Characterization of MgO layers on different alumina and glass substrates by grazing incidence diffractometry and grazing incidence X‐ray reflectometry

Abstract

Magnesium oxide thin films were deposited at an average evaporation rate of 1.8 nm s-' onto different crystalline alumina substrates and amorphous float glass. The deposits were made in an electron-beam evaporator at substrate temperatures between 25OC and 190°C under different oxygen partial pressures. Films of 0.1, 0.5 and 1 pm thickness were deposited. These coatings were investigated by grazing incidence diffractometry (GID) to vary the depth of penetration. For films 0.1 pm thick the additional use of grazing incidence x-ray reflectometry (GIXR) was possible. The deposited films were polycrystalline with different (100) textures depending on the substrate temperature. All the MgO thin-film reflexes measured were strongly broadened compared with the reflexes of a standard polycrystalline MgO material. The crystal size and the microstrain of the MgO coatings were calculated by profile analysis using the Fourier transformation method. It was demonstrated that the x-ray profiles of the MgO reflexes are influenced by the roughness of the substrate surface. Only small gradients were found in the particle sizes and microstrains within the deposited films. The oxygen partial pressure did not significantly influence the film properties measured by GID. The GIXR roughness and mass density measurements agreed with the results of GID. Magnesium oxide films deposited at higher temperatures show a diminished crystallinity and less interface roughness.