Theoretical Studies On Electronic Transport Properties Of Ethylthiophene Molecules

In the last few decades, functional electronic device construction by use of single molecule has become an increasing interest in molecule electronic. With continuous developing in experimental techniques in the late90s, many experimental groups carried out experimental research work on a number of molecular devices, using STM technology, light camera technology, LB film technology, self-assembly technology, organic molecular beam epitaxy technology. They found that some molecular devices have many useful functions, such as molecular switches, molecular memory, negative differential conductance, molecular FET characteristics. At the same time some theoretical groups have devoted to study of electrics properties of single molecules and obtained ample proofs. Although molecular electronic has made significant headway, due to lack of the molecular characteristics and electronic transport mechanism, one cannot guide experiments well. Therefore, the design and simulation of molecular devices in theory can provide theoretical guidance and reduce the twists for experiments.Now, with from the domain of electronic of benzene and its derivatives on the basis of aromatic ring as the main materials to study the molecular devices, organic matter this kind of organic matter to increases the chances of the electron transport. Thiophene molecules has a good conductivity as candidate materials of solar cell. So in this thesis, thiophene molecules are assembled with gold atoms cluster as molecular devices to study their volt-ampere characteristics, electrical and electrical, electrical and electronic transmission spectrum. In order to better achieve the electrodes and the coupling effect of free molecule, choose limited S atomic chemical adsorption on two Au (1,1,1) between groups of clusters, which comprise the so-called extended molecule, can very well simulate the mutual coupling effect on the surface of the molecules and the Au electrode, and form a covalent bond with an ionic bond.Based on density functional theory and nonequilibrium green’s function, the volt-ampere characteristics, differential conductance spectrum, and electron transportation are studied, the influences of k-point choosing to the energies and volt-ampere of the molecular devices are discussed. It is shown that the molecular energies are conregential with the increase of k-point. Secondly, the influences of the molecular length and torsion for the thiophene poymer to the electronic transportation are investigated. It shows that the electric current of the molecular device decreases with the increase of molecular length and torsion.