Effect of Oxygen on the Characteristics of ZnGa2O4 Thin Film Grown by Radio Frequency Magnetron Sputtering

Abstract

The characteristics of the ZnGa2O4 thin films were influenced by the percentage of oxygen during RF sputtering. The Ga/Zn ratio of the thin film increased remarkable when the lower percentage of oxygen was adopted. The excess Ga(superscript 3+) ions were dissolved in the host lattice of the thin films and substitute the Zn2 ions. Because the radius of Ga(superscript 3+) ion is smaller than the one of Zn(superscript 2+) ion, the lattice parameter of the thin film would be reduced by the solution of the excess Ga(superscript 3+). The higher Ga/Zn ratio became, the smaller lattice parameter approached. Meanwhile, the variation of the lattice parameter of the thin film might cause the crystal field different in the host lattice. Due to the various distorted effect of crystal field, the cathodoluminescent properties of the thin film were also different. The ZnGa2O4 thin film, which was deposited with the lower percentage of oxygen (0.25%), would emit blue light near 470 nm. When the higher 02 partial pressure (Ga/Zn ratio decreased) was used during sputtering, the main peak of the emission spectrum of the ZnGa2O4 thin film was shifted to lower wavelength (440 nm). The indirect band gap of the ZnGa2O4 host lattice was calculated to be 4.25 eV.