الفهرس 
Theoretical Background and Literature ReviewOnly 14 pages are availabe for public view
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Abstract
Synthesis of CdSe and ZnSe nanoparticles were performed using the
modified chemical recipe. The structural nature and optical properties of the as-synthesized
nanoparticles were characterized by using: X-ray diffraction (XRD), energy dispersive X-rays
analysis (EDX), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR). The
crystal structure of the CdSe quantum dots was solved and refined from X-ray powder diffraction
data by full-profile Rietveld method. The structure is wurtzite hexagonal, space group P63mc, a =
4.2569(3), c = 7.0022(5) Å, with Cd at (1/3, 2/3,0) and Se at (1/3, 2/3, 0.37904(36)).
High-resolution TEM (HRTEM) was employed to characterize the particle size, shape and morphology of
the CdSe nanocrystals. HRTEM showed monodispersed spherical nanocrystalline CdSe with diameters of
less than 8 nm, and lattice fringe measurements corresponded to d-space values of planes within the
hexagonal wurtzite CdSe that consistent with the value in the standard card ([JCPDS: 77-2307]. The
UV-Vis absorption and PL spectra showed the well-dispersed CdSe nanocrystals in toluene were
recorded at room temperature (RT). It can be seen that the line width of the luminescence spectrum
was symmetric and narrow, which obviously revealed that the as- prepared CdSe QDs were nearly
monodisperse and homogenous with peak position at 566.36 nm, (2.19 eV) and full width at half
maximum (FWHM),
33.26 ±1 nm.
A saturated solution of QD- Cd46Se54 and QD- Zn49Se51 has been prepared in a toluene solvent. The
thin film coated on a pre-cleaned glass substrates using a spin coater unit rotated by 1000 RPM,
with rate of dropping 14 drop/10 sec, then waited for 15 s and re-dropping in the same
rate. This process rebated for several times (3~5) until obtaining the
required thickness.
Transmittance and reflectance data of the as-deposited QD- Cd46Se54 and QD-Zn49Se51 thin
films with different thicknesses in the range (102 nm 119 nm) and (155 nm 183 nm) are used to
calculate the optical constants refractive index (n), absorption index (k) and the absorption
coefficient (α). The dependence of the absorption coefficient on the photon energy at the
absorption edge is well described by Tauc relation with a direct optical gap equal 2.26 eV, 2.37 eV
for QD- Cd46Se54 of thickness (d1=119 nm, d2=102 nm) and 2.58 eV, 2.62 eV for QD-Zn49Se51 of
thickness (d1=183 nm, d2=155 nm) respectively. A detailed study of as-deposited QD- Cd46Se54,
irradiated by 2, 4, 6, and 8 KGy on the optical properties.