Investigation Of Electrical Transport Property For Tetracyclopentadienyl Complex Compounds

With the rapid development of science and technology, the traditionalsemiconductor devices are faced with great technology and economic challenge.Electronic devices are continually miniaturized and have been close to the atomic ormolecular scale. Mankind begin to seek stable and effective miniature components atthe molecular level. Aromatic molecules have unique electrical properties because offree π-electrons in the molecules, which have gained considerable attention of manyexperimental and theoretical researchers. Using the first-principles density functionaltheory (DFT) and non-equilibrium Green’s function (NEGF), the electronic transportcharacteristics for tetracyclopentadienyl modified with C, Si, Be, Mg, Ca atoms havebeen investigated.Firstly, we investigate the electronic transport characteristics for the threetetracyclopentadienyl systems modified with C and Si atoms. The geometricalstructures of complex molecules SiSi@TCP, CSi@TCP, and CC@TCP are optimizedusing DMol3on the basis of the first principle of DFT, and verify the stable structureby frequency analysis. The average bond lengths of left and right moieties for the threemolecules are used to describe their symmetrical properties. The NEGF implementedin ATK is used to calculate the equilibrium conductance, molecular projectedself-consistent Hamiltonian, I–V curve, transmission spectra and density of states.Results show that the equilibrium conductance of SiSi@TCP system is larger thanthose of CC@TCP and CSi@TCP systems by two orders of magnitude. The I–V curvesshow that the SiSi@TCP system demonstrates a switch effect, whereas CC@TCPdemonstrates significant NDR behavior under minus bias. A weaker NDR effect isobserved in the CSi@TCP system at larger bias.In order to find more molecules to make various molecular devices, theelectronic transport characteristics for tetracyclopentadienyl modified withalkaline-earth metal Ca atoms are investigated. Its geometrical structure is optimized,and the equilibrium conductance, the transmission spectra and the I–V curve arecalculated by using ATK. Switch behavior is shown in the results. Finally, we explored the impacts of bridge S atoms between molecule andelectrode on the electronic transport properties of biberyllocene and bimagnesocene.Their geometrical structures with sulfur and without sulfur are all optimized. ThenATK is used to calculate the equilibrium conductance, transmission spectra, I–V curveand so on. Results show that S atoms have a great influence only to biberyllocene onthe equilibrium conductance, but both to biberyllocene and bimagnesocene on the I–Vcurves. The I–V curves show that the biberyllocene and bimagnesocene with sulfurdemonstrate a switch effect, whereas bimagnesocene without sulfur demonstratessignificant NDR behavior both under plus and minus bias. However, biberyllocenewithout sulfur oscillates in its dependence on the bias voltage. These studies canprovide some theoretical guide to design and manufacture various molecular deviceson the basis of tetracyclopentadienyl modification with different atoms.