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  • Synthesis, crystal structure and optical properties of Anderson-type heteropolyanion with cobalt cations
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-16
    Yassine Ammari, S. Abid, K. Horchani Naifer

    A sample inorganic A-type Anderson polyoxometalate (POM) (TeMo6) compound formulated as [Co(H2O)6]3[TeMo6O24] is synthesized in aqueous solution by slow evaporation technique. Single-crystal X-ray diffraction analysis reveals that the obtained compound crystallizes in the centrosymmetric hexagonal space group (R-3c) with a formula unit made up of one [TeMo6O24]6− A-type Anderson anion and three [Co(H2O)3]2+ cations. The molecular Hirshfeld surface indicates that the crystal packing is stabilized by H-bonds interactions to generate 3D supramolecular frameworks. Furthermore, some optical properties such as bandgap energy, refractive index, dielectric constant and optical conductivity of the sample are investigated. The large value of refractive index known in the visible region of electromagnetic spectrum (n = 3.5 at 1.8 eV) reveals that this sample can become a promising candidate for visible optical communication devices. The emission fluorescent spectrum in the solid state at room temperature is measured and the decay lifetime curves are obtained by monitoring the ligand-to-metal charge transfer transition (LMCT). The studies of the colorimetric properties of the sample reveal that the color coordinates (x = 0.33667; y = 0.25564) are located in the region of National Television System Committee (NTSC) in the CIE chromaticity chart and the calculated correlated color temperature value (CCT ~ 5085 K) indicates that the optimized compound could be applied as a cool light emission diode.

    更新日期:2020-01-16
  • Microstructure and dielectric properties of LiTaO 3 ceramics with MnO 2 addition fabricated by hot-pressing sintering
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-16
    Qiang Zheng, Youfeng Zhang

    Abstract Lithium tantalite (LiTaO3) is an excellent single crystal, only a few studies focused on polycrystalline LiTaO3 ceramics, because it is difficult to sintering densification in fabrication process by common sintering. In this paper, LiTaO3 composite ceramics with added 3 wt% MnO2 were obtained by hot-pressing sintering at different temperatures from 1200 to 1350 °C. The sinterability, microstructure and dielectric properties of LiTaO3 ceramics fabricated at sintering temperatures were investigated. The relative density of the LiTaO3 ceramics was significantly enhanced as the sintering temperature increases first and then decreased. The LiTaO3 ceramics achieved the highest relative density (98.6%) and shown homogeneous microstructure when sintered at 1300 °C. The LiTaO3 and manganese oxide phases were observed in the MnO2/LiTaO3 ceramics fabricated at different sintering temperatures. The dielectric properties of MnO2/LiTaO3 ceramics were significantly influenced by the sintering temperatures. The study of dielectric properties revealed that the specimen had excellent dielectric properties when sintering temperature was 1300 °C and the dielectric constant was 78, as it tends to stay invariable at room temperature.

    更新日期:2020-01-16
  • Caloric and isothermal equations of state of solids: empirical modeling with multiply broken power-law densities
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-16
    Roman Tomaschitz

    Empirical equations of state (EoSs) are developed for solids, applicable over extended temperature and pressure ranges. The EoSs are modeled as multiply broken power laws, in closed form without the use of ascending series expansions; their general analytic structure is explained and specific examples are studied. The caloric EoS is put to test with two carbon allotropes, diamond and graphite, as well as vitreous silica. To this end, least-squares fits of broken power-law densities are performed to heat capacity data covering several logarithmic decades in temperature, the high- and low-temperature regimes and especially the intermediate temperature range where the Debye theory is of limited accuracy. The analytic fits of the heat capacities are then temperature integrated to obtain the entropy and caloric EoS, i.e. the internal energy. Multiply broken power laws are also employed to model the isothermal EoSs of metals (Al, Cu, Mo, Ta, Au, W, Pt) at ambient temperature, over a pressure range up to several hundred GPa. In the case of copper, the empirical pressure range is extended into the TPa interval with data points from DFT calculations. For each metal, the parameters defining the isothermal EoS (i.e. the density–pressure relation) are inferred by nonlinear regression. The analytic pressure dependence of the compression modulus of each metal is obtained as well, over the full data range.

    更新日期:2020-01-16
  • A comparative study of the structural, magnetic transport and electrochemical properties of La 0.7 Sr 0.3 MnO 3 synthesized by different chemical routes
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-16
    Kumar Navin, Rajnish Kurchania

    A comparative study of the structural, magnetic, transport and electrochemical properties of the La0.7Sr0.3MnO3 (LSMO) synthesized by sol–gel, solution combustion and solid-state reaction has been discussed in details. Synthesis process controls the structure and morphology of the material which determine the overall characteristics of the material. The sol–gel and solution combustion method provide nanocrystalline material with an average particle size of 23.03 nm 17.9 nm, respectively; while, microcrystalline material with an average particle size of 160 nm is synthesized by solid-state reaction method. The magnetic properties of the material are improved with an increase in particle size from nanoscale to microscale, while resistivity increases with a reduction in the size of the material. The LSMO synthesized by the sol–gel method shows the highest magnetoresistance of 32.3% at 10 K with a 1T magnetic field. The solution combustion method provides LSMO nanoparticles with large surface area and porosity which results in its better electrochemical behavior as compared to the LSMO synthesized by sol–gel and solid-state reaction.

    更新日期:2020-01-16
  • Facile preparation of ZnO nanostructured thin films via oblique angle ultrasonic mist vapor deposition (OA-UMVD): a systematic investigation
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-16
    Hassan Alehdaghi, Maziyar Kazemi, Mohammad Zirak

    Ultrasonic mist vapor deposition (UMVD) is a widely used facile technique to prepare ZnO thin films. The surface properties of prepared thin films can be tuned via easily controllable UMVD deposition parameters. Herein, we utilized an oblique angle (OA) geometry in UMVD system named as OA-UMVD. The angle between incident flow and substrate (θs) was changed from 0° to 45°. Alteration of θs as well as substrate temperature (Ts) resulted in the deposition of ZnO thin films with different morphologies. For mild nozzle–substrate distance (D = 3 cm), fine vertical ZnO nanosheets with length of 123 nm and thickness of 23 nm were obtained for low Ts (330 °C) and small θs (≈ 0°). By increasing both Ts and θs, ZnO nanorods gradually appeared on the surface. Both nozzle–substrate distance (D) and Ts showed similar effect on deposition rate (Rd), and Rd decreased by increase of D and Ts, while deposition rate increased for larger θs. Confocal microscopy results revealed that using low Ts (330 °C), short distance (D = 1.5 cm) and large θs (45°) resulted in high macroscopic surface roughness (MRs) of 98 nm, while high Ts (500 °C), long D (5 cm) and small θs (≈ 0○) created compact and smooth surface with low MRs of 5 nm, in accordance with transmittance results. The ZnO wurtzite crystal structure was approved via X-ray diffraction patterns. The crystallite size in the layers was affected only by Ts, and θs had no significant effect on the layers’ crystallinity. Obtaining different ZnO nanostructures with different MRs via easily and accurately controllable growth parameters is a great advantage for our employed OA-UMVD system, which could be used to prepare ZnO thin films with desired morphologies for widespread application fields.

    更新日期:2020-01-16
  • Correction to: Low-temperature metal-induced crystallization of hydrogenated amorphous Si 1−x Ge x (0.25 ≤ x ≤ 1) thin films with Au solution
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-15
    Shanglong Peng, Xiaoyan Shen, Deyan He

    Unfortunately, Fig 6 in the article was incorrect.

    更新日期:2020-01-15
  • Synthesis of cesium tungsten bronze by a solution-based chemical route and the NIR shielding properties of cesium tungsten bronze thin films
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-14
    Pin-Jhen Wu, Sanjaya Brahma, Horng-Hwa Lu, Jow-Lay Huang

    Abstract In this study, hexagonal Cs0.32WO3 powders were synthesized by a simple solution-based chemical route. The experiment can be performed within a relatively short time and can easily produce large amounts of hexagonal Cs0.32WO3 powders. The CsxWO3 powders as synthesized and after heat treatment were characterized by X-ray diffraction, scanning electron microscopy, differential thermal and thermogravimetric analysis and Fourier transform infrared spectroscopy. CsxWO3 thin films were deposited by an electron beam evaporation method from sintered Cs0.32WO3 powders as the targets. The CsxWO3 films were annealed at different temperatures under Ar and Ar/H2 atmospheres. The effects of annealing on the microstructure, morphology and near-infrared (NIR) shielding properties of the Cs0.32WO3 films are discussed. The results show that the Cs0.32WO3 thin film specimen annealed for 500 °C in an Ar/H2 atmosphere has the highest transmittance (80%) in the visible light region and the lowest transmittance (42%) in the NIR region.

    更新日期:2020-01-14
  • Enrichment of optical, electrical, and magnetic properties of Li + , La 3+ doped BaTiO 3 perovskite multifunctional ceramics
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-14
    K. Madhan, R. Murugaraj

    Abstract Li and La co-doped Ba(1-x)(Lix/2Lax/2)TiO3 (BLLT) ceramics with x = 0.01, 0.02, 0.03, and 0.04 at A—site was synthesized by sol–gel combustion method. The powder X-ray diffraction and Raman analysis showed a good crystalline nature with perovskite tetragonal structure and the grain size of the samples was estimated and compared using a scanning electron microscope. The decreasing trend in the optical band gap upon doping and carrier concentration values was calculated from UV–Vis absorption spectra. Electron paramagnetic resonance g ~ 1.998 for BLLT ceramics confirms that the electrons are localized near oxygen vacancies. The observed signals may be attributed to the reduction of Ti4+/Ti3+ and its related defects. Moreover, the room temperature magnetization versus magnetic field loops showed the mixed weak ferromagnetic and diamagnetic phase. The enhancement of ε′ with respect to the doping of Li and La ion and increase in particle size due to the number of grain boundaries in BLLT ceramics were studied. The polarization versus electric field of BLLT samples indicates the lossy capacitor behavior, which is attributed to the relatively high leakage current caused by the existence of a defect or oxygen vacancies.

    更新日期:2020-01-14
  • Extending bandgap method of concentric ring locally resonant phononic crystals
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-14
    Lijian Lei, Linchang Miao, Chao Li, Xiaodong Liang, Junjie Wang

    Abstract Locally resonant phononic crystals (LRPCs) have the capacity to adjust elastic waves with the structure sizes much smaller than the incident wavelengths, the unique property is called low-frequency bandgap, but it is not easily applied in practical engineering because of narrow bandgap width. Multilayered LRPCs are helpful in generating several bandgaps, in the meanwhile the designs of multilayered LRPCs proposed in previous study result in the larger filling fraction, whereas the bandwidth of LRPCs increases monotonically with filling fraction, thus the pure contribution of concentric ring configuration to the bandwidth extending is less involved. Keeping the filling fraction constant, this paper carefully designs the microstructure of concentric ring locally resonant phononic crystals, and investigates the effects of structure configuration on the bandgap property. To this end, an updated improved plane wave expansion (UIPWE) method is developed to calculate the band structure, and finite element method (FEM) is used to obtain transmission spectra and vibration mode. The results demonstrate that UIPWE method is valid and is able to give precise outcomes, which is verified by FEM. In addition, the concentric ring configuration equivalently produces dual-oscillator system, relative movements between the oscillators generate coupling effect, thus, the bandgaps can be extended by configurating rightly the microstructure of single cell. Further studies about different models indicate that the combination of smaller inner scatterers and larger inner coating layers are beneficial to wider bandgap. These conclusions presented herein provide insights in the design of three-component PCs in multi-frequency vibration control field.

    更新日期:2020-01-14
  • Comparative evaluation of nuclear radiation shielding properties of x TeO 2 + (100– x )Li 2 O glass system
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-14
    M. Kamislioglu, E. E. Altunsoy Guclu, H. O. Tekin

    Abstract In the present investigation, nuclear radiation shielding parameters of xTeO2 + (100–x)Li2O (where x = 95, 90, 85, 80, 75, and 70 mol%) glass system have been examined. Gamma shielding parameters such as mass attenuation coefficients (MAC), half-value layer (HVL), tenth-value layer (TVL), mean free path (MFP), effective atomic number (Zeff), effective electron density (Neff) were calculated. Moreover, neutron effective cross sections (∑R) are determined. The calculations for present materials have been performed in different photon energy ranges (0.01–20 MeV) and using Monte Carlo N-Particle eXtended (MCNPX) simulation code and theoretical results were also obtained with WinXcom program. The results obtained from the MCNPX and WinXcom program were found to be in well harmony. Moreover, for the assessment of radiation shielding success of tellurite glasses, the mass stopping power (MSP) and projected range (PR) were computed for proton and alpha particles using stopping and range of ions in matter (SRIM) code. When the results obtained from the study are examined, it is seen that 95TeLi glass has the lowest HVL, TVL, MFP, TF and the highest (∑R) values. Therefore, the 95TeLi glass has the most perfect radiation shielding achievement than other investigated glasses.

    更新日期:2020-01-14
  • Effect of volume fraction on magnetoelectric coupling effect of Co 0.1 Cu 0.9 Fe 2 O 4 /Ba 0.8 Sr 0.2 TiO 3 composite liquid
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-13
    Heng Wu, Ruicheng Xu, Xiaofeng Qin, Rongli Gao, Zhenhua Wang, Chunlin Fu, Wei Cai, Gang Chen, Xiaoling Deng

    Co0.1Cu0.9Fe2O4 (CCFO) and Ba0.8Sr0.2TiO3 (BST) particles were respectively prepared by chemical coprecipitation and hydrothermal method, then CCFO/BST composite liquid was synthesized by distributing surface modified CCFO and Ba0.8Sr0.2TiO3 particles into insulating silicone oil. Effects of volume fraction (ϕv = 1%, 2%, 5% and 10%) on the microstructure, dielectric, ferroelectric and magnetoelectric coupling effect were comparatively investigated. XRD showed that the pure phase of CCFO and BST particles was successfully prepared. CCFO/BST composite particle shows ferromagnetic behavior due to the contribution of magnetic phase CCFO. The dielectric constant of CCFO/BST composite liquid is about 1/25 of the composite particles, and the dielectric constant value of the composite liquid decreases with increasing the volume fraction because the permittivity of silicone oil is far smaller than that of CCFO/BST composite particles. The relative change of dielectric constant of composite liquid under the action of external magnetic field is greater than that of composite particle due to its mobility of particles in liquid. The values of remnant polarization (Pr), coercive field (Ec) and leakage current of CCFO/BST composite liquid increase monotonically with increasing volume fraction, while excessive volume fraction may result in abnormal phenomenon because of the agglomeration of particles. Magnetic field-induced chain structure of the composite liquid has been observed under a light microscope at a magnification of 200. The maximal magnetoelectric (ME) coupling coefficient is about 89.78 V/(cm Oe), which is obtained in the CCFO/BST composite liquid when the volume fraction is 10%.

    更新日期:2020-01-14
  • Experimental study of the diamagnetism and the ferromagnetism in MoS 2 thin films
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-13
    Asma Bouarissa, Abdelhamid Layadi, Hager Maghraoui-Meherzi

    Abstract A series of MoS2 films were prepared by the chemical bath deposition method at different temperatures (60–80 °C). The film thicknesses range from 0.988 up to 10.25 µm. The films are polycrystalline. Vibrating sample magnetometer (VSM) was used to study the magnetic properties of these MoS2 films. The experiments were done at room temperature with the magnetic field applied in the film plane. The magnetization curves indicate the coexistence of ferromagnetism and diamagnetism. The saturation and remnant magnetizations, the coercive and saturation fields as well as the diamagnetic susceptibility have been measured and are discussed as a function of the film thickness and the synthesis temperature. A change in the magnetic anisotropy is observed, and the magnetization easy axis direction switches from in-plane to out-of-plane as the thickness increases. The magnetic properties are correlated with the structural ones.

    更新日期:2020-01-14
  • Comparative study on the physical properties of rare-earth-substituted nano-sized CoFe 2 O 4
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-13
    Ebtesam E. Ateia, M. K. Abdelmaksoud, M. M. Arman, Amira S. Shafaay

    Nanotechnology manufacturing is rapidly developing and promises that the essential changes will have significant commercial and scientific impacts be applicable in an extensive range of areas. In this area, cobalt ferrite nanoparticles have been considered as one of the competitive candidates. The present study is based on the investigation of the effect of rare-earth (RE) incorporation on the physical properties of CoFe2O4. Rare-earth ions doped cobalt ferrites with composition CoRE0.025Fe1.975O4 where RE are Ce, Er and Sm have been synthesized by citrate auto combustion technique. Characterization is achieved using X-Ray diffraction (XRD) technique for structural analysis. The obtained data show that the samples exhibit a single-phase spinel structure. RE is successfully substituted into the spinel lattice without any distortion and it acts as inhibiting agent for grain growth. Room temperature M–H curves exhibit ferrimagnetism behavior with a decrease in saturation magnetization and coercivity indicating these materials can be applicable for magnetic data storage and magneto-recording devices. The electrical conductivity is studied as a function of frequency in the temperature range of 300–700 K. The conduction mechanism is attributed to the hopping mechanism. The Seebeck coefficient S is found to be positive for Ce indicating that Co/Ce ferrite behaves as a p-type semiconductor. While it is fluctuated between positive and negative for Er/Sm-doped samples throughout the studied temperature range. The cobalt doped with Er3+ and Sm3+ exhibits degenerated semiconductor trends at higher temperatures. Such data offer a new opportunity for optimizing and improving the performance of cobalt ferrite where the physical properties are decisive.

    更新日期:2020-01-13
  • Toroidal dipole-induced coherent forward scattering from a miniaturized cloaking structure
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-13
    V. P. Sarin, P. V. Vinesh, M. Manoj, C. K. Aanandan, P. Mohanan, K. Vasudevan

    Abstract The physical existence of microwave toroidal dipole in a dogbone metallic inclusion-based miniaturized cloaking structure is verified in this paper. The excitation of toroidal dipole moments on the studied composite is verified using multipole scattering formalism. The presence of the toroidal Fano resonance significantly enhances resonant forward scattering from the structure for normal incidence. Multipolar contribution from the electric, magnetic and toroidal moments significantly enhances the scattering cross-section of the composite as compared to a bare cylindrical metallic object. Applicability of the proposed scheme is tested inside an anechoic chamber using reflection measurements on the fabricated structure and is subsequently validated in computer simulations in the microwave frequency regime.

    更新日期:2020-01-13
  • Strain-tunable band alignment of blue phosphorus–WX 2 ( X = S/Se/Te) vertical heterostructures: from first-principles study
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-13
    Honglin Li, Yuting Cui, Wanjun Li, Lijuan Ye, Lin Mu

    In the scope of two-dimensional (2D) material study, blue phosphorus (BP) is a new graphene-like layered structure that has been successfully synthesized in the experiment after it was theoretically proved to be thermostable. These 2D structured functional materials have great potential in the next-generation nanoscale electronic devices for their unique features. Here, we composite BP and monolayer WX2 (X = S/Se/Te) based on van der Waals force (vdW) interaction to obtain well-defined type-II band alignment heterostructures. A systematic theoretic study was conducted to explore the interlayer coupling effects and the bands’ re-alignment of the BP–WX2 heterostructure after the strain was applied. Nowadays, many researches have proved that 2D materials can be used to degrade pollutants or used as a potential photovoltaic cell material to obtain high performance. We here twist BP and WX2 (X = S/Se/Te) into different angles to lay a theoretical framework on the band alignment and carriers’ separation. It reveals that the electronic properties of freestanding BP and WX2 can be roughly preserved in the corresponding heterostructures. Upon applying strain, band alignment exhibits significant adjustability through varying external strain. The heterostructures are type-II in a certain strain range, within which the carriers can be effectively separated spatially. These heterostructures undergo a transition from semiconductor to metal when a certain strain is imposed. This work not only provides a deep insight into the construction of heterostructures, but presents a new possibility for strain engineering that is both flexible and feasible and can be used for diverse applications.

    更新日期:2020-01-13
  • Exploring the direct effect of intermediate band semiconductor materials on the structural, thermal and optical properties of PMMA nanocomposite
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-11
    M. H. Abdel-Kader, Mohamed Bakr Mohamed

    In this work, polymethylmethacrylate (PMMA) doped with SnS2, Sn0.75Fe0.25S2, and Sn0.75Cr0.25S2 nanoparticles films were prepared using both thermolysis and casting procedures. The purity, structural and shape of the nanofillers were confirmed by Rietveld refinement method. The compositional changes for nanocomposite films were studied by energy dispersive spectrometry technique. Nanoparticles morphology and particle size were examined by transmission electron microscopy (TEM) technique. Proper interactions between added nanofillers and the polymer matrix were discussed in detail by Fourier transform infrared spectroscopy technique (FTIR). The variations in the FTIR absorption bands position and their shape proved the effect of doping on the composite films. The effect of dopant elements on the thermal properties of PMMA polymer matrix has been investigated by thermogravimetric analysis (TGA). Results showed an improvement in the degradation temperature of doped polymers compared to undoped ones. Clear regular arrangements of images for nanoparticles and composite films have been represented by scanning electron microscopy (SEM). Different optical parameters have been examined using UV–vis spectroscopy technique. Due to the high transmittance values in the wavelength range of 320–800 nm, the formed composite films could be used as protective window layers for solar cells. The energy gap values decreased from 4.3 eV for undoped PMMA polymer to 4, 3.85, and 3.16 eV depending on the doping element.

    更新日期:2020-01-13
  • Oxyfluoro-tellurite-zinc glasses and the nuclear-shielding ability under the substitution of AlF 3 by ZnO
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-10
    M. I. Sayyed, Hakan Akyildirim, M. S. Al-Buriahi, Eloic Lacomme, Rachid Ayad, Giovanni Bonvicini

    This paper examines radiation-shielding abilities of oxyfluoro-tellurite-zinc glasses in the chemical form of AlF3–TeO2–ZnO under the substitution of AlF3 by ZnO. Gamma-ray- and neutron-shielding properties were tested in terms of mass attenuation coefficient (μ/ρ), half value layer, mean free path, effective atomic numbers (Zeff), effective electron density (Neff) and removal cross-section (ΣR). The μ/ρ values of the glasses were generated by Geant4 simulations over an extended energy range and then the generated data were confirmed via XCOM software. The results showed that both gamma-ray- and neutron-shielding efficiencies of the selected glasses evolved by substituting of AlF3 by ZnO. Nuclear radiation-shielding abilities of the current glass systems were compared with that of some conventional shielding materials and newly developed HMO glasses. It can be concluded that oxyfluoro-tellurite-zinc glasses could be useful to design novel shields for radiation protection applications.

    更新日期:2020-01-11
  • Influence of pH on nano-phosphor YPO 4 :2%Sm 3+ and luminescent properties
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-09
    Jinxiu Wu, Hengjun Jia, Mei Li, Huiling Jia, Zhaogang Liu

    Abstract Nano-phosphors YPO4:2%Sm3+ with different pH values were synthesized with hydrothermal method. The influence of pH on structure, morphology and fluorescence property of nano-phosphor was researched. The product composition, structure, morphology and luminescent properties were characterized and analyzed with X-ray diffractometry (XRD), scanning electron microscopy (SEM and EDS), infrared spectrometer (FT-IR), ultravoilet spectrometer (UV), fluorescence spectrophotometer (FL) and other instruments. The research results indicated that: the tetragonal crystal system structure of pure phase can be obtained at pH 1–5, and the mix phases of tetragonal and hexagon can be obtained at pH 7–9. The product morphology is fusiform at pH 1; spherical at pH 3–5; and bar-shaped at pH 7–9. As pH is gradually increased from 1 to 9, the fluorescence intensity of nano-phosphor is gradually decreased and then increased. The nano-phosphor with pH 1 has the maximum fluorescence intensity and fluorescence lifetime; moreover, it has better fluorescence thermal stability, and its activation energy is 0.233 eV.

    更新日期:2020-01-09
  • Spray-pyrolysis deposited La 1−x Sr x CoO 3 thin films for potential non-volatile memory applications
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-06
    Z. Viskadourakis, C. N. Mihailescu, G. Kenanakis

    In this work, thin films of the La1−xSrxCoO3 (0.05 < x < 0.26) compound were grown, employing the so-called spray-pyrolysis process. The as-grown thin films exhibit polycrystalline microstructure, with uniform grain size distribution, and observable porosity. Regarding their electrical transport properties, the produced thin films show semiconducting-like behavior, regardless the Sr doping level, which is most likely due to both the oxygen deficiencies and the grainy nature of the films. Furthermore, room-temperature current–voltage (I–V) measurements reveal stable resistance switching behavior, which is well explained in terms of space-charge limited conduction mechanism. The presented experimental results provide essential evidence regarding the engagement of low-cost, industrial-scale methods of growing perovskite transition metal–oxide thin films, for potential applications in random access memory devices.

    更新日期:2020-01-06
  • Solution-processed multilayer OLEDs with wide bandgap host
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-04
    Vahid Fallah Hamidabadi, Ali Bahari, Nordin Mirnia

    Abstract In the present work, efficient Solution-processed green light-emitting diodes based on a phosphorescent emitter with wide bandgap host are reported. A maximum efficiency of 25 cd/A was obtained using the green emitter tris[2-(p-tolyl)pyridine]iridium(III) blended with diphenyl-4-triphenylsilylphenyl-phosphine oxide as the emission layer. The maximum luminance exceeded 10,000 cd/m2, indicating that by simply blending a wide bandgap host with a phosphorescent emitter, efficient electroluminescence with a simplified device structure can be obtained.

    更新日期:2020-01-04
  • Production of W-based nanoparticles via spark erosion process along with their characterization and optimization for practical application in gas sensor
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-03
    Purushottam Kumar Singh, S. Mondal, A. K. Das, Santosh Kr. Mishra, D. K. Singh, S. K. Singh

    Tungsten-based (W-based) nanoparticles are produced through electrochemical spark erosion process. In this investigation, the parametric effects of voltage, tool rotation and pulse on time on production rate of W-based nanoparticles are analyzed. The shape and size of the produced nanoparticles are controlled through proper controlling of the referred parameters. Small size particles are obtained with low voltage and pulse on time, but with high tool rotation speed. The ANN-predicted values of this study are in close agreement with the observed experimental values for all the test formulations. It can be concluded that the process optimization via ANN modeling has been found to be very efficient for determining the performance linked with the electrochemical spark erosion process. The devised neural network provided an average prediction error of 1.52% for training and 3.78% in case of testing. The formulated models can predict results which are in close agreement with the test results. The produced W-based nanoparticles are used for sensing the NO2 and CO2 gases.

    更新日期:2020-01-04
  • The effects of varying the annealing period on the structure, morphology and optical properties of MgAl 2 O 4 :0.1% Mn 2+ nanophosphors
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-03
    C. Dlamini, M. R. Mhlongo, L. F. Koao, T. E. Motaung, T. T. Hlatshwayo, S. V. Motloung

    Abstract In this study, magnesium aluminate nanopowders doped with manganese ions (MgAl2O4:0.1% Mn2+) were prepared by citrate sol–gel technique. The consequences on the structural, morphological and optical properties when varying the annealing period (AP) at a fixed annealing temperature of 800 °C and dopant concentration (0.1% Mn2+) were investigated. The AP was varied at the range of 1–6 h. X-ray powder diffraction (XRD) results showed that doping with 0.1% Mn2+ and varying the AP did not influence the crystal structure of the host (un-doped) material. The scanning electron microscope (SEM) images suggested that doping does not influence the morphology of the prepared nanopowders and varying the AP slightly influence the particle size. Transition electron microscopy (TEM) image suggested that the crystallite sizes were below 15 nm. The ultraviolet–visible (UV–Vis) diffuse reflection spectroscopy showed that the band gap of the MgAl2O4:0.1% Mn2+ can be tuned from 5.04 to 4.58 eV with varying AP. Photoluminescence (PL) results showed two emission peaks located at around 413 and 655 nm. They were attributed to the defect levels within the host material and to the (4T1 → 6A1) transitions of Mn2+, respectively. Increasing the AP significantly influences the luminescence of the prepared powders. The CIE coordinate results showed that the bluish emission colour can be changed to the violet region when AP was increased.

    更新日期:2020-01-04
  • 3-D magneto-electro-thermal analysis of layered nanoplate including porous core nanoplate and piezomagnetic face-sheets
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-03
    M. Arefi, M. Kiani, O. Civalek

    Abstract In the present article, three-dimensional size dependent thermal analysis of three-layered nanoplate with porous graded core and two piezomagnetic face-sheets is studied based on nonlocal strain gradient theory considering thickness stretching effect. The sandwich nanoplate standing on an elastic foundation and face layers are exposed to electric/magnetic potentials. Porosity is evenly and unevenly repartitioned thorough thickness of the core. To predict both reduction and enhancement of stiffness in small scales, a nonlocal parameter and a strain gradient parameter is used for analysis. The governing equations are derived using the principle of virtual works based on sinusoidal shear and normal deformation theory. The small size effect is obtained exploiting Eringen’s nonlocal elasticity theory. The influences of the porosity coefficient, temperature parameters, electric/magnetic potential, boundary conditions (simply supported and clamped) and parameters of foundation on bending, electrical, and magnetic behaviors of the sandwich nanoplate are presented and discussed.

    更新日期:2020-01-04
  • Structural and electrical investigations of pure and rare earth (Er and Pr)-doped NiO nanoparticles
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-03
    J. Al Boukhari, A. Khalaf, R. Awad

    Applying the coprecipitation technique, we synthesized PVA-capped Ni0.98RE0.02O (RE = Er md Pr) nanoparticles. Thermogravimetric analysis (TGA) was performed to study the thermal stability of the prepared samples to choose the calcination temperature accordingly. Thermal stability was attained at ~ 823 K with no further thermal decomposition beyond. The crystallinity and phase formation of the prepared samples were confirmed by powder X-ray diffraction XRD. Studying the effect of RE3+ doping on the structural parameters of NiO nanoparticles was facilitated by X-ray peak profile analysis, based on the Debye Scherer model, Williamson–Hall model and size strain plot. The doped samples exhibited smaller lattice parameter and strain, with the minimum strain along the (200) direction. Also, a smaller crystallite size was found for the doped samples, depending on the dopant’s ionic radius, giving rise to higher dislocation density and specific surface area. Transmission electron microscopy (TEM) proved the nanoscale of the prepared samples, in agreement with the XRD outcomes, and revealed slight agglomeration of homogeneous nanoparticles. DC conductivity indicated the semiconducting behavior of the prepared samples, triggered by Ni2+ vacancies. Hopping mechanism was found to be the conduction process with two activation energies, depending on the temperature range of study. The dielectric behavior was explained by Maxwell–Wagner interfacial polarization, in agreement with Koop’s theory. The correlated barrier hopping mechanism CBH was found to be the conduction mechanism. Moreover, the Nyquist plot was investigated. Doping by rare earth elements resulted in an increase in dielectric constant, AC and DC conductivities.

    更新日期:2020-01-04
  • Influence of ZrO 2 on gamma shielding properties of lead borate glasses
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-03
    A. S. Abouhaswa, M. S. Al-Buriahi, M. Chalermpon, Y. S. Rammah

    In this paper, new lead borate glass system in the chemical form of 40B2O3–40PbO–20Li2O3–xZrO2; where x = 0, 0.25, 0.50, 1, and 1.5 mol% has been synthesized. Gamma-ray shielding properties of these glasses have been tested in terms of mass attenuation coefficient (μ/ρ), half value layer (HVL), effective atomic number (Zeff), mean free path (MFP), and exposure build-up factor (EBF). The μ/ρ values of the prepared glasses were generated by FLUKA Monte Carlo simulations over an extended energy range of 0.015–15 MeV, and then, the generated data were verified using the calculated values of XCOM software. The results showed that gamma-ray shielding ability of BPLZ0.00 is superior among the other prepared glasses. Moreover, the gamma-ray shielding properties of the current glass system have been compared with that of some commercial glasses and newly developed HMO glasses. It can be concluded that the prepared glass system could be useful to design and/or develop novel shields for radiation protection applications.

    更新日期:2020-01-04
  • Bio-inspired iron oxide nanoparticles using Psidium guajava aqueous extract for antibacterial activity
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-02
    Ngozi Madubuonu, Samson O. Aisida, Ishaq Ahmad, S. Botha, Ting-kai Zhao, M. Maaza, Fabian I. Ezema

    Abstract Bio-inspired synthesis of iron oxide nanoparticles (FeONPs) has been carried out by eco-friendly, low cost, and facile method using an aqueous extract of Psidium guajava (PG) leaf as a potential reducing agent. The obtained FeONPs were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), and energy-dispersive spectroscopy techniques. The surface plasmon resonance peak of FeONPs was found to be 310 nm. The FTIR spectra analysis indicates the presence of various functional groups in PG extract that are responsible for the biosynthesis of FeONPs. The XRD confirmed that FeONPs were indexed into the cubic spinel lattice structure. The SEM and TEM analysis confirmed the spherical morphology of FeONPs with particle size ranging from 1 to 6 nm. The superparamagnetic nature of the formulated FeONPs was determined using VSM. The FeONPs formulated inhibit the growth of six human pathogenic strains with strong activity chiefly against Escherichia coli and Staphylococcus aureus at low concentration when compared to other standard antibacterial drugs. It is noteworthy that the formulated FeONPs are efficient as an antibacterial agent.

    更新日期:2020-01-04
  • Performance enhancement of thin-film solar cell using Yagi–Uda nanoantenna array embedded inside the anti-reflection coating
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-02
    Abhishek Pahuja, Manoj Singh Parihar, V. Dinesh Kumar

    A modification to the conventional anti-reflection coating (ARC) is proposed to improve the performance of the amorphous silicon solar cells. The performance is improved by replacing the conventional anti-reflection coating (ARC) by a modified ARC. The modified ARC has an embedded array of silver Yagi–Uda nanoantenna. Due to the highly directive and broadband characteristics of Yagi–Uda nanoantenna, the modified ARC minimizes the reflection over large range wavelengths and guides the incoming solar radiation towards absorber layer effectively which results in increased absorption and subsequent increase in the short-circuit current density. Solar cell with proposed ARC exhibits 1.66 times improved short-circuit current density and 1.43 times increased conversion efficiency. To the best of our knowledge, this is the first report on a Yagi–Uda nanoantenna incorporated in a solar cell to improve its performance.

    更新日期:2020-01-04
  • High-performance microwave absorption properties of Ti 3 SiC 2 /Al 2 O 3 coatings prepared by plasma spraying
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-02
    Dong Zhao, Shaoqiu Xia, YongGuang Wang, Mingdi Wang

    Abstract The Ti3SiC2/Al2O3 coatings were prepared by plasma spraying process for the microwave absorption application. The coatings showed a dense structure with a few pores and unmelted region, and the Ti3SiC2 distributes uniformly in the coatings. The XRD was used to identify the phase composition of the coatings. The results indicated that the as-sprayed Ti3SiC2/Al2O3 coatings were composed of α-Al2O3 and γ-Al2O3, Ti3SiC2, TiC and Ti5Si3. The TiC and Ti5Si3 phases resulted from the Ti3SiC2 decomposition during the plasma spraying process. The complex permittivity of Ti3SiC2/Al2O3 coatings enhanced significantly with increasing the Ti3SiC2 content. When the Ti3SiC2 content was 20 wt. % and the coating thickness was 1.3 mm, the RL value of the coating can reach a minimum of − 24.4 dB at 11.1 GHz and RL value ≤ − 10 dB bandwidth in the frequency range of 10.1–12.4 GHz. Spherical instrumented scratch had been carried out on the Ti3SiC2/Al2O3 coatings to investigate the single-point abrasive wear behavior. Typical brittle fracture such as microcracks in the residual groove and grain dislodgement was observed in Ti3SiC2/Al2O3 coatings.

    更新日期:2020-01-04
  • Analysis of varying Gd 3+ concentrations on the structure and optical properties of ZnAl 2 O 4 :0.1% Eu 3+ ; x % Gd 3+ (0 ≤ x ≤ 1.2) synthesized via citrate sol–gel method
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-02
    V. M. Maphiri, Y. Dwivedi, L. F. Koao, R. E. Kroon, S. V. Motloung

    We report the preparation of 0.1% Eu3+; x% Gd3+ (0 ≤ x ≤ 1.2) ZnAl2O4 phosphors using the citrate sol–gel method. X-ray diffraction (XRD) data revealed that all annealed samples consisted of the single phase of cubic ZnAl2O4 structure. The scanning electron microscopic (SEM) images indicated pronounced effect of dual doping on the surface morphology of the phosphor. The estimated crystal sizes estimated by the XRD was confirmed by the high-resolution transmission electron microscopy (HR-TEM) to be approximately around 20 nm. The photoluminescence (PL) spectroscopy results revealed four distinct emission peaks located at 393, 400, 578 and 618 nm. The peaks at around 393 and 400 nm were attributed to the defect levels located at different positions on the host material (ZnAl2O4). The emission peak at 578 and 618 nm were attributed to the 5D0 → 7F1 and 2D0 → 7F2 characteristic transition within the Eu3+ ions. The International Commission on Illumination (CIE) colour coordinates revealed that the emission colour was not influenced by varying the concentration of Gd3+.

    更新日期:2020-01-04
  • A microwave-absorbing property of super-paramagnetic zinc–nickel ferrite nanoparticles in the frequency range of 8–12 GHz
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-02
    Luong Thi Quynh Anh, Nguyen Van Dan

    Microwave-absorbing samples were fabricated using carbon black powder, super-paramagnetic Zn0.8Ni0.2Fe2O4 nanoparticles dispersed in a SiO2 matrix, epoxy resin, and hardener. The paint was then coated onto a steel substrate. The effects of super-paramagnetic Zn0.8Ni0.2Fe2O4 nanoparticles content (0–1.75 wt%) and different coating thickness (1–2.5 mm) on microwave absorption ability in the X-band frequency range (8–12 GHz) have been studied. The results showed that paint sample containing only carbon black (20 wt%) and epoxy resin (80 wt%) expressed low microwave absorption ability at 10 GHz centered frequency (≈ 67% absorption percentage). The super-paramagnetic Zn0.8Ni0.2Fe2O4 nanoparticles strongly affected the microwave-absorbing ability. A sample of 1.5 wt% super-paramagnetic Zn0.8Ni0.2Fe2O4 nanoparticles content exhibited highest microwave absorption at 10 GHz centered frequency (≈ 99% power attenuation). Higher coating thicknesses (1–2.5 mm) led to greater microwave absorption and reached a very high absorption of 2 mm thickness (≈ 99% absorption percentage at 10 GHz centered frequency).

    更新日期:2020-01-04
  • Physical, optical and shielding features of Li 2 O–B 2 O 3 –MgO–Er 2 O 3 glasses co-doped of Sm 2 O 3
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-02
    M. H. A. Mhareb

    The glassy systems acquired much concern for using in diverse implementations. For this cause, different concentrations of samarium oxide co-doped lithium magnesium borate erbium oxide were prepared by the melt-quench technique. Several physical and optical properties of all prepared glass samples were computed. XRD patterns for all prepared samples show the presence of a broad peak and the lack of sharp peaks emphasize the amorphous nature of all prepared glass samples. FTIR confirms the presence of the functional group BO3 and BO4. Ten considerable absorption bands are evident in the UV–Vis–NIR spectra of the S0 glass sample which are attributed to the presence of Er3+ ions. S1–S4 samples revealed additional six peaks that are attributed to Sm3+ ions. In addition, photon and neutron shielding features were evaluated for all prepared samples which enhanced by the increment of Sm3+ contents. In conclusion, the studied glass composition can be useful in several applications such as solid-state laser, telecommunication, and radiation shielding.

    更新日期:2020-01-04
  • Investigation of barium borate glasses for radiation shielding applications
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-02
    M. S. Al-Buriahi, C. Sriwunkum, Halil Arslan, Baris T. Tonguc, Mohamed A. Bourham

    Abstract In this paper, five barium borate glasses in the chemical composition of \(40\hbox {SiO}_2\)–\(10\hbox {B}_2\hbox {O}_3\)–xBaO–(45-x)CaO–yZnO–zMgO (where \(x = 0, 10, 20, 30\), and 35 mol\({y}=z=6\,\hbox { mol}\%\)) have been reported for radiation protection applications. Mass attenuation coefficient (\(\mu /\rho\)) was obtained in the photon energy range of 356 keV–2.51 MeV using PHITS code for the proposed glasses. The \(\mu /\rho\) values generated by PHITS code were verified by using both of FLUKA code and XCOM program. The \(\mu /\rho\) values were then applied to derive effective atomic number (\({Z}_\mathrm{eff}\)), mean free path (MFP), and half value layer (HVL) for all the glasses involved. Additionally, the fast neutron removal cross sections were calculated for each glass. The results reveal that gamma-shielding properties evolve upon adding BaO content in the glasses. It is found that SBC-B35 glass has superior shielding capacity against gamma rays and fast neutrons as compared with different conventional shielding materials and commercial glasses.

    更新日期:2020-01-04
  • Device physics and design of hetero-gate dielectric tunnel field-effect transistors with different low/high- k EOT ratios
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-02
    Chun-Hsing Shih, Nguyen Dang Chien, Huy-Duy Tran, Phan Van Chuan

    Abstract The hetero-gate dielectric (HGD) structure was recently experimentally demonstrated to enhance the electrical performance of tunnel field-effect transistors (TFETs). This study examined the mechanisms underlying the HGD structure functioning and investigated the design of the structure to enhance the electrical characteristics of TFETs with different ratios of low- and high-k equivalent oxide thicknesses (EOT). The on-current enhancement by the source-side dielectric heterojunction, which directly modulates the on-state tunnel width, was much larger than that by the drain-side dielectric heterojunction, which indirectly affects the on-current by modulating the subthreshold tunnel width. The subthreshold swing is improved by the formation of a conduction band well near the source-channel junction. However, the swing improvement is limited by the hump effect when this local potential well approaches the source. The optimal design of the HGD structure and the maximal enhancement of on-current considerably depend on the EOT ratio of low- and high-k dielectrics. The on-current is most enhanced by the optimized HGD structure at a low/high-k EOT ratio of ten times, that is, approximately 160% of the on-current of the uniform high-k TFET counterpart. Due to the continuous trend of increasing the k-values or scaling EOTs, understanding the dependence of device physics and design on the low/high-k EOT ratio is crucial to optimize the performance of HGD-TFETs.

    更新日期:2020-01-04
  • Dynamic testing of nanosecond laser pulse induced plasma shock wave propulsion for microsphere
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-02
    Haichao Yu, Hanyang Li, Xiao Wu, Jun Yang

    The present work introduces a laser pulse micro-propulsion system for microsphere propulsion and uses the micro-propulsion system to investigate the propulsion mechanism, propulsion mode, and potential application. The plasma (or shock wave) generation at the tip of micro-propulsion system due to the laser energy emitted from the system tip exceeds the ionization threshold of air. Meanwhile, the propagation characteristics of shock wave such as propagation distance, velocity and pressure have been calculated, and then succeeded in realizing propulsion of microsphere via shock wave recoil effect. The result demonstrated that the propulsion is dominated by the shock wave ejection mechanism. In addition, the laser energy and microsphere diameters are varied to study the influence on microsphere movement efficiency. The experimental results show that the microsphere movement efficiency depends on the laser energy and microsphere size. Analysis of the experimental and the simulation results suggest that the micro-propulsion system may have significant influence on directional propulsion of particles from the substrate surface.

    更新日期:2020-01-02
  • A critical study on the magnetic properties of ultrafine cobalt ferrite nanoparticles synthesized by polyethylene glycol assisted sol–gel method
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-02
    G. R. Patta, V. Ravi Kumar, B. V. Ragavaiah, N. Veeraiah

    Abstract High coercive single-domain CoFe2O4 nanoparticles with the minimal average size (7.6–12.8 nm) were synthesized by polyethylene glycol (PEG) assisted sol–gel method and subsequent annealing at different temperatures. The prepared samples were characterized by XRD, TEM, TG-DSC, and FTIR techniques. The XRD and TEM studies indicated the size and shape of the particles are highly dependent on annealing temperature. Magnetic properties of the developed cobalt ferrite nanoparticles were found to be dependent on their size and shape. The particles annealed at lower temperatures (about 400 °C) are found to be near spherical in shape and as the annealing temperature is increased from 400 to 800 °C, the shape of the particles is observed to be transformed from spherical to octahedron through intermediate cubic shape. Magnetic parameters viz., saturation magnetization (Ms) and remnant magnetization (Mr) exhibited a study increase with increase of the particle size. The coercive field, Hc exhibited a non-monotonic behavior with distinct maximum at about 700 °C and suggested the transition from single-domain to multi-domain state. The magneto-crystalline anisotropy constant, K, determined from Stoner–Wohlfarth relation, exhibited the maximum value, 10.74 × 106 erg/cm3 for the samples annealed at 800 °C. In addition, the magnitude of (BH)max (which is considered as the efficiency of cobalt ferrite nanoparticles for using as permanent magnets) exhibited the maximum value (1.04 × 106 GOe). Such higher values of these two parameters suggest the possible applications of the studied material in magnetic recording, high density digital recording disks and in magnetic sensors.

    更新日期:2020-01-02
  • The effect of tension twin on the dynamic recrystallization behavior in polycrystal magnesium by atomistic simulation
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-02
    Shichao Song, Yu Wang, Yang Wang, Xi Wang, Zhen Zhang

    Abstract To investigate the \(\{10\bar{1}2\}\) tension twin effects on the dynamic recrystallization structure evolution in magnesium alloys, the compression deformation of a magnesium polycrystal containing an initial \(\{10\bar{1}2\}\) tension twin under different loading directions was simulated by molecular dynamics method. The results showed that the dynamic recrystallization phenomena only occurred when loading normal to twin boundary. By tracking atoms’ motion, it was found that the twin dynamic recrystallization microstructure evolution could be divided into two steps. Step one: basal partial dislocations nucleated near twin boundary, leading to large area of stacking faults; Step two: due to the accumulation of strain energy, non-basal slip systems nucleated in the stacking faults region, promoting the stacking faults to recover to hexagonal close-packed structure and forming the new grains. When loading parallel to twin boundary, the twin boundary migration dominated the deformation process, which released the strain energy and inhibited the nucleation of dynamic recrystallization.

    更新日期:2020-01-02
  • First synthesis of monodispersed microparticles of copper oxide films by pulsed spray pyrolysis (PSP): structural, optical, and morphological investigations
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-01
    A. Chetoui, M. Ghemid, M. R. Khelladi, A. Zouaoui

    This work describes the first synthesis of monodispersed systems by capitalizing on the Leidenfrost effect. We report herein the synthesis of monodispersed particles of copper oxide films by spray pyrolysis technique in pulsed mode. The aim of this work is to investigate the effect of different pulse sequences on the particles’ size. One pulse sequence consists of three spray-on durations \(\tau_{{{\text{on}}}}^{{{\text{spray}}}}\) separated by two spray-off \(\tau_{{{\text{off}}}}^{{{\text{spray}}}}\) time intervals. In this work, we have varied the \(\tau_{{{\text{off}}}}^{{{\text{spray}}}}\) duration from 15 to 45 s by a step of 10 s and the spray-on period is kept constant on 15 s. The effect of the spray-off duration on structural, optical and morphological properties of copper oxide material is reported. Indeed, the obtained films are characterized by XRD, spectrophotometer, Raman spectroscopy, AFM, and SEM. It was revealed that the spray-off duration has a great impact on the copper oxide particles’ size.

    更新日期:2020-01-02
  • Superhydrophobic and superhydrophilic properties of laser-ablated plane and curved surfaces
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-01
    G. S. Boltaev, S. A. Khan, R. A. Ganeev, V. V. Kim, M. Iqbal, A. S. Alnaser

    Abstract We examine the hydrophobic and hydrophilic properties of the plane and curved surfaces of different materials ablated using 5 ns laser pulses in air. The difference in the contact angles between liquid and surface of the modified graphite and AlNiCo alloy rods using different fluencies of the ablating pulses are demonstrated. The wetting contact angle of ablated graphite rod was found to be 147°, i.e., the modified curved surfaces demonstrated the superhydrophobic properties. On the other hand, the superhydrophilic properties, with 7° wetting contact angle, were demonstrated in the case of ablated aluminum alloy. A schematic model was proposed for the application of the graphite rod as a membrane for the oil–water separation.

    更新日期:2020-01-02
  • Large magnetocaloric effect in La 0.75 Ca 0.25–x Na x MnO 3 (0 ≤ x ≤ 0.10) manganites
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-01
    Souhir Bouzidi, Mohamed Amara Gdaiem, S. Rebaoui, J. Dhahri, E. K. Hlil

    We have studied the effect of a partial substitution of Ca2+ by Na+ on the structural, magnetic and magnetocaloric properties of the mixed valence perovskites \({\text{La}}_{{{0}{\text{.75}}}} {\text{Ca}}_{{{0}{\text{.25 - }}x}} {\text{Na}}_{x} {\text{MnO}}_{{3}}\) (0 ≤ x ≤ 0.10), prepared by the flux method. X-ray diffraction studies revealed that our samples crystallize in the orthorhombic structure with a Pbnm space group. Rietveld analysis showed that MnO6 octahedron has a little distortion and that θMn–O–Mn bond angles increase with increasing Na+ content. The field cooled (FC) and zero field cooled (ZFC) magnetizations indicated that our samples have a paramagnetic-ferromagnetic phase transition, when decreasing temperature. A small deviation was observed between FC and ZFC curves. This deviation can be explained by the competition between the ferromagnetic and antiferromagnetic interactions, leading to a glassy behavior. The Curie temperature, TC, increased from 268 K for x = 0 to 278 K for x = 0.10. The magnetizations isotherms of our compounds, with a second-order phase transition, were investigated. For the x = 0.10 sample, the maximum of the magnetic entropy change was found to be 3.15 and 6.44 J kg−1 K−1, under an applied magnetic field of 2 and 5 T, respectively. Moreover, it has important relative cooling power values of about 134.82 and 317.79 J kg−1, under the same applied magnetic field. In addition, rescaled entropy data collapsed into the same curve, which indicates the universal behavior for the magnetocaloric effect (MCE) in our compounds. These materials could be potential candidates as working substances in magnetic refrigeration.

    更新日期:2020-01-01
  • Opto-structural properties of Si-rich SiN x with different stoichiometry
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-01
    F. Tiour, B. Benyahia, N. Brihi, A. Sari, Br. Mahmoudi, A. Manseri, A. Guenda

    Abstract This study deals with the fabrication and characterization of silicon nanoparticles in a SiNx dielectric matrix to have thin films of different gap energies, films essentially based on silicon. Hydrogenated silicon-rich nitride films SiNx:H with different stoichiometry X = N/Si were grown on Si substrate using industrial low-frequency plasma-enhanced chemical vapor deposition (LF-PECVD). Optical, electrical, and structural properties of the obtained films have been studied after rapid thermal annealing at 950 °C. The GIXRD and Raman analysis demonstrate that the films contain simultaneously the hexagonal β-Si3N4 phase and crystalline silicon nanoparticles and the average size of silicon nanocrystallites is within the range of 2.5–11 nm according to the stoichiometry. A strong visible photoluminescence (PL) can be observed in silicon nitride and the evolution of PL with the NH3/SiH4 ratio is correlated with the evolution of the structure. The layers having a luminescence in the visible region present a photocurrent (PC) in the high-energy region. PC spectroscopy has clearly demonstrated the existence of increased absorption on the high-energy side associated with Si-Ncs and confirms the potential of Si-Ncs for photovoltaic applications.

    更新日期:2020-01-01
  • Reduced graphene oxide/silver nanohybrid as a multifunctional material for antibacterial, anticancer, and SERS applications
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-23
    Priya Parvathi Ameena Jose, M. S. Kala, Alphonsa Vijaya Joseph, Nandakumar Kalarikkal, Sabu Thomas

    Abstract Development of multipurpose materials like graphene–silver hybrid nanocomposite has attracted much appreciation in recent years because of their improved synergistic properties like higher effective surface area, high electron mobility, stability, and biocompatibility. Here, we report the synthesis, characterization, and multifunctional properties of reduced graphene oxide/silver (rGO/Ag) nanohybrid. This novel material shows promising results against two antibiotic resistant bacteria—Escherichia coli and Bacillus subtilis. The toxicity study on Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (Bacillus subtilis) was done by the evaluation of cell viability through Resazurin-based Microtitre Dilution Assay (RMDA). We have observed that this nanohybrid is more effective against Bacillus subtilis than Escherichia coli which is different from the conventional observations. With Dalton’s Lymphoma Ascites cells (DLA), we have examined short-term in vitro cytotoxicity of this nanohybrid by trypan blue dye exclusion technique. The anticancer response of this nanohybrid was recorded with Human Colon epithelial carcinoma cells (HCT-15) as well by MTT assay. We also report SERS effect of (rGO/Ag) substrate in detecting very small amounts of Rhodamine B molecules by estimating the analytical enhancement factor.

    更新日期:2019-12-25
  • Optical surface second harmonic generation from plasmonic graphene-coated nanoshells: influence of shape, size, dielectric core and embedding medium
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-21
    Nader Daneshfar, Zeinab Noormohamadi

    Abstract We study optical surface second-harmonic generation (SHG) from the plasmonic nanoshells because they can improve and enhance nonlinear optical effects. We also investigate the SHG from the surface of spherical and cylindrical core-shell nanoparticles coated with a strong nonlinear material such as graphene due to its attractive plasmonic behaviour and unique properties of the surface plasmons in graphene. We demonstrate theoretically a giant and tunable second-order harmonic radiation which enhanced through the excitation of the surface plasmon resonance, can be observed at the surface of both spherical and cylindrical nanoshells because of symmetry-breaking at interface, which makes SHG as a valuable and powerful technique for applications in sensing and surface spectroscopy. We present the surface SHG strongly depends on the particle shape and size, the dielectric of embedding medium and core, the type of metal and graphene as a coating nonlinear material.

    更新日期:2019-12-22
  • Experimental and computational perspectives on linear and non-linear optical parameters of an orthorhombic crystal for optical limiting applications
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-21
    Sarath Ravi, Rakhi Sreedharan, K. R. Raghi, T. K. Manoj Kumar, K. Naseema

    Abstract 4-Dimethylaminopyridinium 3,5-dinitrobenzoate (DMAPDNBA), a charge transfer complex, was synthesized and successfully grown by slow evaporation solution growth technique. Single-crystal X-ray diffractogram reveals that the material crystallizes in orthorhombic system with non-centrosymmetric space group P212121 with cell parameters a = 5.92 Å, b = 13.77 Å, c = 18.64 Å, and V = 1519 Å3. Powder XRD and FTIR spectral investigation were carried out to analyse the crystallinity of the material and for assigning vibrations to identify the different functional groups existing within the material. The optical transmittance in the visible and near IR (400–800 nm) regions with lower cutoff wavelength of 227 nm, luminescence spectrum, and the optical band gap of 5.45 eV sufficiently fulfilled the requirement for non-linear optical applications. The thermal exploration analysis (TG–DSC) confirmed the stable nature of the compound up to 190 °C, and dielectric constant measurement of the obtained sample enhanced the property of non-linear optical activity at higher frequencies. The mechanical property of DMAPDNBA was evaluated using Vickers’s hardness test which confirmed that the material belonged to the soft category. The frequency conversion efficiency of the grown sample was measured to be eightfold that of the reference potassium dihydrogen phosphate, which exploits the potentiality of the charge transfer complex to be used as a promising candidate for various laser-assisted NLO applications. Third-order non-linearity was measured adopting Z-Scan technique, and the optical limiting/switching efficiency of the complex was verified with the optical limiting threshold value of 10.64 J/cm2 and figure of merit property, confirming the capability of the material for switching applications. The threshold value of laser damage was found to be 1.74 GW/cm2. Theoretical investigations were performed using density functional theory (DFT-B3LYP) approach to estimate and predict various linear and non-linear optical properties of the DMAPDNBA complex. The first-order hyperpolarizability value of the DMAPDNBA molecule was found to be 19 times that of the standard organic crystal, urea. In short, all the above findings designate the candidature of the charge transfer complex, DMAPDNBA, for photonic applications.

    更新日期:2019-12-22
  • In situ observation of electric-field induced magnetic domain evolution in (Ba,Ca)(Ti,Zr)O 3 –CoFe 2 O 4 multiferroic films
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-21
    Xianming Ren, Yemei Han, Zhi Tao, Hui Li, Wei Li, Zhengchun Yang, Fang Wang, Jinshi Zhao, Kailiang Zhang

    The integration of ferroelectric and ferromagnetic promises an essential strategy of obtaining high performance electronic devices. In this work, we demonstrate in situ observation of electric field induced magnetic domain structure evolution for 0.5Ba(Ti0.8Zr0.2)O3–0.5(Ba0.7Ca0.3)TiO3–CoFe2O4 (BZT–0.5BCT/CFO) films, which manifests the magnetoelectric (ME) coupling between ferroelectric BZT–0.5BCT and ferrimagnetic CFO. The multiferroic behaviors of BZT–0.5BCT/CFO bilayers thin films were characterized by measuring ferroelectric domains, ferroelectric and ferrimagnetic hysteresis loops. The magnetic domain structure were investigated as functions of electric field, when the sample is applied with a voltage of 3 V, approximately 49.2% of the magnetization domain was varied in CFO thin films. The modulation of the domain structure could be attributed to the strain-induced mechanical transduction between the ferroelectric and magnetic films and modulation of the electron density of the CFO films. Direct observation of electric field induced magnetic domain evolution is significant since it gives a direct evidence of magnetoelectric coupling effect.

    更新日期:2019-12-21
  • Structure and microwave dielectric properties of low-temperature sinterable A 2.5 VMoO 8 (A = Mg, Zn) molybdovanadate ceramics
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-21
    R. Naveenraj, N. S. Arun, R. Ratheesh

    A2.5VMoO8 (A = Mg, Zn) molybdovanadate ceramics have been prepared through conventional solid-state ceramic route. Phase purity of these ceramics was confirmed using powder X-ray diffraction studies. Co-existence of both MoO42− and VO43− tetrahedra in the unit cell of these molybdovanadates has been identified through laser Raman spectroscopy. Sintered A2.5VMoO8 (A = Mg, Zn) ceramics show homogenous and dense microstructure. Mg2.5VMoO8 ceramic has a dielectric constant (εr) of 8.8, unloaded quality factor of 4800 at 10.85 GHz and temperature coefficient of resonant frequency (τf) of -58 ppm/ ℃ whereas Zn2.5VMoO8 ceramic exhibits a dielectric constant of 11.5, unloaded quality factor of 2500 at 9.18 GHz and temperature coefficient of resonant frequency τf of 115 ppm/ ℃.

    更新日期:2019-12-21
  • Synthesis and characterization of cerium oxide nanoparticles using different solvents for electrochemical applications
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-20
    K. Sakthiraj, B. Karthikeyan

    Abstract Cerium oxide nanoparticles were synthesized through sol–gel method using different solvents which include water, acetone, ethanol and ethylene glycol. Cerium (III) nitrate hexahydrate and ammonium hydroxide were used as the precursors. The influence of the solvent on the structural, optical and electrochemical properties was investigated using powder X-ray diffraction, transmission electron microscope imaging, selected area electron diffraction (SAED), Fourier transform infrared spectroscopy (FTIR), UV–visible absorption spectroscopy, photoluminescence (PL) spectroscopy, cyclic voltammetry (CV) measurement and galvanostatic charge–discharge analysis. A significant change in the properties of the samples was observed in all the characterization techniques, and it was well discussed with the already reported data. Especially with the help of electrochemical studies, it was found that ethylene glycol used as a solvent can easily activate the surface defects in the crystal structure rather than other solvents. This may be due to the fact that the nanocrystalline cerium oxide contains interchangeable oxidation states (Ce4+ and Ce3+) resulting from the oxygen vacancy. The atmospheric molecular oxygen can easily react with these surface oxygen vacancies and forms highly active atomic oxygen over the surface of the material which enhances the electrochemical property of the material. The results of the present study provide a promising platform for developing a cathode material for electrochemical applications.

    更新日期:2019-12-20
  • The effect of stoichiometric ratio of Mg/SiO 2 and annealing on physical properties of silicon nanoparticles by magnesium-thermic chemical reduction process using the SiO 2 precursor
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-19
    H. Torkashvand, M. M. Bagheri-Mohagheghi

    In this paper, silicon nanoparticles (Si-NPs) were prepared using silica (SiO2) mineral stone as raw material using magnesium-thermic chemical reduction method. The synthesis process involves extraction of silica (SiO2) powder from the raw material and then Si-NPs was prepared by chemical reduction of silica (SiO2) powder using the magnesium-thermic process. Two processes were done for synthesis: (a) magnesium-thermic reaction and annealing at T = 500 °C, 600 °C and 700 °C at N2 gas and (b) acid washing via HCl and HF. The stoichiometric ratio of Mg/SiO2 = 1:1, 1.5:1, 2:1 and 2.5:1 was also investigated in the chemical reduction conditions. To study the structure and morphology of nanoparticles, X-ray Diffraction (XRD) and Field Emission-Scanning Electron Microscope (FE-SEM) were used. Grown nanoparticles have a polycrystalline structure with spherical form with crystalline size of 20–40 nm. To study the optical band gap of Si-NPs and type of direct or indirect semiconductor, energy gap and absorption behavior of nanoparticles was investigated using the UV–Vis spectroscopy. The indirect band gap and blue shift comparison to bulk was observed at 3.62 eV, 3.47 eV and 3.43 eV for the samples synthesized in the temperatures of T = 500 °C, T = 600 °C and T = 700 °C, respectively. Also, the direct band gap was determined for nanopowders.

    更新日期:2019-12-20
  • Solution-processed sphere-like Cu 2 ZnSnS 4 nanoparticles for solar cells: effect of oleylamine concentration on properties
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-19
    E. M. Mkawi, Y. Al-Hadeethi, E. Shalaan, E. Bekyarova

    Abstract Quaternary Cu2ZnSnS4 (CZTS) nanoparticles of high quality have been synthesized utilizing rotary evaporation technique. The volume of the solvent, oleylamine (OLM), was found to affect the morphological, structural and electrical characteristics of the synthesized structures. The materials were characterized using various analytical techniques. XRD patterns and Raman measurements reveal that CZTS nanoparticles exist in a crystalline state with a kesterite structure. For OLM of 6 mL, transmission electron microscopy reveals the formation of spherical CZTS nanoparticles. Scanning electron microscopy analysis of the nanocrystal thin films clearly shows a crack-free, uniform-grain thin film with a particle size in the range between 1 and 2 µm. Ultraviolet–visible–near infrared (UV–Vis–NIR) spectra showed a direct band gap of 1.47 eV, which is close to the optimum value required for photovoltaic applications. The current synthetic strategy is rapid and simple, and it can be utilized for commercial application. Solar cells were built using the structure glass/Mo/CZTS/CdS/i-ZnO/AZO/Ag and were found to exhibit a conversion efficiency of about 2%.

    更新日期:2019-12-19
  • Research on sliding angles of water droplets on the hierarchical structured superhydrophobic surfaces
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-18
    Meirong Yi, Luqi Liu, Liting Wu, Xiaobing Li

    Certain plant leaves, such as the lotus leaf, are known to be superhydrophobic due to the hierarchical structures on the leaf surfaces. In this paper, two kinds of superhydrophobic plants leaves with hierarchical structured surface, including aged lotus and loropetalum chinense leaves, were introduced. Further, the surface structural models were established for the introduced leaves corresponding to their surface micromorphologies. More importantly, the theoretical modes for predicting sliding angles of liquid droplets on the introduced leaf surfaces were formulated. In addition, the role of surface parameters in determining the superhydrophobicity of hierarchical structured leaves was demonstrated effective. The results of this paper could be used as a guidance for designing desired superhydrophobic property of hierarchical surfaces.

    更新日期:2019-12-19
  • Influence of deposition temperature on the structural and dispersion parameters of TiO 2 thin films
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-18
    A. N. Fouda

    Polycrystalline TiO2 thin films were deposited onto quartz substrates using RF magnetron sputtering technique at different substrate temperatures (573 K, 623 K, 673 K, and 773 K). X-ray diffraction (XRD) measurements revealed the isolation of anatase phase with (101) preferred crystal orientation for the film deposited at 773 K. Moreover, the topographical features of this film clarified the smoothness of the deposited films, with root mean square roughness (RMS) of 0.5 nm. The optical properties of the as-prepared thin films at different deposition temperatures was enlightened through structural correlation. Most of the films were transparent with transmittance intensity extending from 50 to 90% within the visible range. Due to the smoothness of the deposited films, the transmittance and reflectance spectra exhibited an oscillatory behavior. Additionally, from single effective oscillator model, the dispersion parameters were estimated. For the deposited films, the single oscillator energy (Eo), dispersion energy (Ed), lattice dielectric constant (εL), and infinite permittivity (ε∞) extended in the range (3.42 ~ 3.99), (9.83 ~ 24.12), (4.39 ~ 7.75), and (3.88 ~ 7.04), respectively.

    更新日期:2019-12-19
  • Effective mass dependence of the gyrotropic nihility in a BaM/6H-SiC multilayer structure
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-18
    M. Farhadi, M. R. Jafari, M. Shahmansouri

    We investigated the magnetic polaritons in a semi-infinite ferrite-semiconductor binary structure at the microwave region of the spectrum. The permittivity and permeability tensors of the structure depend on the various factors including the characteristic frequencies of the semiconductor and ferrite material, the thickness ratio of two layers, the external magnetic flux density and its frequency. By changing these factors, we can control the optical properties to achieve some extraordinary behaviors. By controlling and adjusting some accessible factors, the longitudinal components of both permittivity and permeability tensors simultaneously acquire zero. This region is identified as the gyrotropic nihility region. At this region, the waves can easily pass through this structure as its resistance to the passage of the electromagnetic waves is negligible. In this paper, we have studied the circumstances under which this extraordinary phenomenon may occur.

    更新日期:2019-12-19
  • Design and performance enhancement of doping-less field effect transistor with the help of negative capacitance technique
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-17
    Lubna Gajal, Naveen Kumar, S. Intekhab Amin, Sunny Anand

    The performance exploration of doping-less negative capacitance FET (NC-FET) has been proposed for the novelty of an exceedingly low power consumption device. A ferroelectric material, PZT (lead zirconate titanate), has been used as a gate insulator to perceive the effects of negative capacitance, and thus doping-less FET is modified into doping-less NC-FET for low power consumption. Ferroelectric materials are similar to dielectric material except for the property of polarization, and PZT gives adequate polarization rate with high dielectric capacitance and better reliability. In this pursuit, hysteresis behavior depends on the thickness of PZT (tFE) therefore suitable tuning of ferroelectric thickness is an important design parameter to optimize the device performance to achieve lower subthreshold swing (SS < 60 mV) at lower threshold voltage for the proposed doping-less NC-FET device. In addition, the thickness of PZT is varied for further improvement where it shows higher tFE values improve the hysteretic behavior and augmented value of PZT thickness preserve the device in a non-hysteretic mode which is responsible for the absolute improvement in this proposed device. After tFE = 6.23 × 10−5 cm, the operation of the proposed device drives the hysteretic mode. In this context, the electrical properties of the device have been inspected to demonstrate the hysteretic and non-hysteretic action.

    更新日期:2019-12-18
  • Structural, optical and magnetic behaviour of cobalt- and ferrous-doped zinc stannate nanoparticles synthesized by hydrothermal method
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-17
    L. Allwin Joseph, R. Ragu, M. Akilan, J. Emima Jeronsia, J. Prince Joshua

    Zinc stannate has attracted substantial interest owing to its unique properties making it a suitable ternary oxide for numerous applications. One of the most promising ternary semiconducting oxides, zinc stannate (Zn2SnO4) is more stable than binary semiconducting oxides such as ZnO and SnO2 because of its attractive physical properties and very high electrical conductivity. Nanoparticles of pure and doped Zn2SnO4 were synthesized via facile hydrothermal technique. Characterization methods such as XRD, FTIR, SEM, UV and VSM were carried out to study the behaviour of zinc stannate. X-ray diffraction analysis confirmed the phase purity and high crystalline nature of the synthesized sample. Scanning electron micrography illustrated its spherical morphology. The increment of bandgap was observed for the doped zinc stannate. The presence of functional groups was confirmed using FTIR spectrum. The magnetic property of the material was analysed using vibrational sample magnetometer and found to exhibit diamagnetic behaviour for pure zinc stannate and weak ferromagnetic property for Co- and Fe-doped Zn2SnO4. The attained results depict the excellent and exceptional structural, optical and magnetic properties which establish the use of Zn2SnO4 nanoparticles in a wide range of applications especially in the field of optoelectronic devices and spintronics.

    更新日期:2019-12-18
  • One-pot synthesis and gas sensitivity of SnO 2 nanoparticles prepared using two Sn salts of SnCl 4 ·5H 2 O and SnCl 2 ·2H 2 O
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-17
    Jing Wang, Shimin Liu, Xin Cao, Zhinuo Wang, Yu Guo, Xiaotong Li, Chaoqian Liu, Weiwei Jiang, Hualin Wang, Nan Wang, Sumei Wu, Hualong Tao, Wanyu Ding

    SnO2 nanoparticles were successfully synthesized by a novel one-pot route using two various Sn salts of SnCl4·5H2O and SnCl2·2H2O as raw materials, respectively. The thermogravimetric-differential scanning calorimeter (TG-DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and gas sensitivity measurement were characterized to determine the influences of salt type and calcination temperature on the thermal effect, crystal structure, crystallite size and gas sensitivity of SnO2 nanoparticles. Results indicated that the two series of samples had different crystallization process, crystallite size and gas sensitivity changed with calcination temperature. SnCl4·5H2O helped to promote crystallization, but SnCl2·2H2O suppressed the crystallization and crystallite growth even at the same calcination temperature. SnO2 nanoparticles calcined at 500 °C using SnCl4·5H2O and 250 °C using SnCl2·2H2O displayed better gas sensitivity because of high crystallinity and small crystallite size, possibly decreasing the number of boundary defects which can cause electron recombination as well as providing more reaction cites, respectively.

    更新日期:2019-12-18
  • Efficient materials for thin-film CdTe solar cell based on back surface field and distributed Bragg reflector
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-17
    Syed Asfandyar Ali Kazmi, Aimal Daud Khan, Adnan Daud Khan, Abdul Rauf, Waqas Farooq, Muhammad Noman, Haider Ali

    Modifications in the physical properties of photovoltaic materials lead to enhanced conversion efficiency of a solar cell. This paper focuses on the suitable material selection for the cadmium telluride (CdTe) solar cell with special emphasis on improving the electrical parameters such as open-circuit voltage Voc, short-circuit current density Jsc, fill factor FF, and efficiency ƞ. Simulation results showed that materials having wide bandgap are more appropriate for each layer in the proposed cell compared to small-bandgap materials. Moreover, the back metal contact, which acts as electrode and also used as light reflector, usually suffers from high intrinsic absorption losses. To reduce such losses, we replaced the metal contact by a highly reflective one-dimensional distributed Bragg reflector, which increases the optical path length in greater amount over a broad span of incident angles and frequencies, and subsequently enhances the performance of the cell. The measured electrical parameters of the proposed cell under global AM 1.5G conditions are JSC = 25.036 mA/cm2, Voc = 1.065 V, FF = 87.56%, and ƞ = 23.94%, respectively.

    更新日期:2019-12-18
  • Critical role of hydrogenation for creation of magnetic Cd–Cu co-incorporated TiO 2 nanocrystallites
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-16
    A. A. Dakhel

    Nanocomposite of titanium dioxide (TiO2) incorporated with cadmium/copper (Cd/Cu) ions was fabricated by the co-decomposition of a mixture of Ti, Cd, and Cu metal complexes. The crystalline structures were studied by the X-ray diffraction (XRD), which confirmed the formation of anatase and brookite mixture. The optical properties of the synthesized samples were measured by diffuse reflection spectroscopy (DRS). The bandgap red shift of host TiO2 due to Cd ions incorporation and blue shift due to Cu ions incorporation was detected and measured. The hydrogenation of the powder samples increased the carrier concentration and, thus blueshifted the bandgap. With the hydrogenation, all the synthesized samples, including undoped TiO2-acquired room temperature ferromagnetic (RT-FM) properties, which was attributed to the generation of oxygen (O) vacancies. The O-vacancies were reduced by extra annealing in air at 600 °C that eliminated the RT-FM. The magnetic measurements on Anatase/Brookite TiO2 nanocomposite doped with 3wt% Cd show a creation of a magnetic property with magnetic saturation of 7.6 memu/g, which increased to 13.1memu/g with 1% Cu co-doping.

    更新日期:2019-12-17
  • Effects of carbonization temperature and substrate concentration on the sensing performance of flexible pressure sensor
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-16
    Shengnan Chang, Jin Li, Yin He, Hao Liu

    Flexible strain/pressure sensors play a vital role in flexible wearable electronics. In recent years, carbonized fabric-based flexible strain/pressure sensors are emerging due to their excellent flexibility and sensing performance, as well as facile preparation and low cost. Sensing performance is a key indicator for evaluating strain/pressure sensors. However, the study on the process variables affecting the sensing performance of carbonized fabric-based strain/pressure sensors is lacking to date. In this paper, a flexible pressure sensor based on carbonized fabric/thermoplastic polyurethane was prepared by simple carbonization. By setting different carbonization temperatures (600–1000 °C) and flexible substrate solution concentrations (4–10%), their influence on the sensor sensing performance was explored and a series of characterizations and tests were implemented under different process conditions. The results showed that the carbonization temperature and substrate concentration greatly influence the sensing performance of the sensor. Furthermore, the flexible pressure sensor using carbonized fabric carbonized at 800–900 °C and substrate solution with 6% concentration possesses superior sensing performance.

    更新日期:2019-12-17
  • Physical origin of the temperature-dependent open-circuit voltage in solar cells
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-16
    Ling-Feng Mao

    After the contribution of hot carriers to the current in solar cells has been considered, a physical and analytical model of open-circuit voltage is proposed. A variety of experiments on the temperature-dependent open-circuit voltage in solar cells that is one critical factor to determine their overall efficiency are successfully modeled based on the consideration of hot carriers. While previous modeling studies focused on numerical techniques, a physical and analytical model of the open-circuit voltage has been developed. Such a study is an important step toward a quantitative model of solar cells, leading to a deeper understanding of the physical effects in these materials. The analysis of the open-circuit voltage reveals how it depends on temperature, the acceptor density, the light-generated current density, the donor density, the bandgap, the effective mass, and the dielectric constant. A material parameter variation is performed to understand its effects on the open-circuit voltage. It will benefit to optimize the device performance by tuning material parameters through the simplicity and analytic nature of the proposed model. It is also helpful to characterize the material properties using the open-circuit voltage.

    更新日期:2019-12-17
  • Synthesis of nano-NiXFe 2 O 4 (X = Mg/Co) by citrate-gel method: structural, morphological and low-temperature magnetic properties
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-16
    Abdul Gaffoor, K. Chandra Babu Naidu, D. Ravinder, Khalid Mujasam Batoo, Syed Farooq Adil, Mujeeb Khan

    A series of Mg-doped NiFe2O4 (NMF) and Co-doped NiFe2O4 (NCF) nanoparticles were synthesized via citrate-gel method. The X-ray diffraction patterns of conventionally heated NMF and NCF nanoparticles confirmed the formation of single-phase cubic spinel structures. Further, the variation of structural parameters as a function of compositions was described. The morphology of NMF and NCF materials was investigated using scanning and transmission electron microscopes (SEM and TEM). In addition, the formation of tetrahedral (A-site) and octahedral (B-site) locations of NMF and NCF was obtained from the Fourier transform infrared spectra (FTIR). Furthermore, the room- and low-temperature magnetic properties were studied for NMF and NCF nanoparticles using magnetization versus magnetic field (M-H) loops and zero field cooled (ZFC) and field cooled (FC) curves, respectively. The results revealed that NMF and NCF nanoparticles exhibited superparamagnetic (SPM) nature at room temperature.

    更新日期:2019-12-17
  • Utilization of carbon nanotubes in removal of heavy metals from wastewater: a review of the CNTs’ potential and current challenges
    Appl. Phys. A (IF 1.784) Pub Date : 2019-12-16
    M. Bassyouni, A. E. Mansi, Alaa Elgabry, Basma A. Ibrahim, Omar A. Kassem, R. Alhebeshy

    Carbon nanotubes-based adsorbents have attracted substantial interest as potential adsorbents for heavy metals removal. However many aspects such as the interaction between the modified carbon nanotubes (CNTs) and the heavy metal ions, quantitative effect of the functional groups and regeneration of CNTs-based adsorbents are not fully understood yet. A critical review was performed to compile an extensive profile from several studies of using pristine and modified CNTs for heavy metals removal. CNTs demonstrated a great potential. However surface modification of CNTs is necessary as pristine CNTs may be ineffective in arsenite [As (III)] or arsenate [As (V)] removal. Isotherms and kinetic models for the removal of heavy metals are discussed in details. A particular focus has been placed on better understanding the mechanism of heavy metals removal using CNTs-based adsorbents, affecting factors, maximum adsorption capacity and regeneration. The effect of adsorbent dose, pH, initial concentration, and contact time were addressed by several researchers, which specifies the consistency and performance of CNTs-based materials https://www.sciencedirect.com/topics/materials-science/nanoparticlesas potential adsorbents. To elucidate the mechanism of adsorption, FT-IR, XPS, SEM, TEM and EDX results have been reviewed and discussed. It is found that Langmuir, Freundlich and second order kinetic models are the most frequently used isotherm to describe heavy metals adsorption. CNTs-based adsorbent can be efficiently regenerated.

    更新日期:2019-12-17
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