中文摘要：

合成了12个OPV分子导线（分成乙酰巯基与氨基端基两个系列）,采用导电原子力显微镜和扫描隧道显微镜-裂分结的方法对该类分子导线的电学性能进行了表征.通过分析单分子电阻与分子长度、温度以及电场的依赖关系,发现OPV分子导线的电子传输机理在临界长度为2.0 nm处发生了由隧穿传导向跳跃传导的转变.通过对比分子末端分别为巯基和氨基的单分子电导值,考察了不同的连接基团对OPV分子导线电子传输性能的影响,发现末端基团只影响分子的接触电阻,但不改变分子导线本身的电子传输机理.利用密度泛函理论和非平衡格林函数方法对OPV分子导线的电学特性进行了理论研究,结果表明分子的前线轨道能级与金电极的相对位置决定了OPV分子导线的电子传输机理.

英文摘要：

To understand the charge transport mechanism of oligo（p-phenylene vinylene）（OPV） molecular wires,twelve OPV molecular wires were synthesized,whose anchoring groups were thioacetyl（SAc） and amine（NH2）,respectively.Conductive probe-atomic force microscopy and scanning tunneling microscopy-break junction（STM-BJ） methods were employed for the characterization of the electron transport properties of these OPV wires.A detailed analysis of the single-molecular resistance as a function of molecular length,temperature as well as electric field,revealed a clear transition of charge transport mechanism from tunneling to hopping at a critical length of 2 nm.The effect of anchoring groups on the charge transport properties was investigated by comparing the single-molecular conductance of OPV wires terminated with dithioacetyl and diamine groups.The results showed that the anchoring groups indeed affect the contact resistance,but they do not change the intrinsic charge transport mechanism.Moreover,the electronic properties of the OPV wires were studied theoretically using a combination of density functional theory and non-equilibrium Green＇s functions method.The calculated results demonstrated that the energy difference between the frontier molecular orbitals and the metal Fermi level played an important role in controlling the conduction mechanism of the OPV wires.