Surface-Enhanced Raman Scattering from Metallic Nanostructures: Bridging the Gap between the Near-Field and Far-Field Responses
Surface-Enhanced Raman Scattering from Metallic Nanostructures: Bridging the Gap between the Near-Field and Far-Field Responses
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DOI：
10.1103/physrevx.3.011001
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发表时间：
2013-01-10
影响因子：
12.5
通讯作者：
Dawson, Paul
中科院分区：
文献类型：
--
作者：
Doherty, Matthew D.;Murphy, Antony;Dawson, Paul
我们在这里提出了一个详细的研究“真实的”纳米结构金属表面的电磁近场和远场响应之间的复杂关系。近场和远场响应指定的表面增强拉曼散射增强因子（Sers EF）和光学消光，分别（光谱）。首先，它表明，金纳米棒和纳米管阵列基板表现出三个不同的局部表面等离子体共振（LSPR）：纵向，横向和腔模式。腔模同时对近场行为（通过Sers EF观察到）和最弱的光学相互作用具有最大的影响：它具有“近场型”特征。横模和纵模对远场行为有显著影响，但对Sers的影响很小：它们具有“远场型”特征。我们确认腔模式的存在下，使用Sers EF光谱，电子显微镜，和电磁建模的组合，从而清楚地说明和解释Sers EF光谱和光学响应之间的相关性（缺乏）的对比字符的三个LSPR。在这样做时，我们实验证明，对于支持多个LSPR的表面，近场和远场特性实际上可以几乎独立地调谐。它进一步表明，微调的光谱位置的LPSR的几何参数的微小变化也可以大大影响这些模式的特性，导致某些不寻常的行为，如远场共振红移作为近场共振蓝移。DOI：10.1103/PhysRevX.3.011001
We present here a detailed study of the complex relationship between the electromagnetic near-field and far-field responses of "real" nanostructured metallic surfaces. The near-field and far-field responses are specified in terms of (spectra of) the surface-enhanced Raman-scattering enhancement factor (SERS EF) and optical extinction, respectively. First, it is shown that gold nanorod- and nanotube-array substrates exhibit three distinct localized surface plasmon resonances (LSPRs): a longitudinal, a transverse, and a cavity mode. The cavity mode simultaneously has the largest impact on the near-field behavior (as observed through the SERS EF) and the weakest optical interaction: It has a "near-field-type" character. The transverse and longitudinal modes have a significant impact on the far-field behavior but very little impact on SERS: They have a "far-field-type" character. We confirm the presence of the cavity mode using a combination of SERS EF spectra, electron microscopy, and electromagnetic modeling and thus clearly illustrate and explain the (lack of) correlation between the SERS EF spectra and the optical response in terms of the contrasting character of the three LSPRs. In doing so, we experimentally demonstrate that, for a surface that supports multiple LSPRs, the near-field and far-field properties can in fact be tuned almost independently. It is further demonstrated that small changes in geometrical parameters that tune the spectral location of the LPSRs can also drastically influence the character of these modes, resulting in certain unusual behavior, such as the far-field resonance redshift as the near-field resonance blueshifts. DOI: 10.1103/PhysRevX.3.011001