分子线电子输运特性的第一性原理研究

Charge Transport Properties of a Molecular Wire Investigated by the First Principle

从第一性原理出发 ,利用密度泛函理论研究了SH -C8H16-SH分子和金表面的相互作用 ,并利用分子前线轨道理论和微扰理论定量地确定了该相互作用能常数 ,然后 ,利用弹性散射格林函数方法研究了该分子与金表面形成的分子线的伏 安特性 .研究结果表明 ,当含有硫氢官能团的有机分子化学吸附于金表面时 ,硫原子将与金原子形成以共价键为主的混和键 ,此时 ,扩展的分子轨道使分子线的电导呈现出欧姆特性 ,而对于局域的分子轨道 ,电子的输运只能通过隧道效应来实现 .对分子线伏 安特性的计算结果显示 ,在零偏压附近 ,存在一个电流禁区 ,随着偏压的增加 ,分子线的电导呈现出平台特征 .

The thiol group can be attached to gold surfaces strongly and thus can be used as a bridge for molecular wires in nanoelectronics. By using the density functional theory, the authors have investigated the interaction between a molecule ( SH-C8H16- SH) and a gold surface with the ab initio method. The frontier orbit theory and the perturbation theory are employed to determine the constant of the interaction energy quantitatively, which is a parameter in describing the current-voltage properties of molecular wires by the elastic scattering Green function method. The numerical results show that the bonding between the sulfur atom and the gold atom corresponds mainly to the covalent bond. Some molecular orbits are extended over molecule and gold cluster that certainly give channels for the charge transport, and other molecular orbits are localized and the charge transport can take place through the tunnel mechanism. When the bias is low, there is a gap for the current of the molecular wire. With the increasing of the bias, the conductance of the wire exhibits in the form of plateaus. The, numerical simulation will be helpful for the design of molecular electronic devices.