Journal of New technology and Materials

An analytical two-dimensional (2D) model to accurately predict the channel potential and electric field distribution in sub-micron GaAs MESFET based on (2D) analytical solution of Poisson’s equation using superposition principle is presented. The results so obtained for current voltage characteristics, Transconductance and drain conductance, are presented and validated against both experimental I-V curves and various Models of the submicron MESFET GaAs. The model is then extended to predict the effects of parasitic resistances Rs and Rd, carriers mobility according to the electric fields and the edges effects on the performance. This model will allow more significant simulation of the component characteristics, with a precision improved for various conditions of Schottky barrier.

The Speckle effect is a discipline with whole share. It is exploited in various scientific fields. On the application plan, it became a very powerful tool for the characterization and the non destructive testing. This technique which makes it possible to control and quantify in real time several parameters such as : the roughness of surface, the vibrations, the constraints, microphonedisplacements, the microstructure of surfaces, can be applied, at the same time, with the objects transparent and diffusing, solidor liquids. The development of flexible tools of capture of images to high resolution (camera CCD) coupled to information processing systems, nowadays makes the techniques speckle particularly important and interesting for industrial control. Ourwork consists in controlling qualitatively and quantitatively the variation thickness extracted the surface of the Duralumin sample (Aluminium alloy) immersed in a Salt water (to 3.5%), by using a camera CCD connected to a computer equipped with a software of image processing PRO-PLUS.

Wastewater treatment is a very important process that consists of applying modern and new technology to improve or upgrade the quality of a wastewater because its disposal whether by surface, subsurface methods or dilution, is dependent on its treatment. In the present work a full study has been carried out dealing with the physicochemical and bacteriological properties of wastewaters after being treated in Oued Athmania Wastewater Treatment Plant. The results revealed that the findings are in conformity with the international standards.

In this work we present a new nonlinear approach for the calculation of the static characteristics of MESFET GaAs with submicron gate. First, we compare the results of the numerical simulations of the three main models for the MESFETs with submicron gate : Ahmed [1], Islam [2] and Memon [3] with experimental results. Then we propose a new approach that takes into account the surface states of the Schottky junction through a new mobility law for the determination of the output characteristics. The thermal effect is also represented in the mobility law. The comparison of our model with the three previous models referring to the experimental data shows that our approach gives the most accuracy result. Also, the proposed model can be used in the case of logic or analog circuits based on submicron GaAs MESFET.

It’s known that indium gallium nitride InGaN alloys has a direct band gap varying from 0.7 to 3.4 eV which covers nearly the whole solar spectrum making it material of choice to make tandem solar cells. In other hand, it’s experimentally known that uses of InGaN/GaN multiple quantum well MQW structures in GaN based devices decreases surface recombination and, thus, enhances devices performance. Here, we present a simulation study of multiple quantum well MQW InGaN/GaN solar cells, where cell’s active region is formed by a number of InGaN quantum wells (QWs) separated byGaN quantum barriers (QBs). We will present indium element content of InxGa1-xN wells and number of InGaN/GaN periods impacts on solar cell parameters.

This project has been focused on structural, morphological, optical and photoluminescence properties of pure ZnO thin film. Here, zinc oxide thin films are grown on glass via facile and low cost sol gel spin coating process @ fixed spinning speed of 1000 RPM. The X-ray patterns, the transmittance, the particle size by the atomic force microscope are investigated. The particle size is equal to 120 nm and the surface roughness is found to be 23.33 nm. The photoluminescence analysis reveals near band emission and strong visible emission 2.11 and 2.80 eV.
Keywords : Spin coated ZnO films ; X-rays pattern ; transmittance ; photoluminescence ; SEM ; TEM ; Electron diffraction ; AFM.

A theoretical study of structural, and electronic properties of NaZnAs compound is presented by performing ab initio calculations based on density-functional theory using the full-potential linear augmented plane wave (FP-LAPW). The generalized-gradient approximation (GGA) and the local density approximation LDA) are chosen
for the exchange–correlation energy. The Engel-Vosko (EVGGA) formalism is applied for electronic properties The calculated structural parameters, such as the lattice constant, bulk modulus and pressure derivative, the electronic band structures and the related total density of states and charge density are presented. The high-pressure α phase of the NaZnAs is investigated and phase transition pressure from tetragonal to high-pressure phase is determined. We have found that the Nowotny–Juza compounds NaZnAs is direct gap semiconductor at ambient pressure. The bonding character and the phase stability of NaZnAs compound are discussed. The nature and the size of the band gap of NaZnAs compound are associated with the bonding character of two Kinds of bonds, namely, Na–As and Zn–As bonds.

In this paper, the effect of the time deposition of metal nanoparticles on the photodegradation of methylene blue is studied. The modified silicon nanowires were used as heterogeneous photocatalysts for the decomposition of methylene blue under UV light irradiation. The above reactions were monitored by UV–Vis spectrophotometer which shows the positive effect of the time deposition of metal nanoparticles on the photodegradation of methylene blue. 91% of the degradation was observed with the hydrogen terminated porous silicon nanowires and the degradation is about 95% for the modified porous silicon nanowires with Au (80min) and the same degree was obtained with Pt (120min) at 200 minutes of irradiation. The rate of the degradation reaches 100% at 90min of illumination with the decorated porous silicon nanowires with Pd nanoparticles.

Micro- and nano-electromechanical systems (MEMS or NEMS)-based fuel delivery in direct methanol fuel cell (DMFC) devices offer opportunities to address unmet fuel cells related to fuel delivery. By applying an alternating electrical field across the actuator, the resultant reciprocating movement of the pump diaphragm can be converted into pumping effect. Nozzle/diffuser elements are used to direct the flow. To make the power system applicable for portable electronic devices, the micropump needs to meet some specific requirements : low power consumption but sufficient fuel flow rate. In this study, a theoretical method have been used to investigate the effects of materials properties, actuator dimensions, driving voltage, driving frequency, nozzle/diffuser dimension, and other factors on the performance of the whole system. As a result, a viable design of micropump system for fuel delivery in DMFC devices has been achieved and some further improvements are suggested. A mathematical model was used to simulate the behaviour of the micropump. The results of mechanical calculations and simulations show good agreement with the actual behaviour of the pumps.

In this paper, a finite difference modeling of single layer organic light emitting diode “OLED” based on MEH-PPV [Poly (2-Methoxy, 5-(2’-Ethyl-Hexoxy)-1, 4-Phenylene-Vinylene)] and DP-PPV [Poly (2, 3-DiPhenyl-Phenylene-Vinylene)] is presented through the simulation of the basic equations i.e. the time independent continuity equations, with a drift diffusion form for current density, coupled to Poisson’s equation. Thus, several parameters are extracted from this model ; J (V) characteristics for the two devices which are compared to the experimental results and the spatial distributions of the potential, the electric field and the carrier concentrations.