CdSe quantum dots possess a tuning energy gap which can control gap values according to the size of the quantum dots, this is made the material able to absorb the wavelengths within visible light. A simple model is provided for the absorption coefficient, optical properties, and optical constants for CdSe quantum dots from the size 10nm to 1nm with the range of visible region between (300-730) nm at room temperature. It turns out that there is an absorption threshold for each wavelength, CdSe quantum dots begin to absorb the visible spectrum of 1.4 nm at room temperature for a wavelength of 300 nm. It has been noted that; when the wavelength is increased, the absorption threshold also increases. This applies to the optical properties and optical constants, where their values start to change from the threshold at 1.4 nm. The obtained results indicate that the range of the absorption coefficient can cover the ultraviolet, visible and to the infrared region when the quantum sizes are relatively large ( the size 9 nm), while the small sizes give small ranges of it, as only the ultraviolet region (the size = 1.4 nm) or part of the visible region ( the size > 1.4 nm ). What resulted from this difference in the results of the absorption coefficient, had a significant impact on the optical properties. Although the material has high transmittance ( reach more 75%), it is considered to have low absorbance ( less than 0.01%), at the same time the reflectivity had been valued between ( 14% to 22%) according to of size dot. The optical conductivity is proportional to quantum dot size, where an increase of it depends on the increasing of quantum dot size. It was also found that the real part of the dielectric constant is much greater than the imaginary part values, this is an indication that; the numbers of polarized charges towards the electric field were much greater than the polarized charges opposite to the direction of the field. It is worth noting that the behaviour of the refractive index is similar to the real part, while the extinction index resembles that of the imaginary part.
This study aims to prepare Cadmium Sulphide (CdS) thin films using thermal Chemical Spray Pyrolysis (CSP) on glass of different temperatures substrate from cadmium nitrate solution. Constant thickness was (430 ± 20 nm) and the effect of substrate temperature on the optical properties of prepared thin films.
Optical properties have been studied from transmittance and absorbance spectral within wavelengths range (360 - 900 nm). The results show that all the prepared films have a direct electron transitions and optical energy gap between (2.31-2.44 eV). They also show that the transmittance and optical energy gap of films prepared from nitrate solution increase with increasing of substrate temperature, then transmittance start do
... Show MoreAbstract In this paper the effect of light exposure duration on Anthracene solution in chloroform is studied. It is found that: the Anthracene solution change its color when it is exposed to light, and that its relative quantum efficiency, Φ, decreases as the light exposure duration, t, increases and this govern by following empirical equation:- Φ = 0.7918-0.0762 In (t)
The ZnTe alloy was prepared as deposited thin films on the glass substrates at a thickness of 400±20 nm using vacuum evaporation technique at pressure (1 × 10-5) mbar and room temperature. Then the thin films under vacuum (2 × 10-3 mbar) were annealing at (RT,100 and 300) °C for one hour. The structural properties were studied by using X-ray diffraction and AFM, the results show that the thin films had approached the single crystalline in the direction (111) as preferred orientation of the structure zinc-blende for cubic type, with small peaks of tellurium (Te) element for all prepared thin films. The calculated crystallite size (Cs) decreased with the increase in the anne
... Show MoreIn this work, MWCNT in the epoxy can be prepared at room temperature and thickness (1mm) at different concentration of CNTs powder. Optical properties of multi-walled carbon nanotubes (CNTs) reinforced epoxy have been measured in the range of (300-800)nm. The electronic transition in pure epoxy and CNT/epoxy indicated direct allowed transition. Also, it is found that the energy gap of epoxy is 4.1eV and this value decreased within range of (4.1-3.5)eV when the concentration of CNT powder increased from (0.001-0.1)% respectively.
The optical constants which include (the refractive index (n), the extinction coefficient (k), real (ε1) and imaginarily (ε2) part of dielectric constant calculated in the of (300-800)nm at different concent
Thin films of pure tin mono-sulfide SnS with thicknesses of (0.85) μm were prepared by chemical spray pyrolysis technique and annealed for two hours with 673K.The effect of annealing on structural and optical properties for films prepared was studied. X-Ray diffraction analysis showed the polycrystalline with orthorhombic structure. It was found that annealing process increased the intensity of diffraction peaks. Optical properties of all samples were studied by recording the absorption and transmission  
... Show MoreIn this study, Epoxy Resin plates was prepared by mixing epoxy(A) and hardner(B)with ratio(A:B) (3:1) with different thickness (0.3-0.96)cm. The effect of thickness on optical properties have been studied (absorption ,transmission ,reflectance) also the optical constant were found like (absorption coefficient, extenuation coefficient and refraction index) for all of the prepared plates. The results have shown that by increasing the thickness of plates., the absorption intensity increase in which at plates thickness (0.3-0.96)cm the absorption intensity were(1.54-1.43) respectively, and since absorption peak for epoxy occur in ultraviolet region and exactly at wavelength(368)nm and energy gap(Eg=3.05 eV) thus their good transmittance in the
... Show MoreThis work describes, selenium (Se) films were deposited on clean glass substrates by dc planar magnetron sputtering technique.The dependence of sputtering deposition rate of Se film deposited on pressure and DC power has been studied. The optimum argon pressure has range (4x10-1 -8x10-2 )mbar. The optical properties such as absorption coefficient (α) was determined using the absorbance and transmission measurement from UnicoUV-2102 PC spectrophotometer, at normal incidence of light in the wavelength range of 200-850 nm. And also we calculated optical constants(refractive index (n), dielectric constant (εi,r), and Extinction coefficient (κ) for selenium films.
Samples prepared by using carbon black as a filler material and phenolic resin as a binder. The samples were pressed in a (3) cm diameter cylindrical die to (250)MPa and treated thermally within temperature range of (600-1000)oC for two and three hours. Physical properties tests were performed, like density, porosity, and X-ray tests. Moreover vicker microhardness and electric resistivity tests were done. From the results, it can be concluded that density was increased while porosity was decreased gradually with increasing temperature and treating time. In microhardness test, it found that more temperature and treating time cause more hardness. Finally the resistivity was decreased in steps with temperature and treating time. It can be c
... Show MoreIn this work a model of a source generating truly random quadrature phase shift keying (QPSK) signal constellation required for quantum key distribution (QKD) system based on BB84 protocol using phase coding is implemented by using the software package OPTISYSTEM9. The randomness of the sequence generated is achieved by building an optical setup based on a weak laser source, beam splitters and single-photon avalanche photodiodes operating in Geiger mode. The random string obtained from the optical setup is used to generate the quadrature phase shift keying signal constellation required for phase coding in quantum key distribution system based on BB84 protocol with a bit rate of 2GHz/s.
The electrical properties of polycrystalline cadmium telluride thin films of different thickness (200,300,400)nm deposited by thermal evaporation onto glass substrates at room temperature and treated at different annealing temperature (373, 423, 473) K are reported. Conductivity measurements have been showed that the conductivity increases from 5.69X10-5 to 0.0011, 0.0001 (?.cm)-1 when the film thickness and annealing temperature increase respectively. This increasing in ?d.c due to increasing the carrier concentration which result from the excess free Te in these films.