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Publisher: Springer-Verlag (Total: 2355 journals)

 Applied Physics A   [SJR: 0.535]   [H-I: 121]   [7 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 0947-8396 - ISSN (Online) 1432-0630    Published by Springer-Verlag  [2355 journals]
• Measurement of semi-polar (11–22) plane AlN/GaN heterojunction band
offsets by X-ray photoelectron spectroscopy
• Authors: Guijuan Zhao; Huijie Li; Lianshan Wang; Yulin Meng; Fangzheng Li; Hongyuan Wei; Shaoyan Yang; Zhanguo Wang
Abstract: Abstract The valence band offset (VBO) of the semi-polar (11–22) plane AlN/GaN heterojunction has been directly measured by X-ray photoelectron spectroscopy. The VBO is determined to be 0.7 ± 0.2 eV and the conduction band offset is deduced to be 2.1 ± 0.2 eV. The VBO of semi-polar AlN/GaN heterojunctions is smaller than the C-plane AlN/GaN heterojunctions due to the polarization effects partially eliminated.
PubDate: 2018-01-13
DOI: 10.1007/s00339-018-1561-1
Issue No: Vol. 124, No. 2 (2018)

• 2D materials in electro-optic modulation: energy efficiency,
electrostatics, mode overlap, material transfer and integration
• Authors: Zhizhen Ma; Rohit Hemnani; Ludwig Bartels; Ritesh Agarwal; Volker J. Sorger
Abstract: Abstract Here we discuss the physics of electro-optic modulators deploying 2D materials. We include a scaling laws analysis and show how energy-efficiency and speed change for three underlying cavity systems as a function of critical device length scaling. A key result is that the energy-per-bit of the modulator is proportional to the volume of the device, thus making the case for submicron-scale modulators possible deploying a plasmonic optical mode. We then show how Graphene’s Pauli-blocking modulation mechanism is sensitive to the device operation temperature, whereby a reduction of the temperature enables a 10× reduction in modulator energy efficiency. Furthermore, we show how the high-index tunability of graphene is able to compensate for the small optical overlap factor of 2D-based material modulators, which is unlike classical silicon-based dispersion devices. Lastly, we demonstrate a novel method towards a 2D material printer suitable for cross-contamination free and on-demand printing. The latter paves the way to integrate 2D materials seamlessly into taped-out photonic chips.
PubDate: 2018-01-13
DOI: 10.1007/s00339-017-1541-x
Issue No: Vol. 124, No. 2 (2018)

• Solvothermal synthesis of tin sulfide (SnS) nanorods and investigation of
its field emission properties
• Authors: Ajinkya Bhorde; Amit Pawbake; Priyanka Sharma; Shruthi Nair; Adinath Funde; Prashant Bankar; Mahendra More; Sandesh Jadkar
Abstract: Abstract In the present study, we report synthesis of tin sulfide (SnS) nano-rods using a simple solvothermal method at different reaction time period. The formation of single phase SnS has been confirmed by X-ray diffraction (XRD) and Raman analysis. The XRD analysis revealed that the predominant phase in all prepared samples is orthorhombic SnS. The formation of nano-rods of SnS was confirmed by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) analysis. To investigate the optical properties of SnS nano-rods UV–visible spectroscopy analysis was carried out. We observed that the band gap of SnS nano-rods decreases with increase in reaction time and can be attributed to the quantum confinement effect. Finally, field emission investigations on the SnS nano-rods at the base pressure of 1 × 10− 8 mbar were carried out and found to be superior to the other chalcogenide nanostructures. As-synthesized SnS nano-rods emitter exhibits excellent field emission properties such as low turn-on field (~ 2.5 V/µm for 10 µA/ cm2), high emission current density (~ 647 µA/cm2 at 3.9 V/µm) and superior current stability (~ 5 h for ~ 1 µA). Thus, the facile one-step synthesis approach and robust nature of SnS nano-rods emitter can provide prospects for the future development of large-area emitter applications such as flat-panel-display devices.
PubDate: 2018-01-13
DOI: 10.1007/s00339-017-1529-6
Issue No: Vol. 124, No. 2 (2018)

• Investigation of magnetic and structural properties of Ni–Zr co-doped
M-type Sr–La hexaferrites
• Authors: Yujie Yang; Fanhou Wang; Juxiang Shao; Duohui Huang; Jin Tang; Khalid Mehmood Ur Rehman
Abstract: Abstract In this research, Ni2+ and Zr4+ co-doped Sr–La hexaferrites Sr0.7La0.3Fe12.0−2x(NiZr) x O19 (0.0 ≤ x ≤ 0.5) were synthesized by the standard ceramic method. The phase identification of the hexaferrites was confirmed by X-ray diffraction analysis. X-ray diffraction analysis showed that all the samples were in single phase M-type hexagonal structure and no impurity phase was observed. Lattice parameters (c and a) increased with increasing NiZr content (x) from 0.0 to 0.5. The morphology of the hexaferrites was analyzed by a field emission scanning electron microscopy (FE-SEM). FE-SEM micrographs showed that the grains exhibited hexagonal shape in a plate-like structure with clear grain boundaries. Magnetization properties of the hexaferrites were carried out at room temperature using a physical property measurement system-vibrating sample magnetometer. The values of saturation magnetization (Ms), remanent magnetization (Mr) and coercivity (Hc) were calculated from magnetic hysteresis (M–H) loops. Ms and Hc decreased with increasing NiZr content (x) from 0.0 to 0.5. Mr and Mr/Ms ratio first increased with increasing NiZr content (x) from 0.0 to 0.1, and then decreased when NiZr content (x) ≥ 0.1.
PubDate: 2018-01-13
DOI: 10.1007/s00339-018-1572-y
Issue No: Vol. 124, No. 2 (2018)

• Tree-shaped fractal meta-surface with left-handed characteristics for
absorption application
• Authors: M. R. I. Faruque; M. M. Hasan; M. T. Islam
Abstract: Abstract A tri-band fractal meta-surface absorber composed of metallic branches of a tree connected with a straight metal strip has been presented in this paper for high absorption application. The proposed tree-shaped structure shows resonance in C-, X-, and Ku-bands and left-handed characteristics in 14.15 GHz. The dimension of the tree-shaped meta-surface single unit cell structure is 9 × 9 mm2 and the effective medium ratio is 5.50. In addition, the designed absorber structure shows absorption above 84%, whereas the absorber structure printed on epoxy resin fiber substrate material. The FIT-based CST-MWS has been utilized for the design, simulation, and analysis purposes. Fabrication is also done for the experimental validation.
PubDate: 2018-01-13
DOI: 10.1007/s00339-017-1498-9
Issue No: Vol. 124, No. 2 (2018)

• ZrO 2 :Sm 3+ nanophosphor: synthesis, Rietveld refinement, optical and
thermoluminescent properties
• Authors: S. Ponkumar; K. Janaki; D. Prakashbabu; H. B. Ramalingam; K. Munirathnam; T. V. M. Sreekanth; S. J. Dhoble
Abstract: Abstract We have synthesized undoped and Sm3+ ions doped ZrO2 nanophosphors by solution combustion method. These nanophosphors crystallized in cubic structure. Rietveld refinement of the samples was performed to estimate lattice parameters. Spherical particles with the sizes of 10–25 nm were observed by transmission electron microscopy. Photoluminescence and thermoluminescence (TL) properties of samples were investigated. Under 400 nm excitation, the nanophosphors have intense red emission at 600 nm. The color coordinates (0.67, 0.33) were located in the red region of CIE diagram. TL properties of nanophosphors were studied by exposing the samples to γ-rays. 5 mol% Sm3+ doped ZrO2 nanophosphor has shown maximum TL intensity after γ-irradiation. To test suitability of the nanophosphors for practical application in dosimetry, the 5 mol% Sm3+ doped ZrO2 sample was irradiated by 14 MeV electron beam in various electron fluence ranging from 100 to 900 Gy and their TL response was recorded.
PubDate: 2018-01-13
DOI: 10.1007/s00339-018-1554-0
Issue No: Vol. 124, No. 2 (2018)

• Synthesis of ZnO nanoparticles for oil–water interfacial tension
reduction in enhanced oil recovery
• Authors: Hassan Soleimani; Mirza Khurram Baig; Noorhana Yahya; Leila Khodapanah; Maziyar Sabet; Birol M. R. Demiral; Marek Burda
Abstract: Abstract Nanoparticles show potential use in applications associated with upstream oil and gas engineering to increase the performance of numerous methods such as wettability alteration, interfacial tension reduction, thermal conductivity and enhanced oil recovery operations. Surface tension optimization is an important parameter in enhanced oil recovery. Current work focuses on the new economical method of surface tension optimization of ZnO nanofluids for oil–water interfacial tension reduction in enhanced oil recovery. In this paper, zinc oxide (ZnO) nanocrystallites were prepared using the chemical route and explored for enhanced oil recovery (EOR). Adsorption of ZnO nanoparticles (NPs) on calcite (111) surface was investigated using the adsorption locator module of Materials Studio software. It was found that ZnO nanoparticles show maximum adsorption energy of − 253 kcal/mol. The adsorption of ZnO on the rock surface changes the wettability which results in capillary force reduction and consequently increasing EOR. The nanofluids have been prepared by varying the concentration of ZnO nanoparticles to find the optimum value for surface tension. The surface tension (ST) was calculated with different concentration of ZnO nanoparticles using the pendant drop method. The results show a maximum value of ST 35.57 mN/m at 0.3 wt% of ZnO NPs. It was found that the nanofluid with highest surface tension (0.3 wt%) resulted in higher recovery efficiency. The highest recovery factor of 11.82% at 0.3 wt% is due to the oil/water interfacial tension reduction and wettability alteration.
PubDate: 2018-01-13
DOI: 10.1007/s00339-017-1510-4
Issue No: Vol. 124, No. 2 (2018)

• Effect of concentration variation on 2.0 µm emission of Ho 3+ -doped SiO
2 –Al 2 O 3 –Na 2 CO 3 –SrF 2 –CaF 2 oxyfluorosilicate glasses
• Authors: Devarajulu Gelija; Deva Prasad Raju Borelli
Abstract: Abstract The concentration variation of Ho3+ ion-doped SiO2–Al2O3–Na2CO3–SrF2–CaF2 glasses has been prepared by conventional melt quenching method. The thermal stability of 1 mol % of Ho3+-doped oxyfluorosilicate glass has been calculated using the differential thermal analysis (DTA) spectra. The phenomenological Judd–Ofelt intensity parameters Ωλ (λ = 2, 4 and 6) were calculated for all concentrations of Ho3+ ions. The luminescence spectra in visible region of Ho3+ ion-doped glasses were recorded under the excitation wavelength of 452 nm. The spectra consists of several intense emission bands (5F4, 5S2) → 5I8 (547 nm), 5F3 → 5I8 (647 nm), 5F5 → 5I7 (660 nm) and (5F4, 5S2) → 5I7 (750 nm) in the range 500–780 nm. The fluorescence emission at ∼2.0 µm (5I7 → 5I8) was observed under the excitation of 488 nm Ar-ion laser. The stimulated emission cross section for 5I7 → 5I8 transition (∼2.0 µm) varies from 8.46 to 9.52 × 10−21 cm2, as calculated by the Fuchtbauer–Ladenburg (FL) theory. However, Mc-Cumber theory was used to calculate emission cross section values about 4.24–5.75 × 10−21 cm2 for the 5I7 → 5I8 transition in all concentrations of Ho3+-doped oxyfluorosilicate glasses. Therefore, these results reveal that the 0.5 mol % of Ho3+-doped oxyfluorosilicate glasses, exhibiting higher emission cross section, has potentially been used for laser applications at ∼ 2.0 µm.
PubDate: 2018-01-13
DOI: 10.1007/s00339-018-1569-6
Issue No: Vol. 124, No. 2 (2018)

• Optoelectrical properties of Ge 10 Se 90 and Ge 10 Se 85 Cu 5 thin films
illuminated by laser beams
• Authors: M. S. El-Bana; S. S. Fouad
Abstract: Abstract The laser irradiation effect on the optoelectrical properties of Ge10Se90 and Ge10Se85Cu5 thin films in the view of Cu-doping effect has been investigated. The illumination effect leads to structural changes in compositions that result from electron–hole excitations, defect creation/modification, and subsequently atomic motions. The dispersion of the refractive index is discussed in terms of the single-oscillator model, non-linear optics, coordination number and lone-pair electrons. Adding Cu to the host glass decreased the band gap (photo-darkening effect). The optoelectrical properties of the studied films have been investigated in the view of the high-frequency dielectric constant $${ \epsilon }_{\infty }$$ , volume and surface energy loss functions VELF and SELF, the dielectric loss factor $$\delta$$ , the plasma frequency $${w}_{\text{p}}$$ , and the damping frequency $${ w}_{\text{d}}$$ . The above mentioned parameters are revealed to be effected upon Cu doping as well as laser irradiation. Our findings can be utilized in device applications for laser-activated switches and memories.
PubDate: 2018-01-13
DOI: 10.1007/s00339-018-1570-0
Issue No: Vol. 124, No. 2 (2018)

• Type-II GaSb/GaAs quantum-dot intermediate band with extended optical
absorption range for efficient solar cells
• Authors: Hela Boustanji; Sihem Jaziri
Abstract: Abstract GaSb/GaAs type-II quantum-dot solar cells (QD SCs) have attracted attention as highly efficient intermediate band SCs due to their infrared absorption. Type-II QDs exhibited a staggered confinement potential, where only holes are strongly confined within the dots. Long wavelength light absorption of the QDSCs is enhanced through the improved carriers number in the IB. The absorption of dots depends on their shape, material quality, and composition. Therefore, the optical properties of the GaSbGaAs QDs before and after thermal treatment are studied. Our intraband studies have shown an extended absorption into the long wavelength region $$1.77 \, \upmu \text {m}$$ . The annealed QDs have shown significantly more infrared response of $$7.2 \, \upmu \text {m}$$ compared to as-grown sample. The photon absorption and hole extraction depend strongly on the thermal annealing process. In this context, emission of holes from localized states in GaSb QDs has been studied using conductance–voltage (G–V ) characteristics.
PubDate: 2018-01-12
DOI: 10.1007/s00339-017-1495-z
Issue No: Vol. 124, No. 2 (2018)

• Structural characterization, electrical conductivity and open circuit
voltage studies of the nanocrystalline La 10 Si 6 O 27 electrolyte
material for SOFCs
• Authors: Paramananda Jena; S. Jayasubramaniyan; P. K. Patro; R. K. Lenka; Amit Sinha; P. Muralidharan; E. S. Srinadhu; N. Satyanarayana
Abstract: Abstract Nanocrystalline La10Si6O27 apatite-type sample was synthesized by the co-precipitation method. Thermal behavior, phase, structure, morphology and elemental composition of La, O and Si of the synthesized La10Si6O27 sample were investigated through TG/DTA, XRD, FTIR, Raman spectroscopy and SEM-EDX measurements respectively. Formation of phase purity of the nanocrystalline La10Si6O27 sample was confirmed by analysing the measured X-ray powder diffraction (XRD) pattern using Rietveld refinement and the calculated average crystallite size of the La10Si6O27 sample was found to be 33 nm. The electrical conductivity of the sintered La10Si6O27 pellet was investigated as a function of temperature ranging from 200 to 800 °C under air and it was found to be 1.92 × 10−3 S cm−1 at 800 °C. The chemical stability of La10Si6O27 powder under oxidizing and reducing atmospheres was confirmed from the analysis of the measured XRD pattern and Raman spectral results. Open circuit potential of a button cell, made up of the La10Si6O27 sample, was tested up to 800 °C with both oxygen and hydrogen at opposite sides of the cell and was found to ~ 1 V. Hence, the results demonstrate that La10Si6O27 could be a promising solid electrolyte material for the solid oxide fuel cell (SOFC) applications.
PubDate: 2018-01-12
DOI: 10.1007/s00339-017-1520-2
Issue No: Vol. 124, No. 2 (2018)

• Morphologies of femtosecond laser ablation of ITO thin films using
gaussian or quasi-flat top beams for OLED repair
• Authors: Hoon-Young Kim; Won-Suk Choi; Suk-Young Ji; Young-Gwan Shin; Jin-Woo Jeon; Sanghoon Ahn; Sung-Hak Cho
Abstract: Abstract This study compares the ablation morphologies obtained with a femtosecond laser of both Gaussian and quasi-flat top beam profiles when applied to indium tin oxide (ITO) thin films for the purpose of OLED repair. A femtosecond laser system with a wavelength of 1030 nm and pulse duration of 190 fs is used to pattern an ITO thin film. The laser fluence is optimized for patterning at 1.38 J/cm2. The patterned ITO thin film is then evaluated through both optical microscope and atomic force microscope. Ablations with a square quasi-flat top beam are demonstrated using slits with varying x–y axes. With the Gaussian beam, the pattern width of the ablated area is shown to range from 9.17 to 9.99 μm when the number of irradiation pulse increases from one to six. In contrast, when slit control is used to obtain a quasi-flat top beam, the ablated pattern width remains constant at 10 μm, despite the increase in the number of pulse. The improved surface roughness is correlated with the quasi-flat top beam through measured Ra values. Furthermore, when using the Gaussian beam, the minimum resolution of the controllable ablation depth on the ITO thin film is found to be 60 nm. In contrast, when the quasi-flat top beam is used, the minimum ablation depth decreases to 40 nm.
PubDate: 2018-01-12
DOI: 10.1007/s00339-018-1553-1
Issue No: Vol. 124, No. 2 (2018)

• Compression and heating of a laser-produced plasma using single and double
induction coils
• Authors: J. R. Creel; J. G. Lunney
Abstract: Abstract The results of an experiment on magnetohydrodynamic compression and heating of a laser-produced plasma in vacuum are described. The plasma was produced by laser ablation of copper at 2 J cm−2. A pulsed magnetic field, with an amplitude of 0.3 T and a period of 2.2 µs, was produced by a three-turn spiral induction coil placed 10 mm above the ablation spot. Time-resolved imaging revealed that the magnetic field had a strong influence on both the plasma between the coil and the target, and on the plasma which flows through the aperture in the coil. The plasma flow through the coil aperture is strongly pinched due to the Lorentz interaction of the induced current and the coil magnetic field. Heating of the plasma is evidenced by strong enhancement of the overall visible light emission and the appearance of Cu+ line emission. Magnetic compression and plasma heating were also observed in a setup using two induction coils separated by 10 mm. This technique could be used to enhance the sensitivity of laser-induced breakdown spectroscopy, increase the ion yield in laser plasma ion sources, or control the ablation plume expansion in pulsed laser deposition.
PubDate: 2018-01-12
DOI: 10.1007/s00339-017-1516-y
Issue No: Vol. 124, No. 2 (2018)

• Assessment of global solar radiation to examine the best locations to
install a PV system in Tunisia
• Authors: Kaouther Belkilani; Afef Ben Othman; Mongi Besbes
Abstract: Abstract The study of the solar radiation is the starting point of any investigation for a new energy, to study and search the best location to install a PV system. A very important factor in the assessment of solar potential is the availability of data for global solar radiation that must be coherent and of high quality. In this paper, we analyze the estimation result of the monthly global solar radiation for three different locations, Bizerte in Northern Tunisia, Kairouan in Middle Eastern Tunisia, and Tozeur in Southern Tunisia, measured on the surface by the National Institute of Meteorology and the meteorological year irradiation based on satellite imagery result PVGIS radiation databases. To get the right measurements with minimum error, we propose a numerical model used to calculate the global solar radiation in the indicated three sites. The results show that the model can estimate the global solar radiation (kWh/m²) at a specific station and over most area of Tunisia. The model gives a good estimation for solar radiation where error between the measured values and those calculated are negligible.
PubDate: 2018-01-12
DOI: 10.1007/s00339-018-1551-3
Issue No: Vol. 124, No. 2 (2018)

• Defects induced by MeV H + implantation for exfoliating of free-standing
GaN film
• Authors: Kai Huang; Tiangui You; Qi Jia; Ailun Yi; Shibin Zhang; Runchun Zhang; Jiajie Lin; Min Zhou; Wenjie Yu; Bo Zhang; Xin Ou; Xi Wang
Abstract: Abstract High-energy ion slicing is promising to produce the free-standing GaN films with thickness in the range of 10–20 µm, which would promote the mass applications of GaN substrates. In this paper, bulk GaN was implanted by 1.6 MeV H ions with the mean projected range Rp of around 17 μm and the thermal evolution of the H-induced defects was investigated in detail. Due to the migration-coalescence mechanism, the H-induced point defects gather to form the initial cavity defects which grow up via the Ostwald ripening mechanism. The cavity defect distribution is determined by the distributions of the implanted hydrogen and the implantation-induced damages. The area ratio of cavity defects in the center damage band of the 1.6 MeV sample was around 3.4%. Annealing at higher temperature enhances the defect migration and recovery. Larger H ion fluence or higher annealing temperature is required to accomplish the exfoliation of a free-standing GaN thick film.
PubDate: 2018-01-11
DOI: 10.1007/s00339-017-1508-y
Issue No: Vol. 124, No. 2 (2018)

• Case study on the dynamics of ultrafast laser heating and ablation of gold
thin films by ultrafast pump-probe reflectometry and ellipsometry
• Authors: T. Pflug; J. Wang; M. Olbrich; M. Frank; A. Horn
Abstract: Abstract To increase the comprehension of ultrafast laser ablation, the ablation process has to be portrayed with sufficient temporal resolution. For example, the temporal modification of the complex refractive index $${\tilde{n}}$$ and the relative reflectance of a sample material after irradiation with ultrafast single-pulsed laser radiation can be measured with a pump-probe setup. This work describes the construction and validation of a pump-probe setup enabling spatially, temporally, and spectroscopically resolved Brewster angle microscopy, reflectometry, ellipsometry, and shadow photography. First pump-probe reflectometry and ellipsometry measurements are performed on gold at $$\lambda _{\mathrm{probe}}= 440\, \hbox {nm}$$ and three fluences of the single-pulsed pump radiation at $$\lambda _{\mathrm{pump}}= 800\,\hbox {nm}$$ generating no, gentle, and strong ablation. The relative reflectance overall increases at no and gentle ablation. At strong ablation, the relative reflectance locally decreases, presumable caused by emitted thermal electrons, ballistic electrons, and ablating material. The refractive index n is slightly decreasing after excitation, while the extinction coefficient k is increasing.
PubDate: 2018-01-11
DOI: 10.1007/s00339-018-1550-4
Issue No: Vol. 124, No. 2 (2018)

• Effect of copper phthalocyanine thickness on surface morphology, optical
and electrical properties of Au/CuPc/n-Si heterojunction
• Authors: P. R. Sekhar Reddy; V. Janardhanam; I. Jyothi; Cirandur Sri Harsha; V. Rajagopal Reddy; Sung-Nam Lee; Jonghan Won; Chel-Jong Choi
Abstract: Abstract Effects of the thickness of copper phthalocyanine (CuPc) film (2, 5, 10, 15, 20, 30 and 40 nm) on the surface morphology, optical and electrical properties of Au/CuPc/n-Si heterojunction have been investigated. The optical band gap of CuPc film was increased with increase in the thickness of the CuPc film. The electrical properties of the Au/n-Si Schottky junction and Au/CuPc/n-Si heterojunctions were characterized by current–voltage (I–V) and capacitance–voltage (C–V) measurements. The barrier height, ideality factor and series resistance were estimated based on the I–V, Cheung’s and Norde’s methods. The barrier heights increased with increasing CuPc interlayer thickness up to 15 nm and remained constant for thickness above 20 nm, associated with the incapability of the generated carriers to reach the interface. The discrepancy in the barrier heights obtained from I–V and C–V measurements indicates the presence of barrier inhomogeneity at the interface as evidenced by higher ideality factor values. It can be concluded that the electrical properties of Au/n-Si Schottky junction can be significantly altered with the variation of CuPc thickness as interlayer.
PubDate: 2018-01-11
DOI: 10.1007/s00339-017-1511-3
Issue No: Vol. 124, No. 2 (2018)

• Spatial localization of nanoparticle growth in photoinduced nanocomposites
• Authors: Anton A. Smirnov; Alexander Pikulin; Nikita Bityurin
Abstract: Abstract Photoinduced nanocomposites are the polymer materials where the nanoparticles can be generated by the light irradiation. The single atoms of metal are formed due to the photoreduction of the metal-containing precursor added to the polymer matrix. Then the atoms precipitate into the nanoparticles (NPs). Similarly, semiconductor NPs are assembled from the monomer species such as CdS, which can be released due to the photodestruction of the appropriate precursor. We analyze theoretically the possibility of spatial confinement of growing nanoparticles in a domain where the elementary species are generated by a three-dimensionally localized source. It is shown that the effective confinement can be achieved only if the size of the generation domain exceeds some critical spatial scale determined by the parameters of the system. The confinement is provided by the trapping of the diffusing elementary species by the growing nanoparticles. The proposed model considers the irreversible particle growth, typical for the noble metals. Both the nucleation and the particle growth processes are suggested to be diffusion controlled.
PubDate: 2018-01-11
DOI: 10.1007/s00339-017-1539-4
Issue No: Vol. 124, No. 2 (2018)

• Modeling a photovoltaic energy storage system based on super capacitor,
simulation and evaluation of experimental performance
• Authors: Mohamed Ali Ben Fathallah; Afef Ben Othman; Mongi Besbes
Abstract: Abstract Photovoltaic energy is very important to meet the consumption needs of electrical energy in remote areas and for other applications. Energy storage systems are essential to avoid the intermittent production of photovoltaic energy and to cover peaks in energy demand. The super capacitor, also known as electrochemical double layer capacitor, is a storage device which has a very high power density compared to conventional battery and is capable of storing a large amount of electrical energy in short time periods, which reflects its interest to be used for the storage of photovoltaic energy. From this principle, this paper represents a three-branch RC model of super capacitor to describe its different dynamics of operation during the charging, discharging and rest phases. After having validated the good functioning of this model with the experimental study of Zubieta, The super capacitor performance has been demonstrated and compared with a conventional battery in a photovoltaic converter chain to power AC machine.
PubDate: 2018-01-11
DOI: 10.1007/s00339-018-1549-x
Issue No: Vol. 124, No. 2 (2018)

• Dark mode engineering in metasurfaces by symmetry matching approach
• Authors: Elena Bochkova; Shah Nawaz Burokur; André de Lustrac; Anatole Lupu
Abstract: Abstract We revisit the engineering of metasurfaces to obtain sharp features in their spectral response. We show that in contrast to conventional approach exploiting indirect mode hybridization mechanism based on strong near-field coupling, a more flexible and efficient engineering of the spectral response can be achieved using a symmetry matching approach for the excitation of dark modes. This distinctly different mechanism takes advantage of the geometry symmetry of the structure with regard to the incident external electromagnetic field for a direct far-field coupling.
PubDate: 2018-01-11
DOI: 10.1007/s00339-017-1497-x
Issue No: Vol. 124, No. 2 (2018)

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