Probing the conduction band edge of transition metal oxides by X-ray absorption spectroscopy

We present a comprehensive picture of how X-ray absorption spectroscopy (XAS) at the O 1s edge, supported by ab initio calculations, can be used to address the electronic properties of the conduction band edges of transition metal oxides. The compounds studied in order to illustrate the method are two of the most versatile transition metal oxides, ZrO2 and TiO2. Special attention is paid to the subtler aspects of the approach, discussing in more detail the kind of information provided and also possible shortcomings and complications. It is shown that the interpretation of the relationship between the Fermi level-referenced O 1s PES peak and the O 1s XAS spectrum can change depending on the electronic properties of the material under study. In order to fully understand the PES-XAS relationship, supporting information from calculations is essential.