Preparation of self-assembly monolayer by scratching Si(100) surface in the presence of aryl diazonium salts

Mechanical scratching and chemical self-assembling can be combined to fabricate nano- or micro-scale functional structures on the oxide-coated silicon. The chemo-active species, such as NO₂C₆H ₄ groups, can be produce from aryldiazonium salt due to the breaking of chemical bond of silicon substrate when the diamond tool scratches the silicon sample in the presence of 4-benzoic nitryl diazonium tetrafluoroborate (NO₂C₆H₄N₂BF₄). 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 (AFM). We propose that chemomechanical reaction, which occurred during scratching the silicon surface, produce NO₂C₆H₄ groups from aryldiazonium salt. The NO₂C₆H₄ groups further bond with surface Si atoms via Si-C covalent bonds as confirmed from Infrared Spectroscopy (IR) results. To better understand the framework of the self-assembly monolayers (SAMs) on Si (100) surface, the first principles calculation at density functional theory levels has been employed to investigate the binding energy, bonds length and bonds angle. The reduced energy of system illuminates that the SAMs can be fabricated easily between aryldiazonium salt and Si (100) surface. The stability of system can be improved and SAMs can firmly stay on Si (100) surface.