Cathodoluminescence of a white ZnGa₂O₄/ZnO phosphor screen

This paper investigates the cathodoluminescence of a white ZnGa ₂O₄/ZnO/ITO/glass phosphor screen. The effect of a ZnO buffer layer and annealing temperature on the luminescence property of a phosphor screen are discussed as well. The films were prepared by the radio frequency magnetron sputtering with optimal deposition parameters. The preferred growth plane for the ZnO buffer layer was found to be (002). The ZnGa ₂O₄ phosphor layer, when deposited on top of ZnO, was amorphous even when it was annealed at 250°C. However, when the annealing temperature was above 300°C, the ZnGa₂O₄ was polycrystalline, and an apparent cathodoluminescence of the ZnGa ₂O₄/ZnO phosphor screen was observed. The ligand field and electron transition probability in the Ga d orbit were altered because of the lattice mismatch between the ZnGa₂O₄ and ZnO films and the thermal treatment. The lowest resistivity and optimal luminescence of a white ZnGa₂O₄/ZnO/ITO/glass phosphor screen was obtained by annealing at 400°C.