A. Sadoun, S. Mansouri, M. Chellali, N. Lakhdar, A. Hima and Z. Benamara
In this work, we have presented a theoretical study of Au/Ni/GaN Schottky diode based on current-voltage (I-V) measurement for temperature range of 120 K to 400 K. The electrical parameters of Au/Ni/GaN, such as barrier height (Φb), ideality factor and series resistance have been calculated employing the conventional current-voltage (I-V), Cheung and Chattopadhyay method. Also, the variation of Gaussian distribution (P (Φb)) as a function of barrier height (Φb) has been studied. Therefore, the modified
relation has been extracted from (I-V) characteristics, where the values of ΦB0 and
have been found in different temperature ranges. The obtained results have been compared to the existing experimental data and a good agreement was found.
In this paper, Cd0.3Zn0.7S thin film has been electrodeposited from aqueous bath containing CdSO4, ZnSO4, Na2S2O3 and EDTA, having pH ~ 14. The structural, optical, morphological, surface wettability and photoluminescence properties of the film were investigated. The XRD pattern showed that the film consisted of mixed phases of CdS and ZnS with polycrystalline structure. The bandgap of the film was evaluated as 2.69 eV. The AFM study revealed that the Cd0.3Zn0.7S thin film contained spherical grains with root mean square roughness of 6.09 nm. The water contact angle measurement showed that the thin film was hydrophilic in nature. Moreover, the PL study revealed that the excitation wavelength was 460 nm.
The present work reports on the optimization of substrate temperature, molar concentration and volume of the solution of nickel oxide (NiO) thin films prepared by nebulizer spray pyrolysis (NSP) technique. NiO films were optimized and characterized by XRD, SEM, EDX, UV-Vis and I-V measurements. Based on XRD analysis, the molar concentration, volume of solution and substrate temperature of the prepared NiO films were optimized as 0.20 M, 5 mL and 450 °C for P-N diode applications. The XRD pattern of the optimized NiO film revealed cubic structure. The surface morphological variations and elemental composition were confirmed by SEM and EDX analysis. The optical properties were studied with UV-Vis spectrophotometer and the minimum band gap value was 3.67 eV for 450 °C substrate temperature. Using J-V characteristics, the diode parameters: ideality factor n and barrier height Φb values of p-NiO/N-Si diode prepared at optimum conditions, i.e. 450 °C, 0.2 M, 5 mL, were evaluated in dark and under illumination.
J. Górka, M. Przybyła, M. Szmul, A. Chudzio and D. Ładak
The article presents problems accompanying the industrial TIG welding (142) of a heat exchanger perforated bottom made of steel clad with titanium B265 grade 1 with tubes made of titanium B338 grade 2. Research-related tests involved the making of test plates containing simulated imperfections formed during orbital welding. The above-named imperfections resulted from insufficient gas shielding during the welding process, the improper positioning of the tungsten electrode (excessively large or overly small circumference, around which the orbital welding process was performed), an excessive electrode travel rate being the consequence of an improperly set welding programme as well as excessively high welding current. Initial tests enabled the development of the orbital TIG welding of titanium tubes with the perforated bottom made of titanium-clad steel, satisfying acceptance criteria applied during commissioning.
Copper oxide and cobalt oxide (Co3O4, CuO) nanocrystals (NCs) have been successfully prepared using microwave irradiation. The obtained powders of the nanocrystals (NCs) were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric (TGA) analysis and Fourier-transform infrared spectroscopy. The obtained results confirm the presence of both nanooxides which have been produced during chemical precipitation using microwave irradiation. TEM micrographs have shown that the obtained nanocrystals are characterized by high dispersion and narrow size distribution. The results of X-ray diffraction confirmed those obtained from the transmission electron microscope. Optical absorption analysis indicated the direct band gap for both kinds of the nanocrystals.
GaN thin films were deposited on p-Si(1 0 0) substrates using RF magnetron sputtering at various RF powers. Influence of RF power on morphological, optical and structural properties of GaN thin films were investigated and presented in detail. XRD results proved that the films were polycrystalline in structure with (1 0 0) and (1 1 0) planes of hexagonal GaN. It was found that increasing RF power led to deterioration of crystal structure of the films due to increased decomposition of GaN. Stress in GaN thin films was calculated from XRD measurements and the reasons for this stress were discussed. Furthermore, it was analyzed and interpreted whether the experimental measurement results support each other. E2 (high) optical phonon mode of hexagonal GaN was obtained from the analysis of Raman results. UV-Vis spectroscopy results showed that optical band gap of the films varied by changing RF power. The reasons of this variation were discussed. AFM study of the surfaces of the GaN thin films showed that some of them were grown in Stranski-Krastanov mode and others were grown in Frank-Van der Merwe mode. AFM measurements revealed almost homogeneous, nanostructured, low-roughness surface of the GaN thin films. SEM analysis evidenced agglomerations in some regions of surface of the films and their possible causes have been discussed. It has been inferred that morphological, optical, structural properties of GaN thin film can be changed by controlling RF power, making them a potential candidate for LED, solar cell, diode applications.
In the present study, nanocrystalline undoped and Fe (5 wt.%) doped ZnO powder has been synthesized by soft chemical route. The structural, nano/microstructural, vibrational and magnetic properties of these samples have been studied as a function of calcination temperature (400 °C to 1100 °C). X-ray diffraction analysis of Fe doped ZnO powder has shown the major nanocrystalline wurtzite (ZnO) phase and the minor cubic spinel-like secondary nanocrystalline phase at 700 °C. At calcination temperature of 700 °C, the magnetization and coercivity have been enhanced in Fe doped ZnO. As the calcination temperature increased to 1100 °C, the major phase of ZnO and minor cubic spinel-like secondary phase turned into bulk in doped ZnO. Interestingly, the reduced magnetization and zero coercivity have been observed in this case. These changes are attributed to the conversion of secondary nanocrystalline ferromagnetic spinel phase to its bulk paramagnetic phase. The degree of inversion i.e. the occupancy of both sites with different symmetry by ferric ions is proposed to be solely responsible for the unusual behavior.
Modifications in morphological and plasmonic properties of heavily doped Ag-TiO2 nanocomposite thin films by ion irradiation have been observed. The Ag-TiO2 nanocomposite thin films were synthesized by RF co-sputtering and irradiated by 90 MeV Ni ions with different fluences. The modifications in morphological, structural and plasmonic properties of the nanocomposite thin films caused by ion irradiation were studied by transmission electron microscopy (TEM), X-ray diffraction (XRD), and UV-Vis absorption spectroscopy. The thickness of the film and concentration of Ag were assessed by Rutheford backscattering (RBS) as ~50 nm and 56 at.%, respectively. Interestingly, localized surface plasmon resonance (LSPR) appeared at 566 nm in the thin film irradiated at the fluence of 1 × 1013 ions/cm2. This plasmonic behavior can be attributed to the increment in interparticle separation. Increased interparticle separation diminishes the plasmonic coupling between the nanoparticles and the LSPR appears in the visible region. The distribution of Ag nanoparticles obtained from HR-TEM images has been used to simulate absorption spectra and electric field distribution along Ag nanoparticles with the help of FDTD (Finite Difference Time Domain). Further, the ion irradiation results (experimental as well simulated) were compared with the annealed nanocomposite thin film and it was found that optical properties of heavily doped metal in the metal oxide matrix can be more improved by ion irradiation in comparison with thermal annealing.
A. El Amrani, R. Si-Kaddour, M. Maoudj and C. Nasraoui
The SiN/SiO2 stack is widely used to passivate the surface of n-type monocrystalline silicon solar cells. In this work, we have undertaken a study to compare the stack layer obtained with SiO2 grown by both rapid thermal and chemical ways to passivate n-type monocrystalline silicon surface. By varying the plateau time and the plateau temperature of the rapid thermal oxidation, we determined the parameters to grow 10 nm thick oxide. Two-step nitric acid oxidation was used to grow 2 nm thick silicon oxide. Silicon nitride films with three refractive indices were used to produce the SiN/SiO2 stack. Regarding this parameter, the minority carrier lifetime measured by means of QSSPC revealed that the refractive index of 1.9 ensured the best passivation quality of silicon wafer surface. We also found that stacks with nitric acid oxidation showed definitely the best passivation quality. In addition to produce the most efficient passivation, this technique has the lowest thermal budget.
In this study, LaxMoyOz powders were synthesized by a cost-effective solid-state synthesis method. Four different heating cycles were designed to investigate the effects of synthesis temperature and holding time on lanthanum molybdate (LMO) formation, phase assemblies, particle size and morphology. X-Ray Diffraction (XRD) and scanning electron microscopy (SEM) studies were performed to observe crystal structure and particle morphology of synthesized powders. The results showed that nearly ninety percent β - La2Mo2O9 (43,3 nm crystal size) phase was obtained at 1000 °C for 6 h holding time. Longer holding times at 1000 °C favor more oxygen-rich compounds which cause recrystallization of various new crystalline phases. The grain size of the synthesized powder was increased from 0,2 µm to 1,5 µm with increasing holding time. In summary, it is possible to manufacture LMO powders rich in β - La2Mo2O9 by one - step solid - state synthesis method. The phase assembles and particle size of LMO powders could also be tailored by optimization of heat treatment cycle.