Negative differential resistance behaviors in porphyrin molecular junctions modulated with side groups

By applying nonequilibrium Green's functions in combination with the density-functional theory, we investigate the electronic transport properties of molecular junctions constructed by the porphyrin molecule with donor or acceptor side groups. The results show that the side groups play important role on the electron transport properties. Negative differential resistance (NDR) is observed in such devices. Especially for the molecule with electron-donating group (-NH2), two NDR appear at different bias voltage regions, and the origins for both NDR behavior are different. A mechanism is proposed for the NDR behavior. (c) 2008 American Institute of Physics.