Abstract:
This thesis is a focus on the chemistry of simple oxygen containing molecules over the oxide surfaces of uranium and titanium. Specifically, the reactivity of several Cl molecules (including CO, HCOOH, HCHO, CO₂ and HCONH₂) and H₂O is studied over the ideal surfaces of TiO₂ (001) and UO₂ (111) single crystals in ultra high vacuum (UHV) conditions. A selected comparison of the reactivity is made by performing similar studies over polycrystalline surfaces of UO₂ (powder and thin film) and U3O₈ at atmospheric, UHV and high vacuum (HV) conditions. The characterisation of the stoichiometric and defected surfaces of the single crystal and polycrystalline surfaces is performed extensively using Raman, X-ray Photoelectron Spectroscopy (XPS), Synchrotron XPS (sXPS), Auger Electron Spectroscopy (AES), X-ray Diffraction (XRD) and Low Energy Electron Diffraction (LEED). The reactivity and thermal chemistry is studied using Temperature Programmed Desorption (TPD). The identification of surface intermediates was performed using in situ Infrared Spectroscopy (FTIR) and Temperature Programmed XPS (TPXPS). The extent of adsorbate induced/thermal surface modification of the post-reacted surface is studied by LEED, XPS, Raman and XRD.