Combustion chemical vapour deposition of Al2O3 films: Effect of temperature on structure, morphology and adhesion

Alumina films were synthesized on Si(100) substrates at different temperatures in the range of 600 to 900 °C using open atmosphere combustion chemical vapour deposition (C-CVD) technique. A custom made premixed-diffusion type burner with an extra coaxial oxygen inlet close to the burner mouth enabled variation of deposition temperature from 600 to 900 °C in steps of 100 (± 10) °C. The presence of γ- and θ-alumina phases were observed in films synthesized in the temperature range of 600-800 °C, whereas at 900 °C single phase θ-alumina films were obtained. Adherent coatings were obtained at temperatures ≥ 700 °C. The grain size and roughness of the films increased with deposition temperature. The films underwent two types of adhesion failures, a continuous ductile perforation and a tensile type hertzian crack due to the presence of interfacial oxide layer, during scratch test. The presence of SiO₂ interfacial layer between substrate and film was discerned from ellipsometric studies.