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.
Rev Sci Instrum. 2023 Feb 1;94(2):023701. doi: 10.1063/5.0133575.
Passive scattering-type, scanning near-field optical microscopy (s-SNOM) has been employed to study localized, long-wavelength infrared (LWIR) surface waves without external illumination. Here, we develop a cryogenic passive s-SNOM instrument in a vacuum chamber with 4 K liquid-helium cooling. Notably, the extremely low-temperature environment inside the chamber enables the realization of passive near-field detection with low background thermal noise. The technique mainly utilizes a highly sensitive LWIR confocal optical system and a tuning fork-based atomic force microscope, and the near-field detection was performed at a wavelength of 10.2 ± 0.9 µm. In this paper, we discuss the cryogenic s-SNOM implementation in detail and report the investigation of thermally excited surface electromagnetic fields on a self-heated NiCr wire deposited on SiO at a temperature of 5 K. The origin of the surface electromagnetic fields was established to be the thermally excited fluctuating charges of the conduction electrons. The cryogenic s-SNOM method presented herein shows significant promise for application in a variety of spheres, including hot-carrier dissipation in ballistic conductors.
被动散射型、扫描近场光学显微镜（s-SNOM）已被用于在无外部照明的情况下研究局域、长波长红外（LWIR）表面波。在这里，我们在一个带有 4 K 液氦冷却的真空室中开发了一种低温被动 s-SNOM 仪器。值得注意的是，腔体内的极低温度环境使得可以实现具有低背景热噪声的被动近场检测。该技术主要利用高灵敏度的 LWIR 共焦光学系统和基于音叉的原子力显微镜，近场检测在 10.2 ± 0.9 µm 的波长下进行。在本文中，我们详细讨论了低温 s-SNOM 的实现，并报告了对沉积在 SiO 上的自加热 NiCr 线在 5 K 温度下热激发表面电磁场的研究。表面电磁场的起源被确定为传导电子热激发的波动电荷。本文提出的低温 s-SNOM 方法在包括弹道导体中的热载流子耗散在内的各种领域中具有广泛的应用前景。
