Novel Method to Prepare Organosilane Monolayers on Solid Substrate

A novel and convenient method to prepare organosilane monolayers was proposed. Pure water was put onto a cleaned silicon wafer and then a toluene solution of n-trichloro(octadecyl)silane (OTS) was spread on it. X-ray photoelectron spectroscopy and atomic force microscopic observation revealed that an OTS monolayer was successfully formed on the solid substrate after the water was evaporated. The static water contact angle of the silicon wafer covered with the OTS monolayer was 105°. Molecular aggregation states of the OTS monolayer were examined by electron diffraction, Fourier transform infrared spectroscopic, X-ray reflectivity, and grazing incidence X-ray diffraction measurements. The prepared OTS monolayer was in a two-dimensional hexagonal crystalline state at 293 K and alkyl chains of the OTS molecules were oriented normal to the surface. Also, the alkyl chains in the monolayer were highly ordered, although the experimental procedure for the monolayer preparation was quite simple. The development of this novel method to prepare a low energy surface will contribute to the material science as well as having industrial applications.