Dense nanosized europium silicate clusters induced light emission enhancement in Eu-doped silicon oxycarbide films

This paper reports on the enhanced switchable red Eu3+ and blue Eu2+ light emissions from Eu-doped amorphous silicon oxycarbide (SiCO) films fabricated by magnetron sputtering followed by annealing. The evolution of the enhanced light emission strongly depends on the annealing process. Thermal annealing below 800 °C enhances the red light emission from Eu3+ ions dissolved in SiCO matrix by threefold compared with that from the as-deposited film. By contrast, thermal annealing above 800 °C changes the dominant luminescence centers from the 5D0→7F2 transition of Eu3+ to the 4f65d→4f7 transition of Eu2+ ions and enhances the blue-light emission by 40-fold. Analysis of the photoluminescence excitation and X-ray photoelectron spectra and transmission electron microscopy results shows that the enhanced red/blue light emission is due to the formation of high-density nanosized EuSiO3 clusters that enable energy transfer from nanosized EuSiO3 clusters to Eu3+ and/or Eu2+ ions. •Luminescent Eu-doped SiCxOy films were prepared at a low temperature of 250 °C.•Thermal annealing causes the enhanced switchable red Eu3+ and blue Eu2+ PL.•The intense light emissions can be observed with the naked eye in a bright room.•The enhanced PL is due to the formation of high-density nanosized EuSiO3 cluster.