Europium-based materials are known for their intense and stable emission in the visible region. Moreover Eu is stable in both its divalent and trivalent oxidation states. In particular, emission of Eu2+ is much stronger, being allowed for electric dipole transition rules and is characterized by a broad peak, centered in the wavelength range 400–600 nm, while that of Eu3+ presents several sharp lines at around 600 nm. These peculiar optical properties make Eu‐based systems an interesting material for photonic applications. The optical and structural properties of Eu2O3 thin films grown by RF magnetron sputtering on Si substrates have been studied. PL emission has been observed at room temperature and it is strongly dependent on the thermal process. In particular, annealing in O2 atmosphere leads to an enhancement of the Eu3+ emission, while films annealed in N2 ambient exhibit a very intense PL …