Vibrational properties of graphene nanostructures: Raman spectroscopy and density-functional theory

石墨烯纳米结构，如纳米带，预计具有迷人的性质，这是由它们的大小和晶体取向，但也由边缘配置确定。尽管有新的方法来制造纳米带，理论预测（主要是窄带与长程有序边缘）和实验数据之间仍然有很大的差距，从更广泛的，不太明确的带。在这里，我们的目标是通过结合高分辨率的振动光谱和适当的不太理想化的石墨烯纳米结构的模拟来缩小这一差距。如果成功的话，局域振动光谱可以给出关于结构性质的必要信息。此外，由于一些振动模式是非常敏感的掺杂和电子结构的其他变化，我们希望获得的电子特性的本地信息。特别是，我们计划现在专注于尖端增强拉曼光谱（TERS），它提供的空间分辨率为~ 50 nm，而传统的光学光谱为~ 500 nm。因此，它似乎有希望获得所需的本地信息，如均匀性，边缘，无序等纳米带中的无序诱导的拉曼模式的全面模拟计划，以区分限制，在边缘（边缘粗糙度），晶体取向，和体缺陷的影响。我们将进一步研究通过分子束外延（MBE）等新方法在不同衬底上制备的石墨烯结构以及离子辐照产生的石墨烯缺陷和折叠。

Graphene nanostructures like nanoribbons are expected to have fascinating properties which are determined by their size and crystallographic orientation, but also by the edge configuration. Despite new approaches for fabrication of nanoribbons, there is still a large gap between theoretical predictions (mostly narrow ribbons with long-range ordered edges) and experimental data obtained from wider, less well-defined ribbons. Here our aim is to diminish this gap by combining high-resolution vibrational spectroscopy and simulations of appropriate less idealized graphene nanostructures. If successful, local vibrational spectroscopy can give the necessary information about structural properties. Moreover, since some vibrational modes are very sensitive to doping and other changes in the electronic structure, we expect to obtain local information on the electronic properties as well. In particular, we plan to focus now on tip-enhanced Raman spectroscopy (TERS), which provides spatial resolution of ~50nm, compared with ~500nm in conventional optical spectroscopy. It therefore seems promising for obtaining the desired local information in nanoribbons like homogeneity, edges, disorder etc. Comprehensive simulations of the disorder-induced Raman modes in nanoribbons are planned in order to discriminate effects from confinement, disorder at the edge (edge roughness), crystallographic orientation, and bulk defects. We will further investigate graphene structures fabricated by novel methods like molecular beam epitaxy (MBE) on different substrates and graphene defects and folds produced by ion irradiation.