A floating hairpin resonator probe is used to measure electron density within the radiofrequency cycle of a parallel plate capacitively coupled plasma at steady state. A time resolution capable of detecting electron density oscillations within the radiofrequency cycle is demonstrated. Electron density oscillations are observed at the drive frequency over a range of operating conditions including 10–250 mTorr (1.3–33 Pa) in argon driven at 13.56 or 27.12 MHz. Localized electron density oscillation amplitudes show moderate agreement with literature and fluid simulations near the powered electrode and disagreement in the plasma bulk. The technique is useful for studying electron heating mechanisms in radiofrequency discharges due to its high time resolution.

Selection reasonable processing parameters for the metallic product by selective laser melting (SLM) is a significant issue to improve the performance of the final product. The optimization for the performance of the product is caused by the comprehensive effect of multiple processing parameters instead of a single parameter. It is urgent to propose a method for evaluating this comprehensive effect, furthermore, providing reasonable processing parameters. In this study, the mesoscopic features (molten pool morphology, free surface, porosity distribution, etc.) under different processing parameters are analyzed. Meanwhile, a powder scale thermal-fluid coupled model is established considering the randomly distributed powder bed and the complex physical phenomena within the molten pool. The simulation results are compared with the results characterized by multiple experimental methods. The integration of simulation and experiment results show that a fast scanning velocity or a larg...

The conversion and utilization of CO 2 is one of the greatest global challenges. Plasma assisted catalysis provide a new resolution to this problem. However, the energy efficiency and conversion rates of the plasma process are still insufficient for industrial applications. The key reasons are the highly complex interaction between gaseous plasma and catalytic materials, especially in packed bed dielectric barrier discharges. Our study fills this critical gap by developing a novel numerical approach to study how the ns pulse driving plasma trigger the heterogeneous reactions on the Ni/ γ -Al 2 O 3 catalyst surface. The development of plasma inside the reactor is in the form of surface ionization wave (SIW) + filamentary microdischarges. The high electron power in the SIW region and the high ion power density in the sheath region on the catalysts surface provide enough energy to trigger heterogenous reactions. The heterogeneous reactions not on...

NanoTiO 2 /epoxy resin composites, a kind of dielectric materials with excellent thermal, mechanical and electrical properties, has extensive promise in the insulation area of power system. Although the semiconductor property of TiO 2 filler can suppress the electric field mutations in the epoxy insulation devices, the doping of TiO 2 will have bad influence on the charge transmission, thus weakening the surface insulation. To solve this problem, filler fluorination with dielectric barrier discharge (DBD) plasma and chemical methods were designed to modify the TiO 2 filler. The effects of two fluorination methods on the micro-structures, electrical parameters, and insulation properties of the materials were studied. The results have shown that both DBD plasma and chemical fluorination methods can effectively introduce fluorine into TiO 2 filler and its epoxy composites, decreasing its dielectric constant and volume resistivity. Th...

The characteristics of nanosecond-pulsed dielectric barrier discharge (nSDBD) in an anti-icing configuration is studied. The mechanisms and energy characteristics of the nSDBD-based plasma-assisted anti-icing are analyzed using a numerical model and existing experimental data. Two-dimensional simulations based on PASSKEy (PArallel Streamer Solver with KinEtics) code are conducted. The code couples a self-consistent fluid model with detailed kinetics, an efficient photo-ionization model, Euler equations and a heat transfer equation for solid materials. The results of icing wind tunnel experiments conducted by two groups are analyzed together. The reduced electric field and the electron density are examined for high-voltage pulses with 800 ns and 20 ns width. The ‘merge’ of counter-propagating surface streamers with the same polarity is numerically observed under high-voltage amplitude. The effects of gas heating and solid heating in time scales of one pulse and one duty cycle are...

A novel 2D dual-layer step-like Janus array film (DSJAF) based on 1D Janus nanoribbon and Janus microfiber as structural units is devised and fabricated by combining conjugate with parallel electrospinning. In DSJAF, the top-layer Janus nanoribbon array film covers the left half of the bottom-layer Janus microfiber array film and the two films bind together to form the step-like composite film, achieving two sets of Janus structures, respectively, from top to bottom on the left half of the DSJAF and from left to right on the top surface of the DSJAF. The specially structured DSJAF exhibits two sets of double anisotropic conduction coming from the two sets of Janus structures, and single anisotropic conduction exists, respectively, in the top-layer film and bottom-layer film, realizing multiple anisotropic conductions. The conductive anisotropic degree of DSJAF is modulated by diverse structural units of Janus microfiber and Janus nanoribbon. Up-conversion luminescence (UCL) and ...

The controlled growth of chalcogenide nanoscaled phase change material structures can be important to facilitate integration and to enable complex architectures for phase change memory and other microelectronic applications. Here, the growth of Sb–Te and In–Ge–Te alloys by metal–organic chemical vapour deposition (MOCVD) on patterned substrates featured with an array of recesses (~130 nm features width) was investigated. High selectivity, with preferential growth on a CoSi 2 metallic layer at the recess bottom with respect to the surrounding SiO 2 masking layer, was obtained, leading to a single-step fabrication of arrays of high-aspect-ratio chalcogenide nanostructures. The growth selectivity, as well as the morphology, composition and microstructure of the grown nanostructures, as a function of the different MOCVD process parameters, were investigated by scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, Ra...

All organic soft dielectrics are growing more and more interest in the electronic industry owing to their light weight, low cost and the flexibility they yield compared to the rigid devices. In the specific field of microwave communicating devices planar printed (patch) antennas on a soft dielectric substrate are sought for their conformability and advantageous compactness. In this article, two soft thermoplastic elastomer blends based on polypropylene (PP) or low-density polyethylene (LDPE) were tested. The fabrication process and the established characterization steps have been fully presented. More specifically, in order to characterize the dielectric film up to 40 GHz, the microstrip ring resonator with coplanar waveguide access has been adapted to a new configuration specimen sample. The results of the characterizations obtained showed very encouraging performances for microwave applications. Indeed, the measured dielectric constant and loss tangent up to 40 GHz were found ...

In this work, it is shown that controllable increases in chemical reactivity of borosilicate glass can be induced through spatially resolved femtosecond laser irradiation at fluence values significantly lower than the damage threshold. The hydrofluoric acid etch rate has been found to be closely correlated to the reduction in optical transmission of the glass at 488 nm, which is, in turn, governed by the production of boron–oxygen hole centers. The combination of laser irradiation below the ablation threshold followed by chemical etching is shown to yield surfaces that have a roughness lower than those achieved by either laser or chemical etching alone. Application of this effect to the manufacture of freeform Laplacian optics is demonstrated.

Electric field induced second harmonic (EFISH) generation using a ns pulse duration laser has been employed for time-resolved measurements of the axial and transverse electric field in a pin-to-pin ns pulse discharge in ambient air, at atmospheric pressure and at 2 bar. The results demonstrate that the time-varying electric field can be measured accurately over the duration of the laser pulse 15–20 ns long, with the temporal resolution (potentially sub-ns) limited by the response time of the detector. Each data set provides time-accurate electric field over a period of up to 10 ns. Time-resolved electric fields over longer time periods are measured by adjusting the laser Q-switch delay, and using the composite data obtained by overlapping the individual data sets. Absolute calibration of the electric field is obtained from the comparison of the experimental data with the Laplacian field distribution in the discharge gap before breakdown, taking into account the residual charge a...

An optically transparent metamaterial structure with simultaneously broadband microwave absorptivity and low infrared (IR) emissivity is proposed. Two specifically designed optically transparent metasurfaces were combined to realize radar and IR bi-stealth. One was designed to control the microwave absorption though properly modifying the impedance and resonance peaks of the meta-atom. The other was designed to control the IR radiation. Within a wide incident angle of ±60°, the proposed structure displays high absorptivity greater than 90% in the region of 6.28–12.29 GHz for TE polarization. For TM polarization, the absorptivity in the region of 7.19–15.26 GHz is greater than 90%. The IR emissivity of the metamaterial structure is about 0.30 in the IR region from 3 µ m to 14 µ m. The perfect consistency between experimental results and simulation results demonstrates that the proposal has practical application of multispectral stealth technology.

We theoretically demonstrate a kind of plasmon coupled cavity to achieve a nanolaser with high intensity and low threshold. The plasmon cavity is composed of the gold film substrate and gold disk array, which supports two strong coupled resonance modes (i.e. surface plasmon polariton (SPP) and localized surface plasmon (LSP)). Compared with the nanolaser with the LSP resonance structure, the scattering cross-section of the LSP-SPP coupled laser is 80 times higher. The coupled cavity nanolaser with different wavelengths can be excited with different plasmon resonance modes by selecting the appropriate gain medium. In addition, a compact tunable dual-wavelength laser can be developed using this coupled structure.

Regarding CO 2 /O 2 -based mixture as an arc quenching gas in high-voltage circuit breakers, the predominant component species present in high numbers at temperatures of 300–20 000 K are determined in consideration of addition of CF 3 CFCH 2 (hereinafter written as C 3 H 2 F 4 ) gas to the CO 2 /O 2 -based mixture. In the determination, not only are 87 gaseous species but also condensed-phase carbon (hereinafter written as C(c)) taken into account as component species. The evaluation results reveal that CO 2 , O 2 , CF 4 and HF in gaseous phase behave as the predominant component species at 300–1000 K for lower content additive-gas, whereas the species C(c) is also generated as the predominant component at the same temperature for higher content additive-gas. Subsequently, reactions of chemical elements C, O, F and H to form the above-described chemical species ar...

The phenomena associated with strain-mediated multiferroic behavior have been quantitatively studied by combining synchrotron x-ray diffraction (XRD), ferromagnetic resonance (FMR) and macroscopic strain measurements (digital image correlation) in a magnetoelectric composite (Ni film on PZT substrate). The ferroelectric and piezoelectric strains have been studied by analyzing the evolution of x-ray patterns (peak intensities and shifts), while the magnetic response is studied by FMR (energy shift of the resonance), during in situ application of electrical voltage. Being given the intrinsic selective phase nature of XRD, the lattice strains have also been measured in the Ni film and have been found to be comparable to the macroscopic one (full transmission from the PZT substrate). The PZT strain has been successfully separated into two contributions, i.e. ferroelectric and lattice strains, the first one being five times higher than the second one. Moreover the last is itse...

In this paper, benefitting from the presence of an ultrathin corrugated metal–insulator–metal ring resonator, for the first time, we proposed a dual-detection microfluidic chemical sensor based on quarter-mode spoof localized surface plasmon (LSP) resonator with higher sensitivity among all the dual/multichannel microwave chemical sensors. First, we study full-mode spoof plasmonic resonator and we show that the resonance modes of the quarter-mode structure are exactly one-fourth of the full-mode structure. By placing two asymmetric microfluidic channels in the strongest E -field regions, the capability of detecting two aqueous solutions is feasible. By utilizing a 85070 E performance probe connected to vector network analyzer, we determined the relative permittivity and loss tangent of fluids under test. Then, the fabricated prototype was tested, and our experimental results collaborate well our simulation predictions. Our proposed RF sensor exhibits 87% growth in se...

The high power and linearity performance of GaN-based HEMT for X-band application was achieved using the barrier layer of sandwich structure and Al 0.05 GaN back barrier. The AlGaN-sandwich-barrier can modulate polarization-graded field for more flat transconductance profile under the high drain bias. Only about 7.5% current collapse (CC) occurs for drain quiescent bias of 40 V. Due to the Al 0.05 GaN back barrier, the three-terminal off-state breakdown voltage (BV DS ) of 260 V and a very small drain-induced barrier lowering (DIBL) of 2.7 mV V −1 is achieved. The AlGaN sandwich barrier combined with Al 0.05 GaN back barrier device exhibits a high current-gain cutoff frequency f T of 42 GHz@ V DS = 10 V, and a high power-gain cutoff frequency f MAX of 130 GHz@ V DS = 60 V. Load-pull measurement at 10 GHz revealed a saturated power density of 7.3 W mm −1

Frequency domain spectroscopy (FDS) measurement has become an important method for the assessment of the condition of the insulation of oil transformers. In recent years, numerous researchers have found that temperature variation affect FDS results. The master curve technique is commonly used to correct the effect of temperature on FDS results. In this paper, an FDS experiment is carried out on a sample transformer. Then, for this transformer, insulation model parameters are determined by using a genetic algorithm based on the FDS results. Then, by using the insulation model parameters, tan δ curves are simulated and compared to real results. Finally, an FDS experiment is conducted on two other transformers at 22 °C, 30 °C, 40 °C, 50 °C, 60 °C, and 70 °C (in order to give sufficient information for a training neural network) and insulation model parameters are calculated via the genetic algorithm. In one of the transformers, the effect of temperature on the FDS curves is c...

In this paper, we propose a refractive index sensor with self-reference performance based on a two-dimensional grating structure, mainly consisting of periodic arrays of triple layer dielectric nanodisks and a continuous substrate separated by a thin gold film. Three reflection dips are observed and manipulated to realize self-reference and high sensing performance due to the excitation of magnetic dipole mode resonance, substrate mode resonance and metal layer assisted guide mode resonance. These hybrid modes have been explained by the distributions of the electric and magnetic fields in the nanostructure. A detailed analysis of the influences of material thickness on the optical properties of the proposed refractive index sensor is also investigated. Moreover, the proposed refractive index sensor demonstrates a high sensing performance, an important application for future biomedical applications, with a bulk refractive index sensitivity of 672 nm RIU −1 (RIU: refract...

From pulsed Townsend measurements in nitrous oxide (N 2 O) we obtain swarm parameters for various electron and in particular anion processes. We discuss various assumptions on the discharge model in literature, and motivate a suitable model. Our findings agree with modern sources on the electron swarm parameters. Contrary to many sources however, we find evidence for electron detachment from O − with a coefficient of ##IMG## [http://ej.iop.org/images/0022-3727/53/13/135202/dab6516ieqn001.gif] ##IMG## [http://ej.iop.org/images/0022-3727/53/13/135202/dab6516ieqn002.gif] m 2 , and we suggest further changes to the commonly accepted discharge model. Based on the obtained swarm parameters, an electric strength dependent on pressure is estimated and compared to breakdown measurements.

The ever-growing energy crisis and environmental degradation have instigated scientists to explore sophisticated, versatile energy conversion systems. Photoconversion, which conveys solar power to chemical energy, has emerged as an eminent energy conversion approach to accomplish the demands. Recent years have seen the rocketing rise of semiconductor heterostructures as an ideal material paradigm for the realization of miscellaneous photoconversion applications ranging from water splitting, CO 2 reduction and environmental purification to photosynthesis. With tailored functionalities from synergetic effects, semiconductor heterostructures come into prominence as the forefront of photocatalyst development. This topical review summarizes the photoconversion applications developed so far by employing semiconductor heterostructures, with a focus on the heterostructure design principle, interfacial charge dynamics and key factors dictating the overall performance. Future re...

We report on the effects of two different molecular beam epitaxy growth modes on the performance of In 0.14 Ga 0.86 As/GaAs quantum well infrared photodetectors (QWIPs). The performance of quantum well (QW) materials are characterized by photoluminescence (PL), x-ray diffraction, and high resolution transmission electron microscope, and a systematic photoelectric characterization is carried out for these InGaAs/GaAs QWIPs. The results indicate that the introduction of continuous low temperature growth can effectively reduce In atom interdiffusion while maintaining the higher PL intensity. QWIPs grown by the low temperature method show the bound-to-bound intraband transition mode as initially designed, whereas the high temperature during the growth makes the operating mode of the device changing to bound-to-quasi continuous mode, which affects the performance of the quantum well infrared photodetectors. Compared with InGaAs/GaAs QWIP fabricated by the temperatur...

The time-dependent properties of an Ar/C 2 H 2 dusty plasma (neutral, ion and electron densities, effective electron temperature and dust charge) are studied using a volume-averaged model for conditions corresponding to experiments on nanoparticle growth. The calculated density evolution for C 2 H 2 , H 2 and C 4 H 2 molecules are compared with time-resolved measurement of the mass peaks of the neutral species and the effects of the dust density on the plasma properties are analyzed. Time evolutions of the main positive and negative ions are also obtained thanks to the calculations. As a consistency check the time-dependence of the dust radius is also obtained numerically, assuming that an increase of the dust radius is due to deposition of hydrocarbon ions and C 2 H radicals on the surface of dust particles. It is shown that for conditions corresponding to the experiment, the ions are the main contributo...

In this work, we conduct a temperature-dependent study of optical centres in ultrapure diamond after 200 keV irradiation by photoluminescence spectra, which are performed in a temperature range of 80–200 K. The zero phonon lines (ZPLs) include sizes of 550.3 nm, 593 nm, and 741 nm (GR1 centre). With an increase in measurement temperature, the ZPLs shift to the lower energy side, together with intensity quenching and an increase in the full width at half maximum. These results are noted in models of lattice contraction and electron–phonon coupling, and their inhomogeneous and homogeneous broadening mechanisms are also carefully distinguished by the Voigt function. The 550.3 nm and 593 nm emissions present harder bonds than the GR1 centre, close thermal quenching energies to the interstitial-related defect, a lower thermal softness than that of the ideal diamond, weak phonon bands at each lower energy side, and different broadening mechanisms with the GR1 centre, indicating that t...

We construct a laminated metamaterial structure of zipper-type monolayer graphene with silica, which is equipped with a distinctively dual plasmon-induced transparency (PIT) phenomenon. The graphene pattern in this structure craftily connects with the electrode so that we can dynamically control the PIT response (via regulating the bias voltage that applied between the electrode and the substrate to control the graphene Fermi energy), in which the range of voltage-regulate is calculated theoretically, proving to be a feasible measure for PIT response-tune. Then, the tuning discipline for this structure is summarized from the calculated result of the coupled mode theory deduced theoretical model and the simulation result. It is found that the structure possesses a great tuning performance within the tuning range we studied; also, as the structure ameliorates the monolayer graphene absorbance from 2.3% to about 50% within a broad dynamic frequency tuning range, the absorption peak...

Plasmonic lithography based on surface plasmon polariton has been proven to breaking the diffraction limit and deliver the super-resolution patterns. However, most previously reported studies suffer from the low energy efficiency and subwavelength excitation grating that obstructs the application in nanofabrication. In this work, a special plasmonic lithography prototype is proposed based on the coupling of the bulk plasmon polariton mode squeezed through the hyperbolic metamaterial (HMM) and the waveguide mode supported in the coupling layer/HMM/photoresist sandwich structure. The results demonstrate that periodic patterns with strong lithography light intensity (>220%) over the whole photoresist layer compared with incident optical intensity, high aspect ratios (1.5:1) and a half-pitch of 57.5 nm can be generated, under the interference of the fourth-order diffracted light of grating. The lithography linewidth can reach 1/16 of the mask period of 920 nm and ~1/8 of the wave...

Atomic oxygen and ozone are essential reactive species in plasma oxidation processes. Pure oxygen discharge is preferable to produce atomic oxygen and ozone while a difficulty in measuring their local densities exists. The ozone density is typically measured by UV absorption, but its resolution is insufficient for measuring the local ozone density in filamentary discharges. The atomic oxygen density can be measured by two-photon absorption laser-induced fluorescence (TALIF) method. However, ozone interference from the in situ atomic oxygen production due to ozone fragmentation by the incident UV light disturbs the TALIF measurement of the discharge-originated atomic oxygen. Therefore, compensation for ozone interference is necessary in atomic oxygen measurements. In this study, we propose a method to separate ozone interference from the discharge-originated atomic oxygen signal by focusing on different TALIF signal dependence on the laser intensity between atomic oxygen d...

The structure, magnetic and thermal properties of (FePt 0.78 –C 0.22 )–BN granular films with various BN volume concentrations are systematically studied. Compared to the FePt–C film without BN doping, the grain size distribution of the FePt grains is reduced by 50% with BN component is 10 vol.%, and the coercivity and the intrinsic switching field distributions of the film are increased 3 times and narrowed by 35%, respectively, when BN component is 6 vol.%. The improvement in magnetic properties is attributed to the enhanced chemical ordering of the FePt L1 0 phase. Based on the 3 ω method, it is found that the relative cross-plane thermal conductivity ##IMG## [http://ej.iop.org/images/0022-3727/53/13/135002/dab680dieqn001.gif] of the FePt–C–BN layer is more correlated to the grain size distribution of the film, which decreases to the minimum value at 10 vol.% BN. Our results indicate that a certain amount of BN doping...

The accuracy control of oxygen-correlated defect densities in the lattice of metal oxide semiconductors is one of the remaining issues restricting the performance of metal oxide-based devices and their commercialization process. This study has successfully realized the gradient control of defects in amorphous InGaZnO through various strategies. X-ray photoelectron spectroscopy results reveal that the 350 °C thermal annealing accompanied with 300 °C pre-treatment is more conducive to improve the quality of a-IGZO and suppress the density of oxygen vacancy defects. Correspondingly, the initial electrical properties of a-IGZO thin-film transistor treated by gradient annealing procedures is superior to those of the devices with one-step 350 °C routine annealing or combined with an intermediate N 2 O plasma treatment. It is demonstrated that the gradient annealing procedures effectively improve the quality of a-IGZO bulk and its adjacent interfaces. More importantly, the not...

Multilayer Zn 50 Sb 50 /Ge 8 Sb 92 (ZS/GS) thin films were proposed and fabricated by alternate sputtering. The crystallization behaviors of nanocomposite ZS/GS thin films induced by heating were investigated by in situ resistance measurement. The crystallization behaviors of ZS/GS thin films can be regulated by tuning the thickness ratio and periods. The multilayer [ZS (8 nm)/GS (4 nm)] 4 ([ZS(8)/GS(4)] 4 ) thin film exhibits a high crystallization temperature (~ 245 °C), a large crystallization activation energy (2.61 eV), and high data retention ability (168 °C). The phase structure and thickness variation of the [ZS(8)/GS(4)] 4 thin film were analyzed through x-ray diffraction (XRD) and x-ray reflection (XRR), respectively. The volume shrinkage during crystallization was as small as 3.9%. The multilayer structure and interface stability were confirmed by using transmission electron microscopy (TEM). A p...

Switchable multi-channel electromagnetic induced transparency (EIT) is achieved in designed terahertz metasurfaces. The underlying physics of the EIT effect is analyzed. The influence of structure parameters on the EIT effect is investigated. A metasurface with a symmetrical unit cell is proposed, by which polarization-independent EIT is achieved. In addition, photosensitive silicon is integrated into the metal layer aiming for active modulation. Tunable EIT with adjustable peak frequency and amplitude is obtained. Moreover, the dynamic control is not limited to a single EIT transparency window. We show that the number of EIT transparency windows can be tailored, and switchable multi-channel EIT are successively realized. The results would provide significant guidance in multifunctional active devices, such as modulators and switches in nanophotonics optics.

Nitrogen fixation is a topic of continuing interest to researchers from generation to generation. Owing to the unique characteristics of plasma, its application to nitrogen fixation has recently attracted attention in the distributed chemical manufacturing field, i.e., making fertilizers on site. The incorporation of nitrogen as either ‘lattice nitrogen’ or ‘chemical nitrogen’, composing functional groups through plasma technology to form nitrogen-containing nanomaterials, is of great importance, since various properties or new functionalities can be achieved for nanomaterials with suitable nitrogen content. This review looks at the state of the art. Firstly, based on generated N-containing nanomaterials such as nitrides, carbonitrides, oxynitrides, oxycarbonitride, and N-doped/implanted nanostructures, the developed plasma-assisted processes and typical cases are classified and displayed. Possible mechanisms related to the N-fixation process using NH 3 and N 2

3R-delafossite CuGaO 2 sample with high crystallinity and single phase was prepared by simple low-temperature hydrothermal method. The fundamental physicochemical properties of 3R-delafossite CuGaO 2 were systematically studied by density functional theory calculations and experimental characterization. Through a series of characterization, analysis, (photo)electrochemical and photocatalytic activity testing, the as-prepared CuGaO 2 samples exhibit the potential for hydrogen production and high photocatalytic degradation for tetracycline hydrochloride (TCH). Furthermore, CuGaO 2 photoelectrode exhibits long-term stability and large photocurrent density. These observations suggest that 3R-delafossite CuGaO 2 is a potential promising photocatalyst driven by visible-light. Finally, possible breakthrough directions of 3R-delafossite CuGaO 2 photocatalyst are discussed.

Memristive devices based on 2D materials, such as WSe 2 and MoS 2 , have been demonstrated to exhibit analogue switching characteristics and enable emulation of ionic interactions involved in synaptic activities. These attractive features hold great potential for construction of energy-efficient artificial neural networks. However, the memristors made from pristine 2D materials typically exhibit a small dynamic range and poor linearity of switching characteristics. The neural network simulated in the basis of such switching characteristics has a poor learning accuracy of ~43%. In this work, we find that Ar plasma treatment can greatly improve both the dynamic range and linearity of analogue switching characteristics of few-layer MoS 2 memristors. The neural network consisting of such plasma-treated memristors is simulated to be able to result in a significantly improved learning accuracy of 94.3% for the MNIST handwritten digits dataset. Our addition...

For heavy ions implanted in low- Z targets it is possible to determine the depth and concentration of introduced heavy impurities by studying the energy spectra of electrons scattered from the surface. Here, we demonstrate this for the case of 30 and 300 keV Au implantation in SiO 2 . For high-energy incoming electrons the elastic peak splits up in different components as the recoil losses depends on the mass of the scattering atom. Heavy impurities also affect the partial intensities and hence changes in the shape of the energy loss spectra are observed. These effects are reproduced by a simple model that uses sample composition, atomic elastic scattering cross sections and target dielectric function as input.

We have studied, experimentally and theoretically, the effect of a layering sequence on the magnonic band structure in dense arrays of both asymmetric- and symmetric cross-section tri-layered Py/Cu/Fe and Fe/Cu/Py nanowires. The spin-wave dispersion for these artificial crystals has been measured with Brillouin light scattering (BLS) spectroscopy. We also carried out numerical simulations of the dispersion using an original model employing a 2D Green’s function description of the dynamic dipole field of the precessing magnetization. The presence of the Cu spacer exchange-decouples the two magnetic layers, which stabilizes two equilibrium states of static magnetization. These are the parallel and antiparallel states, for which the static magnetization vectors for the layers are either co-aligned or anti-aligned to each other, respectively. These states are stable in a range of applied fields that depend on the layer width and their ordering in the stack. The magnetization configu...

In this paper, a nanoscale vacuum channel transistor (NVCT) with a side-gate structure is fabricated by standard electron beam lithography. The states of the proposed NVCTs could be effectively modulated by side-gate bias, exhibiting a drive current (>400 nA), low work voltage (<20 V) and high on/off current ratio (>10 3 ). Moreover, we further optimize the shapes of the electrodes, demonstrating that the electric performance is closely related to the structure parameters. The side-gate NVCT offers an alternative method to fulfill the on-chip vacuum devices with high integration.

This paper presents new contributions to the study of the positive discharge in large air gaps. A model enabling us to determine the voltage U50 and the k -factor in non-standard geometry using the circuit model developed by Beroual’s group for long positive and negative discharges is presented. This model is based on an equivalent circuit diagram, the parameters of which vary with time according to the leader channel characteristics and the geometry/morphology of the discharge. The propagation of the leader is based on a criterion related to the calculation of the electric field at its head and that takes into account the randomness of the discharge path. As with most of models found in the literature, this model applies only to the point-plane type electrodes gap. This paper consists of two parts: (1) the first part, presents how to extend the proposed model to complex geometries such as rod–rod electrode gaps; and (2) the second part presents the experimental tests we a...

The dispersion relations for bulk and surface plasmon-polaritons in a semi-infinite 1D photonic crystal interlayered with graphene are calculated in the presence of an applied magnetic field. The results are applied to SiO 2 as the constituent material in geometry where the layers are arranged in a periodic array with the same layer thickness. The static magnetic field is applied perpendicular to the plane of layers. Numerical results are presented for the modes in THz range, up to 10 THz, to illustrate the important role of the applied magnetic field on the graphene sheets in modifying the polariton dispersion curves, especially for magnetic fields of the order of 1 T. It is found that the polariton frequencies and band gaps have a sensitive dependence on the electron scattering rate parameter (and hence the applied magnetic field strength) in the graphene sheets. Electromagnetic retardation effects are fully taken into account for the bulk bands, while for the surfac...

In this paper, the whispering gallery mode lasing from Sm 3+ doped ZnO micro-spheres operating in the visible wavelength range 550–750 nm is studied. Highly smooth and crystalline Sm 3+ :ZnO micro-spheres of various diameters were synthesized by simple laser ablation of sintered target in air. The dopant concentration has been restricted within the solid solubility limit of 1 mol%. The Sm 3+ ion substitution in ZnO matrix results in the formation of inter-band levels by the characteristic 4f level of Sm 3+ in the forbidden gap of ZnO. Thus, when the micro-spheres are excited with 488 nm, four major visible emissions associated with Sm 3+ ##IMG## [http://ej.iop.org/images/0022-3727/53/13/135302/dab5730ieqn001.gif] transitions namely, transitions from ##IMG## [http://ej.iop.org/images/0022-3727/53/13/135302/dab5730ieqn002.gif] to its low-lying multiplets of ##IMG## {...}

The concept of overmoded coupling pattern for matching with the cut-off resonant condition in a THz sheet beam resonant system is proposed to build up super double-overmoded extended interaction field for high power THz radiation. A physical design procedure is proposed to support the matched overmoded coupling pattern. The three-dimensional electromagnetic characteristic of the super overmoded field is studied to demonstrate the effectiveness of the procedure for clarifying the relationship between the overmoded coupling pattern and cut-off resonant condition. This relationship is analyzed by focusing on (1) the distribution characteristic of the overmoded coupling pattern associated with the specific boundaries inside the structure, (2) the equivalent method for describing the interaction impedance in sheet beam system, (3) magnitude of the internal field strength, and (4) variation of the ohmic loss. The simulation results show the typical cut-off resonant condition can be es...

The disordering process in crystalline GeSb 2 Te 4 films has been studied by means of ion irradiation with 150 keV Ar + ions. The effect of the interfaces and the role of the crystal microstructure has been investigated. The disordering path observed in a randomly oriented polycrystalline material with trigonal structure involves the transition to the disordered rocksalt structure (at fluence 7 × 10 13 cm −2 ) and then to the amorphous phase (at 1.5 × 10 14 cm −2 ). In GeSb 2 Te 4 epitaxially grown on Si(1 1 1) the formation of the disordered rocksalt phase (DRS) occurs at much higher fluence (3 × 10 14 cm −2 ) and it is preceded by the conversion of the stable phase into the ordered rocksalt structure (at 5 × 10 13 cm −2 ), with the formation of ordered vacancy layers, associated to a local variation of the stoichiometry. Even by increasing the flu...

Multifunctional terahertz devices hold great promise for terahertz (THz) optical systems. Here, we present an ultrathin, highly flexible and optically transparent terahertz polarizer based on tin-doped indium oxide (ITO) and flexible conformal films of polyethylene terephthalate. The flexible optical transparent polarizer (FOTP) was theoretically investigated and experimentally characterized by UV–vis spectrophotometry and THz time-domain system. In the FOTP, THz conductivity of ITO films is mainly dominated by DC conductivity. The FOTP reveals a high optical transmittance of more than 60% in the visible region, a high extinction ratio of about 20 dB in the 0.1 THz–2.5 THz and a low insertion loss below 2 dB in the 0.1 THz–1.4 THz. The proposed FOTP can significantly improve the overall performance of THz optical systems and be easily fabricated by commercial display techniques. Our concept opens up a new window for highly flexible and optically transparent THz devices.

Here, we present an analytical modeling of electron mobility in two dimensional electron gas (2DEG)-yielding MgZnO/ZnO heterostructures, to ascertain dominant scattering mechanisms and physical parameters responsible for one-order lower value of electron mobility in sputtering-grown heterostructure as compared to that in molecular beam epitaxy-grown heterostructure. This work extensively probes all scattering components and their physical parameters, such as dislocation density, impurity density, mole fraction, 2DEG density, correlation length and lateral size, for their respective effects on electron mobility of sputtered heterostructure. The results suggest that dislocation density and alloy disorder scattering are the most dominant sources responsible for reduced electron mobility. This work is extremely crucial for achieving high electron mobility by optimizing the material growth parameters to attain low dislocation density, impurity density and interface roughness, for the...

In this study, we investigated the antimicrobial effects of plasma activated fine droplet (PAD) produced from arc discharge plasma on planktonic Listeria monocytogenes and Escherichia coli O157:H7. NaCl (0.9%, w/v) was used as the feeding solution for the plasma discharge. The inactivation mechanism of the PAD treatment was also investigated. PAD mainly contains H 2 O 2 and OCl − , which play a significant role in the inactivation process against L. monocytogenes and E. coli O157:H7. The population of L. monocytogenes and E. coli O157:H7 was significantly reduced by approximately 3 and 4 log units, respectively, within 5 min of exposure to PAD. However, the bactericidal effects of PAD against L. monocytogenes and E. coli O157:H7 showed different trends by showing 0.58 and 4.13 log reductions, respectively, after 1 min of PAD exposure time. The change of membrane integrity was evaluated using two ...

We have investigated the behavior of the optical transduced signal of a photonic integrated polymer micro resonator as an evaporating water droplet is positioned upon it. The photonic chip is fabricated by means of deep-UV photolithography, and the circuits are made of polymer UV210. The device is then arranged in an optical bench so as to perform relevant measurements thanks to a broadband laser for the excitation of the resonators and an optical spectrum analyzer remotely controlled by a Matlab software for the acquisition and treatment of data. By dynamically tracking the free spectral range (FSR) of the optical mode, we come up with a signature of the thermodynamic evaporation process. In order to correlate this signature to the evaporation speed of the water droplet, a lateral camera is disposed to measure the evolution of the geometrical characteristics of the droplet, while weight measurements are performed thanks to a precision balance. These measurements provide a numer...

Komagataeibacter xylinus ( K. xylinus ) has been used for a long time as one of the main cellulose producers among bacterium. In order to gain a better understanding of the physiological and biochemical mechanisms of cellulose production, an efficient and non-invasive visualization method is highly demanded to monitor the morphological changes of K. xylinus during each stage of its development. In this study, a polarization parametric indirect microscopic imaging (PIMI) technique was applied to image the morphology variations of K. xylinus . The optical field with precisely controlled polarization status was incident on the sample and far-field images of the sample were taken under different illumination polarization. In the calculated parametric images, sub-diffraction features related to the morphology details of the K. xylinus were visualized with high contrast and spatial resolution, which is typically irresolvable in conventional microscopic...

The excitation and dissociation of CO 2 admixed to argon and helium atmospheric pressure radio frequency plasmas is analyzed. The absorbed plasma power is determined by voltage and current probe measurements and the excitation and dissociation of CO 2 and CO by transmission mode Fourier-transform infrared spectroscopy (FTIR). It is shown, that the vibrational temperatures of CO 2 and CO are significantly higher in an argon compared to a helium plasma. The rotational temperatures remain in both cases close to room temperature. The conversion efficiency, expressed as a critical plasma power to reach almost complete depletion, is four times higher in the argon case. This is explained by the lower threshold for the generation of energetic particles (electrons or metastables) in argon as the main reactive collision partner, promoting excitation and dissociation of CO 2 , by the less efficient quenching of vibrational excited states of CO and CO<...

Recently, the Janus monolayer with structural symmetry-breaking has been synthesized, which displays many special physical and chemical properties. However, the regulation about its electronic structure as an important application in hydrogen evolution reaction (HER) has not been explored so far. Herein, the H and T phased MoSSe monolayer is considered as model to discuss the contribution of structural deformation to electronic structure and Gibbs free energies, searching for a potential application in HER. The calculations disclose that tensile strain not only efficiently reduces the band gap of MoSSe but also makes the Gibbs free energy of adsorbed hydrogen close to zero. Our calculations provide a new insight into regulating material’s electronic structure and HER performance.

Ferromagnetic metal/oxide heterostructures with tunable perpendicular magnetic anisotropy (PMA) and large tunnel magnetoresistance (TMR) are building blocks of spintronic devices. With unprecedented high performance, the perpendicularly magnetized CoFeB/MgO system has been extensively investigated. Here, we report that Mo/FeNiB/MgO and its inverted structure MgO/FeNiB/Mo show large interfacial PMA with high thermal stability, it ensures spontaneous perpendicular magnetization with effective PMA field of about 5 kOe in Mo/FeNiB(1.2 nm)/MgO and MgO/FeNiB(1.5 nm)/Mo after annealing at 400 °C, comparable to the CoFeB/MgO system. Remarkably, the coercivity of perpendicularly magnetized FeNiB layers in either continuous film or patterned structure of micrometers is smaller than that of the CoFeB counterpart by an order. We have fabricated perpendicular magnetic tunnel junctions with pseudo-spin valve structure Mo/FeNiB/MgO/CoFeB/Mo, which show TMR of 113% at room temperature and 221% ...

We report on the direct observation and simultaneous use of the linear and quadratic electro-optical effect and propose a method by which higher-order susceptibilities of electro-optical materials can be determined. The evaluation is based on the separation of the second- and third-order susceptibilities and the experimental technique uses a slot waveguide ring resonator fabricated in integrated photonic circuit technology, which is embedded by a guest-host polymer system consisting of the azobenzene dye Disperse Red 1 in a poly(methyl methacrylate) matrix as an active electro-optical material. The contribution of both effects on the electro-optical response under the influence of static and time-varying electrical fields is investigated. We show that the quadratic electro-optical effect has a significant influence on the overall electro-optical response even with acentric molecular orientated molecules. Our findings have important implications for developing electro-optical dev...

Semiconductor nanocrystals have shown remarkable performance in the field of displays, solar cells, and photodetectors. But, a rapid method to produce localized stable nanocrystals remains a challenge, impeding the step toward device miniaturization. Here, we present a general and fast approach, femtosecond laser direct writing, for manufacturing these nanocrystals as well as integrating them into substrates in one step. The high peak power of the femtosecond laser induces a nonlinear absorption of the CatX (Cat = Cd or Pb, X = S, Se or Te) precursor at the focal spot. Once the temperature reaches the nucleation temperature, the CatX nanocrystals form immediately. By moving the displacement platform, arbitrary microscale patterns made of nanoscale crystals are obtained, which shows great potential in high-resolution displays and on-chip light sources.

The collection of light emitted from a plasma or other volumetric light source is often collected using an optical collimator coupled to an optical fibre. In this work the spatial dependence of transmission from a light source into a fibre via a variety of collimating lens systems is investigated using a table top optical setup and a full 3D ray tracing simulation. The solid angle emitted from a point source that is accepted into the fibre is found to depend in a complex and unintuitive manner on the spatial position of the source relative to the optical system. Back-illumination is often used to focus the optical system such that it produces a well defined beam, which is then assumed as a ‘line of sight’. However even in these cases there are non-monotonic behaviours within this ‘line of sight’ that mean the often-made assumption of a single acceptance angle or cone of observation is not valid in these systems. This has significant implications for the application of these opti...

The magnetization dynamics of ultrathin epitaxial Fe films on GaAs (0 0 1) with different thicknesses have been investigated by all-optical time-resolved magneto-optical Kerr effect. For the Fe film with thickness of 8 monolayers, the magnetic damping constant along ##IMG## [http://ej.iop.org/images/0022-3727/53/11/115004/dab61cdieqn001.gif] orientation increases by 66% compared with that along ##IMG## [http://ej.iop.org/images/0022-3727/53/11/115004/dab61cdieqn002.gif] orientation, showing the uniaxial anisotropy of magnetic damping. By the measurement of angular dependent time-resolved magneto-optical Kerr effect, the uniaxial magnetic damping is clearly correlated to the in-plane uniaxial anisotropy field of the Fe film. In addition, the anisotropy of the damping constants is found to disappear for the Fe films thicker than 15 monolayers, suggesting that the anisotropic damping originates from the interfacial effect between Fe...

Topologically protected 1D edge states and the 2D surface states have been observed in variant classical wave systems. By extending the quantized polarization, Berry phase, to higher multipole moments, the higher-order topological phases, expressed as 0D corner states, have been theoretically predicted and recently experimentally observed in electric, electromagnetic and acoustic systems. In this paper, we design an elastic phononic plate consisting of a bi-layered hexagonal lattice. The valley-polarized gapless 1D edge state is observed in the elastic phononic plate, by lifting the Dirac cones at the Brillouin zone (BZ) corners. When the bi-layered phononic plates are stacked one by one, the chirality of the oblique columns along the z axis guarantees this 2D elastic phononic plate to be a 3D chiral phononic system. Weyl cones and topologically protected gapless 2D surface states are yielded in this 3D chiral phononic system. The above topological phases are first-order ...

We performed direct microwave power injection into Pt/YIG, a heavy metal/ferrimagnetic insulator bilayer structure. The induced heating effect plays an important role in the interpretation of the ferromagnetic resonance signal. According to our frequency dependent measurements, we found the heat-induced inhomogeneous broadening in addition to the spin Hall magnetoresistance (SMR). From the angular dependent measurement, the thermal signals both in non-resonant and resonant states were observed, consistent with the angular dependence of longitudinal spin Seebeck signal. The heating effect from the injected rf power not only gives rise to the increase of inhomogeneous broadening factor Δ H 0 , but also contributes to the increase of damping constant, Δ α .

Heavy metal elements with strong spin–orbit coupling generally play an important role for perpendicular magnetic anisotropy (PMA) in magnetic heterostructures. We examined interface PMA and related properties in single crystal Fe/MgO(0 0 1) heterostructures in which a very thin W interface layer was nominally inserted as doping. The PMA energy density was reduced with increasing the W layer thickness, in contrast to the results in a similar study using poly-crystal FeB/MgO heterostructures (Nozaki et al 2018 APL Mater . 6 026101), suggesting that the detailed mechanisms of PMA are different between single crystal Fe/MgO and poly-crystal FeB/MgO. X-ray magnetic circular dichroism measurements revealed that anisotropy in the Fe orbital magnetic moments decreased with the PMA energy density, i.e. the PMA observed was interpreted in the framework of Bruno’s model (Bruno 1989 Phys. Rev . B 39 R865). The coefficient of the voltage effect of PMA arising...

We perform a systematic investigation of MnPSe 3 /CrBr 3 two-dimensional (2D) van der Waals heterostructures through first-principles calculations. The most stable stacking configuration of MnPSe 3 /CrBr 3 heterostructures is found to have an indirect type-II band structure. Biaxial tensile strain is employed to tailor the spin–valley properties of the heterostructures in terms of the momentum, energy and spin components of the valleys. A novel opposite spin splitting evolution appears at the K and K′ valleys of the top valance band (TVB) with increasing tensile strain. A change from an indirect to a direct band gap is found at 7% tensile strain. A maximum spin splitting of 34.7 meV at the K′ valley is produced simultaneously with valley polarization under a tensile strain of 10%. The spin components distributed at the TVB are found to be controlled by strain-related competition between direct exchange interaction and indirect superexchange ...

Vacuum breakdown (also known as arc or discharge) occurs when a sufficiently high electric field is applied between two electrodes in vacuum. The discharge is driven by the formation of an intensively glowing plasma at the cathode, which is followed by the ignition of an anode flare that gradually expands and fills the gap. Although it has been shown that the anode electrode does not play a significant role in the breakdown initiation, the nature of the anodic glow is of paramount importance for understanding the breakdown evolution. In this work, we use time- and space-resolved spectroscopy to study the anode flare. By using different anode and cathode materials, we find that excitations from both anode and cathode ions and neutrals contribute to the anodic glow. This implies that the cathodic plasma expands towards the anode without emitting any detectable light and starts glowing only when it reaches and interacts with the anode electrode. This interaction causes the introduc...

When permanent magnets are surrounded by ferromagnetic materials, the magnetic field lines are rerouted in the air gap between them, which provides an approach for the optimum design of the eddy current damper. To improve the conventional tubular eddy current damper design, an enhanced eddy current damper with a ferromagnetic shaft and a ferromagnetic layer is successfully developed in this study. It is passive, cost-efficient and reliable, significantly boosting the damping effect without occupying extra space. To explore the benefits of the ferromagnetic material, analytical models of the magnetic field distributions are derived to estimate the damping coefficient. In addition, the ferromagnetic material configuration and dimensions of the proposed eddy current damper are optimized for better vibration suppression. The experiment results agree reasonably well with the theoretical models and finite element predictions, and demonstrate the effectiveness and efficiency of this in...

We have investigated Ge nanowire (NW) metal–semiconductor–metal (MSM) photodetectors with high specific detectivity and low dark current, in which various sizes Ge NWs were fabricated by three-dimensional (3D) Ge condensation techniques. It has been demonstrated that the photocurrent gain increases significantly from 6.31 × 10 4 to 4.47 × 10 6 with the reduction of Ge NW width from 170 to 35 nm. A low dark current of 5.1 nA and an ultra-high specific detectivity of 1.26 × 10 14 cm·Hz 1/2 ·W −1 at 560 nm under 0.51 V bias are achieved for the 35 nm wide Ge NW photodetector. It has been proposed that the interface states provided by SiGeO x formed during Ge condensation process serve as electron traps to generate photogating effect, resulting in high photocurrent gain and high specific detectivity in the MSM photodetector. The fully complementary metal-oxide-semiconductor (CMOS) compatible and scalable proce...