Cathodoluminescence of rare-earth-doped zinc aluminate films

Eu-, Tb-, and Tm-doped zinc aluminate (ZnAl2O4) thin film phosphors were prepared by the spray pyrolysis technique at an ambient pressure. The effects of preparation conditions on the cathodoluminescence properties of the films were studied. Films containing Tb3+ and Tm3+ ions exhibited green and blue cathodoluminescence, respectively. For films doped with europium, both red emission lines from Eu3+ and a broad blue–green emission band from Eu2+ were observed. The CIE (Commission Internationale de L'Eclairage) chromatic coordinates, dominant wavelength, and color purity were determined for each phosphor. The luminance and efficiency of these phosphors at a current density of 57 μA/cm2 are found to be linearly dependent on the excitation voltage.