Development of self-assembly method using optical near-field with nano-scale controllability in size and position

在先进的纳米光子器件中，需要纳米波导作为远场/近场转换器件。提出了一种可能的器件，金属纳米粒子等离子体波导，并沿着光刻图案的金属纳米点链观察了近场能量转移。在这里，我们利用一种新颖的近场光学解吸效应，开发了一种尺寸和位置控制的超长纳米点链的自组装。采用射频溅射技术在玻璃衬底上制备了宽100 nm、深30 nm的纳米点链。在Al沉积过程中，在垂直于凹槽（E_<90>）的线极化条件下，以2.33 ev （50 mW）光照射，形成了直径为99.6 nm、间距为27.9 nm、长度为100 μm的Al纳米点链，且具有高度的尺寸和位置控制。纳米点尺寸与分离的偏差均小于5 nm。为了确定c…More hain的位置，我们比较了Al沉积前后玻璃基板表面的形貌原子力显微镜（AFM）图像。形貌比较表明，纳米点链在边缘处形成。平行极化E_0时，没有得到点结构。由于电场的边缘增强，E_<90>时凹槽边缘的近场强度比E_0强，强的近场强度导致纳米点链的形成。单侧边缘处的点的形成是由于倾斜照明造成的电场强度分布不对称造成的。这一预测得到了计算的支持。在E_<90>的2.62 ev光（100 mW）下，对Al进行射频溅射，形成了84.2 nm、间距48.6 nm的纳米点。虽然周期与在2.33 ev光照下制备的周期相似，但随着光子能量的增加，点的尺寸成比例地减小，这表明沉积的金属纳米颗粒的脱附形成了尺寸和位置控制的点链。由于等离子体共振，金属点具有很强的光学吸收，这在很大程度上取决于粒子的大小。这可以诱导沉积的金属纳米点在达到共振直径时解吸。随着金属点沉积的进行，生长是由沉积和解吸之间的权衡所控制的，这决定了它们的大小，取决于入射光的光子能量。由于纳米点链是基于等离激元共振形成的，因此所得到的结构应具有高的光学近场能量传输效率。此外，由于我们的沉积方法是基于光解吸反应，它可以广泛应用于与其他金属或半导体一起制造尺寸和位置控制的纳米级结构。少

A nanoscale waveguide is required as a far/near-field conversion device in advanced nanoscale photonic devices. One possible device, a metallic nanoparticle plasmon waveguide, was proposed and near-field energy transfer was observed along the lithographically patterned metallic nanodot chain. Here, we developed the self-assembly of a size- and position-controlled ultra-long nanodot chain using a novel effect of near-field optical desorption.We fabricated a nanodot chain using radio frequency (RF) sputtering under illumination on glass substrate with a 100-nm wide and 30-nm deep groove. During the deposition of Al, illumination of 2.33-eV light (50 mW) with linear polarization perpendicular to the groove (E_<90>) resulted in the formation of a 99.6-nm-diameter Al nanodot chains with 27.9-nm separation that were as long as 100 μm in a highly size- and position-controlled manner. The deviation of both nanodot size and the separation were as small as 5 nm. To identify the position of the c … More hain, we compared topographic atomic force microscopy (AFM) images of the surface of the glass substrate before and after Al deposition. Comparison of the profiles showed that the nanodot chain was formed around edge. Furthermore, no dot structure was obtained with parallel polarization E_0. Since the near-field intensity with E_<90> was strongly enhanced at the edge of the groove in comparison with E_0 owing to edge enhancement of the electrical field, a strong near-field intensity results in nanodot chain formation. The dot formation at the one-sided edge originates from the asymmetric electric-field intensity distribution, owing to the slanted illumination. This prediction is supported by calculations.Al-dot chain formation was also observed with RF sputtering of Al under illumination of a 2.62-eV light (100 mW) with E_<90>, which resulted in the formation of 84.2-nm nanodot with 48.6-nm separation. Although the period was similar to that fabricated under 2.33-eV illumination, the dot size was reduced in proportion to the increase in the photon energy, indicating that the size- and position-controlled dot-chain formation originates from desorption of the deposited metallic nanoparticles. A metallic dot has a strong optical absorption due to plasmon resonance, which strongly depends on particle size. This can induce desorption of the deposited metallic nanodot when it reaches the resonant diameter. As the deposition of metallic dots proceeds, the growth is governed by a trade-off between deposition and desorption, which determines their size, depending on the photon energy of the incident light.Since the nanodot chain forms at the size based on plasmon resonance, the resulting structure should have high transmission efficiency of optical near-field energy. Furthermore, since our deposition method is based on a photo-desorption reaction, it could be widely used to fabricate size- and position-controlled nanoscale structures with other metals or semiconductors. Less