Structural and optical characteristics of gallium oxide thin films deposited by ultrasonic spray pyrolysis

Amorphous gallium oxide thin films were prepared by the ultrasonic spray pyrolysis method using gallium acetylacetonate as source material and water as oxidizer. Samples annealed at 850 degreesC during 1 h show the crystalline beta -phase of Ga2O3. Rutherford backscattering results indicate that both as-deposited and annealed films have the stoichiometric chemical composition without incorporation of carbon impurities. Infrared (IR) spectroscopic measurements show that there is no incorporation of O-H and Ga-OH radicals in any of the studied films. The LR spectra for amorphous films show a broad absorption band from 400 to 900 cm(-1), typical for some amorphous metallic oxides. Meanwhile, for the annealed films the IR spectra show well-defined peaks located at 450 and 670 cm(-1) related to the beta -phase of Ga2O3. The refractive index of the films shows a strong change from 1.846 for the amorphous films to 1.935 for the annealed ones. The optical bandgap energy values are 4.94 eV for the as-deposited films and 4.99 eV for the annealed films. All these changes are associated with a different microstructure of the annealed films. (C) 2001 The Electrochemical Society. All rights reserved.