Due to the generation of electromagnetic hot spots, metallic nanogaps have attracted great attention in various subjects, especially in plasmonics. For fixed nanogaps, using dielectric coating is an efficient way to narrow the gaps while improving their thermal and chemical stability. Herein, it is numerically demonstrated that the utilization of high refractive index dielectric coatings with zero or little loss, like TiO 2 , can lead to the generation of remarkable hot spots at the nanogaps. Two mechanisms work synergistically including the improved light coupling effect and a great leap of local electric field intensities at the dielectric-air interface. For higher refractive index dielectric coatings in practice, like graphene, despite a greater electric field leap at the interface, the weakening light coupling effect turns to play a dominant and negative role owing to the lossy dielectric properties. Our results provide a new perspective for the stabilization and fu...

中文翻译：

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通过优化介电涂层增强等离子体纳米间隙处的局部电场

由于电磁热点的产生，金属纳米间隙已经引起了各个学科的极大关注，尤其是在等离子体激元学领域。对于固定的纳米间隙，使用介电涂层是缩小间隙并提高其热稳定性和化学稳定性的有效方法。在此，从数值上证明，利用具有零损耗或极少损耗的高折射率介电涂层，如TiO 2，可导致在纳米间隙处产生明显的热点。两种机制协同工作，包括改善的光耦合效果和电介质-空气界面处局部电场强度的飞跃。实际上，对于较高折射率的介电涂层（例如石墨烯），尽管界面处的电场跃变更大，由于有损耗的介电特性，减弱的光耦合效应变成起主导作用和消极作用。我们的结果为稳定和未来提供了新的视角。