Engineering of Si surfaces by electrochemical grafting of p-nitrobenzene molecules

The changes of the band bending and of the nonradiative (nr) surface recombination are investigated by use of photovoltage and photoluminescence techniques during the electrochemical deposition of p-nitrobenzene molecules on atomically flat and rough hydrogenated as well as on chemically oxidized Si(111) surfaces. A simple and well-reproducible procedure has been developed for electrochemical grafting of organic molecules on hydrogenated Si surfaces in aqueous electrolytes. The grafting of a monolayer of p-nitrobenzene molecules on atomically flat $p-Si(111):H$ surfaces induces a change of the band bending of about 0.1 eV and the amount of nr surface defects, $Ns,$ is only slightly increased by a factor of about 3 $(Ns<1011 cm−2)$ with respect to the hydrogenated Si surface. The role of the formation of radicals for the engineering of Si surfaces is discussed.