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

This paper reports on the structural, morphology and optical properties of Y2-xO3:Bi-x=0.005 micro-and nanophosphors synthesized via the spin coating method. The influence of different annealing temperatures (9001200 degrees 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 Y2-xO3:Bi-x=0.005 thin films were well-crystallized at 900 degrees C, 1000 degrees C, 1100 degrees C and 1200 degrees C. Additionally, extra diffraction peaks were observed for the sample that was annealed at 1200 degrees 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 Y2-xO3:Bi-x=0.005 thin film. This may also be attributed to inter diffusion of atomic species between the Si substrate and the Y2-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.