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Article
Characterization of SiC/Si Heterojunction Fabricated by Plasma-Induced Growth of Nanostructured Silicon Carbide Layer on Silicon Surface

Author: Oday A. Hammadi
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2016 Volume: 12 Issue: 2 Pages: 9-13
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this work, p-type silicon substrates were etched by plasma-induced etching technique to form nano-scale rough surfaces. These surfaces were coated with ultra-fine graphite paste as a source of carbon to form layers of n-type silicon carbide by plasma-induced bonding technique. The plasma used for this purpose was generated by glow discharge of argon at 0.15 mbar and discharge power of 157.5W. The structures and morphology of these structures were introduced by x-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). These tests confirmed the formation of nanostructured SiC layers on the etched Si substrates. Electrical characteristics showed that the formed n-SiC/p-Si anisotype heterojunction has an ideality factor of 0.45 and the built-in potential was measured to be 2.6V. This technique is reasonably efficient, low-cost and reliable to fabricate heterojunctions from nanostructured compound semiconductors on silicon substrates.


Article
Nanostructured CdSnSe Thin Films Prepared by DC Plasma Sputtering of Thermally Casted Targets

Author: Oday A. Hammadi
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2018 Volume: 14 Issue: 4 Pages: 33-36
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this work, nanostructured cadmium tin selenide (CdSnSe) thin films were deposited on glass substrates by dc plasma sputtering technique. The sputtered target was prepared by the thermal casting of Cd, Sn and Se samples at 350°C. The structural characterizations showed that the prepared targets were polycrystalline while the deposited CdSnSe films exhibited amorphous structure due to the growth of nanostructures on the substrates, which was also confirmed by the scanning electron microscopy. These films showed high absorption in the ultraviolet and visible regions while low absorption was observed in the near-infrared region (>800nm). They have two allowed types of energy band gaps; indirect at 1.233eV and direct at 1.655eV. The dispersion relationship showed that these films have approximately constant refractive index in the visible region, which is attributed to the optical homogeneity of the prepared films.


Article
Conjunctional Freezing-Assisted Ultrasonic Extraction of Silicon Dioxide Nanopowders from Thin Films Prepared by Physical Vapor Deposition Technique

Author: Oday A. Hammadi
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2019 Volume: 15 Issue: 4 Pages: 23-28
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this work, the effects of different extraction parameters on the particle size of the nanopowders extracted from silicon dioxide thin film samples were studied. These nanopowders were obtained by the conjunctional freezing-assisted ultrasonic extraction method. Results showed that extraction parameters such as freezing temperature, ultrasonic frequency and application time are very effective in determining the nanoparticle size, which is very important for many applications and uses of highly-pure nanomaterials and nanostructures.


Article
Analysis of Secondary Electron Emission in Gas Glow Discharges Used for Thin Film Deposition Processes

Author: Oday A. Hammadi
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2020 Volume: 16 Issue: 1 Pages: 15-20
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this study, the emission coefficient of secondary electrons for some common gas discharges employed in thin film deposition processes and techniques was determined as function of some affecting parameters. This coefficient may play negative role in the optimization of discharge plasma employed for practical uses and applications. Therefore, this coefficient is often minimized even though the experimental conditions are shifted from their optima in order to ensure that the consumption of supplied power is high as much as possible. This study was supported by experimental data from a reactive plasma sputtering system used for deposition of some metal oxide and nitride thin films.


Article
Effect of Acidic Environment on the Spectral Properties of Hibiscus sabdariffa Organic Dye used in Dye-Sensitized Solar Cells

Authors: Oday A. Hammadi --- Noor I. Naji
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2014 Volume: 10 Issue: 2 Pages: 27-31
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this work, the spectral properties of the Hibiscus sabdariffa organic dye solved in different solvents were studied by introducing the effect of dye concentration on its absorbance and transmission spectra within the range 400-800nm. As well, the effect of adding acid to the dye solution on these properties was introduced. Results showed that the spectral properties of the dye depend substantially on the type of the solvent, which has to be chosen carefully to achieve the optimum properties of this dye to be used as a sunlight sensing organic medium in dye-sensitized solar cells. Also, the results showed that the spectral properties of this dye are noticeably affected by the presence of acid in the solution. Variation of acidic content in the dye solution was studied and its effect on both absorbance and transmittance was studied. As the acidic content in the solution was increased, the absorbance increased while transmittance decreased that may be attributed to dissociation of dye molecules, formation of new different compounds and/or quenching the spectral activity of the Hibiscus sabdariffa dye molecules.


Article
Characterization of Highly-Pure Silicon Dioxide Nanoparticles as Scattering Centers for Random Gain Media

Authors: Hayder G. Fahad --- Oday A. Hammadi
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2020 Volume: 16 Issue: 2 Pages: 37-42
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this work, silicon dioxide thin films were prepared and deposited on glass substrates by dc reactive magnetron sputtering technique. The film material was extracted from the substrates as powder by conjunctional freezing-assisted ultrasonic extraction method. The structural characterization of the extracted powder confirmed the formation of nanostructures as the particle size was ranging in 19-34 nm. They also confirmed the high purity of these nanostructures as no other compound than silicon dioxide was observed in the final samples. The extracted nanopowder was employed as scattering centers in Rhodamine B dye solution and the spectral measurements showed that the relative enhancement in fluorescence of the dye solution containing silicon dioxide nanoparticles exceeds 25%, which highly encourages considering these results to prepare random gain media. These results can effectively be used to design and fabricate random gain media with low production cost, high spectral quality and good reliability for wavelength narrowing and tuning.


Article
Effect of Adding Nitrogen to the Gas Mixture on Plasma Characteristics of a Closed-Field Unbalanced DC Magnetron Sputtering System

Authors: Firas J. Kadhim --- Mohammed K. Khalaf --- Oday A. Hammadi
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2014 Volume: 10 Issue: 1 Pages: 27-31
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this work, the role of adding nitrogen gas to the discharge gas mixture containing argon was studied by introducing the electrical characteristics of plasma generated between two closed-field unbalanced magnetron electrodes. This role was also related to the presence and absence of magnetron at the electrodes in the fundamental design of such sputtering system. The role of nitrogen gas added to the gas mixture was reasonably observed by enhancing the electrical characteristics of the glow discharge plasma generated between the dual CFUBM electrodes. Adding nitrogen caused to increase the concentration of the charged particles produced by collisional ionization in discharge volume as the mean free path of primary discharge electrons was reduced. A relative reduction in electron temperature was observed as a result of adding nitrogen with increase in electron and ion densities while no observed difference was observed in the ion temperature due to their larger masses compared to those of electrons.


Article
Current-Voltage Characteristics of DC Plasma Discharges Employed in Sputtering Techniques
خصائص تيار-جهد لتفريغ البلازما المستمر المستخدم في تقنيات الترذيذ

Authors: Mohammed K. Khalaf --- Oday A. Hammadi --- Firas J. Kadhim
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2016 Volume: 12 Issue: 3 Pages: 11-16
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this work, the current-voltage characteristics of dc plasma discharges were studied. The current-voltage characteristics of argon gas discharge at different inter-electrode distances and working pressure of 0.7mbar without magnetrons were introduced. Then the variation of discharge current with inter-electrode distance at certain discharge voltages without using magnetron was determined. The current-voltage characteristics of discharge plasma at inter-electrode distance of 4cm without magnetron, with only one magnetron and with dual magnetrons were also determined. The variation of discharge current with inter-electrode distance at certain discharge voltage (400V) for the cases without magnetron, using one magnetron and dual magnetrons were studied. Finally, the discharge current-voltage characteristics for different argon/nitrogen mixtures at total gas pressure of 0.7mbar and inter-electrode distance of 4cm were presented.


Article
Structural Properties of Nickel Oxide Nanostructures Prepared by Closed-Field Unbalanced Dual Magnetron Sputtering Technique

Authors: Firas J. Kadhim --- Oday A. Hammadi --- Mohammed K. Khalaf
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2017 Volume: 13 Issue: 2 Pages: 3-10
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this work, nickel oxide nanostructures were prepared by a closed-field unbalanced dual magnetron plasma sputtering technique. The structural characterizations performed on the prepared samples showed that they were polycrystalline and the optimization of preparation conditions, only two crystal planes; (111) and (012), were observed in the final product. The surface roughness of the nanostructures can be varied by controlling the inter-electrode distance. Minimum particle size of 25nm was determined for the samples prepared at inter-electrode distance of 6cm.


Article
Preparation and Characterization of Silicon Nitride Nanostructures Prepared by DC Reactive Sputtering Technique with Novel Design of Closed-Field Unbalanced Dual Magnetron Assembly

Authors: Firas J. Kadhim --- Mohammed K. Khalaf --- Oday A. Hammadi
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2017 Volume: 13 Issue: 3 Pages: 3-12
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this work, novel design of closed-field unbalanced dual magnetrons system was employed in a DC reactive sputtering system to prepare silicon nitride nanostructures. Two types of silicon wafers (n- and p-type) were sputtered in presence of nitrogen gas to deposit nanostructured silicon nitride thin films on glass substrates. The prepared nanostructured were polycrystalline with six dominant crystal planes: (101), (110), (200), (232), (301) and (321). The surface roughness of the sample prepared at inter-electrode distance of 4cm was higher than other samples prepared at smaller or larger distances and the average and R.M.S roughness were 0.777 and 1.03 nm, respectively. The nanoparticles of minimum size of 30nm were formed and recognized as individual accumulated particles. Two bands of significant absorption were observed around 960 and 1086 cm-1, those are attributed to the Si-N-Si vibration mode in Si3N4 molecule. An absorption peak was observed at 389nm, which is attributed to the quantum size effect of nanostructures. The refractive index of the prepared Si3N4 samples was determined to be 1.38-2.1 and the energy band gap was ranging in 5.1-5.2 eV. The energy band gap was found to increase with decreasing thickness of the prepared film. The wide energy band gap of Si3N4 nanostructures makes them good candidate, as similar as AlN, BN and GaN, for power electronics and optoelectronics operating at high temperatures.

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