The Y₂O₃:Eu films were prepared on sapphire substrates by radio frequency magnetron sputtering. The samples were post-annealed in an air ambient at different temperatures. The Y₂O₃:Eu films prior to annealing did not show photoluminescence (PL), however, after annealing, the films became capable of emitting photoluminescent light. The PL spectra were composed of several peaks originating from the transitions between 4f energy levels of the Eu³⁺ ion, from ⁵D₀ to ⁷F_J where J = 0, 1, 2 ,3, and 4. The PL intensity increased upon annealing at higher temperatures, which was due to the higher degree of crystallinity. The PL intensity decreased above 1200 °C resulting from the formation of yttrium aluminate phases, such as YAM (Y₄Al₂O₉), YAP (YAlO₃), and YAG (Y₃A_l5O₁₂). The unannealed Y₂O₃:Eu films exhibited a high optical transmittance in the visible to lms decreased as annealing temperature increased due to increase in crystallite sizes.

Keywords: Radio frequency magnetron sputtering, Thin films, Sapphire, Annealing, X-ray diffraction