Heterodimeric electon-donor/electron-acceptor charge-transfer complexes chemisorbed onto Au(111) by attachment of the electron-donor to the surface have been characterized by scanning tunneling microscopy and Kelvin probe experiments. Conductance measurements exhibit nearly Ohmic I(V) responses at low bias. The electrical
properties of the charge-transfer complex are vastly different than those of the electron-donor alone which exhibits insulating behavior at low bias. In an extension of this work, strategies are being developed for attachment of charge-transfer complexes to semiconducting or insulating surfaces. Fabrication of nanoscale molecular electronic devices is being investigated by attaching one component of a charge-transfer complex to a silicon surface by chemically directed self-assembly. The single component-functionalized surface is then used as a substrate on which the second component of the charge-transfer complex is deposited by the atomic force microscopy method, dip-pen nanolithography (DPN).
Derivatives of hexamethylbenze (electron-donor) with terminal olefins attached to crystalline silicon surfaces via hydrosilylation form monolayer-functionalized silicon surfaces that are expected to have insulating properties. Well-defined features can be “drawn” onto the donor-functionalized surfaces by DPN using tetracyanoethylene (electron-acceptor) as the "ink." The resulting charge-transfer complex nanostructures have conducting properties suitable for
device function and are flanked by an insulating monolayer, thus creating "wires" made from charge-transfer complexes.