Modulation of Si(100) electronic surface density due to supramolecular interactions of gaseous molecules with self-assembled organic monolayers

We will present the first evidence ever reported in literature of modifications of the carrier surface density in a semiconductor due to weak interactions of gaseous species with self-assembled monolayers (SAMs). SAMs were obtained by nucleophilic reaction onto halogenated Si(100) surfaces, leading to the formation of an array of aromatic rings directly bonded to silicon through a covalent SiC bond. The modulation of the Si surface conductance was studied as a function of temperature (340–570 K) in the presence of trace amounts of oxidants (CO, SOx and NOx) in Ar. A correlation between gas composition and the surface conductance was found and is modelled accounting for weak, reversible interactions between the aromatic ring and the gas molecule.