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

在先进的纳米级光子器件中，需要一种纳米级的波导作为远近场转换器件。提出了一种可能的器件，金属纳米粒子等离子体波导管，并观察到沿着光刻图案的金属纳米点链的近场能量转移。在这里，我们利用一种新的近场光解吸效应实现了尺寸和位置可控的超长纳米点链的自组装，并利用射频溅射技术在玻璃衬底上制备了具有100 nm宽和30 nm深的凹槽的纳米点链。在铝的沉积过程中，2.33 eV的光(50 MW)以垂直于凹槽的线偏振(E&lt；90&gt；)的照射，以高度尺寸和位置控制的方式形成了直径99.6 nm、间距27.9 nm、长达100μm的Al纳米点链。纳米点大小和间距的偏差都在5 nm以内。标识c…的位置此外，我们还比较了沉积铝前后玻璃基板表面的形貌原子力显微镜(AFM)图像。轮廓对比表明，纳米点链是在边缘附近形成的。此外，没有得到平行极化E0的点结构。由于电场的边缘增强，E&lt；90&gt；在沟槽边缘的近场强度比E_0强，所以强的近场强度导致了纳米点链的形成。单侧边缘的光点形成源于倾斜照明引起的电场强度分布不对称。这一预测得到了计算的支持。在2.62 eV(100 MW)的E&lt；90&gt；照射下，Al的射频溅射也观察到了Al点链的形成，形成了84.2 nm的纳米点，间距为48.6 nm。虽然周期与2.33 eV光照下制备的结果相似，但点尺寸随光子能量的增加而减小，这表明尺寸和位置控制的点链形成源于沉积的金属纳米颗粒的脱附。由于等离子体激元的共振，金属点具有很强的光吸收，这种吸收强烈地依赖于颗粒的大小。当沉积的金属纳米点达到共振直径时，这会导致金属纳米点的脱附。随着金属点沉积的进行，金属点的生长受到沉积和解吸之间的权衡，这取决于入射光的光子能量。由于纳米点链的形成是基于等离子体共振的大小，因此所得到的结构应该具有高的光学近场能量的传输效率。此外，由于我们的沉积方法是基于光解吸反应，因此它可以广泛地用于与其他金属或半导体制备尺寸和位置可控的纳米结构。较少

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