Transport Mechanism through Tour Wire Nanostructure: Effect of Functional Group

The purpose of this study is to manifest the roles such as the current-controlling behaviors played by the functional groups. Also, the effect of temperature on the electron transport behavior of the system is analyzed by varying the temperature of the top and bottom electrodes and the central molecular region. We focus on the temperature effect of the phenyl-ethylene oligomer, so-called “Tour Wire” (TW), comprised of phenyl rings separated by triplet-bonded carbon atoms that form a long rigid molecule with
-conjugated delocalized frontier orbitals. To improve the accuracy of the calculation and to reduce the significant computing time the non-vanishing integrals (two electron integrals) are replaced by the associate parameters. The general shapes of the zero transmission spectra for the three TW systems more or less resemble the same with the narrow transmission peak at either side of the Fermi level. By varying the temperature, the energy levels of the isolated molecules are broadened and considerable variation was observed in the transmission of the TW systems. The result shows that for the TW and TW–NH2 systems, the conductance increases with increasing temperature indicating the dominating transport mechanism which is due to thermionic emission. These theoretical results will be helpful to design and fabricate future molecular electronic devices and circuits with specific properties.