Topologically induced confinement of collective modes in multilayer graphene nanocones measured by momentum-resolved STEM-VEELS
Topologically induced confinement of collective modes in multilayer graphene nanocones measured by momentum-resolved STEM-VEELS
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DOI：
10.1103/physrevb.88.155408
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发表时间：
2013-10-07
影响因子：
3.7
通讯作者：
Brydson, R.
中科院分区：
文献类型：
--
作者：
Hage, F. S.;Ramasse, Q. M.;Brydson, R.
在不断扩展的等离子体领域，精确控制等离子体局域化程度对于在纳米尺度上定制光学性质至关重要。在本文中，等离子体激元局域化的程度直接探测通过记录动量转移依赖性（即色散）的等离子体激元共振能量使用电子能量损失谱在像差校正的扫描透射电子显微镜。受限于不确定性原理，动量空间的分辨率可以很容易地通过光束会聚来调整，并且即使在低动量分辨率下，局部化也是可以清楚地识别的。在这项原理验证研究中，该技术被应用于在其顶点处包含不同数量的拓扑缺陷的多层石墨烯锥体。它示出了一个高程度的限制的PI和PI +西格玛体积等离子体达到五个五边形缺陷在锥顶。这种效应归因于拓扑缺陷本身的存在。此外，轻微的负折射观察到的五个五边形锥，主要影响集体激发的π电子。
In the expanding field of plasmonics, accurate control of the degree of plasmon localization is of crucial importance for tailoring optical properties at the nanoscale. In this paper, the degree of plasmon localization is directly probed by recording the momentum transfer dependence (i.e. the dispersion) of plasmon resonance energies using electron energy loss spectroscopy in the aberration-corrected scanning transmission electron microscope. Limited by the uncertainty principle, resolution in momentum space can easily be tuned by the beam convergence, and it is shown that localization is clearly identifiable, even at low-momentum resolution. In this proof-of-principle study, this technique was applied to multilayer graphene cones containing a varying number of topological defects at their apex. It is shown that a high degree of confinement of the pi and pi + sigma volume plasmons is reached for five pentagonal defects at the cone apex. This effect was attributed to the presence of the topological defects themselves. Furthermore, slight negative refraction was observed for the five-pentagon cone, predominantly affecting the collective excitation of the pi electrons.