Vibrational spectroscopy of individual surface adsorbates

本研究的目的是开发一种方法，使测定吸附在固体表面上的单个物质的振动能成为可能。为此，我们研究了吸附物的扫描隧道显微镜（STM）发射光谱。我们发现，在STM光发射过程中，位于尖端下方的吸附质的振动运动通过两个通道被激发。一种是隧道电流的直接激发，另一种是隧道电流激发局部表面等离子体（LSP）的激发。当前者通道占主导地位时，在STM发射光谱中可以看到周期性的精细结构。由于时间精细结构的周期与吸收物的振动能量一致，因此可以通过对STM发射光谱的傅里叶分析来确定其值。当后一种通道（即LSP激励）占主导地位时；阶跃结构出现在振动能量以下…更多的是STM光发射光谱中的量子截止点。量子截止值由测量条件决定。因此，你也能从后一个频道了解振动挽歌。理论研究表明，在当前STM光发射波动理论的框架下，周期性精细结构是可再现的。这种阶梯结构可以理解为一种LSP的拉曼散射。本文还探讨了该方法可以确定的振动模式，从STM光谱中推导出了吸附在Ni、Cu和Ag等基体上的氢原子、氧原子和单分子苯的振动模式。此外，我们成功地从STM光发射光谱中确定了衬底本身的声子能量。结果表明，该方法不仅适用于吸附剂的振动光谱分析，而且适用于固体材料（如纳米材料）的振动光谱分析。少

The purpose of the present research was to develop the method that makes it possible to determine the vibrational energies of individual species adsorbed on solid surfaces. For this purpose, we investigated scanning tunneling microscope (STM)light emission spectra of adsorbates. We have found that vibrational motions of the adsorbate being located beneath the tip are excited through two channels in the STM light emission process. One is the direct excitation by the tunneling current and the other is that by localized surface plasmons (LSP) being excited by the tunneling currant. When the Former channel is dominant, periodic fine structures are seen in the STM light emission spectra. Since the period of tine fine structures agrees with the vibrational energy of the absorbate, one can determine its value through the Fourier analysis of the STM light emission spectra. When the latter channel (i.e, excitation by LSP) is dominant; stepwise structures appear at the vibrational energies below … More the quantum cutoff in the STM light emission spectra. The value of the quantum cutoff is determined by the measurement condition. Hence, one can also know the vibrational elegies from the latter channel.. Theoretical investigations show that the periodic fine structures are reproducible in the framework of the currant fluctuation theory of STM light emission. The stepwise structures can be understood as a kind of Raman scattering of LSP by the adsorbate. The vibrational modes that can be determined by the present method were also explored, those of hydrogen atoms, oxygen atoms, and single molecules of benzene adsorbed on various lands of substrates including Ni, Cu, and Ag were deduced from the STM light emission spectra. Furthermore, we succeed in determining the phonon energies of substrate itself from the STM light emission spectra. This result shows that the present method is applicable to vibrational spectroscopy of not only adsorbates but also solid materials (e g., nano-materials). Less