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

像纳米带这样的石墨烯纳米结构有望具有令人着迷的特性，这些特性不仅取决于它们的尺寸和晶体取向，还取决于边缘的配置。尽管有制造纳米带的新方法，但理论预测(主要是具有长范围有序边的窄带)与从较宽、定义较差的带获得的实验数据之间仍有很大差距。在这里，我们的目标是通过结合高分辨率振动光谱和适当的不那么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，局部振动光谱学可以提供关于结构性质的必要信息。此外，由于一些振动模式对掺杂和其他电子结构的变化非常敏感，我们希望也能获得有关电子性质的局部信息。特别是，我们现在计划将重点放在尖端增强拉曼光谱(TERS)上，它提供了~50 nm的空间分辨率，而传统光学光谱提供了~500 nm的空间分辨率。因此，在纳米带中获得所需的局域信息，如均匀性、边缘、无序等似乎是有希望的。为了区分限制效应、边缘无序(边缘粗糙度)、晶体取向和体缺陷，人们计划对纳米带中无序诱导的拉曼模式进行全面的模拟。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.