Surface-Enhanced Infrared Absorption of Self-Aligned Nanogap Structures
Surface-Enhanced Infrared Absorption of Self-Aligned Nanogap Structures
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DOI：
10.1021/acs.jpcc.6b07851
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发表时间：
2016-10-06
影响因子：
3.7
通讯作者：
Natelson, Douglas
中科院分区：
文献类型：
--
作者：
Li, Yajing;Simeral, Mathieu L.;Natelson, Douglas
等离子体纳米结构通常用于表面增强红外吸收（SEIRA）光谱，以探测表面组装的分子或金属纳米结构周围的介电环境。在这里，我们制造金属纳米间隙结构，使用自对准技术在本征硅衬底和相关的SEIRA光谱与金属纳米结构的几何形状的选择。一个动机是将来自明亮等离子体激元模式的杂交的增强与明亮和黑暗等离子体激元模式之间的杂交的效果进行比较。这些结构提供了低于10 nm的间隙尺寸，并支持强场增强。该结构通过金属下方纳米厚度的原生氧化硅层中Si-O伸缩的增强吸收特征来证明其灵敏度。模拟显示，这一薄层在确定纳米结构的等离子体模式中起着关键作用。光学性质的数值模拟与观察结果一致，即在自对准纳米间隙结构上检测到比纳米棒阵列更强的Si-O拉伸信号，突出了底层原生氧化物中增强的电磁场。
Plasmonic nanostructures are often used in surface-enhanced infrared absorption (SEIRA) spectroscopy to probe surface assembled molecules or the dielectric environment surrounding the metallic nanostructures. Here we fabricate metallic nanogap structures using self-aligned techniques on an intrinsic silicon substrate and correlate resulting SEIRA spectra with the choice of metal nanostructure geometry. A motivation is to compare the enhancement from hybridization of bright plasmon modes with the effect of hybridization between bright and dark plasmon modes. These structures provide a gap size below 10 nm and support strong field enhancements. The structures demonstrate their sensitivity through the enhanced absorption signature of the Si-O stretch in the native silicon oxide layer of nanometer thickness beneath the metal. Simulations reveal this thin layer plays a critical role in determining the plasmon modes of the nanostructures. Numerical simulations of the optical properties are consistent with the observations that stronger Si-O stretch signals are detected on self-aligned nanogap structures than nanorod arrays, highlighting the enhanced electromagnetic fields in the underlying native oxide.