Annealing effect on properties of BaWO4:Eu3+ phosphor thin films grown on glass substrates by radio-frequency magnetron sputtering

Abstract

The effects of the rapid thermal annealing (RTA) temperature on the properties of BaWO4:Eu3+ phosphor thin films grown on glass substrates by radio-frequency magnetron sputtering were investigated. The deposited phosphor thin films were annealed at several RTA temperatures for 30min. The experimental results show that the crystalline phase, surface morphology, transmittance, optical band gap, and photoluminescence intensity depended strongly on the RTA temperature. A preferential orientation along (112) plane and grains with an average size of 40nm were observed for a thin film annealed at 400°C. As the annealing temperature increased, the average transmittance in the wavelength range of 400–1100nm gradually increased, reaching a maximum of 90.8% at 550°C, where the highest optical band gap of 3.98eV was obtained. The dominant emission spectra of the BaWO4:Eu3+ phosphor thin films under excitation at 323nm, regardless of the RTA temperature, exhibited an emission band at 622nm arising from the 5D0→7F2 transition of Eu3+ ions, indicating that the Eu3+ ions in the BaWO4 host lattice were located at sites without inversion symmetry. The results suggest that the optimum annealing temperature for fabricating highly luminescent red-emitting phosphor thin films is 500°C.