Tribological Characteristics Of Self-Assembled Monolayers Based On External Of Field Action

Tribological characteristics of self-assembled monolayer has been investigated widely due to the significant theoretical aspects and for application in microelectromechanical systems(MEMS).In the paper, perfluorooctyltrichlorosilane(FOTS) was successfully used for deposition of SAMs onto silicon substrate.The characterization of monolayers before and after UV radiation were explored by contact angle measuring meter, infrared spectroscopy, X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM).Tribological properties of FOTS SAMs were measured by multi-friction wear tester, the effect of load and sliding velocity were explored. Molecular dynamics simulations was used by Materials Studio software to understand the tribological behavior of FOTS SAMs that was affected by electric field.UV radiation can effectively change the modification of FOTS SAMs surface,which makes that the contact angle becomes small and the surface energy becomes big, the surface becomes uneven and the surface becomes hydrophilic. According to the analysis of atomic force microscopy,the surface roughness was increased significantly by UV radiation.Infrared spectroscopy and X ray photoelectron spectroscopy were analysised and the main reason was that: The oxygen in the air was oxidized into ozone,and C-C bond, C-H bond and C-F bond were fractured because of UV radiation.The surface modification of membrane was changed and the strongly oxidizing ozone changed the group-CH2 into hydrophilic groups-COOH.Tribological characteristics of FOTS SAMs was researched,the experiment results showed that:friction coefficient of FOTS SAMs increased with load and sliding velocity increasing before UV radiation,on the contrary, the friction coefficient becomed irregular after UV radiation.Finally the tribological properties of FOTS under the electric field was researched by molecular dynamics simulation.The results showed that:when the electric field was negative, the friction coefficient increased with the electric field strength increasing; when the electric field was positive, the friction coefficient decreased with the electric field strength increasing, when the electric field strength reached a certain strength, the friction coefficient increased with the electric field strength increasing.