X-ray diffraction analysis of gallium oxide thin films synthesised by a simple and cost-effective method

Wide energy gap beta type gallium oxide (Ga₂O₃) semiconductor material has attracted many researchers’ interests due to its thermal and chemical stability. For synthesising Ga₂O₃ thin films, sol-gel spin coating is a simple and cost-efficient method, especially for spin coating on a cheap substrate such as silicon (Si) substrate. However, little is known about the spin coating growth of the Ga₂O₃ thin films on Si substrate. In this paper, special attention was first paid to the pre-treatment of the Si substrate and the coated layer. Subsequently, the effects of the annealing temperature on the structural, surface morphology and topography properties of the deposited films were investigated. In-depth XRD analysis using Williamson-Hall (W-H) method was performed to evaluate the crystallite size and micro strain of the deposited films. The results revealed the polycrystalline β-Ga₂O₃ thin films were successfully synthesised by sol–gel spin coating followed by annealing at different temperatures. Also, the pre-treatment processes have greatly improved the uniformity of the film’s thickness. As the annealing temperature increases, the average particle size and the sample surface roughness increase dramatically. The XRD analysis results using the W-H and SSP methods revealed that the crystallite size increased when the annealing increased from 900 to 1000°C, but for the sample annealed at 1100°C, the results were affected by the formation of crystalline SiO₂. The analysis results also showed that the micro strain is not the broadening key factor for the Bragg peaks.