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.
Copper oxide thin films were deposited on glass substrate using Successive Ionic Layer Adsorption and Reaction (SILAR) method at room temperature. The thickness of the thin films was around 0.43?m.Copper oxide thin films were annealed in air at (200, 300 and 400°C for 45min.The film structure properties were characterized by x-ray diffraction (XRD). XRD patterns indicated the presence of polycrystalline CuO. The average grain size is calculated from the X-rays pattern, it is found that the grain size increased with increasing annealing temperature. Optical transmitter microscope (OTM) and atomic force microscope (AFM) was also used. Direct band gap values of 2.2 eV for an annealed sample and (2, 1.5, 1.4) eV at 200, 300,400oC respect
... Show MoreIn the present investigation, (NiO:WO3 ) thin films were deposited at RT onto glass substrates using PLD technique employing focused Nd:YAG laser beam at 600 mJ with a frequency second radiation at 1064 nm (pulse width 9 ns) repetition frequency (6 Hz), for 400 laser pulses incident on the target surface .The structural, morphological and optical properties of the films doped with different concentration of Au content (0.03, 0.05, and 0.07) were examined with X-ray diffractometer(XRD), Atomic Force Microscope(AFM) , UV–Vis spectrophotometer . The results show that the films were amorphous with small peaks appearing when doped with AuNPs . The XRD peaks of the deposited NiO:WO3 were enhanced with increasing t
... Show MoreA simple setup of random number generator is proposed. The random number generation is based on the shot-noise fluctuations in a p-i-n photodiode. These fluctuations that are defined as shot noise are based on a stationary random process whose statistical properties reflect Poisson statistics associated with photon streams. It has its origin in the quantum nature of light and it is related to vacuum fluctuations. Two photodiodes were used and their shot noise fluctuations were subtracted. The difference was applied to a comparator to obtain the random sequence.
Aluminum doped zinc selenide ZnSe/n-Si thin films of (250∓20 nm) thickness with (0.01, 0.02 and 0.03), are depositing on the two type of substrate (glass and n-Si) to manufacture (ZnSe/n-Si) solar cell through using thermal vacuum evaporation procedure. physical and optoelectronic properties were examined for the samples. X-Ray and AFM techniques are using to study the structure properties. The energy band gap of as-deposited ZnSe thin films for changed dopant ratio were ranging from (2.6-2.68 eV). The results of Hall effect show that pure and doping films were (p-type), and the concentration carriers and the carriers mobility increases with increase Al-dopant ratio. The (C-V) have shown that the heterojunction were of abrupt type. In add
... Show MoreIn this research thin films of (CdTe) have been prepared as pure and doped by Zn
with different ratios (1,2,3,4,5)% at thickness (400+25)nm with deposition rate (2±0.1)nm,
deposited on glass substrate at R.T. by using thermal evaporation in vacuum . All samples
were annealed at temperature (523,573,623,673)K at 1h.
The structural prop erties of all prepared thin films, doped and undoped have been
studied by using XRD. The analysis reveals that the structures of the films were
polycrystalline and typed cubic with a preferred orientation along (111) plane for the
undoped films with (2,3)% of zinc , and shifting (2ÆŸ) for doped films . The annealing films
at temperature 573 K and Zn:3% show decreasing in
Zinc Oxide (ZnO) thin films of different thickness were prepared
on ultrasonically cleaned corning glass substrate, by pulsed laser
deposition technique (PLD) at room temperature. Since most
application of ZnO thin film are certainly related to its optical
properties, so the optical properties of ZnO thin film in the
wavelength range (300-1100) nm were studied, it was observed that
all ZnO films have high transmittance (˃ 80 %) in the wavelength
region (400-1100) nm and it increase as the film thickness increase,
using the optical transmittance to calculate optical energy gap (Eg
opt)
show that (Eg
opt) of a direct allowed transition and its value nearly
constant (~ 3.2 eV) for all film thickness (150
In this work, lead oxide (PbO) thin films were deposited using D.C. sputtering method on a surface of glass substrates and then thermally annealed at a temperature of 473K with annealing times of (1,2 and 3) hours. The structural, morphological, and optical properties of films were determined using X-ray diffraction (XRD), atomic force microscopy (AFM), FT-IR, and UV-Visible spectroscopy. The structure studies confirmed that PbO films are polycrystalline structures in an orthorhombic phase with average grain size (24.51, 29.64, 46.49, 16) nm with increasing annealing time. From AFM, the roughness of the film surface (3.26, 1.76, 1.61, 1.79) nm as the film annealing time increases. The optical band gap values of the PbO thin fi
... Show MoreIn this paper, Zinc oxide were deposited on a glass substrate at room temperature (RT) and two annealing temperatures 350ºC and 500ºC using laser induced plasma technique. ZnO nanofilms of 200nm thickness have been deposited on glass substrate. X-RAY diffraction (XRD), atomic force microscopy and UV-visible spectrophotometer were used to analyze the results. XRD forms of ZnO nanostructure display hexagonal structure with three recognized peaks (100), (002), and (101) orientations at 500ºC annealing temperature. The optical properties of ZnO nanostructure were determined spectra. The energy gap was 3.1 eV at 300 oC and 3.25eV at 500ºC annealing temperature.
Anew mathematical formula was proposed to describe the behavior of the extinction coefficient as a function of ambient temperature and wavelengths for some of infrared materials. This formula was derived depending on some experimental data of transmittance spectrum versus wavelengths for many ambient temperatures. The extensive study of the spectrum characteristics and depending on Bose-Einstein distribution led to derive an equation connecting the extinction coefficient or the absorption coefficient with the ambient temperature and wavelengths of the incident rays. The basic assumption in deriving process is the decreasing in transmittance value with the increasing temperature which is only due to the changing in extinction coeffi
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