Shahram Solaymani

Bio: Shahram Solaymani is an academic researcher from Islamic Azad University. The author has contributed to research in topics: Thin film & Band gap. The author has an hindex of 27, co-authored 99 publications receiving 1974 citations.

Microstructure and Tribological Properties of FeNPs@a-C:H Films by Micromorphology Analysis and Fractal Geometry

Abstract: This paper analyzes the three-dimensional (3D) surface texture of amorphous hydrogenated carbon films with sputtered iron nanoparticles (FeNPs@a-C:H) deposited by a radio-frequency plasma-enhanced chemical vapor deposition method on the quartz substrates. The prepared FeNPs@a-C:H films were used as research materials. The synthesized samples were deposited at four different pressures of 2.5, 3, 3.35, and 3.5 N/m2 in an acetylene gas atmosphere. The Fe and C contents of the thin films were obtained from X-ray photoelectron spectroscopy. The X-ray diffraction profile and electron diffraction pattern indicate that iron nanoparticles with body-centered-cubic crystalline structure are formed in these films. The localized surface plasmon resonance peak that is the signature of the existence of the iron core nanoparticles appears in visible spectra of these films. The sample surface images were recorded using an atomic force microscope operating in a noncontact mode and analyzed to reveal the statistical, fracta...

Influence of scanning rate on quality of AFM image: Study of surface statistical metrics

Abstract: The purpose of this work is to study the dependence of AFM-data reliability on scanning rate. The three-dimensional (3D) surface topography of the samples with different micro-motifs is investigated. The analysis of surface metrics for estimation of artifacts from inappropriate scanning rate is presented. Fractal analysis was done by cube counting method and evaluation of statistical metrics was carrying out on the basis of AFM-data. Combination of quantitate parameters is also presented in graphs for every measurement. The results indicate that the sensitivity to scanning rate growths with fractal dimension of the sample. This approach allows describing the distortion of the images against scanning rate and could be applied for dependences on the other measurement parameters. The article explains the relevance and comparison of fractal and statistical surface parameters for characterization of data distortion caused by inappropriate choice of scanning rate.

Fractal features of carbon–nickel composite thin films

Abstract: This work analyses the three-dimensional (3-D) surface texture of carbon-nickel (C-Ni) films grown by radio frequency (RF) magnetron co-sputtering on glass substrates. The C-Ni thin films were deposited under different deposition times, from 50 to 600 s, at room temperature. Atomic force microscopy was employed to characterize the 3-D surface texture data in connection with the statistical, and fractal analyses. It has been found that up to 180 s the sputtering occurs in more metal content mode and in greater than 180 s it occurs in more non-metal content mode. This behavior demonstrated a strong link between the structural and morphological properties of C-Ni composite films and facilitates a deeper understanding of structure/property relationships and surface defects in prepared samples. Furthermore, these findings can be applied to research on the mechanisms to prepare and control high-quality C-Ni films.

Stereometric Parameters of the Cu/Fe NPs Thin Films

Abstract: This paper analyses the three-dimensional (3-D) surface morphology of thin films of Fe on Cu nanoparticles (NPs) synthesized by direct-current (DC) magnetron sputtering deposited on glass substrates. Four samples coated with copper and iron and deposited on the glass surface were used as research materials. Thin films were obtained by means of a DC reactive magnetron sputtering method. The copper coating of each sample was 55 nm thick. In addition, the second, third, and fourth samples had a coating of iron, with a thickness of 40, 55, and 70 nm, respectively. The sample surface images were obtained by using an atomic force microscope operating in a contactless mode. The 3-D of the surface samples was divided into motifs of significant peaks and pits using MountainsMap Premium software, which uses the watershed segmentation algorithm. In addition, the highest and lowest points of motifs are localized. The parameters relating to all the segmented motifs consistent with ISO 25178-2:2012 have been generated ...

Effect of preparation methods on the properties of titania nanoparticles: solvothermal versus sol–gel

Abstract: Titania (TiO2) nanoparticles (NP’s) have been prepared by solvothermal and sol–gel techniques using different surfactants such as acetic acid (AA), oleylamine (OM), and AA + OM. The solution was thermally treated at growth temperature 180 °C in solvothermal method. TiO2 powder, prepared using both methods, was subjected to post heat treatment at 550 and 950 °C. The effect of surfactants on the morphology of TiO2 NP’s was studied by transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). The structural and thermal properties of titania NP’s are investigated by means of X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, and differential scanning calorimetry (TGA/DSC). TEM and FESEM images illustrated various shapes of titania NP’s such as irregular spherical, rounded rectangular, truncated rhombic, oval, and rod-like structure in presence of different surfactants. Moreover, TiO2 particles prepared by sol–gel method were almost 40 times greater than those prepared by solvothermal method. In addition to the improvement in the crystallinity, thermal stability has been enhanced due to consolidation of individual particles at higher annealing temperature in solvothermal technique. Furthermore, a reduction in the degradation temperature and phase transformation of TiO2 NP’s were conspicuously corroborated after post-heat treatment.

Carbon Nanotube p-n Junction Diodes

Abstract: We demonstrate a single-walled carbon nanotube p-n junction diode device. The p-n junction is formed along a single nanotube by electrostatic doping using a pair of split gate electrodes. By biasing the two gates accordingly, the device can function either as a diode or as an ambipolar field-effect transistor. The diode current–voltage characteristics show forward conduction and reverse blocking characteristics, i.e., rectification. For low bias conditions, the characteristics follow the ideal diode equation with an ideality factor close to one.

Wide Band Gap Chalcogenide Semiconductors.

Abstract: Wide band gap semiconductors are essential for today's electronic devices and energy applications because of their high optical transparency, controllable carrier concentration, and tunable electrical conductivity. The most intensively investigated wide band gap semiconductors are transparent conductive oxides (TCOs), such as tin-doped indium oxide (ITO) and amorphous In-Ga-Zn-O (IGZO), used in displays and solar cells, carbides (e.g., SiC) and nitrides (e.g., GaN) used in power electronics, and emerging halides (e.g., γ-CuI) and 2D electronic materials (e.g., graphene) used in various optoelectronic devices. Compared to these prominent materials families, chalcogen-based (Ch = S, Se, Te) wide band gap semiconductors are less heavily investigated but stand out because of their propensity for p-type doping, high mobilities, high valence band positions (i.e., low ionization potentials), and broad applications in electronic devices such as CdTe solar cells. This manuscript provides a review of wide band gap chalcogenide semiconductors. First, we outline general materials design parameters of high performing transparent semiconductors, as well as the theoretical and experimental underpinnings of the corresponding research methods. We proceed to summarize progress in wide band gap (EG > 2 eV) chalcogenide materials-namely, II-VI MCh binaries, CuMCh2 chalcopyrites, Cu3MCh4 sulvanites, mixed-anion layered CuMCh(O,F), and 2D materials-and discuss computational predictions of potential new candidates in this family, highlighting their optical and electrical properties. We finally review applications-for example, photovoltaic and photoelectrochemical solar cells, transistors, and light emitting diodes-that employ wide band gap chalcogenides as either an active or passive layer. By examining, categorizing, and discussing prospective directions in wide band gap chalcogenides, this Review aims to inspire continued research on this emerging class of transparent semiconductors and thereby enable future innovations for optoelectronic devices.

Nickel selenide supported on nickel foam as an efficient and durable non-precious electrocatalyst for the alkaline water electrolysis

Abstract: Herein, we describe an in-situ hybridization of Nickel Selenide (Ni3Se2) with a Nickel Foam (NF) current collector as an efficient, ultra-durable electrode for the continuous alkaline water electrolysis. Earth abundant, cost effective, non-precious self-made Ni3Se2/NF electrode delivers an oxygen evolution reaction (OER) overpotential value of 315 mV at a current density of 100 mA cm−2 (versus a reversible hydrogen electrode) in aqueous electrolyte of 1 M KOH. On a static current density of 100 mA cm−2, Ni3Se2/NF electrode shows a good OER stability over 285 h with very small potential loss of 5.5% in alkaline electrolyte. Accordingly, the alkaline water electrolyzer constructed with Ni3Se2/NF (anode) and NiCo2S4/NF (cathode), it requires 1.58 V to deliver 10 mA cm−2 current density, with 500 h continuous operation in 1 M KOH. In addition, we demonstrate that the light-driven water splitting using solar panel, it can be a promising approach to facilitate true independence from electricity in H2 fuel economy. Overall, this methodology is one of the appropriate energy efficient ways to reduce the cost of water splitting devices, as it may simplify the diverse process and equipment.