Search

The spin-resolved transport for monolayer MoS2 through a zigzag nanoribbon superlattice based on the transfer matrix method in the resonant tunneling regime is investigated in the presence of an external perpendicular electric field. The controllable external electric field leads to the so-called Rashba effect, which can modulate the internal spin–orbit coupling. Our investigations show that by controlling the Rashba strength, it is possible to attain 100% spin-polarization and spin-flip, which can be used in designing an optimized spintronic device. In addition, the effects of superlattice specific parameters (D/W), the barrier height (V0), and the number of barriers (N) on the functionality of the system are studied, leading to optimum results for the case of 20 barriers.

In this study, copper nanoparticles were synthesized and identified by laser ablation method. For the synthesis of copper nanoparticles, a constant magnetic field equal to 10 mT and different electric fields equal to 0, 10, 15, 20 and 25 V/Cm were applied and their effect on the properties and morphology of the nanoparticles were investigated. The synthesized nanoparticles were characterized using XRD, FTIR, RAMAN, UV–Vis spectrum, FE-SEM and TEM analyzes. The results of UV–Vis spectrum indicated that the size of nanoparticles was decreased by increasing the applied electric field. RAMAN and XRD analysis showed that the amount of copper nanoparticles were increased with increasing the applied electric field and also FTIR analysis confirmed that copper nanoparticles were formed. The FESEM images showed that with increasing electric field along with constant magnetic field, nanoparticles from spherical to flower-shaped and to rod-like were formed. The purity of the synthesized copper nanoparticles was confirmed by EDX spectra. TEM images of the nanoparticles showed that by increasing the electric field, the crystalline form of the nanoparticles shifted from large scales spherical particles to rod-like nanoparticles and then transformed to rod-like with very small spherical particles.

Based on the density function theory, the electronic, optical, and thermoelectric behaviors of the WS2–GaN interfaces have been investigated at three d1 = 2.8793 A, d2 = 4.0459 A, and d3 = 6.6419 A distances. All compounds have the ground state point with high hardness. The WS2–GaN interfaces for d1 and d3 cases are the p-type semiconductors and the other one is n-type semiconductor, with 1.82 eV, 1.95 eV, and 1.51eVband gap, respectively, with high levels density around the Fermi level. Optical properties have been approximated by the RPA, TDDFT, and BSE approximations, which the last case has better agreement with the electronic nature of these compositions. The main optical response is occurred in the 5 eV optical energy for two x and z directions. The optical response with BSE approximation indicates the semiconductor behavior for all three interfaces in the infrared, visible and ultra-violate edge regions. The Seebeck coefficients for the d1 and d3 distances show that the holes are the charge carriers and for the other one electrons. In addition, the figures of merit at lower temperatures have been shown in WS2–GaN interfaces for d1 and d3 having good thermoelectric efficiencies with high amount of ZT.

The aim of the present study is to explore the 3-D micromorphology of human canine teeth materials using multifractal analysis through atomic force microscopy (AFM). The 3-D surfaces of ten extracted canine teeth of a group of 40 year old men were studied (enamel, inter enamel, inter dentin, and cementum) by AFM images in tapping mode and on square areas of 1 μm × 1 μm (512 × 512 points). The AFM images and surface multifractal analysis confirm the dependency of surface micromorphology to their structure–property of these materials across the length scales of the teeth structural architecture. Surface statistical parameters and hence, multifractal approach have been considered as reliable and sensitive tools for quantifying the 3-D surface microtexture changes of human canine teeth materials. The surface of inter dentin had the most irregular topography (the width spectrum Δα = 2.8361, value bigger than all the other Δα sample values), while the most regular topography (the width spectrum Δα = 2.6804, value lower than all the other sample values) was found in cementum. It has been concluded that multifractal analyses can be used as mathematical tools to explore the 3-D micromorphology of human canine teeth materials.

Due to the application of two-dimensional crystals in different fields, high-quality growth of these materials has attracted more attention from researchers. High-quality monolayer MoS2 with single crystals up to 20 microns in size has been formed on Si substrate by the chemical vapor deposition method. A comprehensive study was carried out on the prepared MoS2 thin films using optical microscopy, atomic force microscopy, x-ray diffraction (XRD) analysis, and Raman spectroscopy. It was concluded that the growth temperature affected the morphology and structure of the synthesized MoS2 sheets. The XRD spectra confirmed that the peak intensity and resolution were highly dependent on the growth temperature. Raman spectroscopy showed that monolayer MoS2 was grown on the silicon substrate at higher temperature, as proved by the Raman frequency difference (∼ 19 cm−1) between two characteristic modes ($$ {\hbox{E}}^{1}_{{2{\rm{g}}}} $$ and A1g). Atomic force micrographs of the films showed the evolution of the surface morphology as a function of the growth temperature.

In this study, Cu nanoparticles were synthesized for the first time using an electric field-assisted pulsed laser ablation in liquid media (EPLAL) process and the influence of electric field on the properties of the synthesized nanoparticles was investigated. As-synthesized nanoparticles were successfully characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron dispersive X-ray analysis (EDX), fourier transform-infrared (FT-IR), Raman spectra, Dynamic light scattering analysis (DLS) and ultraviolet–visible (UV–Vis) spectroscopy. The XRD analysis demonstrated face centered cubic (FCC) structure of pure Cu nanoparticles. The FE-SEM and TEM analyses revealed that increasing the strength of electric field leads to fabricating nanoparticles with narrower range of size distribution. Also, the copper nanoparticles formation were confirmed by the characteristic surface plasmon resonance (SPR) peak in UV–Vis spectra. On the other hand, the UV–Vis spectra displayed the blue-shifts from 588 to 582 nm of SPR peak by increasing the strength of applied electric field, which indicated the size of Cu nanoparticles were reduced. Furthermore, the DLS analysis confirmed that the size of Cu nanoparticles reduced from 115.8 to 91.7 nm by increasing the strength of applied electric field.

In the present study, laser ablation technique (Nd:YAG) has been applied to synthesize platinum nanoparticles (NPs). Also, the effect of applied electric field on the physical, structural, and morphological properties of Pt NPs has been investigated during the nanosecond pulsed laser ablation of platinum. Based on the results extracted from TEM and scanning electron microscopy images, the formation of high percentage of NPs with spherical shape is demonstrated in all samples. The increase of applied electric field creates few rectangular, hexagonal, and rhombic NPs with the average size decreased from 20 to 9 nm. The significant influence of increasing electric field is also observed in UV-vis spectra by appearing the blue shift of the localized surface plasmon resonance peak. The UV-vis spectra also confirm the metallic nature of Pt NPs and the existence of inhomogeneous-sized particles and the coagulation of particle because of the long tail in higher wavelengths. In addition, atomic force microscopy images have been analyzed through MountainsMap Premium program and fractal dimension. As can be seen, increasing the applied electric field make the surface more irregular and the maximum value of Df reveals the most irregular topography for sample with 50 V/cm electric field. Finally, the bending and stretching frequencies of the functional bending groups connected to the NPs surface have been characterized by Fourier transform infrared spectroscopy. Electrical field-assisted laser ablation in liquids method allows a better control of the size, morphology, structure, and chemical composition of nanoparticles.

Molybdenum disulfide (MoS2) has been extensively investigated as the key material for post-silicon electronics, optoelectronics (flexible devices), Li-ion batteries, solar cells, etc. In the work presented, MoS2 nanoparticles (NPs) were obtained via the laser (Nd:YAG, λ = 1064 nm) ablation of a bulk MoS2 in ethylene glycol solution, as a function of the laser fluence, for the first time. The properties of the product were characterized using UV–vis, TEM, SAED, SEM with EDX, XRD, FT-IR, and Raman spectroscopy. The results showed that the synthesized MoS2 NPs have a hexagonal crystalline structure with diameters of 4–160 nm. In addition, most of them had a rounded shape whose λmaxvaried from 212.5 to 216.5 nm depending on the laser fluence. By increasing the laser fluence, the average size of these particles increased from 10 to 18 nm. The shape and size of MoS2 NPs have a significant role in the fields of lubrication, catalysis, electrocatalysis, etc. Laser ablation method is a clean, simple, and reproducible way to produce nanostructures with special properties.

The two-dimensional MoS2 coatings with incomplete head triangles, triangular stars and six-blade stars domain shape have been grown by the CVD method on SiO2/Si and Si substrates and then doped with nitrogen. The shape of MoS2 domains showed remarkable changes after N2 doping. Doping dramatically changed the physical properties of MoS2 coatings. An accurate study was carried out on the prepared MoS2 thin films using optical microscopy, atomic force microscopy (AFM), X-ray diffraction (XRD) and Raman spectroscopy. The X-ray spectrum showed well-defined MoS2 coatings with a strong (103) preferred orientation of a typical hexagonal structure. There were no changes in crystallographic orientations after nitrogen doping, while the peak intensity declined. Raman spectroscopy specified that MoS2 multilayer was proved by Raman frequency difference between two characteristic modes (E 2g 1 and A1g). The position and intensity of Raman modes exhibited sensitivity to nitrogen doping. The AFM results indicated topography and roughness variations with nitrogen doping.

The effect of gamma irradiation dose in the range of 1–10kGy is investigated on the structural, optical and electrical properties of the polyaniline -emeraldine salt (PANI-ES) thin films deposited on the indium tin oxide (ITO) coated glass substrate by spin coating technique. X-ray diffraction patterns show that all deposited PANI films have an amorphous character. Fourier transform infrared spectroscopy (FTIR) confirms the emeraldine salt form of deposited PANI films. The analysis of UV–Vis spectrophotometer indicates a decrease of transmittance intensity and optical band gap with increase of gamma irradiation dose while Urbach energy increases. The photoluminescence (PL) spectra show a strong peak at 429nm due to transition from polaron band to π band in PANI structure which its intensity and peak area increase with irradiation dose increase. Electrical measurement shows that the resistivity of prepared films linearly increases with rise of gamma dose suggesting its possible application as gamma dosimeter in the studied range.

We investigate the effects of different contents of multiwall carbon nanotubes (MWCNTs) on optical and electrical properties of polyaniline (PANI). The MWCNTs/PANI composites are deposited on glass substrates coated with indium tin oxide (ITO) by the spin-coating technique. The scanning electron microscopy shows that nanotubes are coated with the PANI layer and x-ray diffraction patterns show that all deposited composite films have an amorphous character. The analysis of a UV-vis spectrophotometer indicates the blue shift of the absorbance peak and a decrease in optical band gap value by the enhancement of the CNT content in the PANI matrix while the Urbach energy increases. The Raman spectrum shows the blue shift 1404→1417 cm-1 and photoluminescence spectra show an increase in the intensity of characteristic PANI peak at 436nm with the increasing CNT content.

The effects of the perpendicular magnetic field on the multi-barriers system of 5-barriers to 100-barriers are studied. Considering the low-energy Hamiltonian of the system with spin-orbit coupling we modulate the external magnetic field as the Zeeman energy on the orbital magnetic moment. The transport of an incident electron passing through the superlattice created by the top-gated monolayer MoS2 based on the transfer matrix method is investigated and the spin-up and the spin-down transmissions and the spin-polarization for 5-barriers to 100-barriers are obtained. Comparing the results show that in the case of 30-barriers, we have both reliable transmissions for the system and a 100% spin-polarization so that the spin-flip can occur and gives us a desired spintronic device. We also sketched the variations of the transmissions and spin-polarization versus the relative barrier-widths over the well-widths, (D/W), which show the optimum value is 1 by 2, respectively. Finally, we calculate the spin-up and spin-down conductance and total conductivity of the system which shows the so-called resonant tunneling peaks and amplifying the internal spin-orbit coupling with the external magnetic field as the Zeeman energy.

In this paper, using a first principles calculation, a two-dimensional structure of silicon-antimony named penta-Sb $$_{2}$$ Si is predicted. The structural, kinetic, and thermal stabilities of the predicted monolayer are confirmed by the cohesive energy calculation, phonon dispersion analysis, and first principles molecular dynamic simulation, respectively. The electronic properties investigation shows that the pentagonal Sb $$_{2}$$ Si monolayer is a semiconductor with an indirect band gap of about 1.53 eV (2.1 eV) from GGA-PBE (PBE0 hybrid functional) calculations which can be effectively engineered by employing external biaxial compressive and tensile strain. Furthermore, the optical characteristics calculation indicates that the predicted monolayer has considerable optical absorption and reflectivity in the ultraviolet region. The results suggest that a Sb $$_{2}$$ Si monolayer has very good potential applications in new nano-optoelectronic devices.

Tantalum nanoparticles (Ta NPs) were synthesized in ethanol solution by ablation with a 1064 nm Nd:YAG laser. Prepared NPs were investigated by UV-visible absorption spectroscopy, Transmission electron microscopy, X-ray diffraction and Photoluminescence measurement. The average sizes of NPs were calculated to be in the range of 12–18 nm. From the UV-visible studies, the plasmon peak position of Ta NPs was observed in the spectral range of 206–208 nm. The XRD spectra clearly showed the crystalline structure of NPs and various peaks of Ta and Ta2O5. Moreover, the UV region in the PL spectrum included the free exciton and the bound exciton emission correlated with the defect concentration. In fact, the laser ablation in the organic and inorganic solvents is a strong technique to obtain some NPs with particular structures, which are impossible to produce by conventional methods.

The amorphous W/WN films with various thickness (10, 30 and 40 nm) and excellent thermal stability were successfully prepared on SiO2/Si substrate with evaporation and reactive evaporation method. The W/WN bilayer has technological importance because of its low resistivity, high melting point, and good diffusion barrier properties between Cu and Si. The thermal stability was evaluated by X-ray diffractometer (XRD) and Scanning Electron Microscope (SEM). In annealing process, the amorphous W/WN barrier crystallized and this phenomenon is supposed to be the start of Cu atoms diffusion through W/WN barrier into Si. With occurrence of the high-resistive Cu3Si phase, the W/WN loses its function as a diffusion barrier. The primary mode of Cu diffusion is the diffusion through grain boundaries that form during heat treatments. The amorphous structure with optimum thickness is the key factor to achieve a superior diffusion barrier characteristic. The results show that the failure temperature increased by increasing the W/WN film thickness from 10 to 30 nm but it did not change by increasing the W/WN film thickness from 30 to 40 nm. It is found that the 10 and 40 nm W/WN films are good diffusion barriers at least up to 800°C while the 30 nm W/WN film shows superior properties as a diffusion barrier, but loses its function as a diffusion barrier at about 900°C (that is 100°C higher than for 10 and 40 nm W/WN films).

The electronic and optical properties of GaN graphene-based in the pure case and Fe doped at two different positions have been calculated using a density functional theory framework with full potential augmented plane waves plus local orbitals. The GaN sheet is a non-magnetic semiconductor doping Fe to the N (N-site) and Ga (Ga-site) sites has caused the half-metallic and magnetic semiconductors, as seen in the p-type and n-type treatment in the up and down spins for the last case. The optical curves include the real and imaginary parts of the dielectric function, ELF, Reflection, and absorption indexes in the presence of the Fe doped for the N- and Ga-sites were calculated along the x (E||x) and z (E||z) directions. The N-site case's metallic behavior in the infrared (IR) area is too large for the E||x direction and has spontaneous emission. The Ga-site one has the semiconductor behavior along x and z directions by 0.7 eV and 4 eV gaps.

MoS2 nanoparticles (NPs) were prepared by nanosecond (ns) laser ablation in ethylene glycol using a Q-switched neodymium:ytterbium aluminum garnet laser at 1064 and 532 nm laser wavelengths. The influence of laser wavelengths in ns laser production of MoS2 NPs is not yet fully understood. The shape, structure, crystalline phase, stability, and optical and photoluminescence (PL) properties of NPs were studied using TEM, dynamic light scattering, scanning electron microscopy with energy-dispersive x-ray, x-ray diffraction (XRD), ultraviolet–visible (UV–Vis), PL, Fourier transform infrared, and Raman spectroscopy. The UV–Vis absorption spectroscopy showed that the optimum laser wavelength for preparing MoS2 NPs is 1064 nm. Also, the absorption peak intensity of MoS2 NPs prepared at 1064 nm was 3.95 times higher than that at a 532 nm wavelength. In the case of ablation with 1064 nm, the most of NPs had spherical shapes and well dispersed compared with 532 nm. While the samples had the same crystalline structure for both wavelengths, as the laser wavelength increased, the mean particle size decreased from 22 to 13 nm. This is because of a photofragmentation phenomenon.

Copper nanoparticles in carbon thin films (Cu NPs @ a-C: H) were prepared with various copper and carbon content by co-deposition of RF-sputtering and RF-PECVD method to use as catalysts for CNTs growth. The effect of carbon content on the catalytic properties of Cu NPs was investigated in this work. Although Cu NPs has no catalytic properties for CNTs growth, adding carbon improves the process of CNTs growth because of its effect on catalytic activity. In order to find copper and carbon content in the thin film, RBS analysis was used. These observations revealed by atomic force microscopic images. Moreover, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy were performed for CNTs characterization. In this work, Cu NPs layers with various carbon contents were fabricated in the case of investigation on the catalytic properties.

The remarkable size-tunable properties of nanoparticles (NPs) make them a hot research topic with applications in a wide range of fields. Hence, copper (Cu) colloidal NPs were prepared using laser ablation (Nd:YAG, 1064 nm, 7 ns, 10 Hz, 6000 pulses) of a copper metal plate at different laser fluences (LFs) in the range of 1–2.5 J cm−2 in ethylene glycol (EG), at room temperature. Analysis of NPs was carried using different independent techniques such as ultraviolet–visible (UV–vis) spectroscopy; transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. TEM analysis showed that the NPs were spherical with a bimodal distribution and an average particle size of 5 and 16 nm influence of 1.2 J cms−2, and 9 and 22 nm at 2 J cm−2. The UV–vis spectra of colloidal NPs revealed the maximum absorbance at around 584 nm, indicating the formation of Cu NPs, which supported using FTIR spectra. Furthermore, the absorption spectra confirmed the metallic nature of Cu NPs. FTIR spectroscopy was utilized to verify information about the NPs surface state and chemical bonds constructed in the atom groups apparent on their surface.

Tantalum nanoparticles (Ta NPs) were prepared in an ethylene glycol (EG) solution by ablation with a 1064 nm Nd:YAG operating at 10 Hz. Fabricated NPs were characterized by UV-visible absorption spectroscopy, Transmission electron microscopy, Scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy. The average sizes of the NPs were estimated to be in the 14–19 nm range. From the UV-visible studies, the plasmon peak position of the Ta NPs was observed in the spectral range of 213–222 nm. The crystalline nature and phase structure of the Ta NPs were investigated using selected area electron diffraction and X-ray diffraction. Furthermore, for the detection and identification of molecular species absorbed at NPs surface, Raman spectroscopy and Fourier transform infrared spectroscopy analyses were performed.

Nanocrystalline Al-doped ZnO (AZO) thin films were deposited on glass substrates at room temperature by Mather-type plasma focus device using a ZnO target with an Al content of 3 wt%. The effect of number of focus shots on the microstructure, elemental composition, surface morphology and H2 gas sensor performance of AZO deposited thin films were investigated. X-ray diffraction (XRD) analysis confirmed the polycrystalline nature of the all deposited AZO thin films. XRD results also indicated strong dependence of crystallinity and crystallite size of deposited thin films on number of focus shots. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses led to the conclusion that the size of grains/clusters on the surface of thin films and the surface roughness of deposited samples enhance with increasing of focus shots. The experiments and measurements involving the AZO deposited thin films towards hydrogen were carried out at different operating temperatures within 150–400 °C for various concentrations of hydrogen in air. The H2 sensing response enhanced with concentration and operating temperature, and reached its maximum at 300 °C–1000 ppm concentration of hydrogen gas. The results also indicated shorter response times for samples deposited with less focus shots.

In the present study, MWCNTs were synthesized through CVD method, employing CH4 as carbon source over Co-Mo/MgO nanocatalyst at a temperature of 1000 °C and then treated by two methods. First by KOH activation (A-MWCNTs), with a weight ratio of KOH: MWCNTs = 3:1 at 900 °C in He atmosphere and second treated by H2SO4: HNO3 = 3:1 (F-MWCNTs). MWCNT samples were characterized by FE-SEM, TEM, XRD, FT-IR, BET and Raman spectroscopy. The adsorption of H2 gas was performed using volumetric method. Various parameters on adsorption of H2 including surface defects, surface areas, pore characteristics and functional groups have been investigated. Furthermore, it was found that the hydrogen adsorption of P-MWCNTs, A-MWCNTs and F-MWCNTs were 0.67, 1.24 and 0.40 wt%, respectively at room temperature (298 K) while the pressure varied from 0 to 34 bar. The results indicated a considerable rise in the H2 adsorption capacity of A-MWCNTs (85%), due possibly to the high surface area and enhanced micro-pore volume and the defects formed on the surface sites of MWCNTs by KOH activation. In this case, hydrogen molecules adsorption on the defective cavities could have a significant role through van der walls forces. Therefore, it can be concluded that KOH-modified MWCNTs is one of the most significant ways of developing the textural characteristic and improving hydrogen storage properly.

Formation of platinum nanoparticles (Pt NPs) by Nd:YAG laser ablation of a platinum target in polar solvents, viz. distilled water (DW), absolute ethanol (ET), acetone (AC), and ethylene glycol (EG), was investigated. Characterization of the NPs in terms of size distribution, shape, optical properties, phase structure, crystalline nature, and molecular structure was carried out as a function of the nature of the liquid by transmission electron microscopy, scanning electron microscopy, ultraviolet–visible (UV–Vis) absorption spectroscopy, X-ray diffraction analysis, selected-area electron diffraction analysis, Raman spectroscopy, and Fourier-transform infrared spectroscopy. The interaction of the ablation plasma plume species with species produced by decomposition of the liquid resulted in formation of spherical Pt and PtO NPs with diameter ranging from 5 nm up to a maximum of 104 nm. The results evidence that the properties of the NPs were affected by the nature of the liquid, including thermodynamic parameters such as the dipole moment, boiling point, and viscosity.

Human tooth exhibits a structure of a mixture of inorganic hydroxyapatite nanocrystals and organic phases. The aim of this study is to investigate different tissues of human canine teeth surface along with the micro structure parameters of each tissue. X-ray diffraction (XRD) is used to study the amorphous or crystalline nature of each tissue with different mineral compositions and crystalline structures where the highest crystalline quality is related to enamel. The surfaces are also examined by energy-dispersive X-ray spectrometry. Moreover, crystalline quality factor is carried out to estimate the crystallinity of the tissues. Also, based on the basic Scherrer equation, the Williamson–Hall equation is applied to extend the formula for the XRD. Enamel and cementum tissues of a typical human tooth, which look similar, are composed of a large variety of wide lines with different widths through Raman spectra analysis. In addition, the applied scanning electron microscopy extracts similar morphology for all tissues with round granular structures which are denser in the cementum. Atomic force microscopy is finally used for investigation of micro-morphologies of the different tissues and the results are compared with the fractal analysis which ends to the bifractal and anisotropic nature of enamel and cementum along with monofractal and isotropic nature of dentin.

In the present study, structural and mechanical properties of Tantalum samples which affected by nitrogen ion implantation have been investigated. The monofractal analysis of the samples has been carried out. These samples have been implanted with ions at different doses of 5 × 1017 and 7 × 1017 at energy 30 keV. For characterizing the samples, atomic force microscopy (AFM), EDX images analysis, and corrosion measurements, have been used. By varying the ion energy, the statistical characteristics will vary. In order to analyse the morphology of produced rough samples, the correlation function of samples have been studied and their correlation length is evaluated. Based on the statistical concept the power spectral density the height distribution, and the higher-order moments (skewness and kurtosis) of the surface height have been measured. These charactristics are the important criterions for the the monofractal evaluation. Our numerical calculations based on experimental data show the deviation from gaussian distribution. Also, the fractal dimension of the films has been calculated based on rougness exponent results. Indeed, irradiating the surfaces with energetic ions results in producing the self-affine fractal surfaces. This process via an erosion process affects the statistical characteristics which have been calculated for different samples. Because of variation in the morphology of rough samples, the corrosion of samples shows a non-uniform behavior.

Al-doped ZnO (AZO), as one of the most promising transparent conducting oxide (TCO) materials, has now been widely utilized in thin film solar cells. In this research the optimization process of AZO thin films deposited by plasma focus device was carried out by investigation of its physical properties under different deposition conditions for its utilize as a front contact for the Cadmium Telluride (CdTe) based thin film solar cell applications. The effects of number of focus shots and angular position of substrate on the microstructure, surface morphology and photoluminescence properties of the thin films have been systematically studied. X-ray diffraction (XRD) study confirmed the polycrystalline nature of the all deposited AZO thin films. XRD analysis also revealed that crystal structure characteristics of obtained samples strongly depend on deposition conditions (number of shots and angular position). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses revealed the structure growth and enhancement of surface roughness, with increasing of focus shots or decreasing of angular position. From Photoluminescence (PL) emission spectra, the variations of structural defects and band gap energy for all the AZO thin films prepared under different deposition conditions were also discussed.

In this study, different types of graphene were synthesized to investigate hydrogen adsorption capacity at different pressures (0–34 bar) at room temperature (298 K). Graphene and nanoporous graphene were prepared by Chemical Vapor Deposition (CVD) method, using methane as a carbon source at a temperature of 900 °C over copper plates and nickel oxide nanocatalyst. The nickel oxide nanocatalyst was prepared by sol–gel method, whereas graphene oxide was prepared through modified Hummer's method. The products were characterized by X-ray diffraction, field emission-scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller and Raman spectroscopy. The adsorption of hydrogen was done by volumetric method. High adsorption capacity was achieved in nanoporous graphene because of its high pore volume (2.11 cm3/g) and large specific surface area (850 m2/g). Hydrogen adsorption values for nanoporous graphene, graphene and graphene oxide were determined as 2.56, 1.70 and 0.74 wt%, respectively. In addition, the hydrogen adsorption of graphene nanostructures fitted nicely to the selected two-parameter and three-parameter adsorption isotherm models. The adsorption isotherm model coefficients have been found for a 0–34 bar pressure range. The parameter values for all adsorbents showed proper conformity to the model and experimental data. Copyright © 2016 John Wiley & Sons, Ltd.

This paper reports characterization of Al-doped ZnO (AZO) thin films deposited on glass substrates at room temperature by a low energy (1.3 kJ) plasma focus device using a ZnO target with an Al content of 3wt%. A particular focus of investigation is on properties relevant to the usage of thin films as hydrogen gas sensors. Indeed, the dependence of angular position of substrate on structural, morphological and gas sensing properties of AZO thin films is investigated. The results obtained from X-ray diffraction (XRD) reveal that all the films are of polycrystalline zinc oxide in nature, possessing hexagonal wurtzite structure. Also XRD results indicate strong dependence of crystallinity of deposited thin films on angular position of samples. Scanning electron microscopy and atomic force microscopy results reveal the structure growth and enhancement of surface roughness with decreasing the angle with respect to anode axis. The experiments and measurements involving the AZO deposited thin films towards hydrogen were carried out at different operating temperatures within 150–400 °C for various concentrations of hydrogen in air. The H2 sensing response enhanced with concentration and operating temperature, and reached its maximum at 300 °C to 1000 ppm concentration of hydrogen gas. The results also indicated shorter response times for samples deposited at larger angular positions.

This paper investigates the effect of nitrogen ion implantation on tantalum surface structure. In this experiment, nitrogen ions which had an energy of 30 keV and doses of 1 × 1017 to 10 × 1017 ions cm−2 were used. X-ray diffraction analysis (XRD) was applied for both the metallic Ta substrate and the study of new structures that have been created through the nitrogen ion implantation. Atomic force microscopy (AFM) was also used to check the roughness variations prior to and also after the implantation phase. The experimental results show the formation of hexagonal tantalum nitride (TaN0.43) in addition to the fact that by increasing the ion dose, the nitrogen atoms occupy more interstitial spaces in the target crystal. The nitride phase also seen for 3 × 1017 and 5 × 1017 ions cm−2, while it disappeared for higher dose of 7 × 1017 and 1 × 1018 ions cm−2. The FWHM of the dominant peak of tantalum nitride suggest the growth of the crystallite’s size, which is in agreement with the AFM results of the grains.

This paper investigates the effect of nitrogen ion implantation on surface structure as well as resistance against tantalum corrosion. Bulk Ta surface was implanted with 30 keV nitrogen ions at a temperature of 100°C with doses between 1 × 1017 and 1 × 1018 ions/cm2. The implanted samples were characterised by atomic force microscopy, X-ray diffraction analyses and the corrosion test to identify structural, compositional and electrochemical changes at various doses. The experimental results indicate the formation of hexagonal tantalum nitride (TaN0.43), in addition to the fact that by increasing the ion dose, nitrogen atoms occupy more interstitial spaces in the target crystal, a case which can significantly improve corrosion resistance. The maximum extent in the improvement of the micro hardness was 75% and the reduction in the corrosion current was 83%. According to scanning electronic microscopy and corrosion results, in the dose of 1 × 1018 ions/cm2 the highest corrosion resistance was received agains...

Tungsten nitride (WxN) thin films with good crystalline structure, high quality and relatively low resistivity were deposited by hot filament chemical vapor deposition (HFCVD) technique at different mixtures of N2 and Ar gases. Experimental data demonstrate that different N2 contents in gas mixture strongly affect microstructure, phase formation, texture morphology and resistivity of the WxN films. According to X-ray diffraction (XRD) patterns, the growth of tungsten nitride films promotes δ-WN phase for lower N2 contents in gas mixture. At higher N2 contents, a phase transition is observed in the tungsten nitride films. Both hexagonal δ-WN and cubic β-W2N phases coexist, and WN phase approximately disappears with N2 contents in the gas mixture increasing. Scanning electron microscope (SEM) images for deposited films at lower N2 contents in gas mixture indicate a definite dense columnar nanostructure. The electrical resistivity results exhibit a significant drop for the WxN thin films with N2 contents in the mixed gas increasing. The changes in N2 content in gas mixture are found to be responsible for variation in the film resistivity values. Thus, the deposited tungsten nitride thin film at higher N2 contents in gas mixture has noncolumnar microstructure and lower resistivity, which may be used as a superior diffusion barrier.

ZnO is one of the most promising transparent conducting oxide materials, which widely used in thin film gas sensors. In this research, the dependence of the thermal oxidation time on structural, morphological and gas sensing properties of ZnO thin films is investigated. ZnO nanostructures are synthesized by using DC magnetron sputtering for deposition of pure zinc layers on glass substrates and then thermal oxidation of deposited zinc layers to produce zinc oxide (ZnO) thin films. Obtained results from X-ray diffraction revealed that the degree of crystallinity and the average grain size of the ZnO deposited thin films enhance with increasing the thermal oxidation time. Surface topography and growth behavior of ZnO thin films have important role in optimization of gas sensing properties of these films. In this study, scanning electron microscopy and atomic force microscopy have been used to investigate the effective parameters related to the surface topography of the films. Obtained results from these analyzes revealed that the surface topography of ZnO deposited samples strongly depend on thermal oxidation time. Also the effect of thermal oxidation time on the performance of ZnO gas sensors is investigated. The results indicated that the ethanol gas sensing properties of ZnO samples improve with decreasing the size of grains.

Nanocrystalline zinc oxide (ZnO) thin films were synthesized on glass substrates under extremely non-equilibrium conditions of energetic ion condensation during the focus phase in a low energy plasma focus (PF) device. The samples were deposited using multiple focus shots (5, 10 and 20), at constant axial and angular positions with respect to the tip of anode and anode axis (8 cm and 0°), respectively. The argon:oxygen admixture (in 7:3 ratio) was used as a working gas. The structural, morphological, electrical and optical properties of the ZnO deposited thin films were investigated. The results obtained from XRD and SEM analyzes indicated that the size of nanoparticles/agglomerates and the thickness of the ZnO thin films strongly depend on number of shots. AFM analysis revealed that the size of grains and surface roughness of ZnO samples increase with the number of shots. Measurement of the electrical parameters indicated that electrical resistivity is reduced and carrier mobility enhanced with increasing the shots, with no noticeable variations in the carrier concentration. Moreover, the results from optical transmission patterns revealed that optical transmittance and band gap energy decrease with more shots.

Cu–Ni nanoparticles (NPs) thin films were prepared by Direct Current (DC) magnetron sputtering with Cu and Ni targets. The products were used as catalysts for Thermal CVD (TCVD) growing of carbon nanotubes (CNTs) from acetylene gas at 825°C. In order to characterize the nano catalysts, X-ray Diffraction (XRD) and Atomic Force Microscopy (AFM) and to study the synthesized CNTs Scanning Electron Microscopy (SEM) and Raman Spectroscopy were applied. A remarkable CNT grown on the sub-surface of catalyst layer compared to its top is deduced from SEM images. Despite the poor catalytic activity of the top-surface, these considerations led us to conclude more catalytic activity of the sub-surface.

Pt NPs have attracted much attention because of their applications in many aspects such as the electronics industry, fuel cells, cancer therapy, etc. The influence of the applied electric field on the formation of platinum NPs by laser (Nd:YAG, λ = 1064 nm) ablation technique was investigated, for the first time. The TEM images showed that at higher values of the electric field, a variety of shapes like rectangular, hexagon, and rhombic were appeared besides the spherical NPs, as confirmed by SEM investigations. By increasing the applied electric field, the average size of Pt NPs decreased from 20 to 9 nm. In addition, from the XRD spectra, the mean crystalline size, crystal structure, d-spacing, and lattice parameters of NPs were calculated. On the basis of the optical absorption spectra of NPs, we observed a size-dependent blue shift of the SPR peak position when the value of the electric field increased from 0 to 20 V/cm. To identify the stretching and bending frequencies of the molecular functional groups attached to the NPs surface, Raman and FT-IR spectroscopy was applied.

Carbon materials doped with only one kind of C–N bonding configuration are a great outlook for studying doping effects on the electronic structure and electrical properties. Synthesis of nitrogen-doped few-layer graphene films on Cu foil is achieved by low pressure chemical vapor deposition (LPCVD). For investigation of nitrogen doped effect on structural, morphological and electrical properties of graphene the reactive gas was a mixture of CH 4 and NH 3 with the different ratio CH 4 and NH 3 by volume at the constant pressure of the growth chamber. The N-doped graphene (NG) samples were characterized by Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS). Also in this experiment, the I – V characteristic carried out for study of electrical property of N-doped graphene at different gases mixing ratio with keithley 2361 system. The Raman spectroscopy showed D, G and 2D bound in doped and undoped graphene while we find the intensity of the 2D peak decreases and D peak intensity increases with the increase in the percent of NH 3 in gas mixture. Likewise the presence of weak 2D band in all sample suggest that the produced samples are few layer graphene. SEM images showed dendritic-like morphology in undoped graphene and we observed that point like defect created among this morphology by increasing the nitrogen in synthesis process. The XPS results of sample with 25% NH 3 in gas mixture confirm the existence of nitrogen in doped graphene which indicates the nitrogen atoms doped in the graphene lattice are mainly in the form of pyridinic nitrogen. The study on electrical properties emphasized that the dependence of current with voltage for all samples was linear like behavior, and sample conductivity was decreased with increasing the percent of nitrogen in gas mixture. The results showed that nitrogen-doped graphene can be successfully synthesized and also chemical nitrogen doping can be change the electrical conductivity of the graphene.

This paper analyses the thickness influence of Fe on Cu nanoparticles (NPs) synthesised by Direct-current (DC) magnetron sputtering on the three-dimensional (3-D) surface morphology of thin films. The thin films with Cu nanoparticles were deposited on glass substrates then; Fe nanoparticles were added to Cu ones. These nanostructures were investigated at one deposition thickness of Cu and three of Fe (Cu 55 nm, Cu 55 nm/Fe 40 nm, Cu 55 nm/Fe 55 nm, and Cu 55 nm/Fe 70 nm as thin films’ thickness), by means of X-ray diffraction, atomic force microscopy (AFM) and multifractal analysis, in order to evaluate the structure and relation among the 3-D micro-textured surface. The 3-D morphology of surface samples exhibits multifractal features characterized by nano-irregularities of various orders of size and different local densities spread on the surface. The local and global scale properties of 3-D surface geometry were quantitatively estimated using the generalized dimension Dq and the singularity spectrum f(α). The non-uniformity of the nano-irregularities are correlated with the generalized dimension Dq and the spectrum width Δα (Δα = αmax − αmin) of the multifractal spectra f(α). Multifractal approach in correlation with the surface statistical parameters are a sensitive and reliable tool for quantifying the thickness influence of Fe on Cu nanoparticles (NPs) synthesised by Direct-current (DC) magnetron sputtering on the 3D surface morphology of thin films.

We present a comprehensive study of the parameter for graphene growth by low pressure chemical vapor deposition on Cu foil. The growth of graphene was investigated in various conditions, changing the gas pressures, gas ratio, growth temperature and growth time. The synthesized graphene were characterized using Raman spectroscopy and Field Emission Scanning Electron Microscopy (FESEM). By varying the growth time it can be concluded that the domain size increases when the growth time increases. The absence of 2D band in this section suggest that the produced graphene-like films are not monolayer and graphite can be formed in this growth conditions. The FESEM images demonstrate that increasing growth temperature while holding other parameters constant yields in larger domains which may be due to a faster growth at the higher temperature. The Raman spectra also showed the recovery of the 2D peak by increasing the growth temperature, indicating the crystallization of the damaged graphene layer. Hence the quality of grown graphene-like films is highly correlated to the process temperature. We show that the methane-to-hydrogen ratio is critical parameters that affect the structural perfection of graphene like domains. The Raman studies denote graphene like carbon nature due to the appearance of significant G and 2D peaks. Also the 2D peak intensity increases by increasing the H2 concentration in gas mixture, indicating a low graphene layers. The resulting domain size and the nucleation density are maximum at maximum value of H2 concentration. We can conclude that by controlling the growth parameters, the morphology and structure of graphene can be changed. We suggest that graphene can be used for fusion reactor first wall due to its unique physical and chemical properties. Our results provide important guidance toward the synthesis of high quality and uniform graphene films.

An alloy composition of reduced-activation Cr–W–V ferritic steels for nuclear fusion reactors was studied. The formation of nano-metric precipitates through standardized heat treatments in Cr–W–V alloy system is investigated using microscopic observations. Metallography studies have revealed that the micro-structure of alloy after tempering has been Martensite. Also after tempering, the matrix structure of alloy and the formation of nano-scale precipitates on grain and lath boundaries were confirmed by the Scanning Electron Microscope observations. By the application of X-ray Diffraction spectra analysis and transmission electron microscopy (TEM) electron diffraction patterns, it was shown that the type of precipitates extracted from alloy, would be M23C6 and M7C3 that include a cubic and trigonal crystal structure, respectively. TEM analysis has revealed that the morphology of these structural components is mainly spherical and blocky shapes and the average length and thickness of them would be 65 and 50 nm, respectively.

The surface modification of polycarbonate (PC) by 193 nm ArF laser radiation with fluences of 24–62 mJ/cm2 and pulse numbers of 1–100 is reported. Noticeable changes including microcone structures on irradiated surfaces have been observed through scanning electron microscope (SEM). It has been shown that the geometrical characteristics (apex angle and base diameter) of the microcones depend on the incident laser fluence. With the increase of the radiation fluence the microcone apexes become sharper, however, their base diameters increase.

In this paper, we synthesize Cadmium Telluride nanostructures by radio frequency (RF) magnetron sputtering system on soda lime glass at various thicknesses. The effect of CdTe nanostructures thickness on crystalline, optical and morphological properties has been studied by means of X-ray diffraction (XRD), UV-VIS-NIR spectrophotometry, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM), respectively. The XRD parameters of CdTe nanostructures such as microstrain, dislocation density, and crystal size have been examined. From XRD analysis, it could be assumed that increasing deposition time caused the formation of the wurtzite hexagonal structure of the sputtered films. Optical properties of the grown nanostructures as a function of film thickness have been observed. All the films indicate more than 60% transmission over a wide range of wavelengths. The optical band gap values of the films have obtained in the range of 1.62–1.45 eV. The results indicate that an RF sputtering method succeeded in depositing of CdTe nanostructures with high purity and controllable physical properties, which is appropriate for photovoltaic and nuclear detector applications.

Au-Pt alloy nanoparticles (NPs) of different compositions ( Au0Pt100 , Au30Pt70 , Au50Pt50 , Au70Pt30 , and Au100Pt0 were obtained using the nanosecond laser ablation of gold and platinum bulk targets in ethylene glycol, followed by mixing highly monodisperse Au and Pt nanocolloids, for the first time. UV-vis absorption spectra of NPs showed that by increasing the Au content in the Au-Pt NPs, the surface plasmon resonance (SPR) peak red-shifted, from 260 to 573nm in a nonlinear way. In addition, the mean crystalline size, crystal structure, d-spacing, and lattice parameters of NPs were estimated from the XRD spectra. Microscopy studies revealed the most NPs have a spherical or near-spherical shape, and the average sizes of Au0Pt100 , Au30Pt70 , Au50Pt50 , Au70Pt30 , and Au100Pt0 NPs were calculated to be 12.50, 14.15, 18.53, 19.29, and 26.38nm, respectively. Also, the chemical identity of the molecules adhering to the NPs surface was considered by Raman and FT-IR spectroscopy techniques. Among different synthesis methods, the demonstrated technique allows easy synthesis of alloy NPs in aqueous media at room temperature with no formation of by-products.

Platinum nano sized particles (Pt NPs) are superior catalysts for many intentions, such as glucose sensors, cancer therapy, gas sensors, etc. Here, Pt NPs were produced by pulsed laser ablation in C2H6O2 solution using Q-switched Nd:YAG laser, for the first time. Then, the influence of the laser fluence during synthesis of them was investigated; and they were characterized by UV–vis spectroscopy, TEM, FE-SEM, XRD, FT-IR, and Raman spectroscopy. The results showed that with increasing laser fluence, the mean particle size of the spherical NPs enhanced. Meanwhile, they had a polycrystalline cubic structure. Correspondingly, the plasmon peak position of generated NPs in the absorption spectra shifted from 257 to 266 nm, with a rise of laser fluence. The IR and Raman spectroscopy was used to achieve the information about the surface state of Pt NPs. We propose that the optimum adjusted laser fluence is an important factor to increase the ablation efficiency.

Reliable fabrication of lateral interfaces between conducting and semiconducting 2D materials is considered a major technological advancement for the next generation of highly packed all-2D electronic circuitry. This study employs seed-free consecutive chemical vapor deposition processes to synthesize high-quality lateral MoS