Local electronic properties of functionalized graphene studied with scanning tunneling microscopy and spectroscopy

石墨烯是一种以蜂窝状晶格排列的二维单层碳原子，由于其显著的物理性质而引起了人们的极大关注。特别是，它的电子结构，即费米能级附近的电荷载流子模拟无质量相对论粒子(狄拉克费米子)，为利用材料研究中常用的实验技术研究量子电动力学问题提供了完美的基础。此外，石墨烯由于其卓越的高载流子迁移率、机械稳定性、室温弹道传输和可扩展到纳米尺寸，是未来电子设备的理想材料。因此，在原子尺度上研究石墨烯的结构和电子性质是非常重要的，这可以用扫描隧道显微镜和光谱学来完成。本项目S的主要目的是利用扫描隧道显微镜和光谱学来探索官能化对石墨烯结构和局域电子性质的影响。将特别强调(带电)杂质对石墨烯中狄拉克费米子的影响，以及石墨烯纳米带(GNR)(石墨烯的小条纹)的边缘和个别形状对电子结构的影响。特别是后者对于器件应用是最有意义的，因为纳米带有望呈现出随带宽而变化的带隙，并且取决于边缘配置、自旋极化的边缘状态以及局部磁性。通过使用化学气相沉积原位合成(功能化)石墨烯，并采用自下而上的制造程序将有机分子转化为具有特定形状和边缘的GNR，将实现对石墨烯S性质的受控修饰。该项目的结果将对理解官能化如何改变石墨烯的性质做出重要贡献，并将为基于石墨烯和GNRs的器件物理提供有价值的输入。

Graphene, a two-dimensional single sheet of carbon atoms arranged in a honeycomb lattice, is attracting tremendous attention due to its remarkable physical properties. Particularly, its electronic structure, in which charge carriers near the Fermi level mimic massless relativistic particles (Dirac fermions), provides a perfect base for studying questions of quantum electrodynamics with experimental techniques commonly used in materials research. Furthermore, graphene is an ideal material for future electronic devices because of its outstandingly high charge carrier mobility, mechanical stability, room-temperature ballistic transport and scalability down to nanometer size. It is therefore of crucial importance to investigate the structural and electronic properties of graphene on an atomic scale which can be done by using scanning tunneling microscopy (STM) and spectroscopy (STS).This project´s major aim is exploring the influence of functionalization on the structure and local electronic properties of graphene using STM and STS. Particular emphasis will be laid on the impact of (charged) impurities on Dirac fermions in graphene and the influence of edges and individual shapes of graphene nanoribbons (GNR), small stripes of graphene, on the electronic structure. Especially the latter is of prime interest for device applications as nanoribbons are expected to exhibit a bandgap that scales with the ribbon width and, depending on the edge configuration, spin-polarized edge states as well as local magnetism. A controlled modification of graphene´s properties will be achieved by in-situ synthesis of (functionalized) graphene using chemical vapor deposition and by employing bottom-up fabrication routines transforming organic molecules into GNRs with defined shapes and edges. The results from this project will be an important contribution to the understanding of how functionalization modifies the properties of graphene and will provide valuable input for device physics based on graphene and GNRs.