Cirera Borja, Liu Shuyi, Park Youngwook, Hamada Ikutaro, Wolf Martin, Shiotari Akitoshi, Kumagai Takashi
Department of Physical Chemistry, Fritz-Haber Institute of the Max-Planck Society, Faradayweg 4-6, Berlin 14195, Germany.
Instituto de Ciencia de Materiales de Madrid (CSIC), Campus de Excelencia de la Universidad Autónoma de Madrid, c/Sor Juana Inés de la Cruz 3, 28049, Spain.
Phys Chem Chem Phys. 2024 Aug 14;26(32):21325-21331. doi: 10.1039/d4cp01803f.
Tip-enhanced Raman spectroscopy (TERS), combined with low-temperature scanning tunnelling microscopy (STM), has emerged as a highly sensitive method for chemical characterization, offering even sub-molecular resolution. However, its exceptional sensitivity is generally limited to molecules adsorbed onto plasmonic surfaces. Here we demonstrate single-molecule TERS for fullerene (C) adsorbed on the Si(111)-(7 × 7) reconstructed surface. Distinct adsorption geometries of C are manifested in the TERS spectra. In addition, we reveal that formation of a molecular-point-contact (MPC) drastically enhances Raman scattering and leads to the emergence of additional vibrational peaks, including overtones and combinations. In the MPC regime, the anti-Stokes peaks are observed, revealing that vibrationally excited states are populated through optical excitation of the MPC junction, whereas showing no significant vibrational heating by current flow inelastic electron-vibration scattering. Our results will open up the possibility of applying TERS for semiconducting surfaces and studying microscopic mechanisms of vibrational heating in metal-molecule-semiconductor nanojunctions.
针尖增强拉曼光谱（TERS）与低温扫描隧道显微镜（STM）相结合，已成为一种用于化学表征的高灵敏度方法，甚至能提供亚分子分辨率。然而，其卓越的灵敏度通常仅限于吸附在等离子体表面的分子。在此，我们展示了吸附在Si(111)-(7×7)重构表面上的富勒烯（C）的单分子TERS。C的不同吸附几何结构在TERS光谱中得以体现。此外，我们发现分子点接触（MPC）的形成极大地增强了拉曼散射，并导致出现额外的振动峰，包括泛音和组合峰。在MPC状态下，观察到了反斯托克斯峰，这表明通过MPC结的光激发使振动激发态得以填充，而通过电流非弹性电子 - 振动散射未显示出明显的振动加热现象。我们的结果将开启在半导体表面应用TERS以及研究金属 - 分子 - 半导体纳米结中振动加热微观机制的可能性。
