A large-scale sub-5 nm nanofabrication technique is developed based on double layer anodized aluminium oxide (AAO) porous membrane masking. This technique also provides a facile route to form multilayer nano-arrays (metal nanoarrays sandwiched by AAO membranes), which is very challenging for other techniques. Normally the AAO mask has to be sacrificed, yet in this work it is preserved as a part of the nanostructure. The preserved AAO layers as the support for the second/third layer of the metal arrays provide a high-refractive index background for the multilayer metal arrays. This background concentrates the local E-field more significantly and results in a much higher Surface-Enhanced Raman Spectroscopy (SERS) signal than single layer metal arrays. This technique may lead to the advent of an inexpensive, reproducible, highly sensitive SERS substrate. Moreover, the physical essence of the plasmonic enhancement is unveiled by finite element method based numerical simulations. Enhancements from the gaps and the multilayer nanostructure agree very well with the experiments. The calculated layer-by-layer electric field distribution determines the contribution from different layers and provides more insights into the 3D textured structure.

中文翻译：

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夹在阳极氧化铝膜之间的多层纳米阵列：一种廉价，可重现，高度敏感的SERS基质的方法†

基于双层阳极氧化氧化铝（AAO）多孔膜掩膜技术，开发了大规模的亚5纳米纳米制造技术。该技术还提供了形成多层纳米阵列（被AAO膜夹在中间的金属纳米阵列）的便捷途径，这对其他技术而言是非常具有挑战性的。通常，必须牺牲AAO掩模，但在这项工作中，它被保留为纳米结构的一部分。保留的AAO层作为金属阵列第二/第三层的支撑层，为多层金属阵列提供了高折射率背景。该背景比单层金属阵列更集中地集中了局部电场，并导致更高的表面增强拉曼光谱（SERS）信号。这项技术可能会导致廉价，可重现，高敏感度的SERS底物。此外，基于有限元方法的数值模拟揭示了等离子体增强的物理本质。间隙和多层纳米结构的增强与实验非常吻合。计算得出的逐层电场分布确定了来自不同层的贡献，并提供了有关3D纹理结构的更多信息。