Theoretical Study Of Charge Transport In Metal Atom Adsorbed On Para-phenylene Vinylene Molecule

In recent years, molecular electronics has aroused considerable interest. Nano electronic devices have provides a great potential for modern application of science.With the development of molecular electronics theory and experimental a lot of interesting phenomenon have been found. Those attractive properties offered by Nano-devices show the potential advantages of Nano scale structures, such as molecular rectification phenomenon, negative differential resistance(NDR) behavior and current switching, etc. Multifunctional molecular devices can greatly improve the integration density of molecular circuits in the future and have great application value in circuit elements, such as high-speed switches, high-frequency oscillators,amplifiers and logic. Multifunctional molecular must show NDR, rectification, and switch performances meanwhile. Although these behaviors have been observed in many devices(such as inorganic, organic, polymeric and molecular, Nano-composites and bio-molecular systems), but the reason for its origin is diverse and is under debate especially in polymeric and organic materials. Scholars try to control and explain these behaviors from various aspects in theoretical calculation(Reverse the molecular structure, Change the contact position, Use Different anchor, Gate voltage, Adsorb of small molecules, Incorporation of impurity atoms, Join the side group).In this paper, we investigated the electronic transport properties in Para-Phenylene-Vinylene(PPV) molecular that adsorb metal atom base on non-equilibrium Green’s function method combined with density functional theory.The main contents are as follows:(1) We investigated the effect of electronic transport when single metal atom adsorbed on PPV molecular base on non-equilibrium Green’s function method combined with density functional theory. The results show that the phenomenon of charge transfer between the metal atoms and PPV molecules has been observed. The charge transfer is related to the electronegativity, alkali metal atom, alkaline earth metal atoms and transition metal atoms tend to lose electrons to improve the electron transport in PPV molecules. In addition we also found that the NDR phenomenonexists when Ca atom、Sc atom、V atom and Fe atom adsorbed on PPV molecular, but we only found this phenomenon in the negative bias when Au atom adsorbed on PPV molecule.(2) We investigated the effect of electronic transport when multiple Li atoms and Li clusters adsorbed on PPV molecular base on non-equilibrium Green’s function method combined with density functional theory. The results show that charge transfer occurred both multiple Li atoms and Li clusters adsorb on PPV molecular and multiple Li atoms more easily lose electrons. A single Li atom adsorbed on PPV molecules to be more conducive to the electronic transmission than Li clusters adsorption.(3) We investigated the length of PPV molecular and Li/PPV molecule how to affect the electronic transport of PPV molecular base on non-equilibrium Green’s function method combined with density functional theory. The results show that in the case of single PPV molecules, the conductivity of Li/PPV molecules is weaker than PPV molecules. The conductivity of Li/PPV molecules is stronger than PPV molecules with the increase of length. There is a linear relation between the logarithms of conductance and the length of PPV molecular, the Li/PPV molecule does not have such relationship and have volatile relationship.