Development of Angle-Resolved Electron-Stimulated Desorption Spectrometer and its Application to be Detection of Excited Species on Surfaces

我们构建了一种新型的离子光谱仪，称为飞行时间傅里叶变换离子光谱仪(TOFFTIS)，它在很低的能量下具有显著的高探测效率和高能量分辨率。TOFFTIS已安装在超高真空兼容的两轴旋转组件上，并安装在超高真空室中。作为初步实验，我们成功地实现了O~(++)和CO~(++)的电子激发脱附，证明了TOFFTIS具有预期的性能。通过使用TOFFTIS作为高效离子探测器，我们发展了一种新的实验技术--角分辨电子刺激脱附光谱(ARESDS)来研究吸附在固体表面的激发态物种的动态行为。今天，由于分子束外延、有机金属化学气相沉积、X射线/变颗粒光刻等先进材料技术基本上都是基于表面化学过程，因此对固体表面化学反应机理的基本了解是非常必要的。这项新技术利用了撞击电子引起的电子激发引起的离子脱附。众所周知，在电子激发下解吸的离子携带着关于吸附在表面的母体分子的吸附状态的丰富信息。对解吸离子的详细分析将提供基态和激发态的势能面的定量描述。我们还研究了一氧化碳与甲胺和乙炔的共吸附，以及化学吸附氧原子对Mo(112)的化学修饰。

We have constructed a novel ion spectrometer, named time-of-flight Fourier-transform ion spectrometer (TOFFTIS), which has significantly high detection efficiency and high enegy resolution at very low energies. The TOFFTIS has been mounted on an ultrahigh-vacuum compatible two-axis rotation assembly and installed in an ultrahigh-vacuum chamber. As a prelimainary experiment, electron-stimulated desorption of O^+ and CO^+ has been successfully obtained, demonstrating that TOFFTIS has a performance as expected.By using TOFFTIS as a high-efficiency ion detector, we have developed a new experimental technique named angle-resolved electron-stimulated desorption spectroscopy (ARESDS) to investigate the dynamic behavior of excited species adsorbed on solid surfaces. Today, the basic understanding of the mechanism of chemical reactions on solid surfaces is truly demanded, since the advanced material technology, such as molecular-beam epitaxy, organometallic chemical vapor deposition, and X-ray/changed-particle lithogaphy, are based essentially on the surface chemical processes. The new technique utilizes the desorption of ions induced by electronic excitation by impinging electrons. The ions desorbed upon electronic excitations are known to carry rich information about the adsorption state of the parent molecules adsorbed on the surface. Detailed analysis of desorbed ions will provide quantitative description of the potential energy surface, both of ground and excited states. We have also studied on the coadsorption of carbon monoxide with methylamine and acetylene, the chemical modification of Mo(112) by chemisorbed oxygen atoms.