Preparation, characterization and mechanical properties of Y2O3 thin film deposited on sulfonated self-assembled monolayer of 3-mercaptopropyl trimethoxysilane

Silane coupling reagent (3-mercaptopropyl)trimethoxysilane was self-assembled on a single-crystal Si substrate to form a two-dimensional organic monoalyer (MPTS-SAM) and the terminal –SH group in the film was in-situ oxidized to –SO3H group to endow the film with good chemisorption ability. Thus Y2O3 thin film were deposited on the oxidized MPTS-SAM, by enhanced hydrolysis of yttrium nitrate (Y(NO3)3 · 6H2O) solution in the presence of urea (CO(NH2)2) at 80 °C, making use of the chemisorption ability of the –SO3H group. The thickness and refractive index of the films were determined with an ellipsometer. The morphologies of the films were observed on an atomic force microscope. The adhesion strength and friction behavior of the films on the silicon substrate sliding against a steel ball was examined on a UMT-2MT friction and wear test system. It was found that the Y2O3-600 thin film was well adhered to the substrate with a critical load (Lc) of 2.8 N and had excellent antiwear and friction-reduction performance under a low load of 0.2 N. Thus the Y2O3 film might find promising application in the surface-protection of single crystal Si and SiC in microelectromechanical systems (MEMS).