Peis L, He G, Jost D, Rager G, Hackl R
Walther Meissner Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany.
School of Natural Sciences, Technische Universität München, 85748 Garching, Germany.
Rev Sci Instrum. 2023 Jun 1;94(6). doi: 10.1063/5.0139667.
Tip-enhanced Raman spectroscopy (TERS) combines inelastic light scattering well below the diffraction limit down to the nanometer range and scanning probe microscopy and, possibly, spectroscopy. In this way, topographic and spectroscopic as well as single- and two-particle information may simultaneously be collected. While single molecules can now be studied successfully, bulk solids are still not meaningfully accessible. It is the purpose of the work presented here to outline approaches toward this objective. We describe a home-built, liquid helium cooled, ultrahigh vacuum TERS. The setup is based on a scanning tunneling microscope and, as an innovation, an off-axis parabolic mirror having a high numerical aperture of ∼0.85 and a large working distance. The system is equipped with a fast load-lock chamber, a chamber for the in situ preparation of tips, substrates, and samples, and a TERS chamber. Base pressure and temperature in the TERS chamber were ∼3 × 10-11 mbar and 15 K, respectively. Polarization dependent tip-enhanced Raman spectra of the vibration modes of carbon nanotubes were successfully acquired at cryogenic temperature. The new features described here including very low pressure and temperature and the external access to the light polarizations, thus the selection rules, may pave the way toward the investigation of bulk and surface materials.
针尖增强拉曼光谱（TERS）将远低于衍射极限至纳米范围的非弹性光散射与扫描探针显微镜以及可能的光谱学结合起来。通过这种方式，可以同时收集形貌、光谱以及单粒子和双粒子信息。虽然现在已经能够成功研究单分子，但块状固体仍然无法有效地进行检测。本文的目的是概述实现这一目标的方法。我们描述了一种自制的、液氦冷却的超高真空TERS。该装置基于扫描隧道显微镜，并且一项创新是采用了数值孔径约为0.85且工作距离较大的离轴抛物面镜。该系统配备了一个快速负载锁定腔、一个用于原位制备针尖、基底和样品的腔室以及一个TERS腔室。TERS腔室的本底压力和温度分别约为3×10⁻¹¹毫巴和15 K。在低温下成功获得了碳纳米管振动模式的偏振相关针尖增强拉曼光谱。这里描述的新特性，包括非常低的压力和温度以及对光偏振的外部控制，从而可以控制选择规则，可能为块状和表面材料的研究铺平道路。
