Effect of target to substrate distance on the material properties of the Y2SiO5:Ce3+ thin film by pulsed laser deposition
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The effect of the target–substrate distance on the structural, morphological and photoluminescence (PL) properties of the thin film of the Y2SiO5:Ce3+ commercial phosphor studied by the pulsed laser deposition method. The distance between the target and the substrate was in the order of 4.0–6.0 cm with a variation of 0.5. X-ray powder diffraction analysis (XRD) shows that the average crystal size is about 37 nm. As the substrate distance is increased, a substantial reduction in film thickness observed from the measurement of mass before and after deposition. This attributes to the semicircular diffusion of the plasma plume due to the reduction of particle species flow over the deposition area of the substrate. The main PL emission peak was observed at 438 nm, which is attributed to the 5d → 4f transition in Ce3+ orbitals. The 5d orbital is the first excited state in Ce3+ ion energy levels with two close states of 2D3/2 and 2D5/2. The splitting of 5d into suborbital 2D3/2 and 2D5/2 is due to the electron transition between orbitals of the trivalent cerium ion and the host material. This is studied using three excitation wavelengths (276, 303 and 356 nm) in which all their corresponding emission is in the same region peaked at 438 nm. The highest emission occurs with an excitation wavelength of 356 nm for all substrate distances. The CIE gives the blue emission band for the emission wavelength of 438 nm. The maximum ultraviolet–visible spectrum absorbance was observed at around 356 nm. The scanning electron microscope images show that the sizes and the morphology change as the substrate distance changes. The energy-dispersive X-ray spectrometer shows the presence of all the elements of the compound matrix (Y, Si, O and Ce).
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