AbstractTitanium nitrides have good mechanical, tribological, electrical, biomedical, and optical properties; therefore, they are used to harden and protect cutting and sliding surfaces, as semiconductor devices, and as a nontoxic exterior for biomedical applications. The dependence of the mechanical and electrical properties of titanium nitride thin films deposited on silicon substrates by direct-current reactive magnetron sputtering technique on argon gas flow (in the range of 8 to 20 sccm) was investigated. The crystallographic structure of the films was studied by X-ray diffraction (XRD), while surface morphology was studied using atomic force microscopy (AFM). Mechanical and electrical properties of these films were investigated by nanoindentation test and a four-point probe instrument, respectively. The XRD patterns showed titanium nitride (TiN) formation with a face-centered cubic structure for all samples. It was also observed that (111) crystallographic direction was the preferred orientation for TiN thin films which became more pronounced with increasing argon gas flow. The AFM images showed a granular structure for TiN layers. The hardness, crystallite/grain size (obtained from XRD and AFM), and surface roughness increased with the flow of argon gas, while elastic modulus and dislocation density in the films decreased. The study on electrical properties showed that the dependence of voltage with current for all samples was linear, and film resistivity was increased with argon gas flow. Manuscript profile

AbstractCopper thin films of 80-nm thickness were deposited on glass substrate using electron beam deposition at two different deposition angles of 0° and 40°, and they were post-annealed under flow of nitrogen at different temperatures. The structure of the films was analyzed using X-ray diffraction, atomic force microscope, and scanning electron microscope. Investigation on the copper nitride phase formation showed that this phase was not formed in the samples produced at 0°, while those prepared at oblique angle of 40° clearly showed the formation of copper azide phase. This is related to the porosity of the film structure, hence increased surface area for the reaction of nitrogen with copper atoms. Therefore, this is a simple method for preparation of copper nitride films that are not usually formed due to low reactivity of copper (as transition metal) with nitrogen. The results showed that the crystallite size (coherently diffracting domains), grain size, and surface roughness increase with annealing temperature. Manuscript profile

AbstractExtinction spectra of chiral silver nanostructures are calculated by means of Discrete Dipole Approximation (DDA). Dependence of Plasmonic peaks to both structural parameters of nanostructures and direction of the incident light are obtained. This dependence is investigated on variation of chiral dimensions, chiral shape and direction of incident light. We have observed a resonance peak of transverse mode (TM) for the extinction spectra of chiral structure at normal incidence. However, for oblique angle incident light, in addition to the TM mode, a longitudinal mode (LM) appears at longer wavelengths. The latter undergoes a shift to longer wavelengths with increasing the diameter of chirl arm. When the cross-section of chiral is changed to an oval this resonance peak disappears, while some other peaks appear at longer wavelengths that were not present for a chiral with circular cross-section. Extinction spectra of chiral nanostructure with different structural parameters and different rise angles (slanted chirals) showed dependence on the incident light direction. Manuscript profile

AbstractA 2.2-kJ Mather type plasma focus device charged at 18 kV was used to deposit titanium nitride on 304 type stainless steel substrates. The plasma focus device is fitted with solid titanium anode and operated with nitrogen as the filling gas. The process of deposition was done at room temperature, and samples were deposited at a constant distance and at different angles with respect to the anode axis. X-ray diffractometry (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX) were employed to characterize crystalline structure, morphology, nanostructure, distribution, and elemental composition of deposited films, respectively. As the ion flux and energy of the ions change with angular position from the head of the anode (titanium), it is observed that these changes directly affect both surface morphology and the nanostructure of the films. XRD patterns show the growth of polycrystalline titanium nitride thin films of different phases. AFM and SEM images show that the grain size is affected by the energy of ions that reached the surface. Grain size, average roughness, and root mean square decreased by increasing the angle with respect to the anode axis. EDX mapping verifies the elemental distributions of titanium nitride on the surface. In this work we have shown the possibility of production of titanium nitride thin films of different phases, using a Mather type plasma focus system. Manuscript profile

AbstractZirconium thin films were deposited on a glass substrate using direct current magnetron sputtering technique and then post-annealed at different temperatures (100°C to 500°C in steps of 100°C) in an oxygen constant flow. The dependence of crystallographic structure, surface morphology, chemical composition, and electrical and decorative properties of the films on the annealing temperature was investigated. X-ray diffraction showed different phases of zirconium oxide at different annealing temperatures. It is observed that crystallite size and nanostrain increase with annealing temperature. Atomic force microscopy results showed granular structure in all samples, while both grain size and film surface roughness increased with the annealing temperature. Energy dispersive X-ray analysis data showed that the ratio of O/Zr was approximately 1.6, 1.7, 1.9, 2.1, and 2.2 at annealing temperatures of 100°C, 200°C, 300°C, 400°C, and 500°C, respectively. The annealed films at higher temperatures (400°C and 500°C) were transparent, while annealed films at lower temperatures (100°C to 300°C) were grey and brown, respectively. The variation of electrical resistance of samples with applied voltage was approximately constant, while it increased with annealing temperature. Manuscript profile

AbstractThe use of glancing angle deposition technique provides opportunities for the deposition of sculptured nanostructures of different shape. The optical properties of such nanostructures that are a function of the shape of these nanostructures may be investigated, using the discrete dipole approximation theory which is an appropriate method for solving the light scattering problem from objects of different shape and geometry. In this paper, the extinction spectra of Ag/glass-sculptured nano-flowers with threefold symmetry are modeled and calculated, while the results are compared with similar experimental observations. In modeling the nano-flower-shaped sculptured thin films, it is proposed that the nano-flower is formed as a combination of two chiral thin films with different dimensions. This structure was replaced with 1,405 electrical dipoles, and its extinction spectrum was calculated as a function of incident light angle and azimuthal angle. The extinction spectrum consists of both transverse and longitudinal modes of oscillations. The results showed that by increasing the incident angle, due to increase of amplitude of electrical oscillations, transverse oscillations shift towards longer wavelengths. It was also observed that at azimuthal angles close to nano-flower petals, where sharp points or recesses may exist, the intensity of extinction spectrum for longitudinal mode (long wavelengths in the extinction spectrum) increases. Manuscript profile

AbstractThe wettability of solid surfaces is important from the aspects of both science and technology. The Mn nano-sculptured thin films were designed and fabricated by oblique angle deposition of Mn on glass substrates at room temperature. The obtained structure was characterized by field emission scanning electron microscopy and atomic force microscopy. The wettability of thin films samples was investigated by water contact angle (WCA). The 4-pointed helical star-shaped structure exhibits hydrophobicity with static WCAs of more than 133° for a 10-mg distilled water droplet. This sample also shows the rose petal effect with the additional property of high adhesion. The Mn nano-sculptured thin films also act as a sticky surface which is confirmed by hysteresis of the contact angle obtained from advancing and receding contact angles measurements. Physicochemical property of liquid phase could effectively change the contact angle, and polar solvents in contact with hydrophobic solid surfaces do not necessarily show high contact angle value. Manuscript profile

AbstractA method for enhancing the resistance against corrosion of stainless steel 304L coated with 190 nm-thick manganese film and annealed with nitrogen flux at constant temperature (723 K) is reported. The variable quantity in this work is the temperature of the corroding solution (293 K and 333 K). X-ray diffraction analysis was employed to investigate the crystallographical changes of the annealed samples; atomic force microscope and scanning electron microscope were used for the morphology and studying the roughness of their surfaces; polarization analysis, electrochemical impedance spectroscopy, and phase and Bode diagrams, as well as the Kramers–Kronig transformation, were employed to study the susceptibility of the samples to corrosion, at temperatures 293 K and 333 K in 0.4 M H2SO4 solutions. Our results, from all the above analyses, unanimously point to the fact that in the process of enhancing resistance to corrosion, the annealing stage is the most crucial for improving the coating and the crystal structure of the samples and that the adsorption of Mn is not sufficient for the enhancement of the surface layer. Moreover, it was observed that increasing the temperature of the solution decreases the resistance of the samples owing to an increase in the rate of corrosion. Manuscript profile

AbstractMn sculptured thin films were fabricated in form of graded helical square tower-like terraced sculptured Mn thin films (GHSTTS) using oblique angle deposition together with rotation of substrate about its surface normal with fixed rotation angle (90°) and a shadowing block which was fixed at the centre of the substrate holder. The anisotropy of the samples was examined by resistivity measurements at two orthogonal angles. Direct relationship is obtained between resistivity and the anisotropy of the produced samples which showed that both of these parameters increase with decreasing distance from the edge of the shadowing block. Simulation work using the perturbation theory produced results consistent with the experimental observations. Manuscript profile

AbstractAISI 316L-type stainless steel was coated with 300-nm-thick Mn thin films and post-annealed at 673 K with a constant flow of oxygen (250 cm3/min). The films crystallographic and morphological structures were analyzed using X-ray diffraction (XRD) and atomic force microscopy (AFM) before corrosion test and scanning electron microscopy (SEM) after corrosion test. Corrosion behavior of the samples in 0.3, 0.5 and 0.6 M NaCl solutions was investigated by means of potentiodynamic and electrochemical impedance spectroscopy (EIS) techniques. Results showed that the corrosion inhibition of annealed Mn/SS316L in all NaCl solutions with different concentrations is higher than that of bare SS316L. A correlation is achieved between the structural variation of the films with the potentiodynamic and EIS corrosion results. Manuscript profile

AbstractSilver chiral nano-flowers with 3-, 4-, and 5-fold symmetry were produced using oblique angle deposition method in conjunction with the rotation of sample holder with different speeds at different sectors of each revolution. X-ray diffraction, atomic force microscopy, and scanning electron microscopy were employed to obtain the nanostructure and morphology of the films. Their antibacterial, electrical, and hydrophobic properties were investigated. Antibacterial properties were investigated against a range of microorganisms including Escherichia coli ATCC 8739, Staphylococcus aureus ATCC 25923, and Candida albicans PTCC 5027. Electrical conductivity of these films relative to that of bulk sample is reduced by a factor of about 103 due to porosity, surface roughness, and anisotropic structure of these films. Hydrophobicity results show dependence on the symmetry of these chiral nano-flowers. Manuscript profile

AbstractIn this work the corrosion resistance of stainless steel 304L coated with Mn-based thin film and post annealed with flow of nitrogen at 723 K in 0.6 M NaCl solution is reported. The latter was performed at three different solution temperatures of 293 K, 313 K and 333 K. X-ray diffraction analysis was used to determine the crystallographical structure and phases of the annealed samples. Atomic force microscope and field emission scanning electron microscope were employed to determine the morphology of the surface of the samples. Corrosion behavior of the samples in the corroding media was studied by means of electrochemical impedance spectroscopy (EIS) and polarization analysis. Results showed that the sample investigated in the 0.6 M NaCl solution at 293 K temperature has the highest corrosion resistance than those studied at higher temperatures. The correctness of the EIS results was confirmed by Kramers–Kronig transformation, while fitting of the data (Nyquist and Bode diagrams) to suitable equivalent electrical circuits showed that the highest corrosion enhancement is achieved for the Mn-based/SS304L sample in the 0.6 M NaCl solution at 293 K temperature, resulting in a 90.57% corrosion inhibition enhancement factor (η%). Polarization measurements also showed that this sample has the lowest corrosion current density, lowest corrosion rate and highest corrosion potential with a 96% corrosion inhibition efficiency factor (PE%). Consistent results are achieved for EIS and polarization measurements which are then correlated with the nanostructure of the films using X-ray diffraction and atomic force microscope analyses. Manuscript profile

AbstractMn helical star-shaped (pine-tree-like) nano-sculptured thin films with three-, four-and fivefold symmetry on copper substrates were produced using oblique angle deposition method in conjunction with rotation of sample holder at certain angles. Raman spectroscopy of the samples which were subjected to impregnation by 4,4′-bipyridine (C10H8N2) solution was carried out by 632.8 nm wavelength laser. The analysis of the Raman spectra showed enhancement for the 4,4′-bipyridine main bands (1592 and 1297 cm−1) belonging to the C=C stretching mode, aromatic ring stretching ring and in-plane ring mode of 4,4′-bipyridine, same as results obtained for Ag nano-structures. In addition, overtone and combined peaks are detected that may be related to the particular sculptured structure of the thin films fabricated in this work and the laser wavelength used for Raman spectroscopy. UV–Vis (absorption mode) spectra showed consistent observations with the SERS results leading to important role of surface electromagnetic selection rule in intensification of SERS, in addition pointing out the importance of the effect of the size of hot spots on the frequency of the localized surface plasmonic oscillations. Manuscript profile