Study of Surface Adsorption Mechanism by Core-level Deexcitation Spectroscopy

分子在固体表面的吸附可以看作是各种表面反应(如催化反应)的基本过程，因此阐明吸附过程的微观机理是非常重要的。当一个分子吸附在表面上时，吸附键合轨道是通过分子的轨道与表面的杂化形成的，研究杂化机理对于阐明吸附过程的机理是至关重要的。通常用光电子能谱研究吸附成键能级，但在光电子能谱中，吸附能级不可避免地与体带发射重叠，很难分辨出吸附成键能级。这项工作的目的是发展一种方法，利用芯级去激光谱选择性地观察TiC(111)表面的吸附成键能级。当TiC(111)表面暴露在氧气中时，氧被解离地吸附形成(1x1)覆盖层。在Ti3p-3激发的条件下测量了光电子能谱，发现O2p、Ti3d吸附能级共振增强，成为价带谱的主峰。从而证明了用芯级去激发光谱可以选择性地测量吸附成键能级。众所周知，碱金属诱导键合水平很难观察到，因为它的横截面很小。然而，事实证明，利用能级去激发谱可以选择性地观察到成键能级。

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.