Defect and Diffusion Forum Vol. 418

Abstract: In our paper, we interested in the study of the thermodynamic properties of the compound VSb₂. For this, we used the full potential linearized augmented plane wave (FP-LAPW) method implemented in the Wien2k code. The latter is based on the density functional theory (DFT). We also used the Quasi-Harmonic Debye model implemented in the Gibbs2 code. The exchange-correlation energy of electrons was treated using the generalized gradient approximation (GGA) parameterized by Perdew-Burke and Ernzerhof. The calculation of the pressure and the temperature dependence of the thermodynamic properties of VSb₂ material is obtained from that of the electronic structure, within the framework of the Quasi-Harmonic Approximation (QHA). We selected a volumes grid enclosing the equilibrium geometry. At these fixed volumes, the rest of the structural parameters are relaxed and we obtain the energy curve as a function of the volume E(V). The thermodynamic properties such as the primitive cell volume V(Bohr³), the bulk modulus B (GPa), the heat capacities C_V(J.mol^-1.K^-1) and C_P(J.mol^-1.K^-1), the thermal expansion coefficient α (K^-1), the Grüneisen parameter γ, and the Debye temperature θ_D(K) have been studied depending on the temperature (T) in the range [0 ; 500 K], and the pressure (P) in the interval [0 ; 15 GPa]. The increase of the bulk modulus is in agreement with the decrease of the volume, also the volume of the primitive cell and bulk modulus are more sensitive to pressure than to temperature. The thermal expansion is more sensitive at low temperatures than at high temperatures. A specific heat behavior of was found, with a Dulong-Petit limit value of 48.16 J.mol^-1.K^-1. The effect of the pressure on the Grüneisen parameter is opposite to Debye temperature.

Abstract: This work investigates the behavior of the electronic states in ZnO/ Zn1-xMgxO MQWs induced by a staircase-like defect layer bounded by two substrates of the same type (ZnO). We use the interface response theory to calculate the different physical properties of the system. First, westudied a material staircase defect containing three material defects, such where the concentration depends on an increasing step noted P and a parameter X0 which does not exceed 0.35, so that the materials remain crystallized in the same structure. We found that the increase of these parameters induces an augmentation in the potential energy, leading to shifts of the electronic states to higher energies. In the second part, we studied the effect of introducing a geo-material defect with the step P=0.05 and X0=0 as optimal values, and the thickness of the staircase defect layer depends on an increment step noted S. We found that the variation of S influences the number of states that appear in the gap, which gives the possibility to improve the electron transport without using higher energy.Finally, we try to find several staircase defect configurations used in different structures. We found that inside the case of symmetric defect permutation, the position of the defect does not influence the behavior of the electronic states. Still, in the case of antisymmetric permutation, the position of thedefect has an influence on the behavior of the electronic states.

Abstract: We study in this work, the occurrence of defects modes in the transmission spectrum and the band structure of a perfect photonic asymmetric serial loops structure (ASLS) utilized for narrow-band filtering. The perfect structure presents large photonic bandgaps that result from the modes of the loops resonances and the system periodicity. Besides that, the existence of defects within this perfect ASLS, whether at the segment or loop level, or both of them, causes the appearance of two, three, or four defect modes within gaps with good transmission rates and high-quality factors. These defects modes are extremely sensitive to changes in structural parameters. This system can be used to filter or guide the incoming electromagnetic waves. The interface response theory has been used to accomplish the analytical calculation. Green's function of the full system is determinated using this method. It allows us to calculate the dispersion relation and the transmission rate. Therefore, this paper can provide ideas for the design of multi-channel tunable filter using for frequency division multiplexing and microwave and signal processing.

Abstract: In this paper using the transfer matrix method (TMM), we consider an electronic comb-like waveguides system composed by the periodicity of segment semiconductor (GaAs type) of length and grafted in its extremity by one semiconductor resonator (GaAlAs type) of length . These segments and resonators are considered quantum wires. The perfect system in question presents the electronic pass bands and electronic band gaps which allow to control and manipulate the electrons waves whose energy is identical to the energy of the gaps. We insert the defect at the resonator level in the middle of this system in question. Hence, very narrow localized defect states are created in the electronic band gaps, with probably high transmission rate and very important quality factor. These localized defect states shift to low energy by increasing the resonator defect length, while is move to high energy when the resonator defect concentration increases. In this study, we consider that the segments and resonators lengths are very small in front of their sections, so that the propagation of electronic waves occurs only in a single dimension.

Abstract: We have studied the electronic properties in presence of an off-center hydrogenic shallow donor impurity confined in GaAs semiconductor quantum dot with toroidal geometry by considering the infinite confinement potential. This study has been performed within the parabolic band and the effective mass approximations in the presence of an off-center donor impurity. Three-dimensional Schrödinger equations are discretized using the finite difference method on a mesh containing N_r*N_θ*N_φ nodes. The numerical results of the analytical calculations demonstrate that the variation of the geometrical and torus radii (R_g and R_c) has a remarkable effect on the donor energy and the average electron-impurity distance, which is quite remarkable in small hemi-Toroidal quantum dot. On the other hand, we've demonstrated that the donor atom's position has a considerable impact on their energy. Furthermore, our numerical results show that the geometrical radius and donor atom's position significantly affect the electron impurity binding energy.

Abstract: Laser powder deposition (LPD) has been relied on to improve the surface properties of materials. Nowadays, an excellent reinforcement for aluminum and aluminum alloys could be carbon nanotubes (CNTs). The surface of aluminum alloy 2024 (Al Cu4Mg1) is coated with double-walled and multiwalled carbon nanotubes (DWCNTs, MWCNTs) using laser preplaced powder deposition with pulsed Nd:YAG to evaluate its effect on enhancing hardness and corrosion resistance. The laser power, pulse duration, scanning speed, and frequency, were controlled to complete this task. Since the best DWCNT deposited layer was obtained at the optimal process conditions, the Vickers micro-hardness and corrosion resistance of the coated Al 2024 surface improved in the readouts. The results showed that DWCNT improved specific essential surface attributes, namely hardness, abrasive wear resistance, and corrosion resistance, more than MWCNTs, according to the findings. Although MWCNTs have less penetration, their dispersion on the surface is superior to DWCNTs.

Abstract: For the optoelectronics application like (optical waveguides), a nanostructure Lithium Niobate (LiNbO₃) Nano film was produced and placed on a quartz substrate using the pulse laser deposition (PLD) process. The structural, morphological, and optical features of wavelengths od pulsed laser (1064 and 532) nm were investigated for the films of LiNbO₃ Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Ultra-Violet (UV-Vis) spectrophotometer, and Atomic Force Microscopy (AFM) are among the techniques used to describe and evaluate the samples.

Abstract: This manuscript presents the reactive pulsed laser deposition method was used to prepare and deposit the high-quality copper oxide (Cu₂O) Nanofilms using high purity copper metal, Oxygen, and heating at 300 C, at different laser energies rated (800 mj, 1000 mj, and 1200 mj) respectively. The presented results show high ranges of transparent values with the increasing laser energies from 66%-90%. As the laser energies increased the optical energy band gap value was increased from 2.32eV – 2.47eV. Further, the AFM, XRD, I-V, and spectral response tasted and investigated the surface topography, homogeneity, roughness’s, structural and optoelectronic properties for the deposited Cu₂O nanofilms, respectively.

Abstract: The deposition of copper oxide utilizing a pulsed laser deposition technique employing a reactive pulsed laser as a deposition technique is the subject of this study. The wavelength of the pulsed lase used are 1064 nm, the pulse duration is 10 ns, the laser energy of 1000 mj with different substrate temperatures (200, 3300, and 400 oC). The influence of the substrate tampering on the morphological, structural, Photolumencence, and the electrical, and attributes of the fabricated solar cell was recorded and studied using a high purity cupper target and deposited on porous silicon substrates. When compared to a crystalline silicon surface, the results of AFM show a higher possibility of better absorption and hence lower reflection. The presented results revealed the properties of the fabricated solar cell as well as a noticeable improvement in the solar cell's efficiency, whether copper deposition was used or not. The deposited films at 1064 nm were monoclinic structures with a preference for the (111) direction, according to X-ray diffraction (XRD) examination. SEM were used to study the production of nanostructures on the substrate's surface, which led to the formation of small-sized and nanostructured films.

Abstract: The deposition of copper oxide utilizing a pulsed laser deposition technique employing a reactive pulsed laser as a deposition technique is the subject of this study (RPLD), 1064 nm, 10 Nanosecond Q-switch Nd-YAG laser with 350 °C, and 800-1200 mJ energies of laser was used to deposited a high purity target of Cupper and deposited on the quartz substrates synthesized and study the laser energies effect on the optical and photoluminescence properties.