硅烯中晶格缺陷的结构及其性质的研究

The two-dimensional hexagonal materials, represented by graphene, have attracted a great deal of attention lately due to their tremendous potential in applied fields such as nanoelectronics. This program will take the atomic-thick silicon nanomaterial, silicene, as the research object, and the first-principles calculations are adopted to extensively study the geometrical structures and stabilities of various point defects and line defects, and the ab initio molecular dynamics at finite temperatures are used to explore the thermodynamic disturbance on their stabilities. The vibration properties of polycrystalline silicene involving different lattice defects are studied, determining the frequencies of the characteristic vibration modes corresponding to different topological structures, to provide theoretical basis for the experimental identification. The electronic structures, transport properties and I-V characters due to the different polycrystalline silicene are calculated, investigating the electronic scattering law of different topological structures in silicene, and the properties influenced by hydrogen adsorption are also considered. Through the studies in this project, the quantum properties of different polymorphous silicene are determined to provide theoretical guidance for the design and fabrication of silicon nanodevices.

以石墨烯为代表的二维六角晶格材料是当前纳米材料研究的前沿热点课题，在纳米电子学领域有良好的应用前景。本项目以单原子层硅纳米材料—硅烯为研究对象，采用第一性原理数值计算方法研究多种点缺陷和线缺陷的结构及其稳定性，并用有限温度下的从头算分子动力学方法检验热力学扰动对这些结构稳定性的影响；研究含有不同晶格缺陷的多晶硅烯的振动性质，确定不同拓扑结构特征振动模的频率，为实验上合成这些材料提供理论指导；研究不同多晶硅烯的电子结构、输运性质和电导特性，给出硅烯中不同拓扑结构对电子的散射规律, 并考虑氢原子的吸附对这些性质的影响。通过本项目的研究，我们将确定不同多晶态硅烯的量子特性，为硅纳米器件的设计和制备提供理论指导。

在本项目的资助下，我们在近三年开展了与硅纳米材料中晶格缺陷的应力场，及纳米带边界吸附对其几何结构、电子能带及其磁性性质影响的研究工作，取得了一系列的研究成果。主要的成果简述如下：1.研究了硅烯中不同单空位缺陷密度周围的应力场，研究发现单空位缺陷间中五边形周围为压缩力场，而畸变六边形周围为拉力场。随着单空位缺陷密度的增加，相互作用的压力场是硅烯平面畸变，而相互作用的拉力场对硅烯的结构影响较小。与其它六角晶格纳米材料相比，硅烯有较大的泊松比但其面内应力较小，因此它对面内应力的改变应该更敏感；2. 系统的研究了H、OH及OHO在多种纳米带，如硅烯、蓝磷烯、第四单硫族纳米材料的边界吸附对其几何结构、稳定性和电子性质的影响。研究发现，和单个H原子的吸附相同，OH在纳米带边界的吸附对纳米带的几何结构影响较小，而由于边界的吸附使边界原子的悬挂电子钝化，这有利于整个系统的稳定，同时，由于受一维纳米带量子受限应的影响，OH和H吸附的armchair纳米带均为半导体，其带隙随着纳米带宽度的变化而呈一定规律的波动。本项目的研究将为电子学和半导体器件的设计和制备提供理论基础。