The effect of different annealing temperatures on the structure and luminescence properties of Y₂O₃:Bi³⁺ thin films fabricated by spin coating

Graphical abstract: - Highlights: • Y_2−xO₃:Bi_x=0.005 thin films were successfully fabricated by the spin coating method. • The Y_2−xO₃:Bi_x=0.005 thin films were converted into Y₂Si₂O₇:Bi films after annealing. • The conversion affected the PL properties of the Bi⁺ ion in the newly formed host. • A blue shift in emission colour was observed. - Abstract: This paper reports on the structural, morphology and optical properties of Y_2−xO₃:Bi_x=0.005 micro-and nanophosphors synthesized via the spin coating method. The influence of different annealing temperatures (900–1200 °C) on the morphology, crystal structure and the photoluminescence (PL) properties of the synthesized films were studied in detail. The crystal structure of the films was investigated with X-ray diffraction. The presence of the three major diffraction peaks with Miller indexes (2 1 1), (2 2 2) and (4 0 0) indicated that the Y_2−xO₃:Bi_x=0.005 thin films were well-crystallized at 900 °C, 1000 °C, 1100 °C and 1200 °C. Additionally, extra diffraction peaks were observed for the sample that was annealed at 1200 °C. Those extra peaks were due to the formation of the Y₂Si₂O₇ phase owing to the annealing induced changes in the crystal structure and chemical composition of the Y_2−xO₃:Bi_x=0.005 thin film. This may also be attributed to inter diffusion of atomic species between the Si substrate and the Y_2−xO₃:Bi_x=0.005 thin film at the high annealing temperature. Due to structure-sensitive properties of the Bi³⁺ ions, a blue shift of the centre PL emission band from 495 nm to 410 nm was clearly observed and explained in detail. The time-of-flight secondary ion mass spectroscopy results show the Si diffusion from the Si substrate, whereas, the scanning electron microscopy and the atomic force microscopy were used for the morphology analysis.