Influence of substrate heating for microstructure and physical properties of Cu-Al-O thin film

We prepared Cu-Al-O thin films on silicon and quartz substrate by direct current (DC) reactive magnetron sputtering method. The substrate temperatures varied at room temperature (~25℃) and 200℃ with post-annealed at 900℃ in argon atmosphere for 3h. The results indicate that the film prepared at 200℃ is beneficial for the growth of CuAlO2 which acts as the main phase of the film. No Cu2+ compounds exist in the film. The grains are dense in the film and no cracks appear. The transmittance of the film in visible region is higher due to crystal with high quality and the main phase being CuAlO2. The scratch test shows the film experiences elastic deformation, plastic deformation, lateral crack forming, crack evolve and rupturing stage with the critical force being 45N when the progressively increasing load applied to the film. We established the relationship between Cu-Al-O thin film microstructures, opto-electrical properties and adhesion between the film and substrate, shedding light on the preparation of multifunctional p-type semiconductor thin films.