Experiment of the molecular deposition (MD) films with and without alkyl terminal de-posited on the silicon wafer were conducted by using nanoindentation. It was found that MD filmsand alkyl terminated MD films exhibit higher critical load (scratch resistance or adhesive strength)and lower coefficient of friction compared with the silicon substrate. Critical load (scratch resis-tance) increases with the number of layers, and coefficients of friction of those MD film with alkylterminal are still best for the same layer of MD film.
The solidification and interfacial slip in nanometer-scale lubricating films as well as the contact and adhesion of metal crystals have been studied via molecular dynamics simulations. Results show that the critical pressure for the solid-liquid transition declines as the film thickness decreases, in-dicating that the lubricant in the thin films may exist in a solid-like state. It is also found that the interfa-cial slip may occur in thin films at relatively low shear rate, and there is a good correlation between the slip phenomenon and the lubricant solidification. The simulations reveal that a micro-scale adhesion may take place due to the atomic jump during the process of approaching or separating of two smooth crystal surfaces, which provides important information for understanding the origin of interfacial friction.
