材料期刊网

The transport properties of S(9) clusters sandwiched between gold electrodes are investigated with a combination of density-functional theory and the nonequilibrium Green's-function method. In general we find a rather large conductance both when the cluster is oriented with its symmetry axis parallel to the transport direction and when it is perpendicular to it. In both cases the transmission is dominated by several closely spaced and extremely broad cluster molecular orbitals so that the transmission coefficient is almost flat around the gold Fermi level. This is only marginally affected by the external bias so that the I-V characteristic remains almost linear at least up to 1 V and for both the orientations. Furthermore the electron transport is only little affected by the bond length between the cluster and the electrodes, with the largest sensitivity found for the perpendicular orientation. Our results are rationalized by analyzing the device density of states projected over the various molecular orbitals.