Effect of ZnO buffer layer on the cathodoluminescence of ZnGa ₂O₄/ZnO phosphor screen for FED

A ZnGa₂O₄/ZnO phosphor screen for FED was prepared by RF magnetron sputtering. The ZnO buffer layer has a reasonable resistivity of about 5.2×10³ Ω cm and a high transparency larger than 85%. The ZnGa₂O₄ phosphor was polycrystalline on ITO, yet it was amorphous on ZnO. If the ZnGa₂O₄/ZnO phosphor screen was annealed at temperatures above 300°C, then ZnGa₂O ₄ was crystallized. Owing to the lattice mismatch between ZnGa ₂O₄ and ZnO, the grain size of ZnGa₂O ₄ on ZnO was small. As a result, the effective emission area and luminescence of the ZnGa₂O₄/ZnO phosphor screen were enhanced. Auger electron spectroscopy (AES) examination showed that atoms in ZnO did not diffuse into ZnGa₂O₄ film, and the ZnGa ₂O₄ was Zn-deficient. For charge balance, oxygen vacancy defects in the phosphor film were formed to compensate Zn deficiencies; consequently, the probability for electrons transfer from ²E _B to ⁴A₂ of Ga energy levels was improved and the luminescence of the phosphor was increased.