Effects of dry oxidation treatments on the characteristics of gallium oxide thin films prepared using sol-gel spin coating method

In this paper, gallium oxide (Ga₂O₃) thin films were grown on silicon (Si) substrate using a relatively simple and low-cost sol-gel spin coating method followed a dry oxidation process. A series of dry oxidation experiments with different oxygen flow rates (i.e., from 2 L/min – 5 L/min) under 1100°C at 1 h were conducted. The effects of the oxygen gas flow rates on the deposited films’ structural, surface morphology, and optical properties were investigated. All results revealed that crystalline Ga₂O₃ layers were formed. From the X-ray diffraction results, all deposited films exhibit two prominent diffraction peaks corresponding to the monoclinic β-Ga₂O₃ (110) and (002) diffraction planes. FESEM micrographs and AFM images topography revealed that a crystalline layer with nanocrystallite size was formed. The optical band gap energy of the deposited films was extracted from the ultraviolet-violet diffuse reflection spectra. The obtained energy bandgap is within the range of 4.69–4.79 eV, i.e., in reasonable agreement with the reported values. As the O₂ flow rate increased from 2 L/min to 5 L/min, the crystallite size, the surface roughness, and the optical energy band gap of the β-Ga₂O₃ films were decreased with increasing O₂ flow rate.