The optical properties of polyvinyl alcohol (PVA) doped TiO2 and ZnO nanoparticles respectively, were studied. PVA/TiO2 and PVA/ZnO nanoparticles were prepared by the pulsed laser ablation technique (PLA).The optical properties of PVA/ TiO2 and PVA/ ZnO nanocomposite solution have been investigated by transmittance data and absorption spectra. The optical band gap (Eg) was determined and the optical absorption spectra showed that a direct transition. The energy gap of PVA/ ZnO nanoparticles have been observed the decreases its value and increasing in the optical conductivity as compared to PVA/ TiO2.The refractive index (n), extinction coefficient (k) and dielectric constant have been also investigated; it was found that all the above parameters affects by doping.
Abstract
We reported in this work the growth of ZnSe nanoparticles thin films deposited on glass substrates were synthesized by a pulsed laser deposition (PLD) method. The as obtained films were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), UV-VIS Spectrophotometer, and Photoluminescence (PL) spectra. X-ray diffraction study confirmed the transformation the cubic phase of ZnSe nanoparticles into hexagonal phase by increase the laser fluence from (4.77-5.97) J/cm2. The particle size variations were achieved by varying the laser fluence of prepared films. XRD studies and TEM images confirmed the nanometer size was found to lie in the range of 12-80 nm. A UV-VIS study was carried out to measure the band gap of the ZnSe nanoparicles thin films and it showed a blue shift with respect to the bulk value. The PL spectra at room temperature (300K) of the films showed the decrease of maximum values at at 522 nm( 2.379), 521 nm (2.3838) and 520 nm (2.3882 eV) for the laser fluence (4.77, 5.57 and 5.97 J/cm2), respectively. We assigned the variation due a larger number of non-radiative recombination centers appears in the films.
Effects of the number of shots of laser and annealing temperature on the structural, morphological, and optical properties of zinc sulfide nanoparticles (ZnS NPs) thin films, prepared by pulsed laser deposition technique (PLD), were investigated. XRD results show that ZnS NPs exhibit a hexagonal phase at 623k. Transformation in the shape of nanoparticles to nanoflowers and nanorods appeared with increasing number of shots of laser at the same annealing temperature (623K) was observed from scanning electron microscopy (SEM) images. The optical properties were studied from all transmittance data. The experimental results show that the as-deposited ZnS NPs film exhibit a cubic structure and the crystallinity increased in the annealed films. It is also found that the grain size of the as grown samples at 300K, rises linearly from 9 to 11 nm with increasing the number of shots from 1000 to 3000 and rapidly from 10 to 18 nm after annealing at 623K. Additionally, the increase of the number of shots from 1000 to 3000 leads to a decrease in the energy gap values and increases their values after heat treatment keeping their behavior decreasing as the number of shots of laser increases. Also, photoluminescence (PL) measurements explained quenching its value after annealing temperature.
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