Investigation of thermal annealing effects on the optical transparency and luminescent characteristics of Eu-doped Y2O3 thin films

The thermal annealing effects on the optical transparency and luminescent characteristics of the Eu-doped Y2O3 thin films have been investigated. The as-deposited Y2O3: Eu films exhibited an optical band gap of 5.78 eV with a transparency of 89 % at a wavelength of 550 nm. As the annealing temperature increased from 1000 to 1300 degrees C, the optical band gap and transparency of the films decreased from 5.77 to 4.91 eV and from 86.8 to 64.5 % at 550 nm, respectively. The crystalline quality of the films was improved with increasing annealing temperature. The annealed Y2O3: Eu films emitted a red-color photoluminescence (PL) with the highest emission peak near 612 nm. The PL intensity was increased with increasing annealing temperature to 1200 degrees C, resulting from the improvement in the crystalline quality of the films. The PL intensity was decreased with further increasing temperature above 1200 degrees C due to the formation of Y2SiO5 phase by the reaction of the film with the quartz substrate.