The electronic transport properties of one benzene-1,4-dithiolate molecule coupled by two aluminum metal leads were investigated by using first-principles method. The influence of the coupling distance between the molecule and the electrodes on I–V curve was studied thoroughly. Our calculations showed that when the system is in the most stable configuration, where the system total energy is the lowest, and the electron transport is in off-resonant state. Starting from the most stable configuration, when we gradually increase the distance between the molecule and electrodes and so decreasing the coupling strength of the molecule and electrodes, the conductance, as well as the I–V curve, does not decrease immediately but increase quickly at first. Only when we separate the molecule and electrodes far enough, the current begins to drop quickly. The total scattering charge density was presented in order to understand this phenomenon. A one-level quantum dot model is used to explain it. Finally, negative differential resistance was observed and analyzed.
First principles design of divacancy defected graphene nanoribbon based rectifying and negative differential resistance device