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.