The influence of annealing temperature on structure, morphology and optical properties of (In_xGa_1-x)₂O₃ films

In our work, (In_xGa_1-x)₂O₃ films were obtained on sapphire (0001) substrates by radio frequency magnetron sputtering. The influence of annealing temperature on crystalline structure, morphology, transmittance, and the optical band gap was investigated in detail. X-ray diffraction analysis showed that the as-prepared (In_xGa_1-x)₂O₃ film was amorphous and the crystal quality was improved with the increasing of annealing temperature. The (402) ^¯ peak shifted to larger angle with the increasing of annealing temperature. Energy Dispersive Spectrometer analysis showed decreasing trend of In content. X-ray diffraction analysis and Energy Dispersive Spectrometer jointly indicated the peak shift due to the decreasing of In content and variation of tensile stress. The morphology feature of films was investigated by atomic force microscope. The island structure existed in the surface of films at the annealing temperature from 500°C to 900°C and when annealing temperature is 1000°C, islands disappeared and needle-like structure occurred. Transmittance spectra revealed excellence optical properties of films and absorption coefficient spectra showed the decreasing of band gaps of films with the increasing of annealing temperature. It could be attributed to the decreasing of In content and variation of tensile stress.