Semiconducting silicon carbide (4H-SiC) exhibits characteristics of high hardness, notable brittleness, and excellent chemical stability. The commonly employed technique for achieving an ultra-smooth and flat surface is chemical mechanical polishing (CMP), which is utilized to process the 4H-SiC surface. Wet oxidation, as an important process of chemical-mechanical polishing of single-crystal 4H-SiC, directly affects the rate and surface quality of CMP. This paper provides a comprehensive overview of the current research status of wet oxidation of single-crystal 4H-SiC. It discusses the oxidants used in the wet oxidation of 4H-SiC, such as KMnO4, H2O2, K2S2O8. Based on this, it further summarizes commonly employed oxidation-enhancement methods, including photocatalytic-assisted oxidation, electrochemical oxidation, and Fenton reaction. The mechanism of wet oxidation of single-crystal 4H-SiC is analyzed from the aspect of theoretical calculation, and the future research direction of wet oxidation of 4H-SiC is proposed.

The performance and lifetime of silicon carbide (SiC) devices are directly affected by the quality of SiC epitaxial films. On the one hand, the quality of SiC epitaxial films is affected by the quality of substrates. For examples, the stacking faults (SF) in substrates penetrate into the epitaxial layer, forming bar-shaped stacking faults (BSF), and the threading screw dislocation (TSD) penetrate into the epitaxial layer to form pits or Frank-type stacking faults (Frank SF). On the other hand, the quality of SiC epitaxial films is also influenced by the epitaxial growing process. For examples, basal plane dislocation (BPD) in the substrate form Σ-basal plane dislocation (Σ-BPD) in the epitaxial layer under thermal stress or other unstable conditions, the TSD and threading edge dislocation (TED) in the substrate may be etched and derived into pits, and SF and silicon droplets may also be produced. Therefore, high quality SiC substrates and optimized epitaxial growing process are both crucial for obtaining high-quality silicon carbide epitaxial wafers. In this article, based on the SiC epitaxial films grown on 6 inch SiC substrates batch-produced by TankeBlue Company, the defects reproducing process in substrates during epitaxial growing were analyzed, and the formation mechanism and controlling technology of common defects such as BPD, SF, silicon droplets and pits were overviewed. The generation mechanism of Σ-BPD and its eliminating methods were also explored. Finally, we obtained the mass-production technologies of SiC epitaxial films with good thickness and concentration uniformity, and low defect density, which are qualified for making 650 and 1 200 V SiC-based MOSFETs.

:Proton exchange membranes (PEMs) have key functions in fuel cells. They separate the cathode and anode, provide channel for proton transport, and block the fuel permeation in the battery. Perfluorosulfonic acid membrane like Nafion has excellent chemical stability, thermal stability, and high proton conductivity. However, it also has problems such as high cost, poor mechanical performance and low proton conductivity at high temperatures, and easy degradation. Metal organic frameworks (MOFs) are attractive candidates for PEMs due to their high porosity, large specific surface area and controllable internal channels. MOFs have been used as proton conductors directly, or to modify and improve the existing ionic polymer PEMs, and a series of important progresses have been achieved. In this paper, four common proton conduction modes of MOFs structure proton conductors are reviewed, and the related studies of MOFs in different types of ionic polymer composite PEMs are summarized. Moreover, current issues on MOFs proton conductors and their PEMs are pointed out, which provides references and ideas for the development and application of MOFs as PEMs.

NaI (Tl) scintillators are widely used because of their characteristics of high detection efficiency, good temporal characteristics, and minimal temperature influence. In order to meet the needs of nuclear radiation detectors with high detection efficiency, large size and high energy resolution NaI (Tl) scintillators are required. Based on the growth characteristics of NaI (Tl) crystals, the main furnace body, temperature field system, crucible, heating power supply and other components of the large size NaI (Tl) growth crystallization furnace were studied and designed. In conjunction with the control system of the large size NaI (Tl) growth crystallization furnace, innovative fusion method was used to grow NaI (Tl) scintillator materials with a diameter exceeding 300 mm, which provides direction and solutions for the subsequent growth of large size NaI (Tl) crystals in China.

Large size laser crystals are a key component of high-power all solid-state lasers. However, during the crystal growth process, defects such as bubbles and inclusions are inevitably generated, which affect the performance of the laser. In order to quickly and effectively evaluate crystal defects, a three-dimensional imaging system for crystal defects based on sheet beam scanning was established in this paper. In the system, a Powell lens is used to shape a 532 nm point laser to obtain a sheet-like laser. The scattered light generated by crystal defects is obtained through a telecentric lens and CMOS detector to obtain the surface distribution of crystal defects. At the same time, high-precision displacement platforms are used to scan the surface array one by one, completing the three-dimensional distribution scanning of the crystal. Furthermore, combined with digital image processing technology, characterize the surface distribution characteristics of crystal defects and reconstruct the volume distribution characteristics of crystal defects. Based on the above system, intrinsic defects in Yb∶YAG crystals with dimensions of about 50 mm×50 mm×100 mm were measured with a minimum defect detection resolution of 38.69 μm. This article provides a new method for accurately characterizing the internal defects of crystals, and also provides visual data support for high-precision processing of crystal billets in the later stage.

Acoustic hyperbolic metamaterials are artificial materials with hyperbolic dispersion characteristics and strong anisotropy. Their negative refractive properties are the theoretical basis for studying the implementation of high-resolution focused superlenses. In response to the problem that the recognition of far-field noise sources is limited by the resolution of 0.5 times wavelength acoustic Rayleigh diffraction recognition, combined with the excellent control effect of acoustic metamaterials on sound waves, a hyperbolic metamaterial that can achieve sub wavelength super-resolution imaging is introduced, and its negative refractive characteristics are used to design an acoustic hyperbolic structure for working at a frequency of 2 271.5 Hz. The dispersion and negative refraction characteristics of the hyperbolic structure of this configuration were analyzed, and the results show that, the group velocity direction of sound waves propagating in this hyperbolic metamaterial is perpendicular to the wave vector and follows the normal direction of the dispersion curve. The research in this paper provides some design references for realizing arbitrary regulation of sound wave and elastic wave, as well as focusing, locating, identifying and amplifying noise sources.

Based on metal organic chemical vapor deposition (MOCVD), growth mechanism and stress modulation of van der Waals (vdW) heteroepitaxial GaN microwave material were studied with few-layer BN as an interlayer on 4-inch sapphire substrates. The influence of AlN nucleate process on growth mechanism of GaN buffer layer and its correlation with crystalline quality, stress, and electrical properties were discussed. A stress modulation scheme based on AlN/AlGaN composite nucleation process is proposed, achieving stress well in control for large-size vdW heteroepitaxy firstly. The as-grown GaN microwave material possesses a wafer bow of +20.4 μm, fullwidth at half maximum of GaN (002)/(102) peaks of 471.6/933.5 arcsec, root-mean-square roughness of 0.52 nm and electron mobility of 2 000 cm2/(V·s). Finally, large-size wafe-scale GaN microwave material was successfully separated from sapphire substrate by a mechanical lift-off process, providing convenience for transfering to high thermal conductivity substrates and creating conditions for fabricating high-power RF devices.

The mechanical property, electronic structure, and optical properties of tetragonal perovskite PbTiO3 and Ni, Cu, Zn-doped PbTiO3 were studied by first principles. The mechanical property calculations show that Ni-doped PbTiO3 exhibits the highest values for volume modulus, shear modulus, and elastic modulus among the three doping systems. Notably, the Ni-doped system also has the highest Debye temperature. The G/B ratio represents the material’s brittleness and toughness, which is highest for Zn-doped PbTiO3, indicating the highest degree of chemical bond orientation. The G/B range for Ni and Zn-doped systems is 0.56<G/B<1.75, indicating brittle materials, while the intrinsic PbTiO3 and Cu-doped systems have G/B values less than 0.56, indicating ductile materials. The electronic structure reveals that the doped systems have narrower band gaps and reduced transition energies compared to the intrinsic system. The introduction of Ni introduces impurity levels at the Fermi energy level in PbTiO3, while Cu and Zn doping shifts the valence band maximum upwards, causing the Fermi level to enter the valence band and resulting in p-type conductivity for Cu and Zn-doped PbTiO3. The doping of Ni, Cu and Zn expands the absorption range of PbTiO3 to the infrared region and enhances the absorption intensity in the visible light range. Among the intrinsic PbTiO3 and three single-doped PbTiO3 materials, Cu-doped PbTiO3 exhibits the best photocatalytic properties.

Sr2CrOsO6 has the highest magnetic transition temperature (725 K) among the double perovskite oxides. Ca2CrOsO6 was obtained by replacing Sr ions with smaller volume Ca ions, and the magnetic transition temperature was higher than room temperature. Further substitution of Cr ions by Mo ions with more delocalized d orbitals yielded Ca2MoOsO6. The electronic structures and magneto-optical Kerr effects of the double perovskite oxides Sr2CrOsO6, Ca2CrOsO6 and Ca2MoOsO6 have been systematically calculated by density functional theory. The electronic structures indicate that all three materials are semiconductors. The electronic structures of Sr2CrOsO6 and Ca2CrOsO6 are very similar, and the band gap of Ca2MoOsO6 is extremely small, only 0.10 eV. Observing the magneto-optical Kerr effect line, all three materials show significant magneto-optical Kerr effects in the range of infrared to visible spectrum. The maximum Kerr rotation angles of Sr2CrOsO6, Ca2CrOsO6 and Ca2MoOsO6 are 1.18°, 0.98° and 0.65°. The maximum Kerr rotation angle of the three materials is greater than 0.2°, which makes them to be ideal magneto-optical materials. The calculated results show that the inclusion of both 3d(4d) and 5d transition metal ions in the compound contributes to the significant magneto-optical Kerr effect. Analysis of the optical conductivity tensor shows that the peak of the magneto-optical Kerr line of three materials originates from the interband transition and is dominated by the imaginary part of the off-diagonal element of optical conductivity tensor.

Molybdenum disulfide (MoS2) has attracted much attention in the field of electromagnetic wave (EMW) absorption due to its high specific surface area and unique electronic structure, but its high conductivity leads to poor EMW absorption performance. To address this issue, this work introduces CuxSy nanoparticles and constructs a unique CuxSy-MoS2 heterostructure to achieve appropriate impedance matching and attenuation capabilities. By regulating CuxSy nanoparticles, the dielectric loss capacity of heterostructure is adjusted. As a result, CuxSy-MoS2 exhibits excellent EMW absorption performance at low, medium and high frequencies. The CuxSy-MoS2 heterostructure shows a reflection loss (RL) of -72.77 dB at a frequency of 12.68 GHz, with a matching thickness of only 1.99 mm, surpassing most metal sulfide heterostructures. Moreover, it also exhibits a wide effective absorption bandwidth (EAB), reaching 5.1 GHz (12.9~18.0 GHz) at 1.73 mm. This work provides a new strategy for designing MoS2-based absorption materials with strong absorption, broadband and thin matching thickness.

Using first-principles calculations, the different doping structures and electronic properties of Y atom on anatase TiO2(101) surface were carefully studied to improve the photocatalytic activity of the surface. The results show that when Y atom is adsorbed on stoichiometric anatase TiO2(101) surface, the most stable adsorption site is between two 3-fold coordinated oxygen atoms. Meanwhile, when Y atom on anatase TiO2(101) surface with subsurface oxygen vacancy, the most stable adsorption site is between two 3-fold coordinated oxygen atoms that neighboring subsurface oxygen vacancy. In contrast, when Y atom on anatase TiO2(101) surface with surface oxygen vacancy, the most stable adsorption site is on the top of 3-fold coordinated titanium that neighboring surface oxygen vacancy. The charge density results show that Y atom can be stably adsorbed on anatase TiO2(101) surface. Furthermore, the density of states results show Y doped on the surface with surface oxygen vacancy can suppress the band gap from 1.67 eV to 1.44 eV, and induce extra impurity energy levels, which cause a fractional transition of electrons and improve surface photocatalytic ability. This study provides theoretical support for enhancing the surface photocatalytic ability of TiO2 (101) by single atom Y doping.

A Sr(II) complex ［Sr(L)2(H2O)4］n (1) was synthesized with 1,4,5,8-naphthalene tetracarboxylic acid (H4L1) and strontium chloride hexahydrate under solvothermal conditions. The structure was characterized by elemental analysis (EA), single crystal X-ray diffraction (SXRD), powder X-ray diffraction (PXRD), infrared spectroscopy (IR) and thermogravimetric analysis (TGA). The single crystal X-ray diffraction results indicate that H4L1 undergoes in-situ reaction to generate 1,3-dioxo-1H,3H-benzo［de］isomere-6,7-dicarboxylic acid (H2L). In complex 1, each Sr(II) atom is located in the geometric configuration of a square antiprism. The L- ligands connect Sr atoms to form a one-dimensional chain structure. 2D supramolecular structure is formed through hydrogen bonding and π…π stacking interactions. The solid states luminescence behavior of complex 1 was explored. It is found that complex 1 produces a wide emission spectrum band (450~690 nm) at the excitation wavelength of 211 nm, and the maximum emission wavelength appears at 535 nm. Therefore, it can be seen that complex 1 is a potential green light material.

A novel benzenesulfonate-imidazole complex of nickel Ni(Im)6(C6H5SO3)2 was synthesized by solvothermal method with nickel sulfate, sodium benzenesulfonate and imidazole as main raw materials. The structure, composition and thermal stability of complex were characterized by single X-ray crystal diffraction, inductively coupled plasma optical emission spectrometer, infrared spectroscopy, powder X-ray diffraction and thermogravimetric analysis. The molecular structure was determined. The specific surface area and the pore structure were determined by N2 adsorption-desorption test. The result shows that the complex belongs to monoclinic system, P21/c space group, exhibiting a 3D spatial structure. It exhibits high phase purity and thermal stability. The cell parameters of complex are a=8.377 3(4) , b=10.151 8(5) , c=20.526 3(10) , α=90°, β=90.292 0(10)°, γ=90°, V=1 745.63(15) 3, Z=2, Mr=781.52, F(000)=812, μ=0.737 mm-1, Dc=1.487 g·cm-3, R1=0.042 1, wR2=0.110 3. Then, the Knoevenagel reaction was used as a probe to test the catalytic performance of complex. The experimental results show that under room temperature and solvent-free conditions, the complex could complete catalytic reactions in a relatively short time and exhibit high catalytic activity.

A new three-dimension manganese(II) metal-organic framework ［Mn2(5-ana)4(H2O)］n (namely Mn-MOF) has been successfully constructed by the reaction of 5-aminonicotinic acid (5-Hana) and MnCl2 using solution method at room temperature. The structure and properties of Mn-MOF were characterized by X-ray single-crystal diffraction, X-ray powder diffraction, elemental analysis, infrared spectroscopy, thermogravimetric analysis, ultraviolet-visible spectra and luminescent spectra. Structural analysis reveal that the as-synthesized complex crystallized in the monoclinic system and feature a binodal (2,8)-connected coordination network. The ［Mn2(CO2)2(H2O)］ dimeric unit acts as 8-connected node and 5-ana- ligand acts as 2-connected node. Electrostatic potential (ESP) on molecular van der Waals surface analysis of 5-ana- ligand shows that the first reactive site exists in the surface close to the oxygen atoms of carboxyl group with the ESP global minimum of -143.37 kcal·mol-1. The second and third reactive sites exist in the nitrogen atoms of pyridine ring and amino, respectively. Mn-MOF displays good thermal stability at room temperature. Fluorescence spectroscopy measurement reveals that the complex shows emission maximum at 402 nm upon 256 nm light excitation. More importantly, Mn-MOF exhibits sensing selectivity for Fe3+ by fluorescence quenching with the quenching efficiency up to 98.71%, which makes it as a potential luminescent sensor for analyzing Fe3+ in aqueous solution.

A coordination polymer ［Cu2(μ3-OH)(1,3-BIP)(BTC)］n (SNUT-20) was constructed by 1, 3-di(1H-imidazol-1-yl)propane (1,3-BIP), benzene-1,3,5-tricarboxylic acid (H3BTC) and Cu(NO3)2·3H2O under solvothermal method. Its structure was confirmed by elemental analysis (EA), thermogravimetric analysis (TGA), FT-IR and single crystal X-ray diffraction. Single crystal X-ray diffraction exhibits that SNUT-20 is a 3D framework with a tetranuclear copper cluster as a secondary structural unit, which forms a binodal (3, 8)-connected topology by further ligation of mixed ligand. In addition, SNUT-20 exhibits good photocatalytic degradation performance for rhodamine B (RhB), methylene blue (MB) and methyl orange (MO), RhB, MB and MO reach 81.5%, 89.4% and 48.3% of the degradation rates, respectively.

The rapid development of modern completely artificial light-controlled plant growth requires the light source increasingly stringent. Blue-violet phosphor with high luminous intensity and good thermal stability is the key material for plant growth. Herein, narrow-band blue-violet Zn3B2O6∶xBi3+ (0≤x≤0.03) phosphor with excellent thermal stability was synthesized by solid-state reaction. The results of XRD and energy spectra analysis show that Bi3+ successfully entered Zn3B2O6 lattice. The fluorescence spectrum of Zn3B2O6∶Bi3+ phosphor shows narrow-band blue-violet light at 430 nm (3P1~1S0), and the full width at half maximum is only 56 nm. The optimal Bi3+ doping concentration is 0.02. According to the excitation spectrum shape and the lifetime decay behavior, it is proved that Bi3+ only occupies Zn sites in Zn3B2O6. The emission peak intensity and integrated area of Zn3B2O6∶0.02Bi3+ phosphor at 423 K are both 85% of those at room temperature, indicating that the sample has excellent thermal stability and may have potential application in high-temperature devices. The emission spectrum of Zn3B2O6∶0.02Bi3+ phosphor accounts for 70.4% and 84.6% of the absorption spectra (370~525 nm) of chlorophyll a/b, respectively, indicating the potential application of as-prepared blue-violet phosphors in the field of plant growth.

In order to improve the efficiency of tunneling oxide passivated contact (TOPCon) cells, a p-type tunneling oxide passivation contact structure was fabricated on the front of N-type TOPCon cells through high-temperature diffusion, improving the emitter passivation performance and reducing front metal recombination. The effects of different deposition time, drive-in temperature, drive-in time and other process parameters on the passivation performance and doping curve of experimental samples were investigated. The experimental results show that when the deposition time is 1 500 s, the drive-in temperature is 920 ℃, and the drive-in time is 20 min, the boron doped polysilicon layer can achieve better passivation performance and boron doping concentration, with the doping concentration of sample polycrystalline silicon layer reaching 1.40×1020 cm-3. The implied open circuit voltage(iVoc) is greater than 720.0 mV. The photoelectric conversion efficiency of TOPCon cells prepared based on this parameter can reach 23.89%, corresponding to a short-circuit current density of 39.36 mA/cm2, the open circuit voltage (Voc) is 726.4 mV, and the fill factor (FF) is 83.54%

The introduction of heteroatoms into manganese dioxide (MnO2) is an effective method to adjust the active site of electrochemical water oxidation catalysis. Although many modification methods for MnO2 have been studied in electrocatalytic oxygen evolution reaction (OER), few studies have focused on the influence of regulating different crystal forms of MnO2 on catalytic activity. This article prepared four different crystal forms of MnO2 (α-MnO2, β-MnO2, γ-MnO2 and δ-MnO2), and systematically studied the catalytic performance of the catalyst (x-MnO2-Ru) prepared by adding Ru to α-MnO2, β-MnO2, γ-MnO2 and δ-MnO2 for OER. The results of linear sweep voltammetry and chronopotentiometry measurements show that the catalyst prepared by adding Ru to β-MnO2 (β-MnO2-Ru) has the best electrochemical performance. β-MnO2-Ru shows a low overpotential (300 mV at 10 mA·cm-2) and outstanding catalytic activity with small degradation after 24 h operation. It is found that β-MnO2-Ru exhibits excellent electrocatalytic performance due to its abundance of Mn3+and defect oxygen vacancies.

Carbide slag is a typical high calcium industrial solid waste with excellent CO2 absorption performance, but the reaction activity and CO2 absorption performance of pure carbide slag in calcium cycling will decrease with the increase of cycling times. Efficient and stable calcium-magnesium zinc composite absorbents was synthesized using carbide slag as the calcium source, MgO and ZnO as dopants. Effects of synthesis process conditions and doping amount on the absorption performance of CO2 composite absorbent were investigated in a fixed bed reactor, as well as the changes in the internal structure of the absorbent during cyclic absorption. The results show that the absorbent synthesized by dry physical mixing method has a richer pore structure than wet mixing method. Mg and Zn elements are evenly dispersed on the surface of the carbide slag, effectively improving the anti-sintering performance and reaction activity of the carbide slag. The modified composite absorbent has higher CO2 absorption performance during the cycling process, and after 20 cycles, CO2 absorption capacity of the composite absorbent synthesized by dry physical mixing method can still reach 0.42 g/g.