LIGHT-INDUCED REACTIONS OF POROUS AND SINGLE-CRYSTAL SI SURFACES WITHCARBOXYLIC-ACIDS

Light-induced reactions of Si surfaces with carboxylic acids to genera te Si ester-modified surfaces are studied. The reaction proceeds by ph otoelectrochemical oxidation of porous or (100)-oriented single-crysta l n-type Si in formic, acetic, or trifluoroacetic acid electrolyte sol utions, The reaction products at the porous Si surface are identified by Fourier-transform infrared (FTIR) spectroscopy, Derivatization with esters reduces the photoluminescence intensity of porous Si. X-ray ph otoelectron spectroscopy (XPS) of derivatized single-crystal Si is use d to confirm the compositional and bonding information and to demonstr ate that the same chemistry occurs at a single-crystal Si surface. A m echanism is proposed in which illumination of reverse-biased Si remove s electron density from the Si surface, rendering Si-Si bonds suscepti ble to nucleophilic attack by carboxylic acid. The reaction has a mark ed dependence on light intensity and the Si surface can be photopatter ned by illumination through a mask during derivatization, Ester-patter ned porous Si reacts with CH3(CH2)(7)(CH3)(2)SiOCH3, generating an org anosilane-patterned Si surface.