Institute of Industrial Science , the University of Tokyo , Komaba 4-6-1, Meguro-ku , Tokyo , 153-8505 , Japan.
Department of Basic Science , the University of Tokyo , Komaba 3-8-1, Meguro-ku , Tokyo 153-8902 , Japan.
Nano Lett. 2018 Jul 11;18(7):4220-4225. doi: 10.1021/acs.nanolett.8b01178. Epub 2018 Jun 12.
Probing spatial variation of temperature at the nanoscale provides key information for exploring diverse areas of modern science and technology. Despite significant progress in the development of contact thermometers with high spatial resolution, one inherent disadvantage is that the quantitative analysis of temperature can be complicated by the direct thermal contact. On the other hand, noncontact infrared radiation thermometer is free from such contact-induced disturbance, but suffers from insufficient spatial resolution stemming from diffraction-limit in the micrometer range. Combining a home-built sensitive infrared microscope with a noncontact scattering probe, we detected fluctuating electromagnetic evanescent fields on locally heated material surface, and thereby mapped temperature distribution in subwavelength scales. We visualize nanoscale Joule heating on current-carrying metal wires and find localized "hot-spots" developing along sharp corners of bended wires in the temperature mapping. Simulation calculations give quantitative account of the nanoscale temperature distribution, definitely indicating that the observed effect is caused by the nonuniform energy dissipation due to the current-crowding effect. The equipment in this work is a near-field version of infrared radiation thermometer with a spatial resolution far below the detection wavelength (<100 nm, or λ/140) in which local temperature distribution of operating nanoscale devices can be noninvasively mapped with a temperature resolution ∼2 K at room-temperature.
探测纳米尺度的温度空间变化为探索现代科学技术的各个领域提供了关键信息。尽管具有高空间分辨率的接触式温度计在开发方面取得了重大进展，但一个固有缺点是，由于直接热接触，定量分析温度可能会变得复杂。另一方面，非接触式红外辐射温度计不会受到这种接触引起的干扰，但由于微米范围内的衍射限制，其空间分辨率不足。我们结合了自制的灵敏红外显微镜和非接触散射探针，探测到局部加热材料表面上的波动电磁消逝场，从而在亚波长尺度上绘制了温度分布。我们可视化了载流金属线上的纳米级焦耳加热，并在温度图中发现了弯曲金属线上尖锐拐角处出现的局部“热点”。模拟计算定量说明了纳米级温度分布，明确表明观察到的效应是由于电流拥挤效应导致的不均匀能量耗散引起的。这项工作中的设备是一种近场版本的红外辐射温度计，其空间分辨率远低于探测波长（<100nm 或 λ/140），在室温下，可以以约 2K 的温度分辨率对工作纳米器件的局部温度分布进行非侵入式映射。
