Study of Al2O3 nanolayers synthesized onto porous SiO2 using X-ray reflection spectroscopy

The structure of alumina (Al2O3) films with different thickness grown by the atomic layer deposition method on porous silica substrates has been studied using soft X-ray reflection spectroscopy. It was established that synthesized films were amorphous and the proportion of Al coordination (tetrahedral: octahedral) depends on the film thickness. The film growth starts from excess of tetrahedral (AlO4) coordination and thickening of the film leads to increasing of number of octahedral (AlO6) coordination in the structure. A critical thickness of amorphous Al2O3 film exists (in the range of studied films, this is a thickness of 13 nm). For thicker films, the structure of amorphous Al2O3 film corresponds to massive film with the typical proportion of tetrahedrally and octahedrally coordinated sites in the structure.