Effect of oxygen pressure on the microstructure and properties of the Al2O3–SiO2 thin films deposited by E-beam evaporation

Thin, amorphous, transparent, hard and adhesive Al2O3–SiO2 films had been prepared by E-beam evaporation in the oxygen pressure range from 1 × 10− 5 to 1 × 10− 3 Torr and characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), UV–Visible spectroscopy (UVS), nanoidentor and scratch test. The XRD result showed that the amorphous Al2O3–SiO2 film had been deposited on the glass substrate, however, when the films were annealed at 1200 °C for 30 min, only reflection of SiO2 phase appears. As observed by SEM, the surface roughness of the films increased with oxygen pressure. The EDS result indicated that low SiO2 content was found when deposited under high oxygen pressure. High optical transmittance was obtained either under high or low oxygen pressure and the effect of oxygen pressure on transmittance is insignificant. The hardness of the films is higher than 7 GPa, promoting with a factor of 2–3, and negligibly decreases with the increase of oxygen pressure. The critical scratch load higher than 50 N shows the film has good adhesion. Besides, the adhesion of the films decreases with the increase of oxygen pressure.