Gergő Richárd Fejes, Viktor Gonda and Károly Széll
Severe plastic deformation (SPD) is a well-established methodology for the processing of bulk ultrafine grained materials. Among various methods, equal channel angular pressing (ECAP) is the most popular way of creating ultrafine grained materials. The stored energy after ECAP in these substances highly influences the microstructural processes: recovery and recrystallization of the processed materials. We analyzed the recrystallization kinetics of room and elevated temperature ECAP processed copper samples using differential scanning calorimetry (DSC). For the processing of the measurement data we developed a MATLAB processing routine.
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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.
Nanostructures of copper (II) oxide were synthesized through chemical reduction of copper (II) sulfate pentahydrate using phytochemicals present in leaf extracts of Leucas aspera. The crystalline phases and size were assessed by X-ray diffraction data analysis. From the Bragg reflection peaks, existence of monoclinic end-centered phase of copper (II) oxide along with presence of cubic primitive phase of copper (I) oxide and traces of cubic face centered lattices of zero valent copper was revealed. The three Raman active modes corresponding to CuO phase were identified in the sample with permissible merging of characteristic bands due to nanostructuring and organic capping. The surface topography measurement using field emission scanning electron microscope evidenced the occurrence of cylindrical rod shaped morphological structures along with a number of unshaped aggregates in the sample. The effective crystallite size and lattice strain were estimated from Williamson-Hall analysis of Bragg reflection data. Tauc plot analysis of UV-Vis-NIR absorption data in direct transition mode provided an estimation of band gap, viz. 1.83 eV and 2.06 eV respectively, for copper (II) oxide and copper (I) oxide. Thermal degradation study using thermogravimetric curve analysis could reveal the amount of moisture content, volatile components as well as the polymer capping over nanorods present in the sample. It could be seen that upon heating, inorganic core crystals undergo oxidation process and at temperature above 464 °C, the sample was found to be composed solely of inorganic crystallite phase of copper (II) oxide.
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.
Nanocrystalline zinc sulfide thin films were prepared on glass substrates by chemical bath deposition method using aqueous solutions of zinc chloride, thiourea ammonium hydroxide along with non-toxic complexing agent trisodium citrate in alkaline medium at 80 °C. The effect of deposition time and annealing on the properties of ZnS thin films was investigated by X-ray diffraction, scanning electron microscopy, optical transmittance spectroscopy and four-point probe method. The X-ray diffraction analysis showed that the samples exhibited cubic sphalerite structure with preferential orientation along 〈2 0 0〉 direction. Scanning electron microscopy micrographs revealed uniform surface coverage, UV-Vis (300 nm to 800 nm) spectrophotometric measurements showed transparency of the films (transmittance ranging from 69 % to 81 %), with a direct allowed energy band gap in the range of 3.87 eV to 4.03 eV. After thermal annealing at 500 °C for 120 min, the transmittance increased up to 87 %. Moreover, the electrical conductivity of the deposited films increased with increasing of the deposition time from 0.35 × 10−4 Ω·cm−1 to 2.7 × 10−4 Ω·cm−1.
aoufi D., Mater. Res. Express., 6 (2018), 016417.
 K esmez O., A karsu E., C amurlu H.E., Y avuz E., A karsu M., A rpac E., Ceram. Int., 44 (2018), 3183-3188.
 J ung J., J annat A, A khtar M.S., Y ang O., J. Nanosci. Nanotechnol., 18 (2018), 1274-1278.
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 K umar J, N egi V.S., C hattopadhyay K.D., S arepaka R.V., S inha R.K., Measurement, 102 (2017) 96.
Kacper Grodecki, Krzysztof Murawski, Aleksandra Henig, Krystian Michalczewski, Djalal Benyahia, Łukasz Kubiszyn and Piotr Martyniuk
In this paper, we present experimental results of photoluminescence for series of InAs:Si heavily doped samples, with doping level varying from 1.6 × 1016 cm-3 to 2.93 × 1018 cm-3. All samples were grown using MBE system equipped with a valved arsenic cracker. The measurements were performed in the temperature range of 20 K to 100 K. Although the Mott transition in InAs appears for electron concentrations above 1014 cm-3, Burstein-Moss broadening of photoluminescence spectra presented in this article was observed only for samples with concentration higher than 2 × 1017 cm-3. For the samples with lower concentrations two peaks were observed, arising from the band gap and defect states. The intensity of the defect peak was found to be decreasing with increasing temperature as well as increasing concentration, up to the point of disappearance when the Burstein-Moss broadening was visible.
Electrochemical copolymerization of selenophene and thiophene was performed at a constant electrode potential. The obtained homopolymer films and copolymers were studied and characterized with cyclic voltammetry and conductivity measurements, from which conductivity values around 13.35 S · cm-1 were determined. The influence of the applied electropolymerization potential and the monomer feed ratio of selenophene and thiophene on the copolymers properties was investigated. The obtained copolymers showed good stability of the redox activity in an acetonitrile-based electrolyte solution. At higher polymerization potentials and at higher concentrations of thiophene in the feed, more thiophene units were incorporated into the copolymer chain. The conductivities of the copolymers were between those of homopolymers, implying that oxidation of both monomers was possible and the copolymer chains might accordingly be composed of both selenophene and thiophene units.