Journal of the Electrochemical Society, Vol.145, No.7, 2465-2470, 1998
Tribochemical reactions of silicon : An in situ infrared spectroscopy characterization
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 studied in solutions with values of pH 4, 7, and 10. It is shown that the process of material removal (that can be tailored to function as a form of tribochemical polishing) proceeds most intensively in the solution 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 Si-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 commonly, silicic acid (Si(OH)(4)). The simultaneous action of friction and chemical reactions enhances the dissolution of the material at the asperity contact zones, which results in surface smoothing. No evidence of the formation and abrasion of surface silica layer has been found during rubbing.
Keywords:CRYSTALLINE SILICON;ALKALINE-SOLUTIONS;SI(100) SURFACES;NAOH SOLUTIONS;WATER;DISORDER;FREQUENCIES;DISSOLUTION;ABSORPTION;INTERFACE