Impact of Surface Roughness in Nanogap Plasmonic Systems
Impact of Surface Roughness in Nanogap Plasmonic Systems
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DOI：
10.1021/acsphotonics.0c00099
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发表时间：
2020-04-15
期刊：
影响因子：
7
通讯作者：
Smith, David R.
中科院分区：
文献类型：
--
作者：
Ciraci, Cristian;Vidal-Codina, Ferran;Smith, David R.
最近的结果表明，对两个数百纳米尺寸的金属元素之间的分离距离进行了前所未有的控制，这也是中红外波长下自由电子非局域响应效应的基础。然而，由于制造引起的表面粗糙度，大多数金属系统仍然存在一定程度的不均匀性。此类系统中的纳米级粗糙度可能会阻碍对微观相互作用作用的理解。在这里，我们研究了表面粗糙度对中红外频率谐振的同轴纳米孔径的影响。我们表明，尽管随机粗糙度以不可预测的方式改变共振，但仍然可以清楚地观察到非局部效应的影响。粗糙度引起的系统峰值共振扰动与各个样品的有效间隙尺寸有很强的相关性。然后，可以通过对结构整体进行测量来抑制由于制造缺陷造成的波动，其中对大量样本进行平均可以提供对理想系统光学特性的精确测量。
Recent results have shown unprecedented control over separation distances between two metallic elements hundreds of nanometers in size, underlying the effects of free-electron nonlocal response also at mid-infrared wavelengths. Most of metallic systems, however, still suffer from some degree of inhomogeneity due to fabrication-induced surface roughness. Nanoscale roughness in such systems might hinder the understanding of the role of microscopic interactions. Here we investigate the effect of surface roughness in coaxial nanoapertures resonating at mid-infrared frequencies. We show that, although random roughness shifts the resonances in an unpredictable way, the impact of nonlocal effects can still be clearly observed. Roughness-induced perturbation on the peak resonance of the system shows a strong correlation with the effective gap size of the individual samples. Fluctuations due to fabrication imperfections then can be suppressed by performing measurements on structure ensembles in which averaging over a large number of samples provides a precise measure of the ideal system's optical properties.