Blue-emitting Eu²⁺-doped CaAl₂O₄ phosphor thin films prepared using pulsed laser deposition technique with post annealing

Blue-emitting Eu²⁺-doped calcium aluminate phosphor thin films were obtained using the pulsed laser deposition technique with post annealing. As-deposited films were amorphous and showed weak red Eu³⁺ photoluminescence (PL). By annealing in reducing atmosphere (N₂/H₂:2% mixed gas) at 950°C for 3 h, the film was crystallized and showed a PL emission band peaking at about 447 nm, which originated from the 4f⁶5d to 4f⁷ transition of Eu²⁺ ion. It is considered that the deposited film consists mainly of CaAl₂O₄ and partly of other binary compounds of the CaO-Al₂O₃ system. It was determined that the PL intensity of Eu²⁺ in CaAl₂O₄ can be controlled by the laser fluence, target-substrate distance and injection gas.