The connection between plasmon decay dynamics and the surface enhanced Raman spectroscopy background: Inelastic scattering from non-thermal and hot carriers
The connection between plasmon decay dynamics and the surface enhanced Raman spectroscopy background: Inelastic scattering from non-thermal and hot carriers
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DOI：
10.1063/5.0032763
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发表时间：
2020-10
期刊：
影响因子：
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通讯作者：
Shengxian Wu;Oscar Hsu-Cheng Cheng-Oscar-Hsu-Cheng-Cheng-108620018;B. Zhao;Nicki Hogan;An-Tse Lee;D. Son;M. Sheldon
中科院分区：
文献类型：
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作者：
Shengxian Wu;Oscar Hsu-Cheng Cheng-Oscar-Hsu-Cheng-Cheng-108620018;B. Zhao;Nicki Hogan;An-Tse Lee;D. Son;M. Sheldon
最近的研究已经确定，来自等离子体金属纳米结构的反斯托克斯拉曼信号可以用于确定表征金属内部载流子的两个单独的温度-光激发的"热载流子"和与金属晶格热化的载流子的温度。然而，在斯托克斯光谱区域中的相关信号在历史上阻碍了表面增强拉曼光谱（SERS），因为吸附分子的振动峰总是伴随着金属基底的宽背景。金属信号的基本来源及其对光谱的贡献尚不清楚。在这里，我们概述了一个统一的理论模型，描述了温度依赖性的行为和广泛的光谱分布。我们认为，大部分的拉曼信号是从非弹性散射直接与非热载流子，已通过表面等离子体激元的阻尼激发。此外，一个显着的光谱分量（~1%）是由于在升高的热分布的热载流子的子群。我们已经进行了温度和功率依赖的拉曼实验，以显示如何一个简单的拟合过程揭示了等离子体激元退相时间，以及热载流子和金属晶格的温度，为了将这些参数与吸附在金属表面上的化学物种的定量拉曼分析。
Recent studies have established that the anti-Stokes Raman signal from plasmonic metal nanostructures can be used to determine the two separate temperatures that characterize carriers inside the metal -- the temperature of photoexcited "hot carriers" and carriers that are thermalized with the metal lattice. However, the related signal in the Stokes spectral region has historically impeded surface enhanced Raman spectroscopy (SERS), as the vibrational peaks of adsorbed molecules are always accompanied by the broad background of the metal substrate. The fundamental source of the metal signal, and hence its contribution to the spectrum, has been unclear. Here, we outline a unified theoretical model that describes both the temperature-dependent behavior and the broad spectral distribution. We suggest that the majority of the Raman signal is from inelastic scattering directly with non-thermal carriers that have been excited via damping of the surface plasmon. In addition, a significant spectral component (~ 1%) is due to a sub-population of hot carriers in an elevated thermal distribution. We have performed temperature and power-dependent Raman experiments to show how a simple fitting procedure reveals the plasmon dephasing time, as well as the temperatures of the hot carriers and the metal lattice, in order to correlate these parameters with quantitative Raman analysis of chemical species adsorbed on metal surface.