TRIBOCHEMICAL REACTIONS OF SILICON - AN IN-SITU INFRARED-SPECTROSCOPYCHARACTERIZATION

This paper describes the tribochemical reactions of silicon against a polymer pad as studied by attenuated total internal reflection Fourier transform infrared spectroscopy. The evolution of the silicon surface and chemical species formed on the surface during rubbing have been s tudied in solutions with values of pH 4, 7, and 10. It is shown that t he process of material removal (that can be tailored to function as a form of tribochemical polishing) proceeds most intensively in the solu tion with pH 10. The tribochemical reaction of silicon hydrides, e.g., SiHx and SiOSiHx reversible arrow Si-(OH)(x), (x = 1...3) is observed directly and believed to be the limiting step in the material removal process during rubbing in an alkaline solution. Then, hydrolysis of S i-H bonds leads to the formation of silanol groups on the surface (Si- OH), that in turn weaken the Si-Si backbonds and allow material to be removed from the surface in the form of silicon hydroxide or, most com monly, silicic acid (Si(OH)(4)). The simultaneous action of friction a nd chemical reactions enhances the dissolution of the material at the asperity contact zones, which results in surface smoothing. No evidenc e of the formation and abrasion of surface silica layer has been found during rubbing.