经过表面改性的自支撑的锗烯的能带结构和光学性能研究

Among graphene-like two-dimentional materials, germanene holds great promise because of its compatibility with current silicon-based microelectronics. However, research on germanene has been mainly limited to theory up to now. In this work, two-dimentional germanium will be synthesized by chemically exfoliating layered polygermane.The chemical exfoliation is carried out via the reaction between surface modifiers and the hydrogenated surface of germanium layers.Supported with first-principles calculation, we will systematically study the effect of the bonding and functional group of ligands introduced by the surface modification on the band structure of germanene. The structure, optical absorption and photoluminescence of surface-modified germanene are going to be experimentally analyzed. We aim to elucidate the mechanisms for the changes of the band structure of germanene and those of the optical behavior of germanene with surface modification. Previous theoretical work has shown that hydrogenated germanene is a direct badgap semiconductor. The curret work on the surface-modified organic-ligand-passivated germanene should lay a foundation for the practical use of germanene in optoelectronics.

在具有类似石墨烯结构的二维层状材料中，锗烯由于与当前的硅微电子技术具有相当好的兼容性而被寄予厚望。但是，到目前为止有关锗烯的研究还主要处于理论探索阶段。本项目提出通过化学剥离具有层状结构的聚锗烷来制备锗的二维层状结构。由于化学剥离是通过表面改性剂与聚锗烷中被氢钝化的各锗层表面反应而实现的，所获得的锗的二维层状结构就是自支撑的表面经过改性的锗烯。借助第一性原理计算，我们将系统研究表面改性在锗烯表面引入的有机配体的成键类型和所含官能团对锗烯的能带结构的影响。通过分析经过表面改性的锗烯的结构、光吸收和光发射，掌握利用表面改性调控锗烯的能带结构进而其光学行为的规律。已有的理论研究表明被氢钝化的锗烯是具有直接带隙的半导体，而本项目对经过表面改性的被有机配体钝化的锗烯的研究将为锗烯在光电领域的实际应用奠定基础。

在具有类似石墨烯结构的二维层状材料中，锗烯由于与当前的硅微电子技术具有相当好的兼容性而被寄予厚望。本项目研究了锗烯的制备，对其结构进行了表征。分析了表面改性、缺陷（如空位）产生和合金化等对锗烯性能的影响。利用低温扫描隧道显微镜，我们发现在锗烯的制备过程中最重要的是控制锗源的温度以及衬底的温度。过低的锗源温度与过高的衬底温度都会阻碍锗烯的生成，导致致密的锗纳米晶体的出现。锗烯的表面改性如氢化锗烷化、烷氧基化、胺化、苯基化等都会影响的锗烯的电子结构和能带。这说明作为单原子层材料，锗烯的性能对其表面状况非常敏感。我们的研究也表明空位可以调控锗烯的能带，当空位浓度为3.2%时，锗烯的禁带宽度可达其最大值（约0.5 eV）。碳与锗形成合金时的单原子层材料有可能产生带隙，当Ge3C3/C的超晶格出现时，禁带宽度能达到可观的0.26 eV。本项目有关锗烯的制备及其电子和能带结构的调控有望推动锗烯在光电领域的应用研究。