Study of Surface Adsorption Mechanism by Core-level Deexcitation Spectroscopy

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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.