Relativistic electron energy loss spectroscopy of solid and core-shell nanowires
Relativistic electron energy loss spectroscopy of solid and core-shell nanowires
复制标题
固体和核壳纳米线的相对论电子能量损失谱
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
D. Muller
中科院分区：
文献类型：
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作者：
J. Hyun;M. Levendorf;M. Blood;Jiwoong Park;D. Muller
使用来自聚焦相对论性电子束的跃迁辐射，对Ge纳米线展示了具有纳米空间分辨率的近场光谱。在忽略延迟的理论处理中不存在波导模式的激发，因为快速电子与纳米线光学模式的耦合是其相对论性质的结果。在这里，使用局域介电理论分析计算垂直取向的单纳米线附近的疏远电子轨迹的相对论能量损失概率。使用大约 2 纳米尺寸的电子探针，在该几何结构中对多模和零模 Ge 纳米线进行了实验测量。观察结果与延迟计算非常一致。通过比较实验电子能量损失谱与理论色散图来识别光学本征模式。在介电纳米线上添加德鲁德型金属壳可提供与介电波导相同能量范围的表面等离子体激元模式，从而产生可以被入射电子有效激发的强耦合混合模式。这些结果证明了在宽带能量范围内具有纳米空间分辨率的纳米系统光学研究的强大解决方案。
Near-field optical spectroscopy with nanometer spatial resolution using transition radiation from a focused, relativistic electron beam is demonstrated for Ge nanowires. The excitation of the waveguide modes is absent in theoretical treatments that neglect retardation because the coupling of the swift electron to the optical modes of the nanowire is a consequence of its relativistic nature. Here, relativistic energy loss probabilities for aloof electron trajectories near a perpendicularly oriented single nanowire are analytically calculated using a local dielectric theory. Multimode and zero-mode Ge nanowires are experimentally measured in this geometry with a approx2-nm-size electron probe. Observations fall in excellent agreement with the retarded calculations. Optical eigenmodes are identified from comparison of the experimental electron energy loss spectra to theoretical dispersion maps. Adding a Drude-type metallic shell to a dielectric nanowire provides surface-plasmon modes in the same energy range as the dielectric waveguide, leading to strongly coupled hybrid modes that can be efficiently excited by the incident electron. Such results demonstrate a powerful solution for optical studies of nanosystems with nanometer spatial resolution over a broadband energy range.