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Effect of film thickness on microstructure parameters and optical constants of CdTe thin films

Research Abstract
Different thickness of cadmium telluride (CdTe) thin films was deposited onto glass substrates by the thermal evaporation technique. Their structural characteristics were studied by X-ray diffraction (XRD). The XRD experiments showed that the films are polycrystalline and have a zinc-blende (cubic) structure. The microstructure parameters, crystallite size and microstrain were calculated. It is observed that the crystallite size increases and microstrain decreases with the increase in the film thickness. The fundamental optical parameters like band gap and extinction coefficient are calculated in the strong absorption region of transmittance and reflectance spectrum. The possible optical transition in these films is found to be allowed direct transition with energy gap increase from 1.481 to 1.533 eV with the increase in the film thickness. It was found that the optical band gap increases with the increase in thickness. The refractive indices have been evaluated in transparent region in terms of envelope method, which has been suggested by Swanepoul in the transparent region. The refractive index can be extrapolated by Cauchy dispersion relationship over the whole spectral range, which extended from 400 to 2500 nm. It is observed that the refractive index, n increases on increasing the film thickness up to 671 nm and then the variation of n with higher thickness lie within the experimental errors.
Research Authors
E.R. Shaabana, N. Afify, A. El-Tahera
Research Department
Research Journal
Alloys and Compounds
Research Member
Research Pages
PP. 400–404
Research Rank
1
Research Vol
Vol. 482, No. 1-2
Research Year
2009

Particle size-dependent electrical properties of nanocrystalline NiO

Research Abstract
Nickel oxide nanoparticles are formed by chemical precipitation and subsequent drying and calcinations at temperatures ≥523 K. Samples are characterized using X-ray diffraction and BET surface area measurements indicating the formation of a single NiO phase whose crystallite size increases with increasing calcination temperature. The electrical properties are examined by measuring DC and AC conductivities and dielectric properties as functions of temperature. Electrical conductivities first slightly increases with increasing particle size up to 7–10 nm and are about 8 orders of magnitude higher than that of NiO single crystals. Further increasing the particle size above 10 nm, leads to a monotonic decrease of conductivity. The data are discussed in view of variations of grain boundary as well as triple junction volume fractions as the particle size varies. At temperatures above θD/2 (θD is the Debye temperature), the conductivity is ascribed to a band-like conduction due to the large polaron. The activation energy of conduction was found to be minimal for the highly conducting samples of 7–10 nm, and gradually increases to ~0.5 eV with increasing the particle size above 10 nm. For T θD/2, the conductivity is best described by variable–range–hopping models. Model parameters are thus estimated and presented as functions of particle size. Frequency as well as temperature dependencies of the AC conductivity and dielectric constant exhibit trends usually observed in carrier dominated dielectrics.
Research Authors
Salah A. Makhlouf, Mohamed A. Kassem, M. A. Abdel-Rahim
Research Department
Research Journal
Materials Science
Research Member
Research Pages
PP. 3438-3444
Research Publisher
Springer Netherlands
Research Rank
1
Research Vol
Vol. 44, No. 13
Research Year
2009

Photocatalytic self-assembled solid porphyrin microcrystals from water-soluble porphyrins: Synthesis, characterization and application

Research Abstract
In this article, we report on the formation of a photocatalytic porphyrin crystalline structure using two oppositely charged commercially available low cost porphyrins, [meso-tetra(N-methy-4-pyridyl)porphyrin tetratosylate (TMPyP) and zinc-tetrakis(4-sulfonatophenyl)porphyrin (Zn-TPPS)], by self-assembly at room temperature without acidification. Using optical microscopy, the crystals were determined to have a length of 30–55 μm and width of 2–50 μm, depending on the molar ratio of the porphyrins in the starting solution. The porphyrin crystals were characterized by means of powder X-ray diffraction and UV–Vis, fluorescence, and optical microscopic techniques. The UV–Vis absorbance spectrum of the crystalline structure is different than those of the monomer solutions, involving a broadened Soret band that is split into two blue-shifted and red-shifted peaks and broadened red-shifted Q-bands. The crystals exhibit a different emission spectrum from those of the porphyrin solutions in that they are red-shifted, split, and show a dramatic decrease in intensities. A hypothetical model for the crystal structure of the porphyrin crystals is developed. Illumination of the crystals in a 2,4,6-trinitrotoluene solution with a tungsten lamp results in TNT reduction to 1,3,5-trinitrobenzene and 4-amino-2,6-dinitrotoluene
Research Authors
Walid M. Hikal, H. James Harmon
Research Department
Research Journal
Polyhedron
Research Member
Research Pages
PP. 113–120
Research Rank
1
Research Vol
Vol.28. No. 1
Research Year
2009

Patterning of nanoparticulate transparent conductive ITO films using UV light irradiation and UV laser beam writing

Research Abstract
Indium tin oxide (ITO) thin film is one of the most widely used as transparent conductive electrodes in all forms of flat panel display (FPD) and microelectronic devices. Suspension of already crystalline conductive ITO nanoparticles fully dispersed in alcohol was spun, after modifying with coupling agent, on glass substrates. The low cost, simple and versatile traditional photolithography process without complication of the photoresist layer was used for patterning ITO films. Using of UV light irradiation through mask and direct UV laser beam writing resulted in an accurate linear, sharp edge and very smooth patterns. Irradiated ITO film showed a high transparency ( 85%) in the visible region. The electrical sheet resistance decrease with increasing time of exposure to UV light and UV laser. Only 5 min UV light irradiation is enough to decrease the electrical sheet resistance down to 5 kΩ
Research Authors
A. Solieman, A.H. Moharram, M.A. Aegerter
Research Department
Research Journal
Applied Surface Science
Research Pages
PP. 1925–1929
Research Rank
1
Research Vol
Vol. 256, No. 6
Research Year
2010

Patterning of nanoparticulate transparent conductive ITO films using UV light irradiation and UV laser beam writing

Research Abstract
Indium tin oxide (ITO) thin film is one of the most widely used as transparent conductive electrodes in all forms of flat panel display (FPD) and microelectronic devices. Suspension of already crystalline conductive ITO nanoparticles fully dispersed in alcohol was spun, after modifying with coupling agent, on glass substrates. The low cost, simple and versatile traditional photolithography process without complication of the photoresist layer was used for patterning ITO films. Using of UV light irradiation through mask and direct UV laser beam writing resulted in an accurate linear, sharp edge and very smooth patterns. Irradiated ITO film showed a high transparency ( 85%) in the visible region. The electrical sheet resistance decrease with increasing time of exposure to UV light and UV laser. Only 5 min UV light irradiation is enough to decrease the electrical sheet resistance down to 5 kΩ
Research Authors
A. Solieman, A.H. Moharram, M.A. Aegerter
Research Department
Research Journal
Applied Surface Science
Research Pages
PP. 1925–1929
Research Rank
1
Research Vol
Vol. 256, No. 6
Research Year
2010

A studyof DSC non-isothermalpre-crystallizationkineticsofPb10Se90 glass using isoconversional kinetic analysis

Research Abstract
The pre-crystallization kinetics of Pb10Se90 glass was determined under non-isothermal conditions using a differential scanning calorimetry (DSC) technique. Two isoconversional methods, the Kissinger-Akahire-Sunose and Vyazovkin methods, were used to determine the variation of the activation energy for glass transition with temperature. The results show that only one (three-dimensional growth) mechanism is working simultaneously during the amorphous-glass process of the investigated glass.
Research Authors
A.S. Soltan
Research Department
Research Journal
Physica B
Research Pages
PP. 965–968
Research Rank
1
Research Vol
Vol. 405, No. 3
Research Year
2010

application of 2-d homogeneous functions method for automatic interpretation of selected faults using shallow seismic data in Esh El-Mallaha basin, Eastern Desert, Egypt.

Research Abstract
application of 2-d homogeneous functions method for automatic interpretation of selected faults using shallow seismic data in Esh El-Mallaha basin, Eastern Desert, Egypt.
Research Authors
El-Haddad, A. E.; Ibrahim, H. A.; Bakheit, A. A. and Saad, G. A.
Research Department
Research Journal
Presented in the 4th Maghrebian Congress of Applied Geophysics, Tunis, 26-28 March, 2009.
Research Member
Abudeif Abdel-Aal Bakheit Ahmed
Research Publisher
4th Maghrebian Congress of Applied Geophysics,
Research Rank
3
Research Website
4th Maghrebian Congress of Applied Geophysics,
Research Year
2009

application of 2-d homogeneous functions method for automatic interpretation of selected faults using shallow seismic data in Esh El-Mallaha basin, Eastern Desert, Egypt.

Research Abstract
application of 2-d homogeneous functions method for automatic interpretation of selected faults using shallow seismic data in Esh El-Mallaha basin, Eastern Desert, Egypt.
Research Authors
El-Haddad, A. E.; Ibrahim, H. A.; Bakheit, A. A. and Saad, G. A.
Research Department
Research Journal
Presented in the 4th Maghrebian Congress of Applied Geophysics, Tunis, 26-28 March, 2009.
Research Member
Research Publisher
4th Maghrebian Congress of Applied Geophysics,
Research Rank
3
Research Website
4th Maghrebian Congress of Applied Geophysics,
Research Year
2009

application of 2-d homogeneous functions method for automatic interpretation of selected faults using shallow seismic data in Esh El-Mallaha basin, Eastern Desert, Egypt.

Research Abstract
application of 2-d homogeneous functions method for automatic interpretation of selected faults using shallow seismic data in Esh El-Mallaha basin, Eastern Desert, Egypt.
Research Authors
El-Haddad, A. E.; Ibrahim, H. A.; Bakheit, A. A. and Saad, G. A.
Research Department
Research Journal
Presented in the 4th Maghrebian Congress of Applied Geophysics, Tunis, 26-28 March, 2009.
Research Publisher
4th Maghrebian Congress of Applied Geophysics,
Research Rank
3
Research Website
4th Maghrebian Congress of Applied Geophysics,
Research Year
2009

Structural characteristics and tectonic evolution of the area west of the Gulf of Suez, Egypt, using potential field data.

Research Abstract
Structural characteristics and tectonic evolution of the area west of the Gulf of Suez, Egypt, using potential field data.
Research Authors
Ibrahim, H. A.; Bakheit, A. A. ; El-Haddad, A. E. and Saad, G. A.
Research Department
Research Journal
Presented in the 4th Maghrebian Congress of Applied Geophysics, Tunis, 26-28 March, 2009.
Research Publisher
4th Maghrebian Congress of Applied Geophysics,
Research Rank
3
Research Website
4th Maghrebian Congress of Applied Geophysics,
Research Year
2009
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