Photoluminescence properties of Eu-doped CaNb₂O₆ thin films grown by radio-frequency magnetron sputtering

Europium doped calcium niobate (CaNb₂O₆:Eu³⁺) phosphor thin films were deposited on quartz using a radio-frequency magnetron sputtering technique at different growth temperatures in the range of 100–400 °C. The phosphor films grown at different deposition temperatures showed different microstructural and optical properties. The structural characterization indicated that the phosphor films were preferentially (131) oriented. The surface morphology of the thin films exhibited spherical-shaped crystallite grains with an average diameter of 40 nm, and agglomerated islands were observed at a growth temperature of 400 °C. Increased growth temperature resulted in an increase in both the transmittance and photoluminescence intensity, arising from better crystallinity. The emission spectra of the films under excitation at 265 nm showed five dominant emission peaks centered at 541, 597, 618, 656, and 707 nm. The maximum intensity in orange-reddish emission at 618 nm was observed for the phosphor thin film deposited at 400 °C. These results suggest that the CaNb₂O₆:Eu³⁺ phosphor thin film is a promising candidate for use as a red-emitting phosphor thin film for displays and photonic device applications.