Tailoring of graphene's electronic and magnetic properties via edge functionalization

该项目致力于将化学边缘功能化发展成为一种可靠的工具，用于定制石墨烯片和纳米带的电子和磁性结构。实现明确的化学边缘终止的关键策略包括原位饱和石墨烯基面破裂时产生的反应性悬垂键。在此基础上，本文的目标是实现不同的功能化方案，包括高取向热解石墨（HOPG）的边缘功能化石墨烯机械剥离，用于制造尺寸为几微米的边缘功能化石墨烯片，以及基于溶液的剥离方法，以产生更大量的功能化石墨烯片和宽度为几纳米的纳米带。在后者的情况下，设想了一个两阶段的方法，即首先没有确定晶体取向的条带，然后应该获得具有控制边缘几何形状的条带。通过使用两种不同的功能化剂来实现后一项任务，这些功能化剂能够选择性地稳定扶手椅或之字形边缘。附加基团的第一个目的是增强（纳米结构）石墨烯的电学性能，特别是通过赋予前所未有的载流子迁移率和击穿电流密度，以及带隙调谐的可能性。此外，为了使纳米带成为自旋阀器件的有用组件，应利用边缘群来控制局部自旋排列。电子和磁性这两方面的主要目标是探索边缘基团的化学性质以及作为相关约束尺寸的条带宽度的影响。为此目的，实验工作将由优先计划内合作进行的理论研究补充。最后，将边缘功能化石墨烯控制组装到图案衬底上，将作为石墨烯基器件平行制造的工具进行探索。

This project endeavours to develop chemical edge functionalization into a reliable tool for tailoring the electronic and magnetic structure of graphene sheets and nanoribbons. The key strategy to achieve well-defined chemical edge terminations consists of in situ saturating the reactive dangling bonds that are created upon rupture of the graphene basal plane. On this basis, it is targeted to implement different functionalization protocols, including the Edge-functionalized graphene mechanical exfoliation of highly oriented pyrolytic graphite (HOPG) for the fabrication of edge-functionalized graphene sheets with sizes of several micrometers, as well as solutionbased exfoliation methods to yield larger quantities of functionalized graphene sheets and nanoribbons with a width down to a few nanometres. In case of the latter, a two-stage approach is envisioned, whereby first ribbons without defined crystallographic orientation, and then ribbons with controlled edge geometry shall be obtained. Achieving the latter task is projected by the use of two different functionalizing agents capable of selectively stabilizing either armchair or zigzag edges. A first purpose of the attached groups is to enhance the electrical performance of the (nanostructured) graphene, in particular by imparting unprecedented carrier mobility and breakdown current density, as well as the possibility of band gap tuning. In addition, the edge groups shall be exploited toward controlling the local spin alignment, in order to render the nanoribbons into useful components of spin valve devices. The major objective with regard to both, the electronic and magnetic properties, is to explore the influence of the chemical nature of the edge groups, as well as the ribbon width as the relevant confinement dimension. To this end, the experimental work will be complemented by theoretical studies performed in collaboration within the priority program.Finally, the controlled assembly of the edge-functionalized graphene onto patterned substrates shall be explored as a tool for the parallel fabrication of graphene-based devices.