Structure, Morphology, and Optical Properties of Amorphous and Nanocrystalline Gallium Oxide Thin Films

Gallium oxide (Ga2O3) thin films were produced by sputter deposition by varying the substrate temperature (T-s) in a wide range (T-s = 25-800 degrees C). The structural characteristics and optical properties of Ga2O3 films were evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), Rutherford backscattering spectrometry (RBS), and spectrophotometric measurements. The effect of growth temperature is significant on the chemistry, crystal structure, and morphology of Ga2O3 films. XRD and SEM analyses indicate that the Ga2O3 films grown at lower temperatures were amorphous, while those grown at T-s >= 500 degrees C were nanocrystalline. RBS measurements indicate the well-maintained stoichiometry of Ga2O3 films at T-s = 300-800 degrees C. The spectral transmission of the films increased with increasing temperature. The band gap of the films varied from 4.96 to 5.17 eV for a variation in T-s in the range 25-800 degrees C. A relationship between microstructure and optical property is discussed.