Investigation Of Atomic Structures,Adsorption Behaviors Of Anatase TiO₂（001） Films And Contronlling Band Strcuture Through （Cr, N） Co-Doping

Anatase phase TiO2is widely used as photocatalyst. In this thesis, we focus our studies mainly on the surface structure, adsorption behaviors, and the reactive sites of anatasae TiO2(001) thin films and the band strcutrure adjustment through Cr, N doping using various techniques, such as scanning tunneling microsocpy (STM), x-ray diffraction (XRD), photoemission spectrsocopy (PES), joint with First-Pinciples cacluations.In chapter1, we introduce the fundamental principles of STM, PES and pulsed-laser deposition method (PLD) for sample preparation. Followed, we give the detailed configurations of the systems of PLD, STM, PES used in this study. In chapter2, we introduce the catalytical properties of TiO2, its applications, and the importance of growth and characterization of atomically flat anatase phase TiO2surfaces. We give the detailed information about the preparation of atomically flat anatase TiO2(001) thin films via PLD.In chapter3, we show the experimental results on the surface of anatase TiO2(001)-1×4reconstructed films. According to high resolution STM images and adsorption behaviors of small molecules, like H2O, O2, CO2, CO, we suggest that the oxidized anatase TiO2(001)-1×4is not so reactive with these molecules at room temperature. However, the partially reduced surface shows adsorption and relative high reactivity at the Ti-rich point defects. On the basis of our observations, we propose a modificed "ad-molecule model" with a6-fold coordinated terminal Ti atoms, which may well explain our results.In chapter4, we investigate the Cr and N doped TiO2both in rultile and anatase phases. CrN-codoped anatase TiO2(001) films and Cr doped rutile TiO2(110) films and were prepared. According to the PES and UV-Vis adsorption spectrum, we found that the band gap of codoped film was drastically narrowed, which may be further used in photocatalytic investigations. The experiment of dehydrogenation of CH3OH under irradiation shows that Cr doped rutile TiO2has no visible light potocatalytical activity.