Signatures of Small Morphological Anisotropies in the Plasmonic and Vibrational Responses of Individual Nano-objects
Signatures of Small Morphological Anisotropies in the Plasmonic and Vibrational Responses of Individual Nano-objects
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DOI：
10.1021/acs.jpclett.9b01898
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发表时间：
2019-09-19
影响因子：
5.7
通讯作者：
Del Fatti, Natalia
中科院分区：
文献类型：
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作者：
Medeghini, Fabio;Rouxel, Romain;Del Fatti, Natalia
利用空间调制和泵浦-探测光谱研究了蓝宝石衬底上单个金纳米盘的等离子体和振动特性。所测得的消光光谱和时间分辨信号的功能是高度敏感的纳米盘形态从一个完美的圆柱形的微小偏差。与圆形纳米盘截面相比，椭圆形纳米盘截面提升了两个纳米盘的面内偶极表面等离子体共振的简并性，这可以通过控制入射光的偏振来选择性地激发。这种分裂效应，其振幅增加与nanodisk椭圆，相关的检测额外的振动模式的背景下，时间分辨光谱。通过光学和声学数值模型的组合进行测量分析。这使我们能够首先从等离子体响应中估计所研究的纳米盘的尺寸，然后比较其可检测的振动模式的测量和计算频率，发现它们非常一致。这项研究表明，单粒子光学光谱能够提供访问精细的形态特征，在这种情况下，代表一个有价值的替代传统技术，旨在制造后检查亚波长纳米器件形态。
The plasmonic and vibrational properties of single gold nanodisks patterned on a sapphire substrate are investigated via spatial modulation and pump-probe optical spectroscopies. The features of the measured extinction spectra and time-resolved signals are highly sensitive to minute deviations of the nanodisk morphology from a perfectly cylindrical one. An elliptical nanodisk section, as compared to a circular one, lifts the degeneracy of the two nanodisk in-plane dipolar surface plasmon resonances, which can be selectively excited by controlling the polarization of the incident light. This splitting effect, whose amplitude increases with nanodisk ellipticity, correlates with the detection of additional vibrational modes in the context of time-resolved spectroscopy. Analysis of the measurements is performed through the combination of optical and acoustic numerical models. This allows us first to estimate the dimensions of the investigated nanodisks from their plasmonic response and then to compare the measured and computed frequencies of their detectable vibrational modes, which are found to be in excellent agreement. This study demonstrates that single-particle optical spectroscopies are able to provide access to fine morphological characteristics, representing in this case a valuable alternative to traditional techniques aimed at postfabrication inspection of subwavelength nanodevice morphology.