Plasmons in layered nanospheres and nanotubes investigated by spatially resolved electron energy-loss spectroscopy
Plasmons in layered nanospheres and nanotubes investigated by spatially resolved electron energy-loss spectroscopy
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DOI：
10.1103/physrevb.61.13936
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发表时间：
2000-05-15
影响因子：
3.7
通讯作者：
Colliex, C
中科院分区：
文献类型：
--
作者：
Kociak, M;Henrard, L;Colliex, C
我们提出了一个广泛的电子能量损失谱研究的低损耗能量区域，记录在多壳层碳和硼氮化物纳米管和碳超富勒烯。通过将亚纳米探针从真空扫描到纳米物体的中心，在扫描透射电子显微镜中记录光谱的收集。这种实验技术提供了解开和识别纳米颗粒的不同激发模式的独特能力。我们专注于研究近场几何结构中激发的表面模式，其中电子束与纳米物体表面之间的耦合距离得到准确监测。在不同的层状纳米结构（圆柱形或球形，氮化硼，或碳构成）的表面集体激发之间的相似性被指出。在12-13 eV和17-18 eV处的两个表面模在实验上清楚地证明。我们表明，这些模式是准确地描述了一个经典的连续介质模型充分考虑到各向异性的字符和中空的几何形状的纳米粒子。这两种模式被证明是直接相关的介电张量的平面内和平面外的组件。较高的能量模式（面内模式）示出转移到更高的能量与降低的影响参数，作为结果的高阶多极模式的权重的增加，同时达到纳米物体的表面。
We present an extensive electron energy loss spectroscopy study of the low-loss energy region, recorded on multishell carbon and boron-nitride nanotubes and carbon hyperfullerenes. Collections of spectra were recorded in a scanning transmission electron microscope by scanning a subnanometer probe from vacuum into the center of the nano-objects. This experimental technique provides the unique ability of disentangling and identifying the different excitation modes of a nanoparticle. We concentrate on the study of surface modes excited in a near-field geometry where the coupling distance between the electron beam and the surface of the nano-objects is accurately monitored. Similarities between surface collective excitations in the different layered nanostructures (cylindrical or spherical, boron nitride, or carbon constituted) are pointed out. Two surface modes at 12-13 eV and 17-18 eV are experimentally clearly evidenced. We show that these modes are accurately described by a classical continuum dielectric model taking fully into account the anisotropic character and the hollow geometry of the nanoparticles. These two modes are shown to be directly related to the in-plane and out-of-plane components of the dielectric tensor. The higher-energy mode (in-plane mode) is shown to shift to higher energy with decreasing impact parameter, as a result of an increase in the weights of the high-order multipolar modes while reaching the surface of the nano-objects.