Abstract Plasmons are collective longitudinal modes of charge fluctuation in metal samples excited by an external electric field. Surface plasmons (SPs) are waves that propagate along the surface of a conductor. SPs find applications in magneto-optic data storage, optics, microscopy, and catalysis. The investigation of SPs in silver and gold is relevant as these materials are extensively used in plasmonics. The theoretical approach for calculating plasmon modes in noble metals is complicated by the existence of localized d electrons near the Fermi level. Nevertheless, recent calculations based on linear response theory and time-dependent local density approximation adequately describe the dispersion and damping of SPs in noble metals. Furthermore, in thin films the electronic response is influenced by electron quantum confinement. Confined electrons modify the dynamical screening processes at the film/substrate interface by introducing novel properties with potential applications. The presence of quantum well states in the Ag and Au overlayer affects both the dispersion relation of SP frequency and the damping processes of the SP. Recent calculations indicate the emergence of acoustic surface plasmons (ASP) in Ag thin films exhibiting quantum well states. The slope of the dispersion of ASP decreases with film thickness. High-resolution electron energy loss spectroscopy (HREELS) is the main experimental technique for investigating collective electronic excitations, with adequate resolution in both the energy and momentum domains to investigate surface modes. Herein we review on recent progress of research on collective electronic excitations in Ag and Au films deposited on single-crystal substrates.

中文翻译：

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电子限制、量子尺寸效应和薄膜形态对 Ag 和 Au 薄膜中等离子体模式的色散和阻尼的影响

摘要 等离子激元是外电场激发的金属样品中电荷波动的集合纵向模式。表面等离子体 (SP) 是沿导体表面传播的波。SP 在磁光数据存储、光学、显微镜和催化方面有应用。银和金中 SP 的研究是相关的，因为这些材料广泛用于等离子体。由于费米能级附近存在局域 d 电子，计算贵金属中等离子体模式的理论方法变得复杂。然而，最近基于线性响应理论和时间相关局部密度近似的计算充分描述了 SP 在贵金属中的分散和阻尼。此外，在薄膜中，电子响应受电子量子限制的影响。受限电子通过引入具有潜在应用的新特性来修改薄膜/基板界面处的动态筛选过程。Ag和Au覆盖层中量子阱态的存在影响SP频率的色散关系和SP的阻尼过程。最近的计算表明，在表现出量子阱态的 Ag 薄膜中出现了声表面等离子体 (ASP)。ASP 的分散斜率随膜厚而减小。高分辨率电子能量损失谱 (HREELS) 是研究集体电子激发的主要实验技术，在能量和动量域都有足够的分辨率来研究表面模式。