Hybrid molecule-on-silicon nanoelectronics: Electrochemical processes for grafting and printing of monolayers

The hybrid nanoelectronics, i.e., organic molecules deposited on Si exhibiting electronic functionalities is expected to extend the scaling limits of Si microelectronics down to few nanometers. In this review, first we make an overview of the organic molecules exhibiting various functionalities, such as, dielectric, diode, memory and transistor. We then review the literature on electrochemical grafting of organic molecules to Si, which have been carried out using terminal vinyl (CC), ethynyl (CC), halide (Cl, Br, I), tetraalkylammonium salt, diazonium salt and silane as reactant. It has been demonstrated that electrochemistry not only allows grafting of molecules on Si but also provides very useful information on the characteristics of the grafted layers. The electronic functionalities of various electrografted molecules are discussed. An additional advantage of the electrochemical process is that monolayer patterns with spatial resolution in a wide range, i.e. from nanometer to millimeter, can be easily prepared. The recent advances made in the spatial patterning of monolayers using electrochemical lithography are briefly reviewed.