Coordination-resolved Bond And Electron Spectrometrics Of Au Atomic Clusters, Solid Skins, And Oxidized Foils

The study on nano material has been the one hot spot of materials science. The quest rages had never ceased since it was discovery. Nano material has its own novel and fascinating properties which can hardly be seen from its bulk parent, its enormous potential in application attracts great attentions. Exploring the physical mechanism behind the unusual properties of nano material is important and have great value. However, using the classical theroy for nano material directly encounter some different difficulties. Therefore, a new theoretical model to interpret and forecast the properties of nano material reasonablly is highly demanded.We have discussed the unusual properties of nano material in the frame of bond order-length-strength(BOLS) correlation notion from the effect of under-coordinated atoms. The under-coordinated atoms is widely exist in material and account for less percentage in bulk material. So the under-coordinated effect could be neglected. However, the proportion of this atoms is so large in nano material that make a tremendous impact on the properties.A combination of BOLS theroy, tight-binding(TB) approach, X-ray photoelectron spectroscopy(XPS) and zone-selective photoelectron spectrometrics(ZPS) has enabled us to resolve the local bond relaxation and the associated energy level shift of Au skins, surface oxidation and atomic clusters, in addition, the size effect of energy level shift. The work and results are summarized as following:1. The BOLS-TB theory indicates that bonds between undercoordinated atoms become shorter and stronger. These cause local densification of bonding electrons and energy and hence provide perturbation to the crystal potential, results the core level shift. We determine the size dependent core-level shift and decompose the 4f7/2 core-level XPS of Au surfaces. The quantitative information obtained from spectra decomposition such as binding energy of an isolated atom and energy level shift is important. Thus we can forecast some related quantities.2. We analyes 4f7/2 core-level shifts of Au surface during oxidation by using the ZPSmethod. Results show that the O atoms with strong oxidizing disturbs the crystal structure and local potential of surface, and hence the reconsitution of surface morphology and core-level shift. The reconsitution also has an effect on core-level shift.3. The ZPS spectra of Au atomic clusters 4f core-level and d-band revealed its energy shift relative to the bulk. The BE of both 4f core-level and d-band will shift to the deeper. These proved the viewpoint of BOLS. Results show that the d-band BE shift is larger than that of the 4f core-level. In addition, the BE shift of top level of d-band is larger than that of the level on bottom. This means that the width of d-band became narrow and hence reduce the transition energy of valence electrons. The size dependent core-level BE of Au atomic clusters is in accordance with experiments.Theoretical analyes is consistent with experiments, which confirms that the BOLS-TB theory is available in interpret and forecast the energy level shift of undercoordinated systems, which is instructive to the researches and applications.