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van der Waals (vdW) layered materials have shown great potential for future optoelectronic applications owing to their unique and variable properties. In particular, two-dimensional layered materials enable the creation of various circuital building blocks via vertical stacking, e.g. the vertical p–n junction as a key one. While numerous stable n-type layered materials have been discovered, p-type materials remain relatively scarce. Here, we report on the study of multilayer germanium arsenide (GeAs), another emerging p-type vdW layered material. We first verify the efficient hole transport in a multilayer GeAs field-effect transistor with Pt electrodes, which establish low contact potential barriers. Subsequently, we demonstrate a p–n photodiode featuring a vertical heterojunction of a multilayer GeAs and n-type MoS2 monolayer, exhibiting a photovoltaic response. This study promotes that 2D GeAs is a promising candidate for p-type material in vdW optoelectronic devices.

Nickel hydroxide [Ni(OH)2] is an electrochemically-active material used for rechargeable batteries, electrochemical capacitors, and electrochromic devices. Although there have been some studies on Ni(OH)2 thin films deposited by sputtering, the Ni(OH)2 formation has not been fully confirmed. In this study, a Ni metal target was reactively sputtered in atmospheres of O2 and Ar + H2O at substrate temperatures of RT (RT, around 20 °C), −80 °C, and −170 °C, and the aging treatment effects in the air at RT were studied. From optical, X-ray diffraction, and IR absorption measurements, β-Ni(OH)2 thin films were found to be formed after aging the films deposited at −80 °C in Ar + H2O, however, NiO thin films were formed at RT. These results corresponded well with a thermodynamic consideration of Ni(OH)2. At −170 °C, mixed metal and oxide films were formed, presumably because of insufficient Ni oxidation.

Auxetic structures with negative Poisson’s ratio have received much attention due to their attractive behavioral properties in next-generation metamaterials and robotic applications. However, until now, there has been a lack of research into using soft materials to reliably develop a largely-deformable auxetic structures. Here, we develop soft polydimethylsiloxane (PDMS)-Ecoflex auxetic structures using a 3D printing technique, leading to high fabrication reliability and repeatability. Water-soluble filaments are employed to design sacrificial mold structures that quickly dissolve in warm water. By measuring the mechanical properties and light transmittance of soft composite membranes with various mixing ratios of PDMS and Ecoflex, the intrinsic characteristics of the composite membranes are determined. The newly fabricated soft auxetic structures composed of PDMS and Ecoflex composites always exhibit negative Poisson’s ratio during stretching. The negative Poisson’s ratio of the structure is maximized when PDMS and Ecoflex have a 2:1 mixing ratio and nominal strain is less than 5%. Advances in technology to reliably fabricate soft auxetic structures using 3D printers are believed to promote next-generation applications such as wearable sensors and energy-absorbing structures.

In general, as the radio frequency (RF) power increases in a capacitively coupled plasma (CCP), the power transfer efficiency decreases because the resistance of the CCP decreases. In this work, a parallel resonance circuit is applied to improve the power transfer efficiency at high RF power, and the effect of the parallel resonance on the electron energy distribution function (EEDF) is investigated in a 60 MHz CCP. The CCP consists of a power feed line, the electrodes, and plasma. The reactance of the CCP is positive at 60 MHz and acts like an inductive load. A vacuum variable capacitor (VVC) is connected in parallel with the inductive load, and then the parallel resonance between the VVC and the inductive load can be achieved. As the capacitance of the VVC approaches the parallel resonance condition, the equivalent resistance of the parallel circuit is considerably larger than that without the VVC, and the current flowing through the matching network is greatly reduced. Therefore, the power transfer efficiency of the discharge is improved from 76%, 70%, and 68% to 81%, 77%, and 76% at RF powers of 100 W, 150 W, and 200 W, respectively. At parallel resonance conditions, the electron heating in bulk plasma is enhanced, which cannot be achieved without the VVC even at the higher RF powers. This enhancement of electron heating results in the evolution of the shape of the EEDF from a bi-Maxwellian distribution to a distribution with the smaller temperature difference between high-energy electrons and low-energy electrons. Due to the parallel resonance effect, the electron density increases by approximately 4%, 18%, and 21% at RF powers of 100 W, 150 W, and 200 W, respectively.

The doping technique is vital for applying two-dimensional (2D) materials such as transition metal dichalcogenide (TMDC)-based field effect transistors (FETs), which can control the channel polarity and improve the performance. However, as conventional doping techniques for silicon-based FET are not suitable for 2D materials, the realization of heavy doping of TMDC materials is challenging, especially for n-type heavy doping. This study reports a simple, regioselective, controllable, and chemically stable heavy doping method for 2H-MoTe2 crystal via high-density laser irradiation. The polarity of the doping can be controlled by changing the irradiation environment. For the MoTe2-nFET, good performance with enhanced contact properties was obtained using the contact doping method via laser irradiation in a vacuum environment.

Tungsten oxide (WO3) and nickel oxide (NiO) are typical inorganic electrochromic (EC) materials. The color of WO3 changes from transparent to blue by reduction, whereas that of NiO changes from transparent to brown by oxidation. This study fabricated EC devices with an indium tin oxide (ITO)/WO3/NiO/ITO/Nafion/ITO structure. The WO3/NiO double layer and Nafion were used as the EC layer and electrolyte, respectively. The color of the device changed from blue to transparent and then to brown by varying the applied potential from −2.5 to +1.0 V and then to +2.0 V. The WO3 and NiO films were reduced at −2.5 V; the WO3 film was oxidized at +1.0 V, and both were oxidized at +2.0 V. The transmittance in the visible and near-infrared regions changed independently. Hence, the devices are considered applicable for dual-band EC smart windows.

The effects of ion collisions on plasma–sheath formation are investigated experimentally for a low-density and low-pressure discharge. The space potential and ion velocity distribution measurements at high spatial resolution show that the ion collision properties observed in the presheath are maintained in the plasma–sheath transition region. The potential drop in the transition region indicates the existence of ionization as an effect of ion collisions in the transition region owing to the non-negligible density of the electrons penetrating the sheath. Based on comparisons between the space potential measurements and Riemann’s presheath–sheath transition solution, the ion collision length λ i was determined as a key parameter in the presheath and transition region. And it represents that the thermal properties of ions and neutral gases affects space potential by the charge exchange and ionization collisions. The existence of the ion collision effect in the transition region suggests possible influence on the incident conditions of ions and electrons near the sheath edge. Consequently, the energy distributions of ions and electrons incident on the material surface facing the sheath are sensitive to the collisionality and operating conditions.

Plasma generation efficiency in a capacitively coupled plasma (CCP) at high densities or high conductivity tends to be lower due to low plasma resistance. An inductor is installed to a powered electrode in parallel to improve plasma generation efficiency at higher density in the CCP. To reduce the power loss in a system, a parallel resonance is used between the capacitance of the CCP and the inductance of the parallel inductor. When parallel resonance occurs, the impedance of the chamber, including the plasma, increases. Therefore, the current flowing in the system is expected to decrease. At the resonance, the current in the system significantly decreases, and the voltages and currents at the powered electrode significantly increase. This phenomenon indicates that the system power loss is decreased, and the power absorbed by the plasma is increased. As a result, the ion density and the voltage at the powered electrode are increased up to 66% and 25% at the parallel resonance condition, respectively. To understand these increases, a circuit model for the plasma and the parallel inductor is suggested which shows good agreement with the experimental results. This method can be applied to the CCP for improving plasma generation.

The U.S. Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is the world’s most powerful accelerator-driven pulsed neutron source. An H- injector feeds the accelerator with high current (>50 mA), time structured (1ms, 60 Hz) H- beam. The injector consists of an RF-driven, Cs-enhanced H- ion source and an electrostatic low energy beam transport section. In the recent three run cycles, an H- ion source operated ∼4 months for each run with excellent availability near 99.9%. The presently ongoing run is also on track to finish another ∼4 months run with similar high availability. Lately, we have tested a solid-state RF system for the ion source to replace the existing vacuum-tube type RF amplifier for the sake of improving the ease of operation and maintenance. Progress has also been made on the continued development of an external antenna RF H- ion source with a focus on improvement to its plasma ignition scheme.

A polypyrrole-modified Fe3O4/SiO2/TiO2 composite material was successfully synthesized on the FST surface by in situ polymerization of pyrrole. Structural, morphological and magnetic response of Fe3O4/SiO2/TiO2/PPy(FST/PPy) were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction pattern, Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy, etc. Through SEM images, the crystal sizes of the prepared FST/PPy nanoparticles were determined to be about 110 nm. The catalytic activity of FST/PPy was evaluated by the degree of decomposition of rhodamine B under ultraviolet and visible light, respectively. FST/PPy had the photocatalytic activity under the action of the light: the degradation rate of rhodamine B reached 92.8% and 63.5% after 3 h of UV and Vis light irradiation, respectively. Especially, compared with FST, the degradation rate has shown obvious improvement under the action of Vis light. Furthermore, FST/PPy photocatalyst could be easily recycled using a magnet.

Main text A new key comparison of the standards for air kerma of the Korea Research Institute of Standards and Science (KRISS), Republic of Korea, and the Bureau International des Poids et Mesures (BIPM) was carried out in the 60Co radiation beam of the BIPM in March 2022. The comparison result, based on the calibration coefficients for two transfer chambers and expressed as a ratio of the KRISS and the BIPM standards for air kerma, is 1.0006 with a combined standard uncertainty of 1.8 parts in 103. The result agrees within the uncertainties with the direct comparison carried out in 2010. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Main text A key comparison has been made between the air-kerma standards of the KRISS, Republic of Korea, and the BIPM in the low-energy x-ray range. The results show the standards to be in agreement at the level of the standard uncertainty of the comparison of 2.2 parts in 103. The results are analysed and presented in terms of degrees of equivalence, suitable for entry into the BIPM key comparison database. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

We investigated the plasma and electrical characteristics depending on the antenna position in an inductively coupled plasma with a passive resonant antenna. When the powered antenna and passive resonant antenna are installed near the top plate and in the middle of the cylindrical reactor (setup A), respectively, the ion density at the resonance is about 2.4 times to 9 times higher than that at non-resonance. This is explained by the reduction in power loss in the powered antenna (including the matching circuits) and the increase in power absorbed by the plasma discharge. However, when the powered antenna and passive resonant antenna are interchanged (setup B), the ion density at the resonance is not significantly different from that at the non-resonance. When RF power is changed from 50 to 200 W, the ion density at the resonance of setup B is 1.6 times to 5.4 times higher than at the non-resonance of setup A. To analyse this difference, the profile of the z-axis ion density is measured and the electric and magnetic field simulations are investigated. The results are discussed along with the electron kinetics effect and the coupling loss between the antenna and the metal plate.

Main text A first key comparison has been made between the air-kerma standards of the KRISS, Republic of Korea, and the BIPM in mammography x-ray beams. The results show the standards to be in agreement at the level of the expanded uncertainty for the comparison of 4.4 parts in 103. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Main text The CCQM-K10.2018 comparison aimed to evaluate the capabilities of national metrology institutes (NMIs) to prepare and/or value assign primary reference mixtures containing benzene, toluene, ethylbenzene, p-xylene, m-xylene and o-xylene (subsequently referred to as BTEX) in nitrogen. This key comparison was separated into two parallel studies. The first study, deemed the "gravimetric study", evaluated the level of compatibility of BTEX standards provided by NMIs. Seven participating laboratories each submitted one standard at nominal 5 nmol mol-1 BTEX in nitrogen. Comparison measurements were performed by the National Institute of Standards and Technology (NIST) from July to October 2018. The second study, deemed the "comparative study", compared the capabilities of NMIs to measure the amount fractions of BTEX in a mixture provided by NIST. NIST prepared one standard at nominal 5 nmol mol-1 BTEX in nitrogen, which was measured consecutively by three participating laboratories. The participants' measurements took place from August 2018 to March 2019. The comparison protocol adopted for CCQM-K10.2018 was more challenging than for the original comparison, CCQM-K10 in 2001, and the results provide an extended evaluation of the level of compatibility of BTEX in nitrogen standards. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

The interface enclosure for charging commercial electric vehicle (CEV), which is an alternative to the fuel filler of internal combustion engine vehicle, was studied. It supplies the power and the communication signal for charging between the power supply (EVSE) and the battery. It should be long to match the exterior of the vehicle for easy charging, and it requires space between the vehicle frame and the enclosure to connect the charging cable. In order to design the interface enclosure with the cantilever structure which is vulnerable to vibration, analysis-based design through vibration fatigue analysis was conducted, and the reliability of analysis results was reviewed through experiments.

Persistent-mode operation is a key feature of magnetic resonance image systems to improve the required field stability. The superconducting joint is known to be beneficial for reducing all the resistant components in an electrically closed-circuit. The joint technique of magnesium diboride (MgB2) multifilamentary wire, however, is the main obstacle to the use of magnet in practical applications. In response, herein, we designed and developed a unique configuration of superconducting joint to further enhance the interconnection of exposed cores between two 18-multifilamentary wires. It was confirmed that developed joint samples achieved high critical current similar to a non-jointed wire. The proposed joint technique was directly applied to the MgB2 single-turn coil and MgB2 magnet for estimating a joint property through persistent-mode operation. This work provides fundamental insights into the design of persistent-mode MgB2 magnets to boost magnetic resonance image systems.

The quantum confinement effect and interesting optical properties of cesium lead halide (CsPbX3; X=Cl, Br, I) perovskite quantum dots (QDs) and nanocrystals (NCs) have given a new horizon to lighting and photonic applications. Given the exponential rate at which scientific results on CsPbX3 NCs are published in the last few years, it can be expected that the research in CsPbX3 NCs will further receive increasing scientific interests in the near future and possibly lead to great commercial opportunities to realize these materials based practical applications. With the rapid progress in the single-photon emitting CsPbX3 QDs and NCs, practical applications of the quantum technologies such as single-photon emitting LED, quantum lasers, quantum computing might soon be possible. But to reach at cutting edge of stable perovskite QDs/NCs, the study of fundamental insight and theoretical aspects of crystal design is yet insufficient. Even more, it has aroused many unanswered questions related to the stability, optical and electronic properties of the CsPbX3 QDs. Aim of the present review is to illustrate didactically a precise study of recent progress in the synthesis, properties and applications of CsPbX3 QDs and NCs. Critical issues that currently restrict the applicability of these QDs will be identified and advanced methodologies currently in the developing queue, to overcome the roadblock, will be presented. And finally, the prospects for future directions will be provided.

Today, respiratory ventilators are in high demand at the peak of the COVID-19 outbreak. However, there are concerns regarding insufficient supply of ventilators to handle the impending surge due to the high cost, and slow production and deliveries. Thus, the development of a low-cost portable ventilator becomes essential. The mechanical ventilator requires two main components including an active airbag and its venting control system. We developed a reliable active airbag designed with mechanically tunable 3D origami structures. The 3D origami structure based active airbag demonstrates reliable and reconfigurable characteristics. The active airbag's volume can be tuned by controlling the triangular angles in the 3D origami-folding plates. Moreover, its volumetric ratio before and after compression is around 85%. Also, the rotating behavior of 3D origami tube under the compressive force allows more functionalities in the airbag such as the architectured pressure sensing. The 3D printed origami sensor measures the compressed angle to confirm the accuracy of detected pressure in the ventilator circuit. We achieved accurate delivery of targeted air volume with specific airflow rate by 3D printed reconfigurable origami tubes.

A novel tissue engineering strategy using 3D bio-print technology has become a promising therapeutic method for acute myocardial infarction (AMI) in an animal model. However, the application of 3D bio-printed tissue remains limited due to poor graft survival. Therefore, it is a scientific priority to enhance graft survival by precisely adjusting the 3D environment of encapsulated cells. In this study, novel transplantable 3D cardiac mesh (cMesh) tissue with a porous mesh structure was presented using human cardiomyocytes, human cardiac fibroblasts, and gelatin-methacryloyl-collagen hydrogel. Cardiomyocytes and cardiac fibroblasts were well spreaded. The cardiomyocytes were connected with a gap junction channel in bio-printed cMesh and a 3D cardiac patch with an aggregated structure. Porous cMesh demonstrated structural advantages by increased phosphorylation of mTOR, AKT, and ERK signals associated with cell survival. Transplanted cMesh in rats with AMI improved long-term graft survival, vessel formation, and stabilization, reduced fibrosis, increased left ventricle thickness, and enhanced cardiac function. Our results suggest that porous cMesh provides structural advantages and a positive therapeutic effect in an AMI animal model.

Cigarette butts are one of the toxic residues and have a very serious impact on the environment. Recycling cigarette butts has a great advantage in saving the natural source and solving environmental problems. Cellulose diacetate obtained from extraction, purification and acid hydrolysis of cigarette butts and then was blended with low molecular weight partially hydrolyzed polyvinyl alcohol. The blend of cellulose diacetate and partially hydrolyzed polyvinyl alcohol was characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry. To evaluate the viscoelastic properties of the blends dynamic mechanical analysis was performed. The lap shear strength and the 180° peel strength of the adhesive were estimated according to the content of the blends and the biodegradability in water was confirmed. The experimental results showed that the use of cellulose diacetate obtained from cigarette butts in the composition of biodegradable hot melt adhesives can be of great help in solving environmental problems caused by petroleum-based polymers and waste.

To utilize water-responsive hydrogels in biomedical devices and soft robotics, hydrogels with high response speed and good mechanical properties are required. However, fabrication of such hydrogels remains challenging. In this study, a facile method for producing a one-dimensional (1D) hydrogel with water-responsive programmable deformations was developed. A tough hydrogel fiber with an interpenetrating polymer network based on a biopolymer was synthesized using a template-directed method. A 1D hydrogel that shrinks quickly in contact with water was fabricated by simply stretching and drying the hydrogel fiber under ambient conditions. The fabricated 1D hydrogel exhibited excellent mechanical properties, accurately controlled and programmable deformations, and an extraordinarily high degree of deformation with dimensional changes greater than 300%. Based on such 1D hydrogels, one-way soft actuators, which can be bent or can lift a weight when exposed to water, and a chemical sensing platform, which can detect ethanol in a water–ethanol mixture, were developed.

Two-dimensional (2D) molybdenum disulphide (MoS2) transition metal dichalcogenides (TMDs) have great potential for use in optical and electronic device applications; however, the performance of MoS2 is limited by its crystal quality, which serves as a measure of the defects and grain boundaries in the grown material. Therefore, the high-quality growth of MoS2 crystals continues to be a critical issue. In this context, we propose the formation of high-quality MoS2 crystals via the flux method. The resulting electrical properties demonstrate the significant impact of crystal morphology on the performance of MoS2 field-effect transistors. MoS2 made with a relatively higher concentration of sulphur (a molar ratio of 2.2) and at a cooling rate of 2.5 °C h−1 yielded good quality and optimally sized crystals. The room-temperature and low-temperature (77 K) electrical transport properties of MoS2 field-effect transistors (FETs) were studied in detail, with and without the use of a hexagonal boron nitride (h-BN) dielectric to address the mobility degradation issue due to scattering at the SiO2/2D material interface. A maximum field-effect mobility of 113 cm2 V−1 s−1 was achieved at 77 K for the MoS2/h-BN FET following high-quality crystal formation by the flux method. Our results confirm the achievement of large-scale high-quality crystal growth with reduced defect density using the flux method and are key to achieving higher mobility in MoS2 FET devices in parallel with commercially accessible MoS2 crystals.

Recently, flexible electronics have attracted significant attention as they can be integrated on diverse platforms from curved to flexible surfaces. As flexible electronics are used on a curved surface of wearable or manufacturing devices for health and system monitoring, the working environment of such applications forces electronics to be exposed to diverse stimuli such as deformation, temperature, humidity, and gas, resulting in performance changes. Therefore, rather than research on improving the specific performance of electronics, research on maintaining a stable performance in various environmental stimuli has been receiving tremendous interest. Reflecting the latest research trends, this paper introduces efforts in structural designs heading for both improving and maintaining the performance of flexible electronics in diverse environmental stimuli. Firstly, we will sequentially explain the geometric and structural designs introduced for achieving (a) reliable electronics insensitive to undesired mechanical stimuli, (b) reliable electronics in harsh environments, and (c) flexible electrodes. Also, (d) diverse applications of reliable and flexible electronics are introduced. Finally, a perspective on reliable and flexible electronic devices has been presented for suggesting next-generation research.

We developed a high-efficiency source in a capacitively coupled plasma using magnetic resonance wireless power transfer (MRWPT) systems, which has the advantage that the matcher efficiency is very high at low gas pressures (2 mTorr to 20 mTorr) and high density plasmas (about 1 × 1010 cm−3 to 5 × 1010 cm−3). At the non-resonance conditions, most of the RF power is dissipated by the transmitter coil and the plasma is not discharged. However, at the resonance condition, the plasma is discharged as the current flowing through the transmitter coil rapidly decreases, and the matcher efficiency is higher than 90% in all experiments. For analysis, the transformer model with MRWPT systems is developed. The experimental result is consistent with the model, and the results are discussed with the relevant physical mechanisms.

To understand the aggregation mechanism of serum protein dispersed in the solution of distilled water induced by a low temperature atmospheric pressure plasma, we compared the relationship between the amount of aggregation and experimental condition dependencies such as gas species, gas flow rate, and the distance between the plasma device and the solution. In this experiment, pure argon, helium, and/or a mixture of helium and argon gases were used. From statistical analyses of various experimental conditions, it was found that a monotonic supply of total absolute charge in one period was important for protein aggregation. When the coefficient of variation (standard deviations/averaged total absolute charges during one period) is small, the amount of protein aggregation becomes larger. Excess or scarcity of averaged total absolute charges does not appear to relate to protein aggregation phenomena; however, the coefficient of variation strongly relates to the mechanism of protein aggregation. Therefore, a possible serum protein aggregation process by low-temperature plasma treatment was proposed in which the serum protein, which had negative charges in the solution, was locally aggregated through the trigger of charge neutralization induced by a stable charge supply, and/or positively charged aggregated protein on the solution surface attracted serum protein in the solution to the surface.

The integration of electrical contact into 2D heterostructure is an essential approach to high-quality electronic nano-devices, especially field-effect transistors. However, high contact resistance with transition metal dichalcogenides such as molybdenum disulphide (MoS2)-based devices has been a significant fabrication impediment to their potential applications. Here, we have demonstrated the advantage of 1D indium metal contact with fully encapsulated MoS2 within hexagonal boron nitride. The electrical measurements of the device exhibit ambipolar transport with an on/off ratio of 10 2 for holes and 10 7 for electrons. The device exhibits high field-effect mobility of 40.7 cm 2 V − 1 s − 1 at liquid nitrogen temperature. Furthermore, we have also analysed the charge-transport mechanism at the interface and have calculated the Schottky barrier height from the temperature-dependent measurement. These results are highly promising for the use of air-sensitive material heterostructure and large-scale design of trending flexible, transparent electronic wearable devices.

Control of local electron and ion density using passive resonant coils is experimentally investigated in an inductive argon discharge. Four passive resonant coils are installed under a powered coil; each coil has a fan shape and good azimuthal symmetry. Electron energy probability functions and two-dimensional ion density profiles were measured under both resonant and non-resonant regimes. At non-resonance, almost all of the current flows through the powered coil located in the center of the reactor, and the profiles of the electron and ion density are convex. However, at resonance, a large current flows through the passive resonant coil, and dramatic changes are observed in the electron and ion density profiles. At resonance, the electron and ion densities near the passive resonant coil are increased by 300% compared to the non-resonant condition, and radial distributions become almost flat. Experimental results show that the electron and ion density profiles can be effectively controlled by a passive resonant coil at both low pressure (5 mTorr) and high pressure (50 mTorr). These changes in electron and ion density profiles can be understood by the changes of the electron heating and ionization regions.

Uncertainty exists regarding the interaction between the El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) where ENSO is normally expected to be the leading mode. Moreover, the effect of global warming on the relationship between these two modes remains unexplored. Therefore, we investigated the ENSO–IOD linkage for the years 1950–2014 using reanalysis data and high-resolution climate model simulations. The 1950–2014 period is of particular interest as rapid Indian Ocean warming since the 1950s has had a huge impact worldwide. Our results showed that the IOD had robust causal effects on ENSO, whereas the impact of ENSO on IOD exhibited lower confidence. All models demonstrated that the IOD was unlikely to have no causal effects on ENSO, whereas eight out of 15 studied models and the reanalysis data showed significant causal effects at the 10% significance level. The analyses provide new evidence that ENSO interannual variability might be forced by changes in Indo-Pacific Walker circulation induced by the IOD. Weak control of ENSO on the IOD is likely due to nonsignificant effects of ENSO on the western tropical Indian Ocean, implying that the rapid warming environment in the Indian Ocean may fundamentally modulate the relationship between the IOD and ENSO. We find high agreement between the models and reanalysis data in simulating the ENSO–IOD connection. These results indicate that the effects of the IOD on ENSO might be more significant than previously thought.

The exact direction, of the surface energy characterized functional group of self-assembled monolayer (SAM), is proposed for achieving the enhanced electrical stability of indium gallium zinc oxide (IGZO) semiconductor thin film transistor (TFT). The SAM treatment, particularly at the SAM functional group having lower surface energy, makes oxygen molecules difficult to be adsorbed onto IGZO. And such an effect much improves positive bias stability (PBS) and clockwise hysteresis stability to the same tendency. For NH2 and CF3 functional group SAMs with surface energies of 49.4 mJ/m2 and 23.5 mJ/m2, respectively, the IGZO TFT PBS was improved from 2.47 V to 0.32 V after the SAM treatment and the IGZO TFT clockwise hysteresis was also enhanced from 0.23 V to 0.11 V without any deterioration of TFT characteristics. Employing lower surface energy functional group to the SAM, of same head group and body group, does passivate and protect the IGZO backchannel region from oxygen molecules in the atmosphere. Consequently, the enhanced electrical stability of IGZO TFT can be achieved by the simple and economic SAM treatment.

A method is proposed to predict the power generation performance of a pyroelectric generator (PEG) for waste-heat recovery systems in which an external electric field is applied to a ferroelectric material in synchrony with rapid temperature changes. The net generated energy density N D of the PEG at any temperature and electric field is predicted for two thermal-electrical cycles (including the Olsen cycle). This is done by approximating the dependence of the polarization density on temperature and electric field using hysteresis loop measurements. The difference between the predicted and measured values of N D was less than 15%. This method could be used to screen promising candidate materials for PEGs.

Partially saponified low molecular weight (LMW) PVAc was synthesized and blended with a tackifier for use as hot-melt adhesive with water-solubility and biodegradibility. The water-solubility of the partially saponified LMW PVAc was determined as a function of the degree of saponification. PVAc prepared in this study had good water-solubility because its molecular weight was very small and it had lots of hydroxy groups in the polymer chain. As the degree of saponification increased, the solubility of PVAc in water increased. The glass transition temperature and viscoelastic properties of partially saponified PVAc were measured and analyzed by using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). As the temperature increased and the degree of saponification decreased, melt viscosity decreased. The single lap-shear strength and biodegradability of the hot-melt adhesive on based PVAc were systematically evaluated. As the degree of saponification of the polymer increased, the single lap-shear strength of the hot-melt adhesive and the tendency for cohesive failure to occur decreased. The higher the degree of saponification, the faster the rate of biodegradation of the adhesive in natural water.

We show two major modes of East Asian marine heatwaves (MHWs) associated with two contrasting sea surface temperature patterns over the subtropical western North Pacific (WNP). In the first MHW mode, ocean warming over East Asia occurs along with the subtropical WNP from the earlier winter by an El Niño-Southern Oscillation. The basin-wide ocean warming is finally intensified to an extreme warming state around East Asia, where a high-pressure region in zonal waves across the Eurasian continent passes. In contrast, at the early stage, the second MHW mode is unfavorable with ocean cooling. However, MHWs over East Asia occur due to a significant intensification of a zonally elongated high-pressure zone in response to anomalous subtropical convection in addition to mid-latitude zonal waves. Due to the importance of persistent ocean warming as well as immediate atmospheric forcing, MHW inducible oceanic and atmospheric interactions are clearly distinguishable from those of atmospheric heatwaves.

In this study, the effect of growth of intermetallic compound (IMC) layer between Au-Sn solder and electroless Ni/immersion Au (ENIG) on the thermal resistance of a flip-chip (FC) light emitting diode (LED) package was investigated. Two IMC layers were formed at the interface of FC LED package, including Au5Sn and (Ni,Au)3Sn4 that were identified using a transmission electron microscopy (TEM). A thermal aging test was carried out at 200 °C for 1000 h to observe IMCs growth. After 1000 h, the (Ni,Au)3Sn4 thickness increased to about 1.5 µm and the thermal resistance of the FC LED package increased by 3.5 times compared to the initial thermal resistance of 2 K/W. As the (Ni,Au)3Sn4 grew, a calculation of thermal resistance also increased comparing to the initial aging test, thus, the growth of (Ni,Au)3Sn4 layer can be effective factor on the increase of thermal resistances of FC LED package.

We demonstrate the differential detection of UV-A (ultra-violet 320-400 nm region) and UV-C (100-280 nm) using porous two-dimensional (2D) Nb2O5 and additional Ag nano-particle decoration. The 2D Nb2O5, which has band-absorption edge near the UV-A zone, was synthesized by thermodynamic conversion of 2D material NbSe2 (Nb2O5 has lower Gibbs formation energy than NbSe2). For the differential detection (to distinguish with UV-C absorption), we decorated the Ag nano-particles on the Nb2O5 surface. By coating Ag nano-particles, we can expect (i) a decrease in the area of light absorption by the Ag-coated area, and (ii) an increase of surface plasmon absorption by Ag nano-particles, especially the UV-A region, resulting in strong intensity ratio change UV-A/UV-C.

Nanomaterials are the subject of extensive investigations due to their applications in medicine, multimodal imaging, volumetric displays, and photonics. Here, lanthanide-doped bismuth vanadate (BiVO4) upconverting nanoparticles (UCNPs) have been reported. The nanoparticles have been synthesized by a microwave hydrothermal method. As-synthesized nanoparticles are highly crystalline in the tetragonal zircon phase with particles about 200 nm in size. Under 980 nm excitation, intense multicolor visible and near-infrared upconversion emissions are observed. Moreover, broadband infrared downshifting emissions are also observed. Time-resolved emission measurements have been carried out to investigate the involved upconversion and energy transfer mechanism. The BiVO4-based UCNPs may provide a new class of nanomaterials for multifunctional applications.

We developed a high efficiency plasma source in an inductively coupled discharge using a passive resonant antenna, which has the advantage that it could be retro-fitted to existing reactors with minimal change to the reactor. At the resonance, the source has a larger total equivalent resistance that is 3–18 times larger than that at the non-resonance. As the resistance increases at the fixed RF power, the RF current decreases accordingly, which indicates that the power loss in the powered antenna including the impedance matching circuits is significantly reduced. The experimental result shows that the power transfer efficiency is improved by about 30%–70% and the plasma density at the resonance increases 2–8 times higher than that at the non-resonance. For analysis, three-winding transformer model is developed. The experimental results are consistent with the model.

peer-reviewed Nickel (Ni) foam-based symmetric/asymmetric electrochemical supercapacitors benefit from a randomly 3D structured porous geometry that functions as an active material support and as a current collector. The surface composition stability and consistency of the current collector is critical for maintaining and consistency supercapacitor response, especially for various mass loading and mass coverage. Here we detail some annealing environment conditions that change the surface morphology, chemistry and electrochemical properties of Ni foam by NiO formation. Air-annealing at 400 and 800 °C and annealing also in N2 and Ar at 800 °C result in the in situ and ex situ formation of NiO on the Ni foam (NiO@Ni). Oxidation of Ni to NiO by several mechanisms in air and inert atmospheres to form a NiO coating is subsequently examined in supercapacitors, where the electrochemical conversion through Ni(OH)2 and NiOOH phases influence the charge storage process. In parallel, the grain boundary density reduction by annealing improves the electronic conductivity of the foam current collector. The majority of stored charge occurs at the oxidized Ni-electrolyte interface. The changes to the Ni metal surface that can be caused by chemical environments, heating and high temperatures that typically occur when other active materials are grown on Ni directly, should be considered in the overall response of the electrode, and this may be general for metallic current collectors and foams that can oxidize at elevated temperatures and become electrochemically active.