Wafer Scale Gallium Nitride Integrated Electrode Toward Robust High Temperature Energy Storage.

Gallium Nitride (GaN), as the representative of wide bandgap semiconductors, has great prospects in accomplishing rapid charge delivery under high-temperature environments thanks to excellent structural stability and electron mobility. However, there is still a gap in wafer-scale GaN single-crystal integrated electrodes applied in the energy storage field. Herein, Si-doped GaN nanochannel with gallium oxynitride (GaON) layer on a centimeter scale (denoted by GaN NC) is reported. The Si atoms modulate electronic redistribution to improve conductivity and drive nanochannel formation. Apart from that, the distinctive nanochannel configuration with a GaON layer provides adequate active sites and extraordinary structural stability. The GaN-based supercapacitors are assembled and deliver outstanding charge storage capabilities at 140 °C. Surprisingly, 90% retention is maintained after 50 000 cycles. This study opens the pathway toward wafer-scale GaN single-crystal integrated electrodes with self-powered characteristics that are compatible with various (opto)-electronic devices.

Research Progress in Liquid Phase Growth of GaN Crystals.

As a wide band gap semiconductor, gallium nitride (GaN) has high breakdown voltage, excellent structural stability and mechanical properties, giving it unique advantages in applications such as high frequency, high power, and high temperature. As a result, it has broad application prospects in optoelectronics and microelectronics. However, the lack of high-quality, large-size GaN crystal substrates severely limit the improvement of electronic device performance. To solve this problem, liquid phase growth of GaN has attracted much attention because it can produce higher quality GaN crystals compared to traditional vapor phase growth methods. This review introduces two main methods of liquid phase growth of GaN: the flux method and ammonothermal method, as well as their advantages and challenges. It reviews the research history and recent advances of these two methods, including the effects of different solvents and mineralizers on the growth quality and performance of GaN crystals, as well as various technical improvements. This review aims to outline the principles, characteristics, and development trends of liquid phase growth of GaN, to provide more inspiration for future research on liquid phase growth, and to achieve further breakthroughs in its development and commercial application.

Retracted: Anticancer Action of Psilostachyin-A in 5-Fluorouracil-Resistant Human Liver Carcinoma are Mediated Through Autophagy Induction, G2/M Phase Cell Cycle Arrest and Inhibiting Extracellular-Signal-Regulated Kinase/Mitogen Activated Protein Kinase (ERK/MAPK) Signaling Pathway.

An editorial decision has been made to retract this manuscript due to breach of publishing guidelines, following the identification of non-original and manipulated figures. Reference: Jun Liu, Yan Liu, Yan Liu, Lei Huang, Guoliang Wang, Jun Wang, Xiangang Xu, Chengxian Shi, Jianzhao Huang: Anticancer Action of Psilostachyin-A in 5-Fluorouracil-Resistant Human Liver Carcinoma are Mediated Through Autophagy Induction, G2/M Phase Cell Cycle Arrest and Inhibiting Extracellular-Signal-Regulated Kinase/Mitogen Activated Protein Kinase (ERK/MAPK) Signaling Pathway. Med Sci Monit 2019; 25:6711-6718. 10.12659/MSM.916635.

Dependence of conduction characteristics on compensation type and lattice structure of SiC photoconductive semiconductor switches.

Semi-insulating (SI) SiC photoconductive semiconductor switches were prepared using two compensation mechanisms: namely vanadium dopants compensation (4H- and 6H-SiC) and deep level defect compensation (4H-SiC). The bias voltage and current of the high-purity (HP) SI 4H-SiC photoconductive semiconductor switch (PCSS) with a channel length of 1 mm reached 24 kV and 364 A, respectively, and the minimum on-state resistance of approximately 1 Ω was triggered by laser illumination at a wavelength of 355 nm. The experimental results show that, in this case, the on-state characteristics of HP 4H-SiC PCSS are superior to those of the vanadium-doped(VD) 4H and 6H-SiC PCSS devices. HP 4H-SiC PCSS shows remarkable waveform consistency. Unlike for VD 4H and 6H-SiC PCSS, the current waveform of HP 4H-SiC PCSS exhibits a tailing phenomenon due to its longer carrier lifetime.

Anticancer Action of Psilostachyin-A in 5-Fluorouracil-Resistant Human Liver Carcinoma are Mediated Through Autophagy Induction, G2/M Phase Cell Cycle Arrest and Inhibiting Extracellular-Signal-Regulated Kinase/Mitogen Activated Protein Kinase (ERK/MAPK) Signaling Pathway.

BACKGROUND Liver cancer is one of the most common malignancies around the world and one of the major causes of cancer related mortality. The objective of this study was to evaluate the anticancer effect of the natural compound psilostachyin-A on 5-fluorouracil-resistant human liver carcinoma cells and its effects on autophagy, cell cycle, caspase activation, and the ERK/MAPK signaling pathway. MATERIAL AND METHODS Cell Counting Kit 8 (CCK-8) assay was used to evaluate the effects on HepG2 cell viability at different doses of psilostachyin-A. Cell cycle analysis was performed using flow cytometry, and Transwell assay was used to check effects on cell invasion. Transmission electron microscopic studies were done to evaluate autophagy induced by psilostachyin-A, and the western blot method was carried out to evaluate the effects on autophagy and the ERK/MAPK signaling pathway. RESULTS CCK-8 assay revealed that the psilostachyin-A reduced the cell viability of HepG2 cancer cells in a dose dependent manner. Psilostachyin-A also reduced the colony forming potential of HepG2 cells, concentration dependently. The IC50 of psilostachyin was found to be 25 µM. The anticancer effects of psilostachyin-A were due to the induction of autophagy which was accompanied by enhancement of LC3B II expression. Psilostachyin also caused cell cycle arrest by enhancing the accumulation of HepG2 cells in the G2/M phase. Transwell assay showed that psilostachyin-A suppressed the invasion of HepG2 cells. The results also showed that psilostachyin-A could block the ERK/MAPK pathway, indicative of the cytotoxic effects of psilostachyin-A on liver cancer. CONCLUSIONS These preliminary observations suggested that psilostachyin-A might prove beneficial in the treatment of liver cancer.

Finite element analysis of fiber-optic Fabry-Perot pressure sensors based on silicon diaphragms.

Fiber-optic Fabry-Perot pressure sensors based on silicon diaphragms of different thicknesses were fabricated using surface and bulk MEMS techniques in this study. The multi-beam interference resulting from multiple reflecting mirrors with the elastic deformation of the Fabry-Perot sensor was simulated by finite element analysis. The pressure sensitivities of the sensors with different diaphragm thicknesses and the relationship between the pressure and the wavelength shift were simulated. The simulation results were in good agreement with the test results. This study provides guidance for future sensor models and parameter design.

Comparison of Measurements with Finite-Element Analysis of Silicon-Diaphragm-Based Fiber-Optic Fabry-Perot Temperature Sensors.

Silicon-diaphragm-based fiber-optic Fabry-Perot sensors with different intracavity pressures were fabricated by anodic bonding and microelectromechanical techniques. The thermal stress and thermal expansion of the Fabry-Perot (FP) sensor caused by high-temperature bonding and temperature change were simulated by finite-element analysis. The calculated thermal stress is largest in the center and edge regions of the resonance cavity, reaching from 2 to 6 MPa. The reflection spectra and temperature sensitivity of the sensors were simulated by using a two-dimensional wave-optic model in Comsol. Theoretical calculations were also made for the FP cavity without considering silicon-diaphragm deformation and thermal stress. Four sensors with intracavity pressures of 0.01, 0.03, 0.04, and 0.05 MPa were tested at low temperatures, showing a high degree of consistency with the simulation results rather than theoretical calculation, especially for high intracavity pressure. This method is expected to aid the analysis of thermal stress generated during the bonding process and to facilitate better design and control of the temperature sensitivity of the sensor.

Effect of electron avalanche breakdown on a high-purity semi-insulating 4H-SiC photoconductive semiconductor switch under intrinsic absorption.

High-power photoconductive semiconductor switching devices were fabricated from a high-purity, semi-insulating 4H-SiC wafer. A highly n-doped GaN subcontact layer was inserted between the contact metal and the high-resistivity SiC wafer. The minimum ON-state resistance of the device was less than 1 ohm when the energy of a 355 nm laser was 10.5 mJ with a bias voltage of 6 kV. The maximum device lifetime is 3151 pulses, after which the device completely fails. The failure mechanisms are determined using several analysis methods. Under a strong electric field, the failure mechanism differs for the two electrodes. Near the edge of the anode electrode, the switch is damaged due to the thermal stress caused by impact ionization. At the edge of the cathode electrode, the electrode erosion is the main reason for the failure to operate for long periods of time. These two different damage mechanisms are both important factors influencing the device performance. The electron avalanche breakdown at the edge of the anode electrode causes the formation of cracks between the electrodes, which is the root cause of the switch failure.

"W-shaped" injection current dependence of electroluminescence linewidth in green InGaN/GaN-based LED grown on silicon substrate.

Injection current, and temperature, dependences of the electroluminescence (EL) spectrum from green InGaN/GaN multiple quantum well (MQW)-based light-emitting diodes (LED) grown on a Si substrate, are investigated over a wide range of injection currents (0.5 µA-350 mA) and temperatures (6-350 K). The results show that an increasing temperature can result in the change of injection current-dependent behavior of the EL spectrum in initial current range. That is, with increasing the injection current in the low current range, the emission process of the MQWs is dominated by filling effect of low-energetic localized states at the low temperature range of around 6 K, and by Coulomb screening of the quantum confinement Stark effect followed by a filling effect of the higher levels of the low-energetic localized states at the intermediate temperature range of around 160 K. However, when the temperature is further raised to the higher temperature range of around 350 K, the emission process of the MQWs in the low current range is dominated by carrier-scattering effect followed by non-radiative recombination process. The aforementioned current-dependent behaviors of the EL spectrum are mainly attributed to the strong localized effect of the green LED, as confirmed by the anomalous temperature dependence of the EL spectrum measured at the low injection current of 5 µA. In addition, the injection current dependence of external quantum efficiency at different temperatures shows that, with increasing temperature from 6 to 350 K, in addition to the enhanced non-radiative recombination, electron overflow becomes more significant, especially in the higher temperature range above 300 K.

Phase-locked array of quantum cascade lasers with an integrated Talbot cavity.

We show a phase-locked array of three quantum cascade lasers with an integrated Talbot cavity at one side of the laser array. The coupling scheme is called diffraction coupling. By controlling the length of Talbot to be a quarter of Talbot distance (Zt/4), in-phase mode operation can be selected. The in-phase operation shows great modal stability under different injection currents, from the threshold current to the full power current. The far-field radiation pattern of the in-phase operation contains three lobes, one central maximum lobe and two side lobes. The interval between adjacent lobes is about 10.5°. The output power is about 1.5 times that of a single-ridge laser. Further studies should be taken to achieve better beam performance and reduce optical losses brought by the integrated Talbot cavity.

Laser Ablation of 6H-SiC Single Crystals and Spectral Characterization.

Laser micromachining has proven to be a useful tool for precision processing of semiconductors. For Silicon Carbide (SiC) single crystals, ablation with ultraviolet wavelength laser could lead to the maximum absorption efficiency of incident energy. In this paper, laser ablations were performed on 6H-SiC single crystals through a 355 nm solid state laser. Different confining media were also employed to find the optimal processing condition. The surface of SiC after laser ablation was characterized by Raman spectroscopy. Amorphous silicon and nanocrystalline graphite were found to be the main compositions left. For SiC wafers ablation in air, the amorphous silicon exhibited mainly around rather than inside the ablated crater. However, the amorphous silicon showed opposite spatial distribution features for samples processing under liquid. Through analysis of the compositions left on the ablated surface, the ablation mechanism was investigated from another point of view. For liquid confined laser processing,previous studies mainly concentrate on the thickness and viscosity of the liquids, little information has been done on the reducibility of liquids. To investigate the influence of liquid reducibility, the surface morphology and oxygen content of ablation under different confining media were checked by confocal laser scanning microscopy and energy dispersive spectroscopy. Results showed that the reducibility of confining liquid also played a vital role in the ablation process under liquid. Utilizing liquids with deoxidizing ability as confining media will result in a remarkable reduction of surface oxygen content and a more regular morphology.

Surface plasmon enhanced photochemical etching of p-type GaP: a direct demonstration of wavelength selectivity.

We report here on significant enhancement of the photochemical etching of p-type gallium phosphide (GaP) by Au plasmonic nanostructures. The photochemical etching rate of defect (dislocation) states of Au-coated p-GaP samples is ten times higher than blank samples when irradiated with 532 nm laser. It is confirmed that the enhancement of photochemical etching is wavelength selective. Only 532 nm laser can efficiently increase the photochemical etching rate, while lasers of other wavelengths (375, 405, 445, and 473 nm) show limited or negative effects. This observation can be attributed to defect (dislocation) enhanced photochemical etching through localized surface plasmon resonance of Au nanostructures. This method may open a new pathway for controlled fabrication of novel optoelectronic devices.

Experimental evaluation of the impact of ventilation on cooking-generated fine particulate matter in a Chinese apartment kitchen and adjacent room.

Cooking is one of the major contributors to indoor pollution. Fine particulate matter (PM2.5) produced during cooking commonly mix into adjacent rooms and elevates indoor PM2.5 concentrations. The risk of human exposure to cooking-generated PM2.5 is mainly related to the exposure duration and particulate matter (PM) concentration. The PM2.5 concentration is influenced by cooking methods and ventilation patterns. Range hoods and open windows are conventional strategies for lowering the concentration of cooking-generated particles. To decrease PM emissions, kitchen air supply systems have been proposed, providing alternative possibilities for kitchen ventilation patterns. The effects of cooking methods, air supply systems, range hoods, and windows on PM2.5 concentrations must be analyzed and compared. To understand and provide advice on reducing exposure to PM2.5 due to cooking activities, we measured the PM2.5 mass concentration in a kitchen and adjacent room during cooking. The identified factors, including cooking method, range hood use, window status, and air supply system, were varied based on orthogonal design. The delay time between the PM2.5 peak in the kitchen and that in the adjacent room was determined. The degree of exposure risk for cooking-generated PM2.5 was evaluated using the mean exposure dose. The results indicated that the mean PM2.5 mass concentration in the kitchen ranged from 22 to 2296 µg/m3. In descending order, the factors affecting the indoor PM2.5 concentration in the apartment studied were range hood use, cooking methods, window status, and air supply system. The PM2.5 peak in the adjacent room occurred 200-800 s later than that in the kitchen. Other conditions being constant in these experiments, the use of range hoods, air supply systems, and windows reduce exposure doses by 90%, 37%, and 51%, respectively. These research results provide insights for reducing human exposure to cooking-generated PM2.5.

Silicon carbide single crystals for high-temperature supercapacitors.

Designing advanced electrode materials that can be reliably cycled at high temperatures and used for assembling advanced energy storage devices remain a major challenge. As a representative of novel wide bandgap semiconductors, silicon carbide (SiC) single crystals have broad prospects in high-temperature energy storage due to their excellent characteristics such as low thermal expansion coefficient, high temperature radiation resistance and stable chemical properties. In this work, an N-type SiC single-crystal material with a high-density porous structure was successfully designed and prepared by using an improved electrochemical anodic oxidation strategy. Besides, the N-type SiC single crystals were used in electrochemical energy storage as an integrated electrode material, exhibiting superior electrochemical performance. In addition, the high-temperature supercapacitor device assembled with ionic liquids has a wide operating temperature range and maintains a capacity of 88.24% after 5000 cycles at 150 °C. The reasons for its high energy storage performance are discussed through electrochemical tests and first-principles calculation methods. This study proves that the application of SiC single crystals in supercapacitor devices has great potential in the field of high-temperature energy storage, providing a reference for the further development of novel semiconductors in the field of energy storage and optoelectronic devices.

Light transmission enhancement from hybrid ZnO micro-mesh and nanorod arrays with application to GaN-based light-emitting diodes.

A hybrid ZnO micro-mesh and nanorod arrays (MMNR) was fabricated as a light output window for GaN-based light-emitting diodes (LEDs) to enhance the light extraction efficiency. The light output power of GaN-based LEDs with the ZnO MMNR is improved by 95% compared to the original planar LEDs. The ZnO MMNR is manufactured by photolithography techniques and a two-step wet chemical growth process. The incident angle-resolved light transmission of the ZnO MMNR beyond the critical angle of total internal reflection is greatly enhanced. The light diffraction pattern of the ZnO MMNR shows that it possesses both the two-dimensional diffraction grating effect of a ZnO micro-mesh and the light scattering effect of a ZnO nanorod array. LEDs with the ZnO MMNR have greater light extraction efficiency than those with only a ZnO micro-mesh or a ZnO nanorod array. The local optical field patterns of the ZnO micro-mesh and the ZnO MMNR are investigated using confocal scanning electroluminescence microscopy. The microscopic light extraction mechanism of the ZnO MMNR is analyzed in-depth.

Measuring methane emissions during the installation of residential and commercial natural gas meters in China.

Methane is a potent greenhouse gas that accounts for one-quarter of the world's radiative forcing. Methane emissions from the natural gas sector are prevalent throughout the natural gas (NG) chain. Studies have shown that methane emissions from post-meter uses of natural gas are vastly understated. A surge in the number of natural gas users, for example, would amplify the climate impact of methane emissions during the installation of natural gas meters. Thus, quantifying methane emissions during the installation of natural gas meters is critical in light of severe global climate change and urgent reduction targets. In this study, we used a mass balance approach to calculate methane emissions during the separate installation of 1444 residential natural gas meters and 51 commercial natural gas meters. Our results revealed the methane emission had a fat tail distribution. Specifically, the estimated mean methane emissions for household users were 0.008 (0.001-0.022) kg per household and 0.192 (0.013-0.816) kg per commercial user. Extrapolating these statistics to the whole of China, total emissions from 2007 to 2021 were 3.80 million metric tons (MMt) CH4, with an annual average of 0.25 MMt. Notably, in terms of economic development and population size, the provinces with the highest methane emissions were concentrated in the southeast. Our findings close a gap in measuring CH4 emissions in China across the natural gas chain and provide data to support the reduction targets set and the development of reduction technologies.

Research progress of large size SiC single crystal materials and devices.

SiC semiconductor is the focus of recent international research. It is also an important raw material for China to achieve carbon emission peak and carbon neutrality. After nearly 20 years of research and development, we focus on the three types SiC crystals, n-type, p-type and semi-insulating, indicating the development of Shandong University for crystal growth. And defects control, electrical property, atomic polishing, and corresponding device authentication all obtain great progress. Total dislocation density of 6-inch n-type substrates decreases to 2307 cm-2, where BPD (Basal Plane Dislocation) lowers to 333 cm-2 and TSD (Threading Screw Dislocation) 19 cm-2. The full width at half maximum (FWHM) (0004) rocking curves is only 14.4 arcsec. The resistivity reaches more than 1E + 12 Ω·cm for semi-insulating SiC and lower than 20 mΩ·cm for n-type SiC. The impurity concentrations in 6-inch high-purity semi-insulating (HPSI) SiC crystals reach extreme low levels. The devices made of various substrate materials have good performance.

Gallium Nitride Based Electrode for High-Temperature Supercapacitors.

Gallium nitride (GaN) single crystal, as the representative of wide-band semiconductors, has great prospects for high-temperature energy storage, of its splendid power output, robust temperature stability, and superior carrier mobility. Nonetheless, it is an essential challenge for GaN-based devices to improve energy storage. Herein, an innovative strategy is proposed by constructing GaN/Nickel cobalt oxygen (NiCoO2  ï¼‰heterostructure for enhanced supercapacitors (SCs). Benefiting from the synergy effect between the porous GaN network as a highly conductive skeleton and the NiCoO2 with massive active sites. The GaN/NiCoO2 heterostructure-based SCs with ion liquids electrolyte are assembled and delivered an impressive energy density of 15.2 µWh cm-2 and power density, as well as superior service life at 130 °C. The theoretical calculation further explains that the reason for the energy storage enhancement of the GaN/NiCoO2 is due to the presence of the built-in electric fields. This work offers a novel perspective for meeting the practical application of GaN-based energy storage devices with exceptional performance capable of operation under high-temperature environments.

Intrarenal small artery thrombosis in a transplant recipient patient infected with Covid-19 after kidney transplantation: A rare case report.

Currently, renal arteriovenous thrombosis induced by Covid-19 infection in patients after renal transplantation is very rare. We present a recent kidney transplant recipient who developed Covid-19 infection and later developed intrarenal small artery thrombosis. Finally, the patient's respiratory tract infection symptoms gradually disappeared after treatment. However, hemodialysis replacement therapy has to be continued due to the injury of the transplanted kidney function. In this case, we first reported that Covid-19 infection may induce intrarenal small artery thrombosis after kidney transplantation, which caused local ischemic necrosis of the transplanted kidney. We found that patients are at a high risk of Covid-19 infection at the early stage after kidney transplantation, and their clinical symptoms may be severe. In addition, even with anticoagulant therapy, Covid-19 infection may still increase the risk of thrombosis to some extent for patients who have undergone kidney transplantation, and we need to be alert to this rare complication in the future clinical work.

High-Performance Diamond Phototransistor with Gate Controllable Gain and Speed.

This paper presents a fabricated solar-blind phototransistor based on hydrogen-terminated diamond. The phototransistor shows a large photocurrent and enhancement of responsivity over conventional two-terminal diamond-based photodetector. These enhancement effects are owing to the internal gain of the phototransistor. The fabricated phototransistor exhibits a high photoresponsivity (R) of 2.16 × 104 A/W and a detectivity (D*) of 9.63 × 1011 jones, with gate voltage (VG) and drain voltage of approximately -1.5 V and -5 V, respectively, under 213 nm light illumination. Even at ultralow operating voltage of -0.01 V, the device records satisfactory performance with R and D* of 146.7 A/W and 6.19 × 1010 jones, respectively. By adjusting the VG, photocurrent generation in the device can be continuously tuned from the fast photoconductive effect to the optical gating effect with high optical gain. When VG increases from 1.4 to 2.4 V, the decay time decreases from 1512.0 to 25.5 ms. Therefore, responsivity, dark current, Iphoto/Idark, and decay time of the device can be well tuned by VG.