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In this dissertation core level electron spectroscopy has been employed to study various aspects of metal oxide films grown under ultra-high vacuum conditions.

Studies on in situ ion insertion of lithium into thin TiO₂ systems were performed. The electronic and geometric properties are investigated in detail, along with an estimation of charge transfer from Li to Ti.

A detailed study of chemical vapour deposition of ZrO₂ on Si(100)-(2x1) was performed. ZrO₂ is found to be an insulator, i.e. its electronic levels are decoupled from the substrate and the Zr levels are best referenced to the local vacuum level. The alignment of the valence and conduction band has been determined.

Combinatorial chemical vapour deposition of TiO₂ and ZrO₂ on Si(100)-(2x1) was realized. A film with graded stoichiometry consisting of pure TiO₂ and ZrO₂ on the opposing ends and mixed composition of both oxides in the middle was obtained. A detailed study of the electronic levels revealed that ZrO₂ remains an insulator in the monolayer regime and that modification of ZrO₂ with a small amount of TiO₂ leads to a more symmetric alignment of the bands relative to Si.

The influence of a core hole on the O 1s x-ray absorption spectrum in TiO₂ and ZrO₂ is elucidated. Supported by O 1s photoemission measurements and ab initio calculations it is concluded that the static final state picture as well as dynamical threshold effects must be considered in order to determine the location of the conduction band minimum within the XAS framework.

Finally a Co modified Co:ZnO film was shown to display ferromagnetic properties. It could be evidenced that Co with oxygen as nearest neighbours was responsible for the magnetism and not metallic Co.