基于硼烯和石墨烯的分子二极管设计及其整流机理的第一性原理研究

Constructing functional nanoelectronic devices based on single molecules is one of the most important research frontiers in nanoelectronics. As key components in logical circuits, molecular diodes play an essential role in the development of molecular devices. However, their application is severely hindered by the difficulties in preparation and the low efficiency of rectification. The novel two-dimensional (2D) materials, borophene and graphene, are promising candidates to break through the deadlock to build high-performance molecular diodes due to their excellent electrical properties. In this proposal, azulene-like molecular diodes based on borophene and graphene will be constructed, and their electronic transport properties will be studied by using the nonequilibrium Green’s function method in combination with density functional theory. Furthermore, the rectification mechanism of molecular diodes which are modulated by various factors, such as clipping pattern, doping, defects and stretching, will be deeply investigated. Besides, the conjugation effect of azulene-like molecules will be analyzed to understand the relationship between molecular intrinsic properties and rectifying behaviors of molecular diodes. In addition, the method of describing local charges will be further developed to simulate various ions for the cases of devices working in solvents. Accordingly, the ionic effect in solvents on rectifying properties of single molecular diodes will be clarified. This proposal will provide a significant theoretical foundation for understanding the electronic transport properties of molecular diodes based on 2D materials, and exploring design schemes of high-performance molecular diodes.

利用单分子构筑功能性纳米电子器件是纳电子学的前沿研究领域之一。分子二极管作为逻辑电路的关键组成部分，在分子器件的发展过程中起着至关重要的作用。但目前分子二极管构建难度大且整流效率低严重制约了其应用。新型二维材料有望突破此限制，它优异的电学特性为高性能分子二极管的构造提供了重要的基础。本项目将以硼烯和石墨烯两种二维材料构建的薁类共轭分子二极管作为研究对象，采用基于密度泛函的非平衡格林函数方法研究其电荷输运特性。深入探究剪裁、掺杂、缺陷和拉伸等几何结构修饰对分子二极管整流效果的调控机理，揭示薁类分子的共轭效应与二极管整流性能之间的关系。在此基础上，针对实验中离子溶液环境的情况，通过发展描述局域电荷的方法表征带电离子，阐明溶剂效应对分子二极管整流效果的影响。本项目的开展将为人们理解基于二维材料分子二极管的电荷输运性质和探究高性能分子二极管的设计方法提供重要的理论依据。

分子电子学作为纳电子学的主要分支是采用单分子构筑纳米电子器件实现功能化的有效途径。设计并探究单分子结的电荷输运性质不仅有利于发现新奇的物理现象，而且有利于构建功能性分子器件。近年来新型二维材料的发展进一步推动了分子电子学的进程，其尺寸限域而具有的独特电学特性为设计高性能分子器件提供了可能性。本项目采用基于密度泛函的非平衡格林函数理论，探究了薄膜材料连接单分子形成纳米器件的结构模型，理解了基于薄膜材料构建的准一维分子结的形成机理。在此基础上，进一步研究了单分子器件的电荷和自旋输运性质。一方面，通过探索二维材料石墨烯、硅烯和锗烯的电学特性，采用剪裁纳米带、氢化二维材料等结构修饰方法，实现了整流比高达10000的巨整流效应。另一方面，借助对称结构石墨烯纳米带波函数的宇称特性，设计出具有自旋整流、自旋过滤和巨磁阻等特征的多功能自旋分子器件。本项目对探究二维材料的电学性质，理解单分子结的电荷与自旋输运机理，提升分子器件工作性能，理论指导实验设计功能性分子器件等具有重要的意义。