is dep endent on the immersion time. Alkanethiol in the SAM aligns normal to the s ubstrate, when the molecule undergoes close packing. A stable SAM embedded in a well-ordered monolayer is controlled by the intermolecular interaction of alkanethiol as well as the interaction between sulfur and gold.