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The effect of multifilament coated conductors on reducing shielding currents was studied by numerical electromagnetic field analyses. We compared the behaviours of the shielding currents in stacked double pancake coils and layer-wound solenoid coils (SLCs) wound with the following conductors: a monofilament coated conductor, a copper-plated two-filament coated conductor, and an insulated two-filament coated conductor. Shielding-current-induced fields (SCIFs) in the layer-wound SLCs wound with copper-plated two-filament coated conductors decay more rapidly than in stacked double pancake coils wound with copper-plated two-filament coated conductors. In addition, we examined the behaviour of the shielding currents in the coils with and without normal metal terminals. The normal metal terminals made the decay time constants of the SCIFs in pancake coils longer, while the decay time constants of SCIFs did not change notably in the layer-wound SLCs with and without normal metal terminals.

We present a study of the electrical, structural and chemical properties of Ti contacts on atomic layer deposited α-Ga2O3 film. Ti forms an ohmic contact with α-Ga2O3. The contact performance is highly dependent on the post-evaporation annealing temperature, where an improved conductivity is obtained when annealing at 450 °C, and a strong degradation when annealing at higher temperatures. Structural and chemical characterisation by transmission electron microscopy techniques reveal that the electrical improvement or degradation of the contact upon annealing can be attributed to oxidation of the Ti metallic layer by the Ga2O3 film in combination with the possibility for Ti diffusion into the Au layer. The results highlight that the grain boundaries and inclusions in the Ga2O3 film provide fast diffusion pathways for this reaction, leaving the α-Ga2O3 crystallites relatively unaffected—this result differs from previous reports conducted on β-Ga2O3. This study underlines the necessity for a phase-specific and growth method-specific study of contacts on Ga2O3 devices.

We report for the first time the possibility of co-extrusion of silver and potassium halide crystals to produce double-clad polycrystalline IR fibres. This combination allows the disadvantages inherent in each of the crystals separately to be overcome. The resulting fibres have stable long-term transmission and can be used to transmit CO2 laser radiation. The loss in the fibre at a wavelength of 10.6 μm constitutes 0.75 dB m−1.

A recent single–pore model for performance of cathode catalyst layer (CCL) in a low–Pt PEM fuel cell is further developed and used to fit experimental polarization curves. Analytical formula for the limiting current density is derived, which contains oxygen diffusivities in the void pore and ionomer film covering Pt/C agglomerates. Least–squares fitting of model to experimental polarization curves returns CCL proton conductivity and parameters of oxygen transport in the pore and film.

In recent years, gas electron multiplier (GEM) neutron detectors have been developing towards high spatial resolution and high dynamic counting range. We propose a novel concept of an Al stopping layer to enable the detector to achieve sub-millimeter (sub-mm) spatial resolution. The neutron conversion layer is coated with the Al stopping layer to limit the emission angle of ions into the drift region. The short track projection of ions is obtained on the signal readout board, and the detector would get good spatial resolution. The spatial resolutions of the GEM neutron detector with the Al stopping layer are simulated and optimized based on Geant4GarfieldInterface. The spatial resolution of the detector is 0.76 mm and the thermal neutron detection efficiency is about 0.01% when the Al stopping layer is 3.0 μm thick, the drift region is 2 mm thick, the strip pitch is 600 μm, and the digital readout is employed. Thus, the GEM neutron detector with a simple detector structure and a fast readout mode is developed to obtain a high spatial resolution and high dynamic counting range. It could be used for the direct measurement of a high-flux neutron beam, such as Bragg transmission imaging, very small-angle scattering neutron detection and neutron beam diagnostic.

A GaN-based high electron mobility transistor (HEMT) with p-GaN islands buried layer (PIBL) for terahertz applications is proposed. The introduction of a p-GaN island redistributes the electric field in the gate–drain channel region, thereby promoting the formation of electronic domains in the two-dimensional electron gas (2DEG) channel. The formation and regulation mechanism of the electronic domains in the device are investigated using Silvaco-TCAD software. Simulation results show that the 0.2 μm gate HEMT with a PIBL structure having a p-GaN island doping concentration (N p) of 2.5 × 1018 cm−3–3 × 1018 cm−3 can generate stable oscillations up to 344 GHz–400 GHz under the gate–source voltage (V gs) of 0.6 V. As the distance (D p) between the p-GaN island and the heterojunction interface increases from 5 nm to 15 nm, the fundamental frequency decreases from 377 GHz to 344 GHz, as well as the ratio of oscillation current amplitude of the fundamental component to the average component I f/I avg ranging from 2.4% to 3.84%.

As the main distribution place of deep-level defects and the entrance of water, the interface is critical to determining both the power conversion efficiency (PCE) and the stability of perovskite solar cells (PSCs). Suitable interface design can dramatically passivate interface defects and optimize energy level alignment for suppressing the nonradiative recombination and effectively extracting the photogenerated carriers towards higher PCE. Meanwhile, a proper interface design can also block the interface diffusion of ions for high operational stability. Therefore, interface modification is of great significance to make the PSCs more efficient and stable. Upon optimized material choices, the three-dimensional halide perovskite graded junction layer, low-dimensional halide perovskite interface layer and organic salt passivation layer have been constructed on perovskite films for superior PSCs, yet a systematic review of them is missing. Thus, a guide and summary of recent advances in modulating the perovskite films interface is necessary for the further development of more efficient interface modification.

A lateral insulated gate bipolar transistor (LIGBT) based on silicon-on-insulator (SOI) structure is proposed and investigated. This device features a compound dielectric buried layer (CDBL) and an assistant-depletion trench (ADT). The CDBL is employed to introduce two high electric field peaks that optimize the electric field distributions and that, under the same breakdown voltage (BV) condition, allow the CDBL to acquire a drift region of shorter length and a smaller number of stored carriers. Reducing their numbers helps in fast-switching. Furthermore, the ADT contributes to the rapid extraction of the stored carriers from the drift region as well as the formation of an additional heat-flow channel. The simulation results show that the BV of the proposed LIGBT is increased by 113% compared with the conventional SOI LIGBT of the same length L D. Contrastingly, the length of the drift region of the proposed device (11.2 μm) is about one third that of a traditional device (33 μm) with the same BV of 141 V. Therefore, the turn-off loss (E OFF) of the CDBL SOI LIGBT is decreased by 88.7% compared with a conventional SOI LIGBT when the forward voltage drop (V F) is 1.64 V. Moreover, the short-circuit failure time of the proposed device is 45% longer than that of the conventional SOI LIGBT. Therefor, the proposed CDBL SOI LIGBT exhibits a better V F–E OFF tradeoff and an improved short-circuit robustness.

We present an analysis of parallel electron energy transport in the scrape-off layer (SOL), considering the convective and conductive channels, as well as the radiation and neutral inelastic energy transfer channels involving atomic deuterium. Kinetic effects in both equilibria and conductive transients are explored by utilizing the capability of the SOL-KiT code to treat electrons as either a fluid or kinetically. We find kinetic effects in multiple channels, with an emphasis on those occurring during the investigated conductive transients. Energetic electron effects in the heat flux, as well as a modification of ionization rates of up to 40% compared to Maxwellian rates during perturbations in detached conditions, are reported and discussed.

We present the first parallel electron transport results obtained using the newly developed 1D transport code SOL-KiT. With the capability to switch between consistent kinetic and fluid models for the electrons, we explore and report the differences in both equilibrium and transient simulations. Significant kinetic effects are found during transients, especially in the behaviour of the electron sheath heat transmission coefficient, which shows up to an eightfold increase. Equilibria are obtained for an input power scan with parameters relevant to medium size tokamaks. Detached equilibria are found to persist to higher input powers when electrons are treated kinetically. Furthermore, non-monotonic behaviour of the electron sheath heat transmission coefficient is observed in the power scan, with values being up to 40% above the classical value. We discuss the implications of the pr

An extrinsic electron induced by a dielectric (EID) AlGaN/GaN MOS high-electron-mobility transistor (HEMT) on Si substrate was designed and investigated. The EID structure with SiO2 deposition and subsequent high-temperature annealing, which induces two-dimensional electron gases (2DEGs) on fully depleted AlGaN/GaN hetero-epitaxial layers with thin AlGaN barrier layer, was applied to access and drift regions in the HEMT. The fabricated HEMT exhibited enhancement-mode operation with a specific on-resistance of 7.6 mΩ cm2 and a breakdown voltage of over 1 kV. In addition, electron state analysis using hard X-ray photoelectron spectroscopy revealed that changes in the chemical states of Al and energy level lowering at the SiO2/AlGaN interface affect the induction of 2DEG in the EID structure. The proposed HEMTs should become a strong candidate for highly reliable high-power switching devices due to the damage-less fabrication without dry etching or fluorine plasma exposure processes on the semiconductor layers.

Hexagonal boron nitride (h-BN) is an important insulating layered material for two-dimensional heterostructure devices. Among many applications, few-layer h-BN films have been employed as superior tunneling barrier films. However, it is difficult to construct a heterostructure with ultra-thin h-BN owing to the poor visibility of flakes on substrates, especially on a metallic surface substrate. Since reflectance from a metallic surface is generally high, a h-BN film on a metallic surface does not largely influence reflection spectra. In the present study, a thin Au layer with a thickness of ∼10 nm deposited on a Si substrate with a thermally grown SiO2 was used for visualizing h-BN flakes. The thin Au layer possesses conductivity and transparency. Thus, the Au/SiO2/Si structure serves as an electrode and contributes to the visualization of an ultra-thin film according to optical interference. As a demonstration, the wavelength-dependent contrast of exfoliated few-layer h-BN flakes on the substrate was investigated under a quasi-monochromatic light using an optical microscope. A monolayer h-BN film was recognized in the image taken by a standard digital camera using a narrow band-pass filter of 490 nm, providing maximum contrast. Since the contrast increases linearly with the number of layers, the appropriate number of layers is identified from the contrast. Furthermore, the insulating property of a h-BN flake is examined using a conductive atomic force microscope to confirm whether the thin Au layer serves as an electrode. The tunneling current through the h-BN flake is consistent with the number of layers estimated from the contrast.

The effect of annealing on the physical properties of an SnS thin film and also on SnS/CdS heterojunction band alignment was studied. Vacuum annealing has greatly improved the crystalline quality of SnS and an average grain size of 1.6 μm was achieved. Sulfur-rich secondary phases observed on the surface of as-grown SnS thin film were eliminated after vacuum annealing, resulting in a decrease of the resistivity and an increase of the carrier concentration of the film. A maximum hole mobility of 17 cm2 V−1 s−1 was obtained for SnS thin films annealed at 400 °C. A transition of SnS/CdS heterojunction from “spike” type to “cliff” type was observed when the vacuum annealed SnS thin film was post-air-annealed at 200 and 250 °C. The band alignment of SnS/CdS heterojunction could be adjustable between “spike” type to “cliff” type via vacuum annealing followed by post-air-annealing.

Perovskite solar cells (PSCs) are the most promising commercial photoelectric conversion technology in the future. The planar p–i–n structure cells have advantages in negligible hysteresis, low temperature preparation and excellent stability. However, for inverted planar PSCs, the non-radiative recombination at the interface is an important reason that impedes the charge transfer and improvement of power conversion efficiency. Having a homogeneous, compact, and energy-level-matched charge transport layer is the key to reducing non-radiative recombination. In our study, NiO x /Sr:NiO x bilayer hole transport layer (HTL) improves the holes transmission of NiO x based HTL, reduces the recombination in the interface between perovskite and HTL layer and improves the device performance. The bilayer HTL enhances the hole transfer by forming a driving force of an electric field and further improves J sc. As a result, the device has a power conversion efficiency of 18.44%, a short circuit current density of 22.81 mA⋅cm−2 and a fill factor of 0.80. Compared to the pristine PSCs, there are certain improvements of optical parameters. This method provides a new idea for the future design of novel hole transport layers and the development of high-performance solar cells.

Cu2ZnSnS4 (CZTS) is interesting as a light absorption layer for thin-film solar cells because it consists of only earth-abundant materials such as copper, zinc, tin, and sulfur. The poor adhesion between CZTS and molybdenum (Mo), which is the back metal contact material, causes CZTS to peeling off during the chemical bath deposition (CBD) for the formation of CdS as a buffer layer. This induces severe degradation of the solar cell performance. In this study, we investigated the effect of annealing following back contact metal layer formation on CZTS stability and solar cell performance. By annealing Mo/soda lime glass at 400 °C in atmosphere, Mo was oxidized, and the surface roughness of Mo increased. On the Mo surface, the CZTS peeling off was suppressed during the CBD process, resulting in an improvement in the shunt resistance.

Au layer thickness dependence (9–34 nm) of Ge crystallization in the metal-induced layer exchange process has been investigated. It has been found that Ge crystals are (111) oriented when the Au layer is as thin as 9 nm, whereas crystal grains are randomly oriented when the Au layer is as thick as 34 nm. The difference is discussed in terms of the difference in the position of nucleation sites of Ge crystals.

This paper investigated the multi-level 2-bit/cell operation utilizing a Hf-based metal/oxide/nitride/oxide/silicon (MONOS) nonvolatile memory (NVM) device with a HfO2 and HfON tunneling layer (TL). The 2-bit/cell operation is realized by utilizing the localized charge injection method. It was found that drain-current–gate-voltage (I D–V G) characteristics of the programmed states were affected by asymmetry localized in a trapped location along the channel direction. Moreover, the amount of localized trapped charge is strongly affected by drain-source voltage (V DS) in the case of HfON TL. HfON TL shows distinguishable separated all programmed states compared to HfO2 TL. Finally, it was found that all programmed states of HfO2 and HfON TL show similar characteristics according to the channel length and width (L/W) of 2–10/15–90 μm.

Atomic layer etching (ALE) of thin film GaN (0001) is reported in detail using sequential surface modification by BCl3 adsorption and removal of the modified surface layer by low energy Ar plasma exposure in a reactive ion etching system. The estimated etching rate of GaN is ∼ 0.74 nm/cycle. The GaN is removed from the surface of AlGaN after 135 cycles. To study the mechanism of the etching, the detailed characterization and analyses are carried out, including scanning electron microscope (SEM), x-ray photoelectron spectroscopy (XPS), and atomic force microscope (AFM). It is found that in the presence of GaCl x after surface modification by BCl3, the GaCl x disappears after having exposed to low energy Ar plasma, which effectively exhibits the mechanism of atomic layer etch. This technique enables a uniform and reproducible fabrication process for enhancement-mode high electron mobility transistors with a p-GaN gate.

Temperature-dependent and driving current-dependent electroluminescence spectra of two different InGaN/GaN multiple quantum well structures SA and SB are investigated, with the In composition in each well layer (WL) along the growth direction progressively increasing for SA and progressively decreasing for SB. The results show that SB exhibits an improved efficiency droop compared with SA. This phenomenon can be explained as follows: owing to the difference in growth pattern of the WL between these two samples, the terminal region of the WL in SB contains fewer In atoms than in SA, and therefore the former undergoes less In volatilization than the latter during the waiting period required for warming-up due to the difference in the growth temperature between well and barrier layers. This results in SB having a deeper triangular-shaped potential well in its WL than SA, which strongly confines the carriers to the initial region of the WL to prevent them from leaking to the p-GaN side, thus improving the efficiency droop. Moreover, the improvement in the efficiency droop for SB is also partly attributed to its stronger Coulomb screening effect and carrier localization effect.

Pd/Co2MnSi (CMS)/NiFe2O4 (NFO)/Pd multilayers were fabricated on F-mica substrate by magnetron sputtering. The best PMA performance of the multilayer structure Pd(3 nm)/CMS(5 nm)/NFO(0.8 nm)/Pd(3 nm) was obtained by adjusting the thickness of the CMS and NFO layers. F-mica substrate has a flatter surface than glass and Si/SiO2 substrate. The magnetic anisotropy energy density (K eff) of the sample deposited on F-mica substrates is 0.6711 Merg/cm3 (1 erg=10−7 J), which is about 30% higher than that of the multilayer films deposited on glass (0.475 Merg/cm3) and Si/SiO2 (0.511 Merg/cm3) substrates, and the R Hall and H C are also significantly increased. In this study, the NFO layer prepared by sputtering in the high purity Ar environment was exposed to the high purity O2 atmosphere for 5 min, which can effectively eliminate the oxygen loss and oxygen vacancy in NFO, ensuring enough Co–O orbital hybridization at the interface of CMS/NFO, and thus effectively improve the sample PMA.

Funder: H2020 Marie Skłodowska-Curie Actions; doi: https://doi.org/10.13039/100010665, Hexagonal boron nitride (h-BN) is well-established as a requisite support, encapsulant and barrier for 2D material technologies, but also recently as an active material for applications ranging from hyperbolic metasurfaces to room temperature single-photon sources. Cost-effective, scalable and high quality growth techniques for h-BN layers are critically required. We utilise widely-available iron foils for the catalytic chemical vapour deposition (CVD) of h BN and report on the significant role of bulk dissolved species in h-BN CVD, and specifically, the balance between dissolved oxygen and carbon. A simple pre-growth conditioning step of the iron foils enables us to tailor an error-tolerant scalable CVD process to give exceptionally large h-BN monolayer domains. We also develop a facile method for the improved transfer of as-grown h-BN away from the iron surface by means of the controlled humidity oxidation and subsequent rapid etching of a thin interfacial iron oxide; thus, avoiding the impurities from the bulk of the foil. We demonstrate wafer-scale (2 inch) production and utilise this h-BN as a protective layer for graphene towards integrated (opto) electronic device fabrication., European Union's Horizon 2020 research and innovation program under Grant Agreement No number 785219. European Union's Horizon 2020 research and innovation program under Grant Agreement No number 796388. the Royal Commission for the Exhibition of 1851. EU Marie Skłodowska-Curie Individual Fellowship (Global) under grant ARTIST (No. 656870). EPSRC (EP/P005152/1, and Doctoral Training Award EP/M508007/1). U.K. Department of Business, Energy and Industrial Strategy (NPL Project Number 121452).

We have measured acoustic signals emerging in the melting of a thin (about 2 μm) ice layer, which is sandwiched between two substrates, under high-power laser irradiation at a wavelength of 2940 nm. A negative-pressure acoustic signal arising from the difference in the specific volumes of water and ice was found to occur in the ice melting. The amplitude of this signal was comparable to the amplitude of the positive-pressure signal produced under laser irradiation of the same layer of water. The shapes of acoustic signals were measured for different energy densities of the incident radiation. The variation of negative-pressure pulse shape with increasing radiation energy density was interpreted as a continuity break of the medium. The temperature and pressure in the layer were estimated in the heating of water and the melting of ice.

In this work, we systematically investigated the carrier transport of hysteresis-free amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) incorporating high-k (HfO2) x (Al2O3) y gate dielectrics with different composition and permittivity by atomic layer deposition. A dielectric surface morphology dominated interface scattering carrier transport mechanism is demonstrated, and the effect of the dielectric polarization and the interface states on the carrier mobility is discovered in TFT devices gated by high quality dielectrics with negligible charge trap effect. Accordingly, an a-IGZO TFT gated by (HfO2)0.5(Al2O3)0.5 dielectric with the smoothest surface exhibits the best performance in terms of a preferable field-effect mobility of 18.35 cm2 V−1 s−1, a small subthreshold swing of 0.105 V decade−1, a high on/off current ratio of 4.6 × 106, and excellent stability under positive bias stress.

An impact of the vacuum anneal of Al/Ge(111) structure on the Ge segregation has been investigated to get an insight into the precise control of ultrathin Ge crystalline growth. The Al/Ge(111) structure was prepared by thermal evaporation of Al on wet-cleaned Ge(111) and then vacuum annealed without air exposure to promote Ge formation on the Al surface. The Ge formation and its chemical bonding features were evaluated by X-ray photoelectron spectroscopy analysis. In addition, changes in the average Ge thickness depending on annealing temperature and time were crudely estimated. We found that the annealing temperature had a greater effect than time on the control of sub-nanometer scale Ge growth.

AlGaN/GaN high electron mobility transistors (HEMTs) on GaN substrates with different thicknesses of GaN channel and C-doped buffer layers were fabricated and characterized with conventional DC and side-gate (SG) measurements. In SG measurement, drain current (I D) was measured while SG bias (V SG) was applied through a separate SG contact that surrounds the device active region. Whereas all HEMTs have comparable DC measurement results (∼500 mA mm−1 I D, −2 V threshold voltage and ∼130 mS mm−1 transconductance), SG measurements show drastically different performances among the samples. Comparing HEMTs with and without C-doped buffer layer, results demonstrate that HEMT with doped buffer was stable against SG modulation until −15 V V SG, whereas the HEMT without doped buffer was modulated near 0 V, and hence unstable against SG bias. Comparing HEMTs different channel thicknesses, the HEMT with a thicker 900 nm channel was more resistant to SG modulation than the HEMT with a thinner 100 nm channel. Therefore, these results highlight the importance of buffer doping and channel thickness to buffer stability.

Transition metal dichalcogenide (TMD) heterostructures are promising for a variety of applications in photovoltaics and photosensing. Successfully exploiting these heterostructures will require an understanding of their layer-dependent electronic structures. However, there is no experimental data demonstrating the layer-number dependence of photovoltaic effects (PVEs) in vertical TMD heterojunctions. Here, by combining scanning electrochemical cell microscopy (SECCM) with optical probes, we report the first layer-dependence of photocurrents in WSe2/WS2 vertical heterostructures as well as in pristine WS2 and WSe2 layers. For WS2, we find that photocurrents increase with increasing layer thickness, whereas for WSe2 the layer dependence is more complex and depends on both the layer number and applied bias (Vb ). We further find that photocurrents in the WSe2/WS2 heterostructures exhibit anomalous layer and material-type dependent behaviors. Our results advance the understanding of photoresponse in atomically thin WSe2/WS2 heterostructures and pave the way to novel nanoelectronic and optoelectronic devices.

The formation of an interfacial layer is believed to affect the ferroelectric properties in HfO2 based ferroelectric devices. The atomic layer deposited devices continue suffering from a poor bottom interfacial condition, since the formation of bottom interface is severely affected by atomic layer deposition and annealing process. Herein, the formation of bottom interfacial layer was controlled through deposition of different bottom electrodes (BE) in device structure W/HZO/BE. The transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy analyses done on devices W/HZO/W and W/HZO/IrO x suggest the strong effect of IrO x in controlling bottom interfacial layer formation while W/HZO/W badly suffers from interfacial layer formation. W/HZO/IrO x devices show high remnant polarization (2P r) ∼ 53 μC cm−2, wake-up free endurance cycling characteristics, low leakage current with demonstration of low annealing temperature requirement as low as 350 °C, valuable for back-end-of-line integration. Further, sub-5 nm HZO thicknesses-based W/HZO/IrO x devices demonstrate high 2P r and wake-up free ferroelectric characteristics, which can be promising for low power and high-density memory applications. 2.2 nm, 3 nm, and 4 nm HZO based W/HZO/IrO x devices show 2P r values 13.54, 22.4, 38.23 μC cm−2 at 4 MV cm−1 and 19.96, 30.17, 48.34 μC cm−2 at 5 MV cm−1, respectively, with demonstration of wake-up free ferroelectric characteristics.

We performed single-walled carbon nanotube (SWCNT) growth on flexible stainless-steel foils by applying alcohol catalytic chemical vapor deposition (CVD) using an Ir catalyst with an alumina buffer layer. When the alumina thickness was 90 nm, vertically aligned SWCNTs with a thickness of 4.6 μm were grown. In addition, Raman and transmission electron microscope results showed that the diameters of most SWCNTs were distributed below 1.1 nm. Compared with conventional CVD growth where Si wafers are used as substrates, this method is more cost effective and easier to extend for mass production of small-diameter SWCNTs.

The effect of nitrogen flow and growth temperature on extension of GaN on Si substrate has been studied. By increasing the nitrogen flow whose outlet is located in the center of the MOCVD (metal–organic chemical vapor deposition) gas/particle screening flange and by increasing the growth temperature of HT-AlN and AlGaN buffer layers near the primary flat of the wafer, the GaN layer has extended more adequately on Si substrate. In the meantime, the surface morphology has been greatly improved. Both the AlN and GaN crystal quality uniformity has been improved. X-ray diffraction results showed that the GaN (0002) XRD FWHMs (full width at half maximum) decreased from 579 arcsec∼ 1655 arcsec to around 420 arcsec.

In this work, we present a physics-based analysis of two-dimensional electron gas (2DEG) sheet carrier density and other microwave characteristics such as transconductance and cutoff frequency of AlxGa1−xN/GaN high electron mobility transistors (HEMT). An accurate polarization-dependent charge control-based analysis is performed for microwave performance assessment in terms of current, transconductance, gate capacitances, and cutoff frequency of lattice-mismatched AlGaN/GaN HEMTs. The influence of stress on spontaneous and piezoelectric polarization is included in the simulation of an AlGaN/GaN HEMT. We have shown the change in threshold voltage (Vt) due to tensile and compressive strain with different gate lengths. Also, the influence of stress due to the change in nitride thickness is presented. Our simulation results for drain current, transconductance, and current-gain cutoff frequency for various gate length devices are calibrated and verified with experimental data over a wide range of gate and drain applied voltages, which are expected to be useful for microwave circuit design. The predicted transconductance, drain conductance, and operation frequency are quite close to the experimental data. The AlGaN/GaN heterostructure HEMTs with nitride passivation layers show great promise as a candidate in future high speed and high power applications.

Helicon waves have been recently proposed as an off-axis current drive actuator due to their expected high current drive efficiency in the mid-radius region in high beta tokamaks. This paper focuses on a numerical study to better understand effects of scrape-off-layer (SOL) turbulence on helicon wave propagation and absorption on the DIII-D tokamak using a recently developed helicon full-wave model with turbulent density inputs from synthetic single wavelength SOL turbulence and first-principles HERMES multi-wavelength turbulence models. With both input turbulence models, three key effects are observed: the helicon wave can scatter to undesirable locations in the plasma, large helicon wave electric fields can form in localized regions near the SOL turbulence, and the helicon wave can mode convert to slow waves in the SOL. This is shown to cause helicon wave refraction to undesirable locations and strong helicon wave absorption in the SOL resulting in significantly less helicon wave power in the core plasma. Using synthetic SOL turbulence, the simulations additionally show that high amplitudes and long wavelengths greater than a few cm on average have the largest effect on modifying the helicon wave propagation and absorption; the modeling predicts, for example, that approximately 60% of helicon power can be absorbed in the SOL for ñ/n ∼ 0.8 and lambda_perp ∼ 0.05 m. Several potential physical mechanisms that may explain the interaction of helicon waves with SOL turbulence in these simulations are discussed.

A liquid-crystal (LC)-based floating electrode-free (FE-free) coplanar waveguide (CPW) phase shifter with an additional LC layer is demonstrated for the first time. An LC layer is overlain on the electrodes of the original model; this change increases the amount of electric flux that the proposed structure can confine in the tunable region, and thereby greatly increases the figure-of-merit (FoM) while maintaining the benefits of the simple coplanar structure. We simulated the variations in the phase shifter’s FoM, characteristic impedance, and driving voltage while sweeping the additional LC layer thickness up to 300 μm with each electrode condition at 28 GHz. In the case of electrode thickness variation, the FoM increased as electrode thickness increased, regardless of the presence of the additional LC layer. However, in the case of the signal electrode width variation, we obtained an opposite FoM tendency depending on the presence of the additional LC layer. This work shows the possibility of an efficient LC-based FE-free CPW phase shifter design for a given LC layer and electrode conditions.

In this work, thermal atomic layer deposition (ALD) was used to synthesize vanadium (V)-doped TiO2 thin nanofilm on polypropylene (PP) hernia meshes. Multiple layers of (Al2O3 + TiVO x ) nano-films were coated on the PP hernia mesh surface to provide a layer with a total thickness of 38 nm to improve its antibacterial properties, thereby, prevent mesh-related post-surgery complications. Highly conformal V-doped TiO2 nanofilm were deposited on PP mesh at a temperature of 85 °C. Rats and rabbits have been used to evaluate the tissue reaction on coated PP hernia meshes and biomechanical testing of the healed tissue. Five rabbits and ten rats have been implanted with ALD coated and uncoated (control) PP meshes into the back of rats and abdominal wall of rabbits. Histology of the mesh-adjacent tissues and electron microscopy of the explanted mesh surface were performed to characterize host tissue response to the implanted PP meshes. The effect of V-doped TiO2 coating on a living organism and fibroblast functions and bacterial activities were studied. The present results indicated that ALD coating improves adhesion properties and exhibited enhanced antibacterial activity compared to uncoated PP mesh. It was shown that V-doped TiO2 coatings were highly effective in inhibiting S. aureus and E. coli adhesion and exhibited excellent antibacterial activity. We found that V-doping of TiO2, unlike bare TiO2, allows generated and further procured strong redox reactions which effectively kills bacteria under visible light. We have reported comparative analysis of the use of undoped (bare) TiO2 and V-doped TiO2 as a coating for PP meshes and their action in biological environment and preventing biofilms formation compared with uncoated PP meshes. The PP meshes coated with V-doped TiO2 showed significantly lower shrinkage rates compared with an identical PP mesh without a coating. We have shown that ALD coatings provide non-adhesive and functional (antibacterial) properties.

In this work, a thinner (100 nm) and thicker (150 and 200 nm) ternary organic photovoltaic (OPV) are fabricate by D18 as donor, Y6 as acceptor and NC70BA as third component materials. The addition of the hollow 3D spherical structure of NC70BA into D18:Y6 binary films is helpful for improving phase separation and smooth surface of ternary photoactive layer, and form more continuous electron transport channels in ternary photoactive layers. It is enhance photovoltaic performance under not only thinner photoactive layer thickness but also thicker photoactive layer thickness. Our results demonstrate the feasibility of employing D18:Y6 as a binary photovoltaic layer and fullerene derivative NC70BA as a third component material and has construct high-efficiency thickness-insensitive ternary OPVs; this approach would promote the development of thicker photoactive layer ternary OPVs to fulfill the requirements of solution coating processes.

InAs quantum dots (QDs) are grown on an In0.53Ga0.47As interlayer and embedded in an InP(100) matrix. They are fabricated via droplet epitaxy (DE) in a metal organic vapor phase epitaxy (MOVPE) reactor. Formation of metallic indium droplets on the In0.53Ga0.47As lattice-matched layer and their crystallization into QDs is demonstrated for the first time in MOVPE. The presence of the In0.53Ga0.47As layer prevents the formation of an unintentional non-stoichiometric 2D layer underneath and around the QDs, via suppression of the As-P exchange. The In0.53Ga0.47As layer affects the surface diffusion leading to a modified droplet crystallization process, where unexpectedly the size of the resulting QDs is found to be inversely proportional to the indium supply. Bright single dot emission is detected via micro-photoluminescence at low temperature, ranging from 1440 to 1600 nm, covering the technologically relevant telecom C-band. Transmission electron microscopy investigations reveal buried quantum dots with truncated pyramid shape without defects or dislocations.

In this paper, low-frequency noise characteristics of commercial AlGaN/GaN high electron mobility transistors with different substrates and devices with and without a p-GaN gate layer are measured and discussed. The noise power spectral density (PSD) of various devices are compared and analyzed under linear-region operation. The 1/f noise behavior exhibits carrier number fluctuation as the dominant cause. Devices with p-GaN gate layer fabricated on Si substrate show the highest normalized noise PSD. Results show that not only flicker noise (1/f noise) exists but that it also accompanied by generation–recombination noise (g–r noise) in the device on SiC substrate. The extracted g–r noise related traps show an activation energy of ∼0.37 eV, which is mostly caused by spatial charges trapping/detrapping with the deep acceptor in the GaN buffer layer.

The irrational NH3 emission routinely poses a significant threat to human health and environmental protection even at low dose. In addition, high miniaturization and low power-consumption has been the critical requirements of Internet of Things. To meet these demands, it is greatly pressing to develop a novel gas sensor with the capability to detect trace NH3 without external heating or light-irradiation elements. In this work, the organic conducting conjugated polymer PEDOT:PSS was combined with inorganic nitrogen-doped transition metal carbides and nitrides (N-MXene Ti3C2T x ) for chemiresistive NH3 sensing at room temperature (20 oC). By means of the organic–inorganic n–p heterojunctions via the synergistic effect, the results show that the composite film sensor with the optimal mass ratio of 1:0.5 between N-MXene and PEDOT:PSS components delivered favorable NH3 sensing performance than individual N-MXene or PEDOT:PSS counterparts in terms of higher response and quicker response/recovery speeds under 20 oC@36%RH air. Besides, decent repeatability, stability and selectivity were demonstrated. The incorporated N atoms served as excellent electron donors to promote the electron-transfer reactions and augment the sorption sites. Simultaneously, partial oxidation of MXene brought about some TiO2 nanoparticles which acted as spacers to widen the interlayer spacing and probably suppress the MXene restacking during the film deposition, thus favoring the gas diffusion/penetration within the sensing layer and then a quick reaction kinetic. The modulation of consequent build-in field within the heterojunctions was responsible for the reversible NH3 sensing. In addition, pre-adsorbed water molecules facilitated to establish a swift adsorption/desorption balance. The proposed strategy expanded the application range of MXene based composite materials and enrich the current sensing mechanisms of NH3 gas sensors.

We have demonstrated that by using the thermal evaporator, wafer-scale and uniform bi-layer MoS2 can be grown on graphene surfaces without introducing significant damage to the graphene channel. Compared with the top-gate transistors fabricated on standalone graphene films, the field-effect mobility value enhancement from 9.3 to 35.0 cm2 V−1·s−1 is observed for the device fabricated on the MoS2/graphene hetero-structures, which suggests that the MoS2 layer can act as an efficient passivation layer to the graphene channel. Similar field-effect mobility values obtained for the device with only a mono-layer MoS2 passivation layer are also demonstrated.

Gyrokinetic simulations of long wavelength ion temperature gradient (ITG) turbulence in the scrape-off layer (SOL) of a field-reversed configuration (FRC) find that zonal flows are nonlinearly generated and are the dominant mechanism for the nonlinear saturation of the ITG instability. After the ITG saturation, zonal flows remain undamped and gradually suppress the turbulent transport to a very low level. In the simulations with collisions, collisional damping gradually reduces zonal flow amplitude to a lower level, which allows finite ITG turbulence intensity and ion heat transport in the SOL. The steady state turbulence intensity and ion heat transport are found to be proportional to the collision frequency. This favorable scaling suggests that minimizing collisions (e.g. increasing temperature, reducing impurity content, etc) and preserving toroidal symmetry could improve plasma confinement in the FRC.

LiNi0.8Co0.15Al0.05O2 (NCA), a promising ternary cathode material of lithium-ion batteries, has widely attracted attention due to its high energy density and excellent cycling performance. However, the presence of residual alkali (LiOH and Li2CO3) on the surface will accelerate its reaction with HF from LiPF6, resulting in structural degradation and reduced safety. In this work, we develop a new coating material, LiH2PO4, which can effectively optimize the residual alkali on the surface of NCA to remove H2O and CO2 and form a coating layer with excellent ion conductivity. Under this strategy, the coated sample NCA@0.02Li3PO4 (P2-NCA) provides a capacity of 147.8 mAh g−1 at a high rate of 5 C, which is higher than the original sample (126.5 mAh g−1). Impressively, the cycling stabilities of P2-NCA under 0.5 C significantly improved from 85.2% and 81.9% of pristine-NCA cathode to 96.1% and 90.5% at 25 °C and 55 °C, respectively. These satisfied findings indicate that this surface modification method provides a feasible strategy toward improving the performance and applicability of nickel-rich cathode materials.

Molybdenum disulfide (MoS2) mono/bilayer have been systematically investigated using atmospheric-pressure mist chemical vapor deposition (mist CVD) from (NH4)2MoS4 dissolved in N-methyl-2-pyrrolidone as a precursor. Film deposition was performed by alternating MoS2 mist storage within a closed chamber and mist exhaust, i.e. sequential mist supply mode at different furnace temperatures, storage times of precursor, and repetition cycles of mist supply on thermally grown SiO2 (th-SiO2) and mist-CVD grown Al1−x Ti x O y (ATO) layers coated on p+-Si substrates. The average size of the MoS2 flake and their number of stack layers could be controlled by tuning the deposition parameters combined with substrate pretreatment. Field-effect transistors with MoS2 atomic mono/bilayer as a channel layer exhibited mobility up to 31–40 (43–55) cm2 V−1 s−1 with a threshold voltage of −1.6 (−0.5) V, subthreshold slope of 0.8 (0.11) V dec.−1, and on/off ratio of 3.2 × 104 (3.6 × 105) on th-SiO2 (ATO) layers as gate dielectric layers without mechanical exfoliation. These findings imply that mist CVD is available for the synthesis of metal transition metal dichalcogenide and metal oxide layers as channel and gate dielectric layers, respectively.

A total of 84 laying hens, ISA Brown, 60 weeks age, were used, randomly distributed into four treatment groups with 3 replicates for each treatment. The treatments were distributed as follows: T1: added the premix to diet supplied by Nuscience Company. T2: added the premix to diet supplied by Provimi Company. T3: added the premix to diet supplied by Max Care Company. T4: added the premix to diet supplied by INTRACO Company. The results show that there were no significant differences in the relative weight of the shell, except for the mean, a significant superiority of T2 and T4 compared T3, a significant differences in the shell thickness. There were no significant differences in the relative weight of albumin, and a significant superiority in the general average, where T2 outperformed on T4. There were no significant differences in the yolk index. T3 and T2 were significantly superior to T1.

To address the contradiction between carrier collection and light absorption of organic solar cells because of the limited carrier mobility and optical absorption coefficient for the normally employed organic photoactive layers, a light management structure composed of a front indium tin oxide (ITO) nanograting and ultrathin Al layer inserted in-between the photoactive layer and the electron transport layer (ETL) is introduced. Thanks to antireflection and light scattering induced by the ITO nanograting and suppression of light absorption in the ETL by the inserted Al layer, light absorption of the photoactive layer is significantly enhanced in the spectral range of 400 to 650 nm that also covers the main energy region of solar irradiation for the normally employed active materials such as the P3HT:PC61BM blend. The simulation results indicate that, compared with the control device with a planar configuration of ITO/PEDOT:PSS/P3HT:PC61BM (80 nm thick)/ZnO/Al, the short-circuit current density and power conversion efficiency can be improved by 32.86% and 34.46% after incorporating the optimized light management structure. Moreover, good omnidirectional light management is observed for the proposed device structure. Given the simple structure and excellent performance, this study is therefore believed to provide valuable exploration of light management structures for thin film-based optoelectronic devices.

A numerical-analytical technique for analyzing the physical effects of the formation of fields of hydroacoustic waves in the area in front of a flat three-layer hydroacoustic screen and in the space behind the screen at normal incidence of a stationary hydroacoustic wave on it is presented. The engineering model of the screen uses the assumption that its components are made of anisotropic functional-gradient materials with exponential inhomogeneity in thickness, and thin, absolutely flexible, inextensible coatings can be applied to the outer and contact surfaces of the layers. The technique is based on the analytical integration of the equations of wave deformation of the screen components and obtaining complex amplitude characteristics for the reflected and generated hydroacoustic waves behind the screen when solving a system of algebraic equations with a functional matrix, which follows from the boundary conditions for the investigated problem. Parametric descriptions for the characteristics of the investigated physical fields are obtained and examples of numerical analysis of the considered engineering model are presented.

In this study, the role of the oxygen in AlGaN/GaN HEMTs before and after semi-on state stress were discussed. Comparing with the electrical characteristics of the devices in vacuum, air and oxygen atmosphere, it is revealed that the oxygen has significant influence on the electric characteristics and the hot-carrier-stress-induced degradation of the device. Comparing with the situation in vacuum, the gate leakage increased an order of magnitude in oxygen and air atmosphere. Double gate structure was used to separate the barrier leakage and surface leakage of AlGaN/GaN HEMT, it is found that surface leakage is the major influencing factor in gate leakage of SiN-passivated devices before and after semi-on state stress. During semi-on state stress in the oxygen atmosphere, the electric-field-driven oxidation process promoted the oxidation of the nitride layer, and the oxidation layer in the SiN/AlGaN interface leads to the decreasing of the surface leakage.

In blue quantum dot light emitting diodes (QLEDs), electron injection is insufficient, which would degrade device efficiency and stability. Herein, we employ chlorine passivated ZnO nanoparticles as electron transport layer to facilitate electron injection into QDs effectively. Moreover, it suppresses exciton quenching at the QD/ZnO interface by blocking charge transfer channel. As a result, the maximum external quantum efficiency of blue QLED was increased from 2.55% to 4.60%, and the operation lifetime of blue QLED was nearly 4 times longer than that of the control device. Our work indicates that election injection plays an important role in blue QLED efficiency and stability.

The phenomenon of urban heat island (UHI) and global warming are significant issues now in relation to sustainable urban development. The application of green roofs is an intention to weaken the impact of UHI by reducing heat gain on the building surface that is emitted to the environment. In addition, green roofs also reduce heat transmission from solar radiation received by the roof to the indoor. Utilization of plastic bottle waste from PET (Polyethylene Terephthalate) will cut down the weight of the green roof system, which also develops the heat resistance value of the roof. This research is an initial study that suggests a green roof application that is more environmentally friendly with the principle of reusing PET waste as a sustainable building material to increase thermal resistant of the system. The analysis concentrates on describing the thermal behavior of the green roof system with the inclusion of PET bottles as a drainage layer. The investigation was carried out by preparing a cubical model of 60cm x 60 cm x 60 cm with a green roof system. Thermal performances were assessed by measuring the temperature of each layer of the green roof using thermocouple wire. The environmental variables measured were solar intensity, ambient air temperature, and air humidity, where the sensors placed close to the models. This analysis demonstrates the influences of green roofs in reducing solar radiation heat. Even though the decreasing of room temperature between the models was not significantly different, this initial results show that, by introducing PET, still display a further performance in reducing heat gain from solar radiation. However, it is necessary to adjust the evaluation models. Heat accumulation in room raised the indoor temperature to be higher than the roof temperature, so that the behavior of the green roof with the purpose of PET is not obviously distinguishable. A trial model with ventilation opening will release heat from enclosed space and it could evaluate clearly the rate of heat flow from the roof.

In this study, GSTAR modeling was carried out with the inverse of distance weight matrix obtained from Geoelectrical Resistivity data at several peatland locations around the Universitas Tanjungpura, Pontianak. This data can identify the subsurface layer of the soil through the electric current that binds into the soil. However, due to the limitation of the tool to measure the resistivity value, it can only measure 1/5 of the depth of the observation length. To overcome this problem, predictions are made at the next depth using the GSTAR model. The study began by measuring the resistivity value of the land using the geoelectric method and mapping it. Through this GSTAR modeling, predictions are made for the unobserved subsurface to determine the type of soil layer. Knowing the type of deeper soil layer can help contractors build plant concrete stakes to keep buildings safe on peatland. The results of the GSTAR(1.1) model are not accurate enough to estimate the resistivity value data. This is possible because the correlation between rock ages is not the same, so further analysis is required.

In the present work zinc sulfide (ZnS) nanoparticles (NPs) were synthesized on silicon wafer by femtosecond pulsed ablation processing of ZnS bulk target using an electrostatic field in argon gas atmosphere. The morphology, size distribution and structural characterization of obtained ZnS NPs were investigated using scanning electron microscope (SEM), dynamic light scattering (DLS) technique and X-ray diffraction (XRD). Dominant size of obtained NPs lies in the range 10-20 nm, NPs are in spherical shape, particles of other shape and agglomerates of particles are absent. XRD investigation of synthesized NPs identified hexagonal wurtzite structure. There is a structural phase transition from the sphalerite ZnS bulk (target) structure to the structural phase of wurtzite (obtained NPs).The optical characterization of synthesized by laser ablation ZnS NPs was carried out using a photoluminescence (PL) measurement. ZnS NPs show a strong broad PL emission spectra covering the entire visible electromagnetic spectra region (range from 380 to 800 nm) centered at 513.7 nm.