Electrochemical Methoxylation of Porous Silicon Surface

An electrochemical process aiming at the grafting of methoxy groups on the hydrogenated porous silicon surface at room temperature has been designed. This takes place through partial anodic dissolution of porous silicon in anhydrous methanol. A dissolution mechanism is proposed by analogy with that of the anodic dissolution of silicon in aqueous fluoride media. The methoxylated surface exhibits improved optical characteristics (increased photolum†nescence efficiency, blue shift of the emission), similar to porous silicon anodically oxidized in a nonfluoride aqueous electrolyte. Its stability against aging is also improved as compared to that of the hydrogenated surface, but without reaching the stability of anodically oxidized porous silicon. This residual sensitivity to aging is ascribed to the nonnegligible amount of SiH species which remains on the methoxylated surface upon the modification process.