Department of Materials Science and Engineering , National Tsing Hua University , Hsinchu 30013 , Taiwan.
Department of Physics , National Taiwan University , Taipei 10617 , Taiwan.
ACS Sens. 2019 Nov 22;4(11):2900-2907. doi: 10.1021/acssensors.9b01225. Epub 2019 Oct 21.
We present experimental and theoretical studies of a metamaterial-based plasmonic structure to build a plasmonic-molecular coupling detection system. High molecular sensitivity is realized only when molecules are located in the vicinity of the enhanced field (hot spot region); thus, introducing target molecules in the hot spot region to maximize plasmonic-molecular coupling is crucial to developing the sensing technology. We design a metamaterial consisting of a vertically oriented metal insulator metal (MIM) structure with a 25 nm channel sandwiched between two metal films, which enables the delivery of molecules into the large ravinelike hot spot region, offering an ultrasensitive platform for molecular sensing. This metamaterial is applied to carbon dioxide and butane detection. We design the structure to exhibit resonances at 4033 and 2945 cm, which overlap with the C═O and -CH vibration modes, respectively. The mutual coupling of these two resonance modes creates a Fano resonance, and their distinct peaks are clearly observed in the corresponding transmission dips. In addition, owing to its small footprint, such a vertical-oriented MIM structure enables us to increase the integration density and allows the detection of a 20 ppm concentration with negligible background noise and high selectivity in the mid-infrared region.
我们提出了一种基于超材料的等离子体结构的实验和理论研究，以构建等离子体-分子耦合检测系统。只有当分子位于增强场（热点区域）附近时，才能实现高分子灵敏度；因此，将目标分子引入热点区域以最大化等离子体-分子耦合对于开发传感技术至关重要。我们设计了一种超材料，由一个垂直取向的金属-绝缘体-金属（MIM）结构组成，其中有一个 25nm 的通道夹在两个金属膜之间，这使得分子能够进入大的 Ravine-like 热点区域，为分子传感提供了一个超灵敏的平台。这种超材料应用于二氧化碳和丁烷的检测。我们设计的结构在 4033 和 2945cm 处表现出共振，分别与 C═O 和-CH 振动模式重叠。这两个共振模式的相互耦合产生了一个 Fano 共振，并且在相应的传输陷波中可以清楚地观察到它们的明显峰值。此外，由于其较小的尺寸，这种垂直取向的 MIM 结构使我们能够增加集成密度，并允许在中红外区域以可忽略的背景噪声和高选择性检测到 20ppm 的浓度。
