Development of manipulation technique of metal nanoparticles for plasmonics

本课题的目的是建立一种在扫描电子显微镜下通过微操作移动金属纳米粒子来制造等离子体共振结构的技术。第一年，通过操纵技术证实了等离子体共振结构的可行性。用尖端半径为20 ~ 30 nm的石英探针将直径为100 nm的银微球装入检测器中。这些二聚体显示出长轴偏振的红色散射峰。这些峰被确定为在单个球体中激发的偶极散射共振模式的反对称键模式。然而，我们遇到了一个严重的问题，即扫描电镜观察会影响共振特性。这是由于电子束辐照导致污染物质沉积造成的，这迫使我们改变了原来的研究计划。另一方面，通过系统的理论计算，我们成功地发现了不需要微操作技术的新型等离子体共振结构，获得了纳米级的间隙。因此，在第二年，我们重点建立了新结构的设计方法，并研究了它们的等离子体共振特性。新的发现是，在邻近的金属纳米颗粒中，等离子体共振被认为是二维光波在金属包覆/电芯波导中通过开放端反射传播的法布里-珀罗共振。简而言之，重点是利用微操作技术实现具有有限空腔长度的金属包层波导，而不是利用纳米间隙对粒子进行机械排列。在熔融石英衬底上沉积金/硅（厚度D=1.7 ~ 56nm）/金多层膜，并通过离子束铣削去除其周长（L=55 ~ 495nm），在其边缘制备宽度为3微米、长度为L纳米的矩形腔谐振器。正如理论计算所预测的那样，随着空腔长度的减小，反射倾角发生蓝移。少

The aim of this project was to establish a technique to fabricate plasmon resonance structures by moving metallic nanoparticles by use of micromanipulation in a scanning electron microscope.In the first year, the feasibility of plasmon resonance structures by manipulation technique was confirmed. Silver microspheres of 100 nm diameter were arranged into dieters with quartz probes with a tip radius of 20-30 nm. These dimers showed red scattering peaks for long-axis polarization. These peaks were identified as anti-symmetric bonding mode of dipolar scattering resonance modes excited in individual spheres. However, we encountered a serious problem that the resonance properties are affected by the SEM observation. This is caused by the deposition of contamination materials by electron beam irradiation, which forced us to change the original research plan.On the other hand, we succeeded in discovering new types of plasmon resonance structures which do not require micromanipulation technique … More s to obtain nanometric gap, as a result of systematic theoretical calculation. Therefore, in the second year, we focused on establishing the designing method of the new structures, and investigate their plasmon resonance properties. The new findings was that the plasmon resonance in closely neighboring metallic nanoparticles is regarded as the Fabry-Perot resonance of two-dimensional lightwave propagating in metal-clad/dielectric-core waveguides by the reflection at the open ends. In short, the important point is the realization of metal-clad waveguide with a finite cavity length rather than the mechanical arrangement of particles with a nanometric gap by use of micromanipulation technique. Gold/silica(thickness D=1.7-56nm)/gold multilayers were deposited on fused silica substrates, and at their edges rectangular cavity resonators of 3-micrometer width and L-nanometer length (L=55-495nm) were fabricated by removing their circumferential areas by ion beam milling. As has been predicted by theoretical calculation, the blue shifting of reflection dips was observed as the cavity length decreases. Less