Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : ZnO

Synthesis of Dopant Zno Thin Films with Al Using Dip Coating for Gas Sensors

S.H. Sabeeh; R.H. Jassam

Engineering and Technology Journal, 2017, Volume 35, Issue 8, Pages 842-844

The sol-gel technique (dip coating method) used to synthesize pure Zinc Oxide and Aluminum doped Zinc Oxide thin films on glass substrate for gas sensing application. Zinc acetate dehydrate was used as source of Zinc ions. The influence of annealing temperature of pure ZnO thin films with three different temperatures (300,400,and 500 ) °C, Aluminum dopant concentration with two different concentration (3wt% and 5wt% ) and annealing temperature for AZO thin films with three different temperatures (300,400,and 500 ) °C on gas sensing properties was studied. The results show that ZnO was to be sensitive toward CO gas and its sensitivity decrease with increase in annealing temperature of pure ZnO and (5wt.%) AZO thin films. It is found that the sensitivity of pure ZnO thin films decrease from 67% at 300 °C to 54% and 38% at 400 and 500 °C respectively. Likewise, for 5wt. % AZO thin film the sensitivity improved by increase the Aluminum dopant concentration with fixed annealing temperature 500 °C. It is found that the sensitivity increase form 49% to 57% when doped with Al at (3 wt. %) and (5 wt. %) respectively.

Nano rods and flowerlike synthesis by hydrothermal growth method without catalysts

Thamir A.A. Hassan; Abdulkareem M. Ali; Ali Qassim

Engineering and Technology Journal, 2015, Volume 33, Issue 6, Pages 1120-1126

This study we don't use any catalyst or buffer layer before the reaction by hydrothermal method was used to prepare ZnO nano rods and flowerlike. The process has taken place inside Teflon lined stainless steel autoclave with volume 50 ml (homemade). ZnO nano rods and flowerlike were successfully synthesized using ZnO nanoparticles (20 nanometer) and NaOH (concentrations 3M) was the starting materials for the chemical reaction under stirring. The suspension was transferred into a Teflon lined sealed stainless steel autoclave and kept at 90 0C for 24 h,48 h and 72 h. The influence of the synthesis process on the morphology, the crystallinity and structural properties are studied by X-ray diffraction and field emission scanning electron microscope (FE-SEM), the experimental pattern of the films show that diffraction peaks can be assigned to the Wurtzite hexagonal-shaped ZnO as shown in the FE-SEM pictures, also the morphology of the films studied by atomic force microscope shows that the prepared thick films have high roughness specially for the powder prepared 46 h .

Characterizations study ZnO-TiO2 nano rods thick films as Photo detector

Raad Sadoon; Osama AbdulAzeez

Engineering and Technology Journal, 2015, Volume 33, Issue 6, Pages 1075-1081

First,ZnO nanorod s were su ccessfu lly synthesized by simple evaporation
method,u sing single stage controllable horizontaltu be fu rnace and qu artz tu be withou tcatalyst.The ZnO nano powd erwas mix ed with (10 and 20%)of TiO2 powd er(weightratio),then ZnO -TiO 2 thickfilms were synthesized u singsimple,low-cost efficient screen print techniqu e. The thick films were heated at 500 C ˚ for one hou rto remove the organic bind erand anyimpu rities.The prepared thickfilms were examined withX -Ray,and FESEM to stu d y the stru ctu raland morphology of the films,the X -ray results show that the films are polycrystalline with sharp and high intensity peaks indicating
high crystalinity of the product.The FESEM pictures show nanorods with diameters less than 100 nm and several micrometers in length
of ZnO withTiO 2 nanoparticles.ZnO -TiO 2 device was built up by electroding the thick films.The I-V characterization of the films were
studied in dark and light,then photo detection parameters were estimated and it was found to be efficient and high response in UV range detection

The heat exchange Intensification in Nano-homo junction semiconductor materials

Mahmood Radhi Jubayer

Engineering and Technology Journal, 2015, Volume 33, Issue 5, Pages 819-829

In this work, it was examined mechanisms that control internal cooling device (nano-homojunction diode)depending on thermoelectric Peltier effect, resulting in structures that are optimized thermal management. Peltier coefficient for short-length diode is theoretically investigated. It is found that the cooling power is governed by the carrier concentration, current density and the ratio of n-type region width to p-type region width. It has been determined the optimum value of the cooling power at the junction of ZnO in the optimum density at doping symmetrically on a certain value.The cooling power, temperature difference (temperature between the contact and the junction) and dimensionless figure of merit are found in this material for different thicknesses, then comparing between them. It has been simulated the homojunction diode using a MATLAB software with numerically calculated the Peltier coefficient for each layer in these diodes.It has been found that nano-homojunction introduce a significant improvement in the internal cooling performance.

Fabrication of electro spinning 1D ZnO Nano fibers as UVPhotoconductor

Raad S. Sabry; Firas S. Mohammed; Roonak Abdul Salam A.Alkareem

Engineering and Technology Journal, 2015, Volume 33, Issue 5, Pages 884-894

The electrospinning technique was used to fabricate 1D nanofibers of Zinc Oxide (ZnO). Polyvinylpyrrolidone (PVP) ̸ zinc acetate Nano fibers electrospun using solution containing PVP dissolved in ethanol and zinc acetate in distilled water were mixed, followed by calcination at 500°C for 3hours to remove the polymer. XRD pattern show the hexagonal wurtzite structure of ZnO NFs without any impurities. FESEM pictures show a network of nanofibers with diameters less than 100 nm and several micrometers in length of ZnO, these nanostructures increase the ratio of surface area to volume and improve the physical properties of the materials. The Photoluminescence (PL) of the films was studied and the energy gap and the optical properties were estimated. A photoconductor device was constructed by electroding the films with silver conducting electrode (IDE) using screen print method, The result shown that the resistance of the nanofiber films decrease dramatically when exposes to UV light. In addition, the change of conductivity with the change of wavelengths was studied also the photoconductivity was examined under different bias voltage.

Annealing Effect on Structure and Optical Properties of ZnO Thin Films Prepared by Spray Pyrolysis

Selma M.H. Al-Jawad

Engineering and Technology Journal, 2015, Volume 33, Issue 1, Pages 160-171

Polycrystalline films ZnO has been grown onto glass substrates by chemical spray pyrolysis (CSP) method. They were given heat treatment at different temperatures and constant time and for different times with constant temperature in air. The change in structural and optical properties was studied by means of X-ray diffraction (XRD), SEM, and optical absorption measurements. Structural analysis by X-ray diffraction pattern showed annealed ZnO film has high-orientation along c - direction (0 0 2), which remained the same with different heat treatment. The lattice constants of ZnO thin films were also obtained from XRD data. It is found that, with the increase of different heat treatments, the lattice constant a increases from 3.208 Å to 3.254 Å, and c increases from 5.125 Å to 5.219 Å. Where at higher annealing temperature and time the lattice constant c and a approach from bulk value. Other orientations corresponding to (1 0 0) and (1 0 1) are presented with very low relative intensities as compared to that of (0 0 2) plane. The transparency is increasing with increasing annealing temperature and time due to decreasing in films thickness with increasing annealing temperature and time. Change in bandgap energy from 3.2 to 3.01 eV was observed for different heat treatments.

Characteristics Study of ZnO Thin Films by Rapid Thermal Oxidation Treatment Technique

Uday Muhsin Nayef; Mohammed Jamal Jasim

Engineering and Technology Journal, 2015, Volume 33, Issue 1, Pages 37-44

In this paper preparation of good quality transparent conductive ZnO thin films by post-oxidation of vacuum evaporated Zn, on glass and silicon (p-type) as substrates, the oxidation was achieved in a short time (90 sec) which is known as rapid thermal oxidation. One growth parameter has been considered to specify the optimum conditions the film thickness are (200,300,400 &500 nm).
The XRD spectra revealed a high oriented grain in the (002) lattice system which is hexagonal wurtzite and proved that the ZnO films have a polycrystalline structure. Also, the morphological properties of ZnO films show that all films have a homogeneous surface morphology and it appears, to change significantly as a function of thickness.The energy gap of ZnO films decreases as the thickness increases. The FTIR spectra indicate the existence of the distinct characteristic absorption peak at 472.56cm-1 for Zn-O stretching mode.
Study of effect I-V and C-V measurements of ZnO films with the increase thickness. The photovoltaic properties confirmed that the photovoltaic depends strongly on the bias voltage and the amount of current produced by a photovoltaic device which is directly related to the number of photons absorbed. C-V results demonstrated that the fabricated heterojunction is of abrupt type. Also, the width of the depletion layer (w) follows the same behavior (V_bi ) decreased while the charge carrier density (N_d ) was increased with the thickness increase.

Synthesize Nano ZnO-ZrO2 Composite by Combustion Method and Studying their Dielectric Properties

Fadhil A.Chyad

Engineering and Technology Journal, 2012, Volume 30, Issue 8, Pages 1342-1350

Combustion method had been used to prepare a composite material from doping
ZnO by 10 mol% ZrO2 . XRD showed a good crystalline powder comparing with
ASTM cards. Dielectric properties such dielectric strength, dielectric constant,
dielectric loss and tangent loss have been measured .All the dielectric properties
have decreased as the frequency increasing .
The particle size has great effect on the dielectric properties of the composite
which decreased as the particle size increased .

Effect of Reinforced by Zinc Oxide Powder on the Mechanical Properties forUn-saturated Polyester Matrix Composite Material

Engineering and Technology Journal, 2011, Volume 29, Issue 10, Pages 474-484

This research is devoted to the preparation of polymer matrix composite materials by (Hand Lay-Up ) method, where the composite material was prepared from the unsaturated polyester resin (UP) as a matrix reinforced by Zinc Oxide with volume fractions (0% , 1% , 2% , 3% ,4% ) .several of mechanical tests were done and these includes Impact, Bending, Flexural Strength, Shear Stress and Hardness, Result of the
tests shows that the values of (Bending elastic modulus, Flexural Strength , Fracture Toughness, Hardness and Shear Stress) increase with the increase of Zinc Oxide particle volume fraction, but the values of Impact Strength decreased with the increases of volume fraction of Zinc Oxide particles.

Optoelectronic properties of ZnO/PS/n-Si Heterojunctions

Khawla S. Khashan

Engineering and Technology Journal, 2008, Volume 26, Issue 4, Pages 442-448

In this work a colloid of nanocrystalline ZnO particles is prepared by
chemical method, and then sprayed on porous silicon substrate which is prepared
by electrochemical etching under a current density of 15mA/cm2 for 10 min. The
initial radius of the ZnO particles is found to be (2.2 nm). FTIR spectra exhibit the
presence of Zn – O bond which indicates the formation of ZnO particles. Also
spectra reveals the formation of SiHx (x=1-2) and Si-O bond which indicates the
presence of porous layer. High performance rectifying was obtained, with high
photoresponsivety of 0.54 A/W at 400 nm. The corresponding quantum efficiency
was 166.7%.The results show that ZnO on porous silicon (PS) structures will act as
good candidates for making highly efficient photodiodes.