Effects of Relative Orientation of Molecules on Electron Transport in Molecular Devices

Effects of relative orientation of the molecules on electron transport in molecular devices are studied by the non-equilibrium Green function method based on density functional theory. In particular, two molecular devices with planar Au₇ and Ag₃ clusters sandwiched between the Al(100) electrodes are studied. In each device, two typical configurations with the clusters parallel and vertical to the electrodes are considered. It is found that the relative orientation affects the transport properties of these two devices completely differently. In the Al(100)--Au₇--Al(100) device, the conductance and the current of the parallel configuration are much larger than those in the vertical configuration, while in the Al(100)--Ag₃--Al(100) device, an opposite conclusion is obtained.