Visualization of subnanometric phonon modes in a plasmonic nano-cavity via ambient tip-enhanced Raman spectroscopy
Visualization of subnanometric phonon modes in a plasmonic nano-cavity via ambient tip-enhanced Raman spectroscopy
复制标题
DOI：
10.1038/s41699-019-0121-7
复制
发表时间：
2019-10-14
影响因子：
9.7
通讯作者：
Tanaka, Takuo
中科院分区：
文献类型：
--
作者：
Balois, Maria Vanessa;Hayazawa, Norihiko;Tanaka, Takuo
声子从材料的振动谱中提供了晶格的物理化学性质的信息。特别是光学声子，可以使用基于光的技术在微米和纳米尺度上进行探测，例如微拉曼和尖端增强拉曼光谱（TERS）。然而，选择规则控制着声子的可及性，因此也控制着可以提取的样本信息。在此，我们同时观察了单层石墨烯中无缺陷区域的允许和禁止光学声子模式，分别研究了纳米尺度的应变变化和拉曼峰的等离子体激活。通过TERS成像，以0.7 nm的空间分辨率可视化了应变变化和低至5 nm的纳米尺寸域。此外，这种亚纳米限制不仅激活了D和D‘禁声子模式，还激活了它们的D + D’组合模式。利用我们的环境系统中的TERS，无缺陷石墨烯和其他二维纳米材料的完整声子表征现在是可能的，这将有助于亚纳米应变分析和探索无缺陷材料的固有特性。
Phonons provide information on the physicochemical properties of a crystalline lattice from the material's vibrational spectrum. Optical phonons, in particular, can be probed at both micrometre and nanometre scales using light-based techniques, such as, micro-Raman and tip-enhanced Raman spectroscopy (TERS), respectively. Selection rules, however, govern the accessibility of the phonons and, hence, the information that can be extracted about the sample. Herein, we simultaneously observe both allowed and forbidden optical phonon modes of defect-free areas in monolayer graphene to study nanometre scale strain variations and plasmonic activation of the Raman peaks, respectively, using our home-built TERS system in ambient. Through TERS imaging, strain variations and nanometre-sized domains down to 5 nm were visualised with a spatial resolution of 0.7 nm. Moreover, such subnanometric confinement was found to activate not only the D and D' forbidden phonon modes but also their D + D' combination mode. With our TERS in ambient system, the full phonon characterisation of defect-free graphene and other 2D nanomaterials is now possible, which will be useful for subnanometre strain analysis and exploring the inherent properties of defect-free materials.