Fabrication and tribological properties of a self-assembled silane bilayer on silicon

A self-assembled bilayer film of 1,2-bis(triethoxysilyl) ethane-octadecyltrichlorosilane (BTSE-OTS) was prepared on single-crystal silicon substrates by utilizing BTSE as an intermediate layer. The surface morphology of the film was characterized by small round protuberances, with a surface roughness of about 1.82 nm. Moreover, the BTSE-OTS bilayer film displayed comparable hydrophobicity and nano-scale friction behaviors to the OTS monolayer owing to their identical surface composition and similar surface morphology. The investigation of the micro-tribological properties revealed that the BTSE-OTS bilayer film possessed much higher anti-wear durability and load-carrying capacity than the OTS monolayer while maintaining the low friction coefficient (~ 0.05). The BTSE-OTS bilayer film may find expanded applications in the lubrication of micro-/nano-electromechanical systems as compared to the conventional OTS monolayer.