Mandelbaum Ya'akov, Tkachev Maria, Sanjeev Abhijit, Zalevsky Zeev, Zitoun David, Karsenty Avi
Faculty of Exact Sciences, Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel.
Advanced Laboratory of Electro-Optics (ALEO), Department of Applied Physics/Electro-Optics Engineering, Lev Academic Center, Jerusalem 9116001, Israel.
ACS Omega. 2024 Nov 13;9(47):46796-46812. doi: 10.1021/acsomega.4c04775. eCollection 2024 Nov 26.
Plasmonic nanostructure arrays, designed for performance as pixels in an advanced SERS imaging device, were fabricated by gallium focused ion beam (FIB). Though the FIB is best suited for etching holes and negative structures, our previously reported simulations favor protrusions. Herein, we report on the FIB methodology to "sculpt" positive structures by "ion-blasting" away the surrounding material. Nanoprotrusions and nanoholes with different aspect ratios are compared experimentally with depth and height controlled by the dwell time. The amplitude and spectra of optical absorption and scattering from the two species are compared as a function of structure height. Measurements were performed using ASI's model Rainbow hyperspectral camera, demonstrating the utility of hyperspectral microscopy for plasmonic imaging applications. Both the scattered and absorbed radiation display the broad peak qualitatively similar to the localized surface plasmon (LSP) scattering spectrum of gold nanospheroids. The intensity of the scattered light from the protrusions-measured in dark-field-was observed to be an order of magnitude higher than that from the nanoholes, consistent with simulation predictions. Poor contrast against bright background specular reflection is inherent in bright-field reflection mode; image-processing succeeded in detecting patterns indiscernible to the eye. To extract the absorption the full hyperspectral image field was exploited, allowing the sample to serve as its own reference. The resulting spectra display a plasmonic resonance which grows stronger and increasingly red-shifted at increasing heights, corroborating visual observations of changes in sample hue.
用于先进表面增强拉曼散射（SERS）成像设备像素性能的等离子体纳米结构阵列，是通过镓聚焦离子束（FIB）制造的。尽管FIB最适合蚀刻孔洞和负性结构，但我们之前报道的模拟结果更倾向于突起结构。在此，我们报告了一种通过“离子轰击”去除周围材料来“雕刻”正性结构的FIB方法。通过实验比较了具有不同纵横比的纳米突起和纳米孔，其深度和高度由驻留时间控制。比较了这两种结构的光吸收和散射的幅度及光谱随结构高度的变化。使用ASI公司的Rainbow型高光谱相机进行了测量，证明了高光谱显微镜在等离子体成像应用中的实用性。散射光和吸收光都显示出与金纳米球的局域表面等离子体（LSP）散射光谱定性相似的宽峰。在暗场中测量的突起散射光强度比纳米孔的散射光强度高一个数量级，这与模拟预测一致。亮场反射模式固有的问题是与明亮背景镜面反射的对比度差；图像处理成功地检测到了肉眼难以分辨的图案。为了提取吸收光谱，利用了整个高光谱图像场，使样品能够作为自身的参考。所得光谱显示出等离子体共振，随着高度增加，共振增强且红移增加，这证实了对样品色调变化的视觉观察。
