Surface structure of TiO2-anatase (001) films

The main objective of this six months internship was to grow TiO2-anatase (001) layers on top of substrates such as strontium titanate, SrTiO3, and study and optimize their structure. Films were grown by Molecular Beam Epitaxy (MBE) deposition technique. This was achieved by optimizing the deposition parameters and conditions. Once the deposition is done, the surface structure is analyzed using the Low Energy Electron Diffraction (LEED), while chemical composition and the presence of contaminants was investigated by Auger Electron Spectroscopy (AES). The experimental set-up allowing to record and analyze quantitative LEED has been implemented only at the end of the internship and it was not possible to record the intensity of LEED diffraction spots versus electron energy. On the other hand, a film was studied by surface x-ray diffraction, recording a full data set for determining the structure. This data analysis is beyond the objective of this internship. The earlier mentioned experimental methods were employed to examine films grown on various substrates under diverse physical conditions. The research seeks to achieve an in-depth understanding of how atoms are organized on the surface of these specifically oriented TiO2-anatase films grown on particular substrates. This understanding is important for optimizing the potential applications of these films, particularly in photocatalysis, where the TiO2-anatase (001) is newsworthy due to its photocatalytic behavior. The results obtained during this internship demonstrate the effectiveness of using MBE to deposit TiO2-anatase (001) thin films with well-aligned crystalline structures on various substrates under controlled conditions. LEED analysis allowed to examine the surface structure and atomic arrangement, demonstrating the influence of the substrate on the orientation and quality of the film. Auger Spectroscopy identified the chemical composition, revealing the presence of titanium, oxygen and traces of iridium, providing essential information on any defects and contaminants. Different deposition parameters, such as substrate temperature and oxygen pressure, showed a significant impact on the film quality, with oxygen crackers improving oxidation and reducing defects. Finally, the observed surface reconstructions were consistent with theoretical models [1] [2] and confirmed the epitaxial orientation of the films, in agreement with previous studies on thin film growth.