Identification of individual surface adsorbates

我们已经成功地证明，固体表面上的单个吸附物可以识别与扫描隧道显微镜（STM）的光发射光谱。STM已被证明是一个非常强大的工具，可视化表面纳米结构与原子空间分辨率。虽然吸附在表面上的原子或分子可以通过STM可视化，但它们的种类不能单独从STM图像中识别。在表面科学和纳米技术的许多领域中，用于识别单个吸附物的方法是非常期望的。当电子从STM的尖端注入样品表面时，发射可见光。由于由STM针尖发射的电子束的横截面是原子尺寸的量级，隧穿电子被选择性地注入到具有相应尺寸的区域中。因此，当尖端位于通过常规STM操作成像的吸附物上方时，激发的光谱（即，STM光发射光谱）将反映其性质。本项目的目的是证明表面吸附物可以通过STM光发射光谱来识别。为此，我们测量了吸附物和基底的各种组合的STM光发射光谱; Cu（110）、Ni（110）和Ag（110）上的氧原子，Ni（110）上的氢原子，Cu（110）、Pt（110）和Ni（110）上的CO分子，以及高度有序热解石墨（HOPG）上的罗丹明6 G分子。我们发现，这些吸附物的光谱是不同的那些相应的基板。这一结果清楚地表明，表面吸附物的识别成为可能的STM光发射测量。

We have successfully demonstrated that individual adsorbates on solid surfaces can be identified with scanning tunneling microscope (STM) light emission spectroscopy. STM has proven to be a very powerful tool for visualizing surface nano-structures with atomic spatial resolution. While an atom or a molecule adsorbed on a surface can be visualized by STM, their species cannot be identified from the STM image alone. Methods for identifying individual adsorbates are highly desirable in many fields of surface science and nanotechnology. When electrons are injected into a sample surface from the tip of a STM, visible light is emitted. Since the cross-section of the electron beam emitted by the STM tip is on the order of the atomic size, the tunneling electrons are selectively injected into the area with the corresponding size. Hence when the tip is located over an adsorbate imaged by the conventional STM operation, the excited optical spectrum (i.e., STM light emission spectrum) will reflect its properties. The purpose of the present project was to demonstrate that surface adsorbates can be identified by STM light emission spectra. For this purpose we have measured the STM light emission spectra of various combinations of adsorbates and substrates ; oxygen atoms on Cu(110), Ni(110) and Ag(110), hydrogen atoms on Ni(110), CO molecules on Cu(110), Pt(110), and Ni(110), and Rhodamine 6G molecules on highly ordered pyrolytic graphite (HOPG). We found that the optical spectra of these adsorbates are different from those of the corresponding substrates. This result clearly indicates that identification of surface adsorbates becomes possible by STM light emission measurements.