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, SO, and NO,) 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. (C) 2001 Elsevier Science B.V. All rights reserved.