Ahmadivand Arash, Pala Nezih
Department of Electrical and Computer Engineering, Florida International University, 10555 West Flagler Street, Miami, FL 33174 USA.
Appl Spectrosc. 2015;69(2):277-86. doi: 10.1366/14-07589. Epub 2015 Jan 1.
In this work, we have investigated the hybridization of plasmon resonance modes in completely copper (Cu)-based subwavelength nanoparticle clusters from simple symmetric dimers to complex asymmetric self-assembled structures. The quality of apparent bonding and antibonding plasmon resonance modes for all of the clusters has been studied, and we examined the spectral response of each one of the proposed configurations numerically using the finite-difference time domain (FDTD) method. The effect of the geometric sizes of nanoparticles used and substrate refractive index on the cross-sectional profiles of each of the studied structures has been calculated and drawn. We proved that Fano-like resonance can be formed in Cu-based heptamer clusters as in analogous noble metallic particles (e.g., Au and Ag) by determining the coupling strength and interference between sub-radiant and super-radiant resonance modes. Employing certain Cu nanodiscs in designing an octamer structure, we measured the quality of the Fano dip formation along the scattering diagram. Accurate tuning of the geometric sizes for the Cu-based octamer yields an opportunity to observe isotropic, deep, and narrow Fano minima along the scattering profile that are in comparable condition with the response of other plasmonic metallic substances. Immersing investigated final Cu-based octamer in various liquids with different refractive indices, we determined the sensing accuracy of the cluster based on the performance of the Fano dip. Plotting a linear diagram of plasmon energy differences over the refractive index variations as a figure of merit (FoM), which we have quantified as 13.25. With this method, the precision of the completely Cu-based octamer is verified numerically using the FDTD tool. This study paves the way toward the use of Cu as an efficient, low-cost, and complementary metal-oxide semiconductor (CMOS)-compatible plasmonic material with optical properties that are similar to analogous plasmonic substances.
在这项工作中，我们研究了完全基于铜（Cu）的亚波长纳米粒子簇中从简单对称二聚体到复杂不对称自组装结构的等离子体共振模式的杂交。研究了所有簇的表观成键和反键等离子体共振模式的质量，并使用时域有限差分（FDTD）方法对每个提出的构型进行了数值光谱响应研究。计算并绘制了所用纳米粒子的几何尺寸和衬底折射率对每个研究结构的横截面轮廓的影响。我们证明，通过确定亚辐射和超辐射共振模式之间的耦合强度和干涉，在基于铜的七聚体簇中可以像在类似的贵金属颗粒（如金和银）中一样形成类法诺共振。在设计八聚体结构时使用某些铜纳米盘，我们测量了沿散射图的法诺凹陷形成的质量。对基于铜的八聚体的几何尺寸进行精确调整，有机会观察到沿散射轮廓的各向同性、深且窄的法诺极小值，其与其他等离子体金属物质的响应情况相当。将研究的最终基于铜的八聚体浸入具有不同折射率的各种液体中，我们根据法诺凹陷的性能确定了簇的传感精度。绘制等离子体能量差随折射率变化的线性图作为品质因数（FoM），我们将其量化为13.25。通过这种方法，使用FDTD工具对完全基于铜的八聚体的精度进行了数值验证。这项研究为将铜用作一种高效、低成本且与互补金属氧化物半导体（CMOS）兼容的等离子体材料铺平了道路，该材料具有与类似等离子体物质相似的光学性质。
