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Due to their high efficiency and low ‎cost, electrostatic electron accelerators with a moderate energy, are used in the industry. In an electrostatic accelerator, the acceleration tube plays the role of dividing ‎the potential of the high-voltage terminal so that it accelerates the beam incrementally in a straight line. In this ‎paper, an acceleration tube for a Dynamitron accelerator with a voltage of 500 kV is designed by CST Studio ‎Suite software. In this design, an electron gun with flat cathode, and a current of 50 mA was used. In order to ‎extract the beam from the electron gun, two filters are used: electrodes and the lens electrode, with voltages of 495 and ‎‎481 kV, respectively; besides for electron acceleration, 13 electrodes with a potential step of 37 kV have been ‎designed. To hold the electrodes and prevent electrical discharges between the electrodes, insulating ‎sheets made of Pyrex are used. At the end of the acceleration tube, a 50mA beam current, a waist radius of less than 0.5 ‎mm, a 73nm radian emittance, and a 0.15μperv beam were obtained. The dimensions of the acceleration tube ‎and the results of investigating the change in the radius of the electrodes, the displacement and deviation of ‎the angles of the first electrode relative to the axis of the acceleration tube are presented in this paper‎.‎

Combination therapy including radiotherapy (RT) and photothermal therapy (PTT), as an alternative treatment for cancer treatment, recently has generated substantial interest. Graphene-based nanocarbons and gold content metallic nanoparticles, as one of the most attractive materials with their extraordinary physical and chemical properties, are extremely useful in this regard. We herein reported the effects of combination of cancer therapy including RT (doses of 2 and 4 Gy) and PTT (808 nm laser irradiation, NIR irradiation) as radio-photothermal therapy (RPTT) of KB oral squamous carcinoma cell line in the presence of Fe3O4@Au/reduced graphene oxide (rGO) nanostructures (NSs) at different concentrations. Fe3O4@Au/rGO NSs with different rGO contents have been synthesized by hydrothermal reaction method. They characterized by XRD, FE-SEM, TEM, EDS, FTIR and TGA. Cell viability for cytotoxicity, RT, PTT and RPTT were studied by MTT (3-[4,5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide) assay. High photothermal conversion efficiency of Fe3O4@Au/rGO NSs reaches to 61%. The resulting Fe3O4@Au NPs with approximate size of about 10–60 nm covered the rGO nanosheets with 40 wt% rGO at concentration of 20 μg ml−1, exhibited satisfactory cytotoxicity. They provided significant cell destruction under RT, PTT and specially RPTT in dose of 4 Gy. Furthermore, they have good biocompatibility on the healthy cells. Our results show that Fe3O4@Au/rGO NSs integrated with radiosensitization, photothermal therapy and their combination promising for nanomedicine and clinical applications.

This study represents the detailed calculation of damage by Auger electrons of radionuclides 99 m T c , 111 I n , 125 I and 123 I to DNA molecules at cellular scales, using Geant4-DNA toolkit. The average number of breaks in DNA are shown as a function of distance from the center of the DNA axis to position of Auger electron decay and compared with results obtained for different models of DNA used by others. The highest damage occurs for electrons with energies below 1 keV, and in proximity of DNA molecule. The calculation of DSB yield per Gy per Dalton is carried out for above radionuclides. The most considerable damage occurs when the distance between an Auger electron-emitting atom and DNA is about 2.5 nm, and 50% decreases happen when the distance is about 3.5 to 4 nm. DSB yield are comparable with other experimental and simulation data, and show a good agreement between our results and other works.

Conventional semiconductor components can be used for modeling and simulating molecular structures, so the progress in molecular electronics can be accelerated by creating a link between molecular electronics and semiconductor technology. Little work has been done so far on molecular electronic modeling. The present work attempts to focus on molecular electronic modeling by proposing a typical model and discussing its theory. Moreover, the circuit components used for modeling the molecules are introduced. An asymmetric oligo phenylene ethynylene (OPE) molecular diode and a four-benzene molecular diode are designed using the presented typical model. Furthermore, using LTspice software, the currents are obtained from the model and molecules for both OPE molecular diode and four-benzene molecular diode to confirm their appropriate performance. Then transmission spectrum, potential drop profile, and rectification ratio are obtained and analyzed for the four-benzene molecular diode using Atomistix ToolKit (ATK) software. Finally, various molecular gates and molecular memory logic circuits including NOT, NAND, NOR, SR Flip Flop, and D flip-flop are designed using the four-benzene molecular diode model.

Modeling in molecular electronics is of great importance, and the use of semiconductor components for this type of modeling accelerates the development process in this field. In this work, a typical circuit model is proposed for modeling molecular components. Accordingly, an asymmetric oligo-phenylene vinylene (OPV) molecular diode and a bipyridine-biborinine molecular diode are modeled. A good agreement is observed between the current curves from the proposed circuit models and the atomic simulations of the molecules. Additionally, the electron density, the distribution of molecular orbitals, and the potential drop profile at + 1 and - 1 V are obtained and analyzed for the bipyridine-biborinine molecular diode using the density functional theory (DFT) in combination with the non-equilibrium Green's function (NEGF). Using different molecular gates and circuits based on the molecular devices, we have modeled the ternary NOT logic gate, ternary NOR logic gate, ternary NAND logic gate, negative ternary inverter (NTI) logic gate, positive ternary inverter (PTI) logic gate, ternary buffer, ternary decoder, and ternary half adder.

Due to the strong effect of nanoparticles’ size on the magnetic and structural properties of Fe3O4 (magnetite) nanoparticles, the size selection proportional to desired magnetization especially superparamagnetic characteristic of these particles is very important. In this work, at first, the Fe3O4 nanoparticles successfully synthesized by a novel precipitating agent, ethylenediamine (EN), with an ultrasonic treatment (40 kHz, 150 W) by the co-precipitation method. Then, in order to accurately investigate the synthesis conditions on the physical properties of Fe3O4, the influence of reaction temperature, reaction time, and precipitating agent are studied. The structural and magnetic properties of the as-prepared nanoparticles are characterized by X-ray diffraction (XRD), Rietveld refinement, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM) analysis. It is found that the EN produces magnetite nanoparticles with a larger size and desired saturation magnetization (Ms). The absence of impurity phases in all of the synthesized nanoparticles and formation of the spinel structures at low temperature (30 °C) can be due to the influence of the ultrasound waves.

The high thermal conductivity of Uranium nitride (UN) makes it one of the best fuels for future fast neutron reactors. Combining density functional perturbation theory and semi classical Boltzman approach, we obtained the anharmonic properties of phonons and electrons, quantitatively. The electrical and thermal properties such as electrical conductivity (σ), electron thermal conductivity (Ke), lattice thermal conductivity (KL) and Seebeck coefficient (S) under various external hydrostatic pressures have been calculated as an effective controlling probe. We showed that the application of high compressive hydrostatic pressure increases the electrical and thermal conductivity due to the significant coupling within the deformation potential. Furthermore, this enhancement is addressed by the weakly correlated nature of U5f electron that treats as the itinerant carriers. The large contribution of U5f states at Fermi level is accompanied by the Wiedemann-Franz coefficient (L) and reaches to the value of free electron model, exhibits that this model is much applicable at extreme pressures. It is found that Seebeck coefficient depends on the temperature and pressure due to the disparate contribution of electron-phonon coupling at higher temperature. For this complex material, figure of merit is only determined by S2 parameter. Our results suggest that the external pressure can be exploited as a significant probe to control KL/Ke ratio for Uranium Nitride based structures on identifying materials with higher figure of merit efficiency than available at present.

Undoubtedly radionuclide therapy is the next phase of nuclear medicine development. 188Re-HEDP and 186Re-HEDP are therapeutic radiopharmaceuticals which have been used to treat bone metastases. With regard to their complementary features, in this study, as new idea their combined effects have been investigated with preparing the cocktail of 188/186Re-HEDP with radiochemical purity nearly 99%. The 188/186Re-HEDP biodistribution was checked in rats’ tissues up to 72 h. The produced 188/186Re-HEDP properties suggest a new bone palliative radiopharmaceutical to overcome bone metastases.

Aluminum is widely used in the electrical, automotive, transport and aerospace industries due to its remarkable properties, such as low density and relatively low costs. However, due to the low hardness and low yield strength, there are limitations in application of aluminum. To solve these limitations, aluminum is made with other hard materials in the form of nanocomposites. For this purpose, in this work, using B4C nanoparticles, Aluminum-boron carbide nanocomposites (Al-B4C) nanocomposites were prepared via ball milling processing. The ball milling process was carried out at room temperature under argon atmosphere using a planetary ball milling for 10 h at 300 rpm. The B4C nanoparticles content employed in these nanocomposites were 0, 5 and 10 wt%. To investigate the structural, mechanical and electrical properties of the Al-B4C nanocomposites, the powders were pressed and then sintered under argon atmosphere at 650 °C. The structure, density, hardness and electrical conductivity of the Al-B4C nanocomposites sintered tablets were investigated by X-ray Diffraction (XRD), Field Emission Scanning Electron microscopy (FESEM) with energy dispersive x-ray spectroscopy (EDS), Archimedes method, nanoindentation and eddy current test, respectively, and the results are discussed. The XRD patterns confirmed the presence of aluminum and B4C and the lack of any interphase and secondary phase in the Al-B4C nanocomposite. Distribution of B4C nanoparticles in Al-B4C nanocomposite was described via EDS assisted elemental mapping images. Moreover, with the addition of 5 and 10%wt. B4C nanoparticles in aluminum matrix, the hardness values of the Al-B4C nanocomposites was measured to be 138HV and 172HV which were higher than 67HV for the pure aluminum, respectively. Consequently, nanoindentation analysis showed that the hardness of Al-B4C nanocomposites was better than that of pure aluminum. Density values of Al-B4C nanocomposites were measured to be 2.5776 g/cm3 and 2.4949 g/cm3 which were lower than 2.6346 g/cm3 for the pure aluminum, respectively. Electrical conductivity of Al-B4C nanocomposites was measured to be 23%IACS and 13%IACS which were lower than 39% IACS for the pure aluminum, respectively. To evaluate the effect of particle size on the properties of Al-B4C composites, under the same conditions of Al-B4C nanocomposites preparation, Al-B4C microcomposites were prepared. With increasing B4C content, the hardness of Al-B4C nanocomposites were obtained higher than those for Al-B4C microcomposites. This behavior has been explained by Hall–Petch Model and Orowan strengthening. The density of the Al-B4C nanocomposites was obtained higher than those for Al-B4C microcomposites and the electrical conductivity of Al-B4C nanocomposites less than the resulting for Al-B4C microcomposites.

In this chapter, we try to investigate the mechanism of the electronic structure of condensed matter and molecules, briefly. Many of their properties, which are related to the material's structure and atomic position in the chemical compositions, can be concluded directly by the many-body Hamiltonian, fundamental quantum mechanical equation, for the electrons. One of the important techniques for examining the properties of a many-body system (such as solids and molecules) is called the density functional theory (DFT). In this theory, instead of the ground state function, we consider the single-particle electron density of the ground state. The DFT shows that the energy of the ground state in a many-particle system is expressed in terms of a function of the single-electron density. Minimizing this function allows us to calculate the density of the actual ground state and the properties related to the ground state. The success of DFT is to provide simple and precisely reasonable approximations of the function to be minimized. Characteristic of the density functional method compared with the many-body theory, it is possible to achieve a single-particle Schrodinger equation with an effective potential for studying the electron density of the ground state of the particle. Additionally, the calculation based on time-dependent density functional theory (TD-DFT) can be used to study the effect of short laser pulses on a solid or molecular system and calculate the resulting photoelectron spectrum. For example, we try to calculate the electronic and optical properties (such as the charge density, electrostatic potential, density of states (DOS), the effect of ultraviolet–visible spectrum, HOMO and the LUMO states) of three organic molecules: anthracene, indigo, and isoindigo, and also the solvent effects on them as isolated systems. The geometry optimizations and electronic calculations are carried out using DFT as implemented in the Siesta as well as Gaussian packages. Finally, the electronic properties of ideal MoS2 monolayer as a periodic system are investigated based on the DFT using the Siesta package.

In recent years, modeling and simulation techniques have been pioneered in the field of prediction existence or ability to synthesize new structures and to study physical and chemical properties. One of these methods is first-principles computations, which are based on the Kohn–Sham density functional theory (DFT). In this work, we predict a new kind of two-dimensional (2D) carbon allotrope by a tiny size building block with interesting properties. A systematic study of the structural and electronic properties on a non-hexagonal flat carbon allotrope has been performed in two different phases that consist of pentagonal (P $$\equiv \{C_5\}$$ ) and heptagonal (H $$\equiv \{C_7\}$$ ) rings, as well as a carbon nanotube (CNT), by using the DFT computational method. Hence, we obtain optimized lattice structures, bond lengths, density of states (DOS), band structure, the isosurface, and the difference charge density for these both novel two-dimension (2D) materials. The results show that regardless of the type of structure, the nanostructures are electrically metallic. It is anticipated that the results of the present work can be useful in the experimental synthesis of these materials and their potential applications in the future.

In this work, the stereometric 3-D surface topography as well as the optical properties of the Al doped ZnO (AZO), and Al/Cu co-doped ZnO (CAZO) thin films were investigated. These films were deposited with different thicknesses of 50 and 150 nm. The effect of dopants (Al, Cu) and sputtering parameters on the microstructures, crystalline structures, and fractal features were probed by Atomic Force Microscopy (AFM), X-ray diffraction, and Rutherford back scattering. AFM analysis of 3-D surface texture provided a deeper insight into their characteristics and implementation in graphical models and computer simulation. Studying surface roughness of samples at nanometer scale revealed a fractal structure which confirmed the relationship between the value of the fractal dimension and surface roughness parameters. Moreover, the optical properties of AZO and CAZO thin films and the relationship between their optical band gaps and their varied thicknesses were evaluated by Ultraviolet–visible spectrophotometry.

The influence of uniaxial and biaxial strains on electronic and transport properties of phosphorene nanoribbons (PNRs) is investigated within the tight-binding Green’s function theory by including an iterative procedure. For this purpose, we use tensile and compressive strains and employ the electronic band structure, effective mass and current–voltage curve, to explore the transport mechanism of PNR devices. Our results based on the band structure show that pseudogap in zigzag PNR (zPNR) is tunable under the strains. Hence, the tunneling transmission is controllable between two edge states of zPNRs. Obviously, we observe that the compressive strains can disturb the electron distributions leading to the induced charge polarization in armchair PNRs (aPNR). Also, in some particular cases there is massive–massless Dirac fermion transition in aPNRs. We found that the p-type zPNR devices can be designed under the compressive strains and the n-type aPNR devices can be modulated under the tensile strains. Our results show that the strains can be used as a way to control and improve the negative differential resistance phenomena in zPNRs. In aPNRs the current and threshold voltage under a finite bias can be changed several times with the uniaxial and biaxial strains. Thus, PNRs can be utilized for the development of flexible electronic and field effect transistor nanodevices.

In this work, the properties of the photonic bandgap (PBG) and Omni-directional photonic bandgap (Omni-PBG) of a quasi-one-dimensional photonic crystal (PC) are studied, in both TE and TM polarization modes. The PC is made of SiO2 and AlxGa1−xAs layers, alternatively, where x is the content of aluminum atoms in the GaAs slab. Using the transfer matrix method (TMM), the calculations are carried out within Maxwell's equation framework, to express the magnetic field of each medium in terms of electric. This model reduces the numerical calculation time and enables us to investigate the PBG and the Omni-PBG properties in the superlattices. We show that by varying the content and geometrical parameters, one can easily block the transmittance of the electromagnetic wave in the PC. The numerical results may be useful in designing of optical filtering nano-devices.

In order to accurately investigate the effect of cobalt substitutions in tin ferrite (SnFe2O4) properties, we prepared CoxSn1-xFe2O4 nanoparticles for different Co concentrations, x = 0.0, 0.25, 0.50, 0.75, and 1.00 using a simple co-precipitation method. X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX) and diffuse reflectance spectra (DRS) are used to study of structural, magnetic, morphology, and optical properties. The XRD and FTIR results confirmed the formation of cubic spinel structure. The lattice parameter and unit cell volume of tin ferrite nanoparticles were found to increase by entering and increasing Co+2 content in 0.25, and then significantly decrease for higher contents. In accordance with the XRD results, a slight shift in main band υ1 ( Fe tetra + 3 − O ) to lower wavenumber and then to higher wavenumber were observed in the IR spectra of Co content x 0.25, respectively. In turn to, saturation magnetization, remanent magnetization and anisotropy constant of SnFe2O4 nanoparticles were gradually increased for x = 0.50 and then decreased for x > 0.50.

In this work, we present a detailed investigation of the influences of intrinsic spin–orbit coupling (ISOC) as well as Rashba spin–orbit coupling (RSOC) on thermoelectric properties of molybdenum disulfide ( $$\hbox {MoS}_2$$ ) nanoribbons with armchair and zigzag edges, theoretically. For this purpose, we generalize the tight-binding model including the effects of the ISOC on all the atoms and a RSOC induced by a vertical electric field. By the calculation of the quantum spin-dependent transmission function from the recursive non-equilibrium Green’s function model using the multi-band Slater–Koster tight-binding method, the electrical and thermal currents flowing to the right lead can be obtained from the Landauer–Buttiker formulae. Hence, the temperature-dependent electrical conductance (G), the thermal conductivity ( $$\kappa $$ ), the Seebeck thermopower (S), and the thermoelectric efficiency (ZT) are discussed. The results predict a noticeable semiconducting behavior with n type, which exhibits a linear temperature dependence of the gap energy for both nanoribbons. The predicted ZT values demonstrate that the $$\hbox {MoS}_2$$ nanoribbons can be optimized to exhibit very good thermoelectric performance in which its value is not affected under influence of the electric field-induced RSOC in the ZMoS $$_2$$ nanoribbon (regardless of the AMoS $$_2$$ nanoribbon). Based on the used model, a large Seebeck coefficient is obtained in both types of the nanoribbons. Our results may be useful in designing novel thermoelectric devices based on two-dimensional materials as one of suitable nanoscale device.

In this paper, the electronic, phononic, elastic and thermodynamic properties of Ti x Zr 1 − x N are investigated using the first principle density functional theory (DFT) calculations. The parameters like electron effective mass, bonding forces, mechanical stability, incompressibility and thermodynamic stability of this compound are studied with different compositions of Ti (x= 0.125, 0.25, 0.375, 0.50). Absence of negative modes in phonon dispersion and phonon density of states results, low slope of the stress–strain curves, high elastic modulus and a large negative Gibbs free energy indicate the dynamic stability, high hardness, and thermodynamic stability of the compound. Our findings for electronic band structure, phonons, and elastic properties suggest that the Ti x Zr 1 − x N can be a suitable compound for the thermoelectric and hard coating applications.

In this work, the effect of vacancies on magnetic properties and spin-dependent behaviors of monolayer and bilayer armchair and zigzag graphene nanoribbons is investigated using first principles calculations based on density functional theory (DFT). The armchair and zigzag graphene nanoribbons are composed of 6 rows and 4 rows of carbon atoms with the edges closed by the hydrogen atoms, respectively. Our results show that vacancies affect the magnetic properties and spin polarization of the graphene nanoribbons. It is seen that the monolayer armchair graphene nanoribbon with one vacancy in its supercell (24 carbon sites + 8 hydrogen sites) gives the magnetic moment of 0.79 μ B , while magnetic moment in the monolayer zigzag graphene nanoribbon with one vacancy in its supercell (24 carbon sites + 6 hydrogen sites) is 1.72 μ B (for site α ) and 1.84 μ B (for site β ). The highest and lowest values of magnetic moment in different configurations of the bilayer armchair (zigzag) graphene nanoribbons with one vacancy in each layer of the supercell give 1.54 μ B and 1.29 μ B (3.51 μ B and 2.72 μ B ), respectively. Numerical values of the magnetic moment in different configurations depended on the distance of vacancies from each other and from nanoribbon’s edge as well as their orientations.

In this work, we present a detailed investigation of the influences of intrinsic spin-orbit coupling (ISOC) as well as Rashba spin-orbit coupling (RSOC) on the spin-resolved transport properties and net spin polarization of molybdenum disulfide (MoS2) nanoribbons including different configurations. For this reason, we generalize the tight-binding model by including the effects of the ISOC on all the atoms and a RSOC induced by a vertical electric field. The results predict a noticeable spin polarization in along to the field for the armchair MoS2 nanoribbon close to the Fermi level, which is originated mostly from edge states. Where as, the induced spin polarization in the zigzag MoS2 ribbons is much smaller than that of the considered armchair ones. Contrary to the RSOC, which it can not introduce significant spin polarization in the ZMoS2 the ribbon with width about 1–2 nm, the combination effect of an exchange field and Rashba spin-orbit interaction induces a spin-selective current especially close to the Fermi level. The numerical results may be useful to engineer and design magnetic-field-free spintronic devices based on the MoS2 nanoribbons.

In the presence of elastic planar strain distributions, electronic properties of molybdenum disul de (MoS2) monolayer are investigated within Density Functional Theory (DFT) calculations as implemented in SIESTA package. Three types of planar strain are considered with some di erent intensity values, and uniaxial strain along the armchair and zigzag directions as well as biaxial strain. We present a systematic study of the strained MoS2 monolayer by focusing on the calculation of Total Density Of State (TDOS), Partial Density Of State (PDOS), electron charge density, and electrostatic potential using post processing tools. In most cases, the states due to Mo atoms have dominant association in the TDOS close to the Fermi level of MoS2 monolayer under strain. As a consequence of the strain, S atom takes electron from Mo atom and becomes negatively charged. In addition, the tensile and compressive strains introduce the charge polarization in twoopposite directions per three types of strain for both sheets, which is in line with the experimental study. As another important result, the strain-induced charge polarization is proportional to the intensity value of strain.

In the present work, we have used ab initio molecular dynamics (AIMD) and non-equilibrium Green’s function (NEGF) formalism to investigate the scaling behavior of electron transport in ultra-thin films of Ge2Sb2Te5 (GST). The relation between the thickness of GST and its electron transport properties are studied in both crystalline (c-GST) and amorphous (a-GST) phases. For thin films with lower than 36 A thickness, we have observed a dramatic increase in the conductivity of the amorphous phase and an associated reduction in the conductance contrast between the two phases. Metal-induced gap states (MIGS) near the electrodes are observed in the density of states and the transmission coefficient of a-GST. The disappearance of the bandgap of a-GST due to the overlap of MIGS is responsible for the sharp reduction of crystalline to amorphous conductance ratio (ON/OFF). The ON/OFF ratio of the devices is about one order of magnitude upon downscaling the ultra-thin film of the active bit to 36 A. This estimation is the ultimate scalability for the simulated PCM device. When the thickness of GST further scales down, the reliable read operation is not possible. Our results show very good agreement with experimental work and it seems promising to engineers and designers of ultra-thin PCM devices.

The effect of doping on the transport properties of HfH2 is explored using first-principles method and semi-classical Boltzmann approach. Thermoelectric properties such as electrical conductivity, Seebeck coefficient, electron and lattice thermal conductivity of doped and pure samples are calculated under various temperatures. The calculated results show that electrical and thermal conductivities increased with electron carrier concentrations similar to results reported by other studies in the low doping regime. While in the hole carrier concentration regime, irregular behavior is observed, especially in density of carriers equal to n = 4.6 × 1023 cm−3. Also, the lattice thermal conductivity and absolute value of Seebeck coefficient have been decreased with electron carrier concentration but these properties have irregular trend in the hole doping regime. Our results suggest that for achieving lower electron thermal conductivity with respect to pure HfH2, hole doping is much effective. Furthermore, the dispersive and large contribution of 5d orbital of Hf near the Fermi state and very low variation of L (Wiedemann-Franz factor) compared to the value of the free electron model L 0 , for pure and doped samples indicate that electrons in HfH2 have itinerant behavior and free-electron model is suitable to describe the transport properties of pure and doped samples of HfH2.

In this work, the mechanical properties of transition metal nitrides (TMN) applicable as hard coatings are theoretically studied. Zirconium nitride (ZrN) is chosen as our case study and effects of pressure on its mechanical properties are investigated. Density functional theory (DFT) with general gradient approximation (GGA) and local density approximation (LDA) methods is used to simulate the structural, electronic, phonon and elastic properties of the compound in its bulk (cubic NaCl structure) and thin film states. Density of states (DOS) and band structure calculations show that the compound behaves like a metal. Electronic charge density and phonon calculations reveal the high hardness of the compound. Finally, the lattice constant and volume variations versus the pressure according to Murnaghan equation of state confirm that ZrN is appropriate for hard coating applications.

In this work two samples of Ag/Cu/Cu2O and Al:ZnO (AZO) multilayers, on glass substrates were prepared. The Ag/Cu layers were obtained by the physical vapor deposition (PVD) method, while the Cu2O and AZO layers were deposited by DC reactive magnetron sputtering. The structural and morphology properties of the considered samples were studied. The X-ray diffraction (XRD) showed that the first junction signifies a crystal structure of compounds of Ag, Cu and Cu2O, but the latter sample showed an amorphous structure. It was shown that the roughness of glass/Ag/Cu/Cu2O layers was substantially lower than the roughness of AZO layer deposited on glass substrate. In addition, the microstructure consideration revealed that the glass/Ag/Cu/Cu2O surface morphology was highly homogenous with average grain size of 35 nm. Moreover, we investigated the properties of the Cu2O/AZO heterojunction. The low turn-on voltage of about 0.64 V was obtained, which indicate that the heterojunction acts as a rectifier diode. The ideality factor was determined to be 10.28.

A systematic study has been done on the structural and electronic properties of carbon, boron nitride and aluminum nitride nanotubes with structure consisting of periodically distributed tetragonal (T ≡A2X2), hexagonal (H ≡A3X3) and dodecagonal (D ≡A6X6) (AX=C2, BN, AlN) cycles. The method has been performed using first-principles calculations based on density functional theory (DFT). The optimized lattice parameters, density of state (DOS) curves and band structure of THD-NTs are obtained for (3, 0) and (0, 2) types. Our calculation results indicate that carbon nanotubes of these types (THD-CNTs) behave as a metallic, but the boron nitride nanotubes (THD-BNNTs) (with a band gap of around 4 eV) as well as aluminum nitride nanotubes (THD-AlNNTs) (with a band gap of around 2.6 eV) behave as an semiconductor. The inequality in number of atoms in different directions is affected on structures and diameters of nanotubes and their walls curvature.

Molecular electronics technology removes limitations on miniaturization of semiconductor-based devices. With shrinking device sizes, we can expect smaller but more efficient devices. This branch of research also speeds up the devices, which enables us to have faster processors in the future. In order to have progress in this branch of research, we need to have modeling based on realities. Due to the availability of semiconductor-based devices, they can be used to further the goals of modeling in this field. Here, a specific procedure for the design and modeling of the molecular logic circuit based on the transistor structures is provided. That is, we use the circuit modelling for a gated oligo-phenylene vinylene (OPV) molecule as a NMOS molecular transistor's swithch and a methyl molecule as a resistor. We also benefited from the capabilities of the LTspice simulator software. Connecting these components, we could successfully conduct the circuit simulation of the combinational logic circuits, such as decoder, encoder, multiplexer, and comparator logical molecules, and prove the validity of the model.

We investigate the electronic and transport properties of a MoS 2 monolayer transducer with some simple gas molecules, such as CO, CO 2 and NO to explore theoretically sensing capabilities of this monolayer. The calculations are performed using nonequilibrium Green's function (NEGF) formalism based on the density functional theory (DFT) as implemented in the TranSIESTA code. Exposure to the NO gas molecule influences dramatically the electron transmission and the current–voltage characteristics of the MoS 2 monolayer. The results predict that the MoS 2 monolayer transducer can monitor the NO gas molecule to 10 4 order among these molecules between ±0.9 V bias window using the current–voltage characteristic with high sensitivity and selectivity. Here, post-processed analyses predict that the sensing mechanism is based on the charge transfer, which it in turn causes remarkable electrostatic gating to occur for the NO adsorbate. The numerical results may be useful to engineer and design gas sensor based on the MoS 2 monolayer.

In this paper, spin-dependent electrical transport properties are investigated in a single-crystal magnetic tunnel junction (MTJ) which consists of two ferromagnetic Fe electrodes separated by an MgO insulating barrier. These properties contain electric current, spin polarization and tunnel magnetoresistance (TMR). For this purpose, spin-dependent Hamiltonian is described for Δ1 and Δ5 bands in the transport direction. The transmission is calculated by Green's function formalism based on a single-band tight-binding approximation. The transport properties are investigated as a function of the barrier thickness in the limit of coherent tunneling. We have demonstrated that dependence of the TMR on the applied voltage and barrier thickness. Our numerical results may be useful for designing of spintronic devices. The numerical results may be useful in designing of spintronic devices.

One of the most promising methods of heat generation is using the nanosources, as absorbent light, under near-infrared (NIR) irradiation. Here, the Fe3O4@Au/rGO nanocomposites (NCs) with various graphene content (10, 25, and 40 wt%) synthesized by hydrothermal reaction method. The heat generated by Fe3O4@Au/rGO NCs suspensions under NIR laser irradiation (808 nm) in various concentration and times has been experimentally determined. The physical characteristics of these nanocomposite were studied using FE-SEM, TEM, XRD, XPS, FTIR, UV–vis, and Raman techniques. TEM and FE-SEM images displayed the spherical shape of Fe3O4@Au NCs which had varying diameter from 20 to 30 nm, coated to rGO sheets (with ~1 μm lateral dimension). The results demonstrate that the temperature of suspension under NIR laser irradiation raises from 5 to 40 °C with the increase of both the graphene contents and concentration. The Fe3O4@Au/rGO NCs are proposed as promising nanosources for heat generation under NIR laser irradiation and are useful for photothermal therapy, biomedical imaging, photothermal imaging, catalysis, and sensors applications.

Using the first-principle calculations, we study the electronic band structure, density of state (DOS), effective mass, quantum capacitance, transmission spectrum, and current–voltage characteristic of armchair silicene nanoribbons (ASiNRs) doped with aluminum (Al) and phosphorus (P) atoms. ASiNR is an intrinsic semiconductor, and depending on the type of impurity atoms applied, it becomes an n -type and p -type semiconductor. Our numerical results show several open energy windows and different peaks in the transmission spectra under various applied bias. These effects cause nonlinear behavior in the current–voltage curves. Also, the value of current density for four samples is obtained as J pure > J Al > J P > J Al&P at a fixed voltage. The threshold voltage for these samples are given as V pure th > V Al th > V P th > V Al&P th . The effective masses of carriers increase in the pure and doped ASiNR systems are calculated from the band structures spectra. Moreover, the quantum capacitance of the pure and doped ASiNR is investigated for direct and reverse biases. The results of this work may be useful in novel phenomena such as nanoelectronics applications and near-infrared photodetectors.

Rhenium therapeutic radioisotopes, namely rhenium-186 and 188, are radionuclides that have been used in combination with various ligands to provide different radiopharmaceuticals for the treatment of different diseases for many years. Each of these radioisotopes has its own special attributes, which make it appropriate to destroy special-sized tumors. High energy, long range beta particles in 188Re can give this certainty that large tumors can be eradicated with high efficiency. On the other hand, 186Re with low energy, short range beta particles is adequate item to ruin small tumors with minimum side effects and high yield. Thus, each of these radioisotopes has features that can cover just part of the treatment individually. So we thought accompanying 186Re and 188Re must have the best outcome to treat tumors with various sizes. Irradiating natural rhenium with neutrons has this potential to produce parallel 186Re and 188R together. We are looking for investigating whether the natural rhenium irradiation, in addition the concurrent production of these radioisotopes, gives us the appropriate radioactivity values to produce compositional radiopharmaceuticals? In this research, the experimental and theoretical assessments of 186Re and 188R simultaneous production to reach compositional radiopharmaceutical by natural rhenium irradiation in the Tehran research reactor, as well as the type and amount of produced impurities have been investigated. The results showed that experimental data are in good agreement with theoretical calculations. The maximum relative error in data has been calculated 8%. The results showed that, in the simultaneous production 186Re and 188R via the natural rhenium irradiation method, the amounts of impurities are trivial compared to the main products, and the activities of main products are properly enough to produce compositional radiopharmaceuticals.

Electronic and magnetic properties of a molybdenum disulfide (MoS2) monolayer with some intrinsic and extrinsic vacancies are investigated using ab initio method in the presence of planar strain distributions. The calculations are carried out within the density functional theory (DFT) as implemented in SIESTA package. By using fully relaxed structures and applying a full spin-polarized description to the system, we concentrate on created magnetic moment due to the vacancies under different planar strains. The results show that the extrinsic MoS6 vacancy induces a net magnetic moment of 6.00 μB per supercell. Also, it is found that the pure MoS2 monolayer for the most cases does not show any magnetic properties under the planar strain. While the net magnetic moment of MoS2 monolayer with the vacancies enhances as the planar tensile strain is applied. The tunable magnetic moment of MoS2 monolayer may be utilized for the development of spintronic and flexible electronic nano-devices.

A theoretical study of electronic properties on MoS2 nanoribbon is made on focusing the calculation of zero bias transport in the presence of disorders. Disorders including intrinsic and extrinsic vacancies and also weak uniform scatter defects are considered. The calculations are based on the tight-binding Green's function formalism by including an iterative procedure. The Slater–Koster transformations are used to determine the parameters. This model reduces the numerical calculation time. The unsaturated atoms at the edge of armchair (zigzag) ribbon induce some mid-gap states with nearly high (low) localization, which act as scattering centers. The antiresonances of created quasi-localized states due to vacancy cause the conductance of the armchair nanoribbon to decrease. Finally, the zigzag ribbon provides the highest sensitivity as well as selectivity between the smaller energy range, in the presence of the single weak scatter with potential value of 2 eV at the edge of the ribbon.

In this work, electronic properties of bare and doped graphene layers in the presence of N, B and a type of defective impurities are investigated under adsorption of CO, NO, NH3 and NO2 molecules on it's external surface. We use a fully self-consistent density function theory (DFT) based calculations as implemented in SIESTA package. The local-density approximation (LDA) is considered for the exchange-correlation function. Total density of state (TDOS), partial density of state (PDOS) and charge density calculations are also considered to elucidate the difference in the CO, NO, NH3 and NO2 gases detection mechanism of pristine and doped graphene structures. With regard to that the charge transfer is occurring between the graphene sheet and gaseous molecules, the NO2 and NH3 molecules are considered as the recipient and donor of electrons, respectively. We show that the states contributed by the adsorbed CO and NO molecules are quite localized near the center of original band gap and they suggest that the charge transport in such systems cannot be enhanced considerably, while NO2 and NH3 molecules adsorption acts as the acceptor and donor, respectively. Our results can serve as a base for developments in designing nano-electronic devices.