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Evaluation of surface roughness of metal films using plasmonic Fano resonance in attenuated total reflection
摘要： Attenuated total re?ection (ATR) by surface plasmon polariton (SPP) is a method for evaluating the dispersion relation of SPP from the position of a dip in the re?ection spectrum. However, recent studies have shown that the dips are displaced from SPP resonance because they are produced by a type of Fano resonance, i.e., the interference between the resonant re?ection process accompanied by resonant excitation of SPP and the direct re?ection process without resonant excitation. This result suggests that the system properties dif?cult to be achieved in the dispersion relation of SPP can be characterized using the ATR method. In this study, we investigate the effect of surface roughness due to nanosized dimples created in the initial stage of pitting corrosion on the ATR spectrum, from the viewpoint of Fano resonance. Using the temporal coupled-mode method, it is shown that the Fano resonance in ATR is caused by the phase change of direct re?ection because of the absorption on the metal surface, and the spectral shape is determined by this phase, along with the ratio of the external (radiative) decay rate to the total decay rate of the resonant mode. Moreover, it is clari?ed that the internal and external decay rates extracted from the ATR spectrum provide information on corrosion, such as the effective thickness of the metal ?lm and the randomness in dimple distribution.
关键词： surface plasmon resonance,Fano resonance,pitting corrosion,attenuated total re?ection,surface roughness
更新于2025-09-16 10:30:52
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Measuring the plasma-wall charge by infrared spectroscopy
摘要： We show that the charge accumulated by a dielectric plasma-facing solid can be measured by infrared spectroscopy. The approach utilizes a stack of materials supporting a surface plasmon resonance in the infrared. For frequencies near the Berreman resonance of the layer facing the plasma the re?ectivity dip —measured from the back of the stack, not in contact with the plasma— depends strongly on the angle of incidence making it an ideal sensor for the changes of the layer’s dielectric function due to the polarizability of the trapped surplus charges. The charge-induced shifts of the dip, both as a function of the angle and the frequency of the incident infrared light, are large enough to be measurable by attenuated total re?ection setups.
关键词： Berreman resonance,surface plasmon resonance,plasma-wall charge,attenuated total re?ection,infrared spectroscopy
更新于2025-09-09 09:28:46