Electrochemical grafting on SOI substrates using aryl diazonium salts

Silicon surface functionalization is a straightforward way to develop hybrid organic/inorganic devices. Using electrochemical grafting of substituted aryl diazonium salts, we obtained organic layers covalently grafted to thin silicon layer surfaces characterized by XPS, ellipsometry and electrochemistry. Electrochemical characteristics of the reduction grafting process were shown to be correlated to several parameters such as the electron affinity of the used molecule, and more importantly to the nature of the silicon: its doping nature and density, its thickness and its preliminary surface treatment. Compared to bulk silicon, we obtained that peak potential values were shifted because of geometrical effects and that the doping density has to be well controlled to anticipate the grafting possibility. By tuning the doping density for p-doped thin silicon layer substrates, we measured a noticeable grafting for the higher doping of 1.6 × 1019 cm−3 and complete electrochemical passivity for the lower doping density of 1 × 1015 cm−3.