Influence of Al content on the properties of MgO grown by reactive magnetron sputtering

DC reactive magnetron sputtering was applied to deposit mixed oxide thin films. To modify the stoichiometry of the thin film in a flexible way, co-sputter deposition with metal targets mounted on two separate magnetrons was used. A series of coatings was produced with a stoichiometry of the thin film ranging from MgO, over MgxAlyOz to Al2O3. The influence of the stoichiometry on several properties of these thin films was investigated. Surface energy, crystallinity, hardness, refractive index and surface roughness were measured. A clear relationship between all properties and the stoichiometry was found, indicating a critical composition region where the properties exhibit an abrupt change. To understand this behaviour, the crystallographic and morphology were studied using a combination of XRD, SEM and TEM, indicating that the addition of Al influences the growth mechanism of MgO