Study of Surface Adsorption Mechanism by Core-level Deexcitation Spectroscopy

分子在固体表面上的吸附可以看作是催化反应等各种表面反应的基本过程，因此阐明吸附过程的微观机理是非常重要的。分子在表面上吸附时，分子轨道与表面轨道之间的杂化作用形成吸附成键轨道，研究杂化机理对阐明吸附过程的机理具有重要意义。通常用光电子能谱研究吸附键能级，但在光电子能谱中，吸附能级不可避免地与体带发射重叠，难以分辨吸附键能级。本工作的目的是发展一种利用芯能级去激子谱选择性地观察TiC（111）表面吸附键能级的方法，当TiC（111）表面暴露于氧时，氧被解离吸附，形成（1x 1）覆盖层。在Ti 3 p-3激发条件下测量光电子能谱时发现，O2p^Ti3d吸附能级共振增强，成为价带谱的主峰。从而证明了利用芯能级退激光谱可以选择性地测量吸附成键能级。已知的是，由于小的横截面，碱金属诱导的键合水平难以观察。然而，它被证明是可以选择性地观察到的成键水平，通过使用obcore级退激光谱。

Adsorption of molecules on solid surefaces can be viewed as a elemental process of various surface reactions such as catalytic reactions, thus it is very important to elucidate the details of the microscopic mechanism of adsorption process. When a molecule adsorbs on a surface, the adsorption bonding orbital should be formed through the hybridization between the orbitals of the molecule and the surface, and it is essentially important to investigate the hybridization mechanism to elucidate the mechanism of adsorption process. Usually, the adsorption bonding levels are studied with photoemission spectroscopy, however, the adsorption level is inevitably overlapped with the bulk band emissions in the photoemission spectra and it is difficult to resolve adsorptioh bonding levels. The purpose of this work is to develop the method to observe the adsorption bonding levels selectively by the use of core-level deexciation spectroscopy.As the TiC (111) surface is exposed to oxygen, oxygen is adsorved dissociatively forming (1x1) overlayr. As the photoemission spectrum is measured under the conditiuon where Ti3p-3dexcitation occurs, it has been found that the O2p^Ti 3dadsorption level is resonantly enhanced to become main peak in the valence band spectra. Thus it is proved that adsorption bonding level can be selectively measured using core-level deexcitation spectroscopy. It is known that the alkali metal induced bonding level is difficult to observe due to the small cross section, . However it is proved that the bonding level can be selectively observed by the use obcore-level deexcitation spectroscopy.