外力和门电压下分子器件微观结构的表征

The properties and efficiency of molecular devices is determined by its structure. However, the uncertainty of the structure in molecular junctions still hinder its step to applicable molecular devices. The combination of inelastic electron tunneling spectroscopy with theoretical simulations proves important approach to confirm the conformations in molecular devices. In this project, the structure of molecular junctions controlled by tip-lording force will be studied using the density functional theory (DFT). Based on the inelastic scattering Green’s function theory, the inelastic electron tunneling spectroscopy can be obtained. The relationship of the tip-lording force and gate voltage with the structure of molecular devices could be established by using the DFT calculation and molecular dynamics simulation, and the characterization of the structure of molecular devices could also be achieved combined them with the inelastic electron tunneling spectroscopy. This research mainly includes the impact of tip-lording forces and gate voltage on the structure and transport properties of molecular devices. It is believed that this theoretical approach will simulate the structure of molecular junctions in a more real environment and reflect the relationship between function and structure of molecular devices comprehensively and accurately. The theoretical basis for constructing stable nanoelectronic devices can also be provided based on this project.

分子器件的微观结构决定着其性能和工作效率，但是其结构的难以确定阻碍着分子器件的进一步发展。非弹性电子隧穿谱的探测与理论相结合，为人们确定分子器件的结构信息提供了重要的途径。本项目将基于密度泛函理论（DFT）重点探讨分子结拉伸过程中外力（探针对有机分子施加的力）对分子器件微观结构的调控；利用非弹性散射格林函数方法，研究分子器件的非弹性电子隧穿谱。利用DFT计算和分子动力学模拟结合的方法，建立外力、门电压与分子器件微观结构的关系，结合非弹性电子隧穿谱实现对分子器件的微观结构的表征。研究内容主要包括外力和门电压对分子器件微观结构和输运性质的调制。本项目能更好的模拟实验的制备及测量环境，全面准确地反映分子器件功能与结构的关系，并为构造稳定的纳电子器件提供理论依据。

近年来分子器件的结构及其输运性质一直是人们的一个研究热点，但是相关的实验和理论工作仍存在许多待解的问题。本项目基于密度泛函理论（DFT）研究了对4-硫甲基苯甲酸（M1）、1,4-对硫甲基苯（M2）和4-硫甲基苯钾酸酯（M3）的拉伸过程、力学稳定性及其输运特性。理论计算所得的分子结断裂对应的拉断力和分子电导与实验结果吻合的较好[Phys. Chem. Chem. Phys. 14: 13841–13845 (2012)]；同时利用非弹性散射格林函数方法研究了分子间作用力对双辛烷硫醇分子结非弹性电子隧穿谱的影响，研究结果表明在分子间距较小时会出现较多的横向振动模式，有利于链间隧穿的产生，该结果与Okabayashi等人的推测相符[Phys. Rev. Lett. 104: 077801 (2010)]。