Most microelectromechanical systems (MEMS) are fabricated using semiconductor and ceramic materials such as Si, and SiO2, and Al2O3 which are hard, brittle materials and are not commonly used for mechanical devices. MEMS components are very small and lack power or much inertia when in motion, so they are highly susceptible to the influence of adhesive and surface forces. MEMS lubrication schemes involving vapor phase lubrication have been proposed as a means of continuously replenishing lubricant films on MEMS surfaces.

 

We present synchrotron based near edge x-ray absorption fine structure (NEXAFS) spectroscopy results of vapor deposited monolayers and submonolayers on SiO2 and Al2O3 substrates under different process conditions. NEXAFS is a powerful non-destructive method in which soft x-rays are absorbed followed by the excitation (transition) of electrons from a core K- or L-level to partially filled into empty low-lying antibonding molecular states. Bond orientation information is deduced from the changes in the intensity of the resonances upon rotating the substrate normal in the plane of incidence of the polarized synchrotron beam.

 

Carbon K-shell NEXAFS performed at different incidence angles revealed that the vapor deposited fluorodecyltrichlorosilane (FDTS) molecules on silicon and alumina substrates produced self-assembled monolayered films that have high surface coverage and can be highly oriented. Using the NEXAFS technique, dichroic ratios (based on the σ*C-F resonance) of the order of 0.5 have been obtained, thus revealing that these FDTS films have a high degree of molecular orientation. Orientation and coverage comparisons for water wiped and isopropylalcohol wiped FDTS as well as directly vapor deposited FDTS will be presented. The implications for the design of surfaces and interfaces for stiction control in MEMS devices will also be discussed.