Dejene, F. B.Haile, Hagos Tsegay2021-09-132021-09-132020-11http://hdl.handle.net/11660/11271The thin film phosphor Y2SiO5:Ce3+ were deposited on the Si (100) substrates using 266 nm Nd: YAG pulsed laser. The conditions used for deposition were; substrate to target distance, substrate temperature, variable deposition gases, variable deposition pressure and variable deposition time to characterize the material properties on the thin films. When the material characterises by varying the distance of the substrate from the target, the crystalline size was found to be 19.93 nm. A substantial reduction in thickness were observed as a function of increasing substrate to target distance. 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. In all deposition conditions, the PL emission has been observed in the blue region. This emission is attributed to the electronic transition of 5d → 4f in the Ce3+ orbitals. Where the excited state 5d orbital further splits in to 2D3/2 and 2D5/2 closed states. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements has been observed with different textures which varies with deposition parameters. In all deposition conditions the particles have been observed spherical in shape. When the thin films are deposited by varying the temperature of the substrate, it was deposited at 150, 250, 350, 450 and 600 0 C to characterize the material properties of the thin films of Y2SiO5: Ce3+ at these deposition temperatures. The resulted material was structurally monoclinic with a prominent diffraction peak of 29.20. An increment in surface thickness was observed from a deposition temperature of 150 to 450 ° C and began to decrease from 450 ° C to 600 ° C. The decrease in surface thickness ascribes to reduction in deposition rate. Similar emission and excitation were observed at 465 and 337 nm respectively which is in the same range with the thin films deposited at variable substrate to target distance. The maximum decay time has been observed at a deposition temperature of 450 0C. SEM images and EDS measurements show a significant change in morphology among each image and stoichiometric variations resulting from the change in substrate temperature respectively. When the films are deposited at different background gases (Vacuum, Nitrogen, Argon and Oxygen), a prominent peak at a diffraction peak of 15.7 0 were observed. The PL emission was also observed at the blue spectral region. The thin films show uniform distribution of grains with small agglomerated topographic areas. Maximum UV-VIS absorbance was observed at Argon depositions. The energy bandgap varies between 3.14 and 4.33 eV. The activation energy was obtained in the range of 0.1733 and 0.1938 eV. The maximum activation energy was obtained under the argon deposition. The influence of oxygen deposition gases on the material properties of thin films at a deposition pressures of 1.5, 20, 40, 60 and 100 mTorr with substrate temperature of 250 0C was also investigated. The deposited material was structurally monoclinic with prominent diffraction peak of 28.90. The Raman spectroscopy measurement also shows prominent emission intensity which could be resulted from the crystallized surface of the films. Spherical nano particles have been observed in all depositions. The surface roughness and agglomeration of the thin films have showed variation as a function of deposition pressures. The excitation and emission wavelengths were observed at 244 and 470 nm respectively. The average nanoparticles size varies between 25.71 to 40.4 nm. Maximum average activation energy of 0.438 eV was obtained at a deposition pressure of 1.5 mTorr. Moreover, the influence of deposition time on the structural, photoluminescence, morphological and optical properties of Y2SiO5:Ce3+ thin films was also investigated at a deposition time of 30, 60, 90, 120 and150 minutes. The deposited material was structurally end centered monoclinic with a prominent diffraction angle observed at 30.6 0. Maximum crystallite size was observed at a deposition time of 60 minutes. The Rayleigh, stokes and anti-stokes scattering were observed at 536, 6.9 and 980 Cm-1 respectively. The nanoparticles are uniformly distributed with a size of 0.2 to 0.4 μm. The calculated band gap from the deposition time of 90 and 120 minutes were 2.49 and 1.79 eV respectively. The excitation wavelengths were observed at 269 and 282 nm which ascribes to the two crystallographic sites of Ce3+ and the emission wavelength was observed at 473 nm which might be due to the recombination probability of the excited Ce3+ electrons from the excited state to the holes created in the ground state. The phosphor powder was synthesised by combustion route by various molar concentration of TEOS. All the samples were annealed at a temperature of 800 0C for about 4 hours. The average nanoparticle size from the TEM measurement was found to be 13.8 nm. High percentage of weight loss were observed at 0.014 M. The deionized water and residual organic materials were evaporated at 95 0C and 600 0C respectively. The excitation wavelength was observed at 220, 308 and 340 nm and a single emission wavelength has been observed at 483 nm. Maximum TL emission were observed at a TEOS concentration of 0.021 M. More over the maximum activation energy were observed at 0.014 and 0.015 M respectively which is related to the trap depth of the trapped electrons.enThesis (Ph.D. (Physics))--University of the Free State (Qwaqwa Campus), 2020Y2SiO5:Ce3+Pulsed laser depositionThin filmsPhotoluminescenceRE ionsElectronic transitionPhosphorEmission/excitationMorphologyDecay timeAtomic force microscopyScanning electron microscopyGrazing X-ray diffractionThermoluminescenceThesisUniversity of the Free State