Charge Transport Properties of a Molecular Wire Investigated by the First Principle

The thiol group can be attached to gold surfaces strongly and thus can be used as a bridge formolecularwires in nanoelectronics. By using the density functional theory, the authors have investigated the interaction between a molecule (SH-C8H16-SH) and a gold surfacewith theab initiomethod. The frontier orbit theory and the perturbation theory are employed to determine the constant of the interaction energy quantitatively, which is a parameter in describing the current-voltage properties of molecular wires by the elastic scattering Green function method. The numerical results show that the bonding between the sulfur atom and the gold atom corresponds mainly to the covalent bond. Some molecular orbits are extended over molecule and gold cluster that certainly give channels for the charge transport, and other molecular orbits are localized and the charge transport can take place through the tunnel mechanism. When the bias is low, there is a gap forthe currentof the molecularwire. With the increasingof the bias, the conductance of thewire exhibits in the form of plateaus. The numerical simulation will be helpful for the design of molecular electronic devices.