Effects of Defect, Doping, Geometrical Configuration, and Size on Plasmon Excitations for Three Silicon Nanostructures

摘要

We investigate systematically the plasmon excitations for three silicon (Si2, Si6, and Si10) nanostructures (NS) based on time-dependent density functional theory and find that there are two obvious plasmon structures (pi-like and pi-sigma plasmons) in Si2 and Si10 NS, but only one pi-sigma plasmon is found in Si6 NS. Meanwhile, their plasmon excitations are rather sensitive to the polarization direction, especially for Si6 NS which is highly desirable for photosensitive switch materials in the visible region. Additionally, we also analyze in detail the effects of defect, doping, geometrical configuration, and size on their plasmon excitations and find that defects in Si10 NS would suppress the pi-sigma plasmon excitations but enhance the pi-like plasmon peak intensities in the visible region. When the defected Si10 NS are offset by other atoms, their pi-sigma plasmon excitations are increased, but their pi-like plasmon peak intensities are nearly unchanged, which indicates that the Si atom with threefold coordination is more beneficial in increasing the plasmon peak intensity in the visible region. We prove that the rectangular NS are the best choice for plasmonic materials, compared with triangular and hexagonal NS, and their larger nanostructural size is more beneficial in increasing plasmon peak intensities in high-energy regions. Our results reveal the physical mechanism for some geometrical parameters that affects plasmon structures in three silicon allotropes, providing a simple and qualitative perspective on optical performance, and thus are useful to design and control optical materials in the future.

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