Influence of Annealing Temperature on the Properties of ZnGa2O4 Thin Films by Magnetron Sputtering

Zinc gallate (ZnGa2O4) thin films were grown on sapphire (0001) substrate using radio frequency (RF) magnetron sputtering. After the thin film deposition process, the grown ZnGa2O4 was annealed at a temperature ranging from 500 to 900 degrees C at atmospheric conditions. The average crystallite size of the grown ZnGa2O4 thin films increased from 11.94 to 27.05 nm as the annealing temperature rose from 500 to 900 degrees C. Excess Ga released from ZnGa2O4 during thermal annealing treatment resulted in the appearance of a Ga2O3 phase. High-resolution transmission electron microscope image analysis revealed that the preferential crystallographic orientation of the well-arranged, quasi-single-crystalline ZnGa2O4 (111) plane lattice fringes were formed after the thermal annealing process. The effect of crystallite sizes and lattice strain on the width of the X-ray diffraction peak of the annealed ZnGa2O4 thin films were investigated using Williamson-Hall analysis. The results indicate that the crystalline quality of the deposited ZnGa2O4 thin film improved at higher annealing temperatures.