A combination of chemical and mechanical method has been proposed to fabricate modified surface on the oxide-coated silicon. When the diamond tool scribes the silicon sample in the presence of 4-benzoic acid diazonium tetrafluoroborate (COOHC6H4N2BF4), the chemoactive COOHC6H4 radical can be generated from aryldiazonium salt due to the breaking of chemical bond of silicon substrate. They may then induce grafting of an organic monolayer on the substrate via Si-C connection. The surface morphologies before and after chemomechanical reaction are characterized with atomic force microscopy. X-ray photoelectron spectroscopy confirms the presence of COOHC6H4 and shows a steady increase in the amount of carbon on the exposed fresh Si surface. Infrared spectroscopy suggests that COOHC6H4 groups bond with surface Si atoms via Si-C covalent bonds. To the best of the authors knowledge, this is the first report of the chemomechanical preparation of self-assembled monolayers on oxide-coated silicon in the presence of aryldiazonium salt. The method described in this article will have important implications for building nano- or microscale functional structures.