Table of Content

15 November 2023, Volume 52 Issue 11

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Reviews

Research Progress on Surface/Subsurface Damages of 4H Silicon Carbide Wafers

LI Guofeng, CHEN Hongyu, HANG Wei, HAN Xuefeng, YUAN Julong, PI Xiaodong, YANG Deren, WANG Rong

2023, 52(11):  1907-1921. 

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4H silicon carbide (4H-SiC) substrate wafers without surface/subsurface damages and low surface roughness are ideal substrates for the development of power electronics and radio frequency (RF) microwave devices, which hold great promise in applications of new energy, rail transportation, smart grid and 5G communication. The processing of 4H-SiC substrate wafers includes slicing, grinding, lapping, polishing and cleaning. However, the surface damages (SDs) and subsurface damages (SSDs) introduced during the processing of 4H-SiC substrates affects the properties of 4H-SiC substrates and epitaxial layers, and thus the performance and reliability of devices based on 4H-SiC. This paper focuses on the formation and removal mechanisms of SDs/SSDs during the processing of 4H-SiC substrate wafers. Based on the detection method of SDs/SSDs, the morphologies and characterization approaches of SDs/SSDs are reviewed. Finally, three commonly used technologies for the removal SDs/SSDs, along with their technical advantages, development challenges and trends, are briefly discussed.

Research Progress of MOFs-Derived Nano-Electrode Materials for Supercapacitors

GUO Rongnan, LI Taiwen, WANG Dong, WANG Tianhan, PEI Qi, WANG Yuanyuan

2023, 52(11):  1922-1930. 

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Supercapacitors have attracted much attention because of their high power density, fast charging/discharging speed, and long cycle life. However, the low energy density restricted their wide application. Developing novel and efficient electrode materials is imperative to improve the electrochemical performance of supercapacitors. Metal-organic frameworks (MOFs) have attracted extensive attention in the field of energy conversion and storage, owing to their large specific surface area, controllable pore size, rich active sites and easy synthesis. Nevertheless, due to the inferior structural stability and low conductivity of MOFs, the electrochemical performance of supercapacitors with MOFs electrode materials is unsatisfactory. MOFs derivatives, prepared from the MOFs precursor, possess excellent structural stability and conductivity, thus prominently improve the electrochemical performance of supercapacitors. This work mainly focuses on the MOFs-derived electrode materials for supercapacitors, including MOFs-derived carbides, oxides, hydroxides, phosphides and sulfides. The synthesis strategies of electrode materials for supercapacitors are discussed, providing guidance for the research of nano-MOFs-derived materials for supercapacitors.

Research Articles

Preparation and Characterization of Single Crystal Diamond with High Purity and Low Dislocation Density

HU Tingting, MU Lianxi, WANG Peng, TU Juping, LIU Jinlong, CHEN Liangxian, ZHANG Jianjun, OUYANG Xiaoping, LI Chengming

2023, 52(11):  1931-1938. 

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With its excellent properties such as high thermal conductivity, strong radiation resistance and high electron mobility, diamond has become one of the most suitable materials for radiation detectors. Detector-grade diamond requires low impurity content, low dislocation density and other defects. However, it is very difficult to keep low impurities and low dislocations simultaneously in the actual crystal growth process. In this study, microwave plasma chemical vapor deposition (MPCVD) method was used to grow diamond layer on two high-quality HPHT diamond substrates with the previously optimized process conditions. The nitrogen impurity content and structure of the HPHT substrate and growth layer were characterized and analyzed. The results show that, the content of nitrogen impurity on two HPHT substrates are 7.1×10^-6% and 4.04×10^-8%, respectively, whereas in their epitaxial diamond layers, the nitrogen impurity content are 2.1×10^-7% and 5×10^-8%, respectively. The full width at half-maximum of the rocking curve shows that the dislocation density of the MPCVD growth layer is comparable to the HPHT substrate, though some dislocations were introduced into the MPCVD growth layer, which increases the stress. Overall, the dislocations in the HPHT substrate and epitaxial layer of single crystal diamond are in the same order of magnitude. The high-purity single crystal diamond prepared in this work may be used in nuclear radiation detection and semiconductor fields.

Nature and Cultivated Diamond: Quality Characterization and Color Causes Analysis

PAN Yue, LIU Shucheng, ZHANG Xiaoming, ZHANG Bangxuan, YAO Di, HU Kuo, ZANG Chuanyi, ZHOU Qiang, LIU Zhaodong, LIU Bingbing

2023, 52(11):  1939-1945. 

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Diamond is a typical superhard multifunctional material with excellent properties such as the highest hardness, ultra-wide band gap and the highest thermal conductivity. The reserve of natural diamond is small and the price is expensive. Color diamonds are a very small part of nature diamonds and their coloring mechanisms are extremly complicated. It is a effective method to synthesize diamond by high temperature and high pressure method, but it is still a great challenge to modulate and realize color diamonds. In this paper, the quality, structural defects and impurities of color (pink and green) diamonds were studied by Raman, photuluminescence, infrared and visible absorption technologies, and the quality, defect changes with temperature and the cause of color were studied in detail. It is found that the coloring mechanism was related to electrically neutral N₂V defect (H₃), shear stress, plastic deformation and NV⁰/NV^- color center etc. Obtaining color diamonds by various methods is not only for their highly valued gemstones, but also helps people to further understand the formation mechanism of diamond, and provides a new reference for the cultivation of colored diamonds.

Luminescence Performance of LYSO:Ce Scintillator with Different Surface States

YAN Weipeng, LI Binkang, DUAN Baojun, ZHU Zijian, LI Peng, SONG Guzhou, SONG Yan

2023, 52(11):  1946-1951. 

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The surface states of scintillator will affect its scintillation performance such as fluorescence emission intensity and spatial resolution, and then affect the test results of radiation detection system. By means of theoretical simulation and experimental research, this paper systematically explored the spatial distribution of fluorescence intensity of LYSO:Ce scintillator under four surface states (two sides polished, exit side polished only, inlet side polished only and two sides unpolished) when excited by radiation, and the influence of scintillator thickness on its spatial resolution. The results show that the relative fluorescence intensity of the four states at 0° normal direction is 0.49:0.64:0.89:1, and the fluorescence intensity gradually decreases with the emission angle increase. As the surface polished degree decreases, the spatial distribution of fluorescence emitted from scintillators becomes uniformly. When the thicknesses of the scintillator are 0.3, 1.0 and 5.0 mm, the spatial resolutions of two sides polished are 1.70, 1.36 and 1.12 lp/mm, respectively. The spatial resolutions of exit side polished are 1.5, 1.2 and 1.0 lp/mm, respectively. The spatial resolution decreases with the scintillator thickness increases, and the spatial resolution of two sides polished is improved by about 12% compared to exit side polished only.

Optimization Design of Key Structure of Polycrystalline Silicon Reduction Furnace Based on Fluent

SUN Zegang, GE Zihao, SHI Rongqiu, FEI Tianwen

2023, 52(11):  1952-1960. 

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The improved Siemens method is the main method for polycrystalline silicon production, and the polycrystalline silicon reduction furnace is the main equipment for polycrystalline silicon preparation. Aiming at the problem of irregular size of polycrystalline silicon produced by the uneven flow field, temperature field, and radiation field of traditional polycrystalline silicon reduction furnaces. This article optimizes the design of the furnace top sealing head structure, air outlet layout, and silicon rod chassis layout of the reduction furnace. Using the Do radiation module of Fluent software, a gas-solid radiation simulation analysis was conducted on a polycrystalline silicon reduction furnace. The cloud and streamline diagrams of the flow field, temperature field, and radiation field before and after optimization were compared. The results show that the exhaust design of the up-outlet effectively improve the gas flow velocity in the furnace, reduce gas reflux, increase gas flow uniformity, effectively solve the temperature dead zone generated at the top of the furnace, and balance the temperature difference between the upper and lower parts of the furnace; the elliptical top head optimizes the overall space of the reduction furnace, reduces design costs, effectively inhibits the generation of gas vortices in the circular head, and increases the uniformity of gas flow in the furnace; at the same time, a parallel circular symmetric silicon rod is used to increase the overall radiation amount, optimizing the uneven radiation phenomenon between the outer ring silicon rod and the central silicon rod in traditional reduction furnaces, effectively preventing the generation of irregular silicon rods, improving the production of polycrystalline silicon, and providing a new solution for the design of polycrystalline silicon reduction furnaces.

Construction of Anisotropic Simulation Etching Model and Morphology Simulation of Mono-Crystalline Silicon

ZHANG Hui, QIAN Jun, HONG Lili

2023, 52(11):  1961-1970. 

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In order to simulate the morphology and structure of mono-crystalline silicon under different etching conditions such as temperature, concentration, with or without surfactant, the atomic structure model of mono-crystalline silicon is constructed and the relationship between the etching rates of main crystal planes and the corresponding atomic structure are analyzed. A surface atomic etching function (Si-RPF) suitable for mono-crystalline silicon etching simulation is proposed. The numerical relationship between the macroscopic etching rate of crystal planes and the microscopic removal probabilities of atoms is clarified and a Kinetic Monte Carlo (Si-KMC) anisotropic wet etching process model is constructed based on genetic algorithm. Based on the step flow theory, the process model can explain the cause of the anisotropy of silicon etching from the perspective of microscopic atoms, clarify the role of different types of atoms in the etching process, and realize the accurate simulation of the three-dimensional etching morphology of silicon substrate under different etching conditions. By comparing the experimental data and simulation results of silicon etching with or without the addition of surfactant, the simulation results of Si-KMC etching process simulation model can reach more than 90% simulation accuracy.

Ultra-Wideband Three-Dimensional Frequency Selective Surface

CHEN Zhaoran, YAO Xiayuan

2023, 52(11):  1971-1979. 

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Compared to traditional two-dimensional frequency selective surfaces, three-dimensional frequency selective surface has become a hot research direction due to its ability to generate more resonance points, provide larger bandwidth, efficiently meet miniaturization requirement, and bring more stable frequency response. A novel three-dimensional frequency selective surface with a multi-level orthogonal diamond structure is proposed in this paper. Its basic unit structure is an orthogonal diamond-shaped metal wire, and a polymer with dielectric constant of 2.2 is injected externally as support structure. The common bandwidth of this frequency selective surface exceeds 9.2 GHz with a relative bandwidth exceeding 50%, and the average insertion loss of TE and TM polarization does not exceed 1 dB when the incident angle in the range of 0° to 50°. This three-dimensional frequency selective surface has three resonance points. Their formation reasons are the resonance of the orthogonal diamond metal structure, the resonance generated by the coupling between the structure and the dielectric end face, and the first-order Fabry Perot resonance of the dielectric end face. If the dielectric constant of the filling medium is adjusted, higher order of Fabry Perot resonance can be utilized, and a spatial filter with broader bandwidth requirement can be designed. At the same time, the impact of this three-dimensional frequency selective surface on the far-field pattern of the antenna is also evaluated.

Growth of High-Quality Centimeter-Size Single-Crystal Graphene on High-Temperature Annealed Cu (111) Substrate

QI Jianhai, CHEN Yang, YUE Yuanyuan, LYU Bingchen, CHENG Yuang, ZHU Fengqian, JIA Yuping, LI Shaojuan, SUN Xiaojuan, LI Dabing

2023, 52(11):  1980-1988. 

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Two-dimensional (2D) graphene has shown great potential of breakthrough of Moore's law limitation due to its atomic thickness in electronic devices. Up to now, chemical vapor deposition (CVD) is a widely applied method for graphene growth due to its low-cost, large-area production, and easy control in layer number. However, the CVD-grown graphene usually suffers from relatively low quality derived from the polycrystalline nature of catalytic metal (e.g., Cu) substrates. Herein, single-crystal Cu (111) substrates were fabricated by a high-temperature annealing process, initial nucleation of graphene on it has been well controlled, and high-quality and centimeter-size single-crystal graphene was achieved. The Cu (111) substrate provides onefold orientation for the graphene growth according to their lattice matching relation, and domain boundaries of neighboring graphene nuclei could stitch together. The as-grown single-crystal graphene has an average sheet resistance of 607.5 Ω · sq^-1. Compared to that of grown on the pristine polycrystalline Cu (1 415.7 Ω · sq^-1), it shows high electrical conductivity. High-temperature annealing purified the Cu foils, and induced a clean graphene surface with lower roughness. The quality of graphene is further verified by using it in a field-effect transistor (FET), resulting in a maximum switch ratio of 145.5 and carrier mobility of 2.31×10³ cm² · V^-1 · s^-1. Based on these results, we believe that the single-crystal graphene in present work is also feasible for fabricating other high-performance electronic devices.

Preparation of Onion Carbon-Based Bipolar Plate and Its Application in PEMFCs

CHEN Liuling, ZHANG Weike, ZHANG Lan, LIANG Zhuanzhuan, GAO Bowen, LI Qiwang

2023, 52(11):  1989-1996. 

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Metal-core carbon nano-onions (CNOs) with uniform size(50~140 nm) were prepared by chemical vapor deposition (CVD) method with methane as carbon source. The synthesized CNOs were purified by microwave heating to obtain an onion carbon material with a purity of 99%, and it was used as conductive bipolar plate in proton exchange membrane fuel cells (PEMFCs) stack. The characterization and analysis of CNOs show that the synthesized CNOs are embedded with Fe-Ni nanoparticles. The contact angle test reveals that the wetting angle of the onion carbon-based bipolar plate manufactured by injection molding is less than 91°, and the hydrophilicity is enhanced compared to the commercial graphite bipolar plate, which is helpful to electron transmission. The output power of the stack formed using onion carbon-based bipolar plates reaches 58 W at 13.2 V, which is 21% greater than that of the commercial graphite bipolar plate stack (48 W), according to the endurance and power test of the self-breathing stack. Onion carbon-based composites have been shown in studies to enhance the power density, efficiency, and longevity of PEMFCs stack.

Influence of Deposition Temperature on Interface Bonding Properties of WC-Co/SiC/Diamond with Different Co Content

YANG Junru, YUE Yanping, LYU Hao, REN Baofei, CHEN Gongling

2023, 52(11):  1997-2006. 

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Interface models of diamond-coated cemented carbide tool WC-Co/SiC/Diamond with Co mass fraction of 6%, 8%, 10% and 12% were constructed. The influences of different deposition temperatures on the interface bonding strength were simulated with the molecular dynamics method, and the reasons were analyzed from perspectives of adhesion work and bond length distribution. The adhesion work analysis indicates that, compared with the other three Co content interface models, the two interfaces in WC-6%Co/SiC/Diamond interface model have the highest adhesion work values at seven deposition temperatures. At different deposition temperatures, both interfaces of WC-6%Co/SiC and SiC/Diamond in WC-6%Co/SiC/Diamond have the highest adhesion work values of 2.468 and 5.394 J/m² at 1 123 and 1 173 K, respectively. The analysis results of bond length distribution indicate that, at any deposition temperature, compared with the other three Co content interface models, the maximum value of the bond length distribution range at each interface of WC-6%Co/SiC/Diamond is smaller. The interface model obtained by sequentially depositing SiC layer on WC-6%Co substrate at 1 123 K and diamond coating on SiC layer at 1 173 K has the shortest interface bond length, the largest bond energy, and the best interface bonding property.

Improvement of Interface Properties and Optical Properties in Bilayer MoS₂/VS₂ Van der Waals Heterojunctions

PAN Chengfeng, SHI Anqi, SUN Dazhong, LI Shasha, WANG Bing, NIU Xianghong

2023, 52(11):  2007-2013. 

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The electronic structure and optical properties of van der Waals heterostructures with different layers of MoS₂ and VS₂ stacks were studied by first-principles calculations based on density functional theory. The stability of two heterojunctions at room temperature was verified through ab initio molecular dynamics. In addition, both heterojunctions exhibit p-type Schottky contact. But compared to the heterojunction composed of monolayer MoS₂, the barrier height in the heterojunction formed by the stacking of bilayer MoS₂ and VS₂ significantly decreases from 0.36 eV to 0.08 eV, effectively forming a low contact resistance and reducing the energy loss of carrier transport. The calculation of the light absorption spectrum indicates that the heterojunction composed of bilayer MoS₂ has higher absorption peaks. The research results provide a theoretical basis for the design of heterojunctions based on MoS₂ and their applications in high-performance optoelectronic devices.

First-Principles Study on Hydrogen Storage Performance of Li- and Ca-Decorated VO₂ Monolayer

HOU Yinyin, MA Liangcai

2023, 52(11):  2014-2023. 

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The exploitation of new hydrogen storage materials with high-capacity and reversible performance could play a very important role in the large-scale utilization of hydrogen as an energy source. The hydrogen storage performances of Li and Ca atoms decorated as well as Li/Ca co-decorated VO₂ monolayer system were comprehensively investigated based on first-principles calculations. The metal atoms are stably adsorbed on the surface of the VO₂ monolayer without forming metal clusters. Three and six hydrogen molecules can be absorbed by a Li atom and Ca atom, respectively, and its average adsorption energy is larger than 0.20 eV/H₂. Charge density differences and density of states of H₂ adsorbed systems were analyzed, and the results reveal that both the polarization mechanism and orbital hybridization are responsible for the adsorption of hydrogen molecules. The hydrogen storage capacity of the Li-decorated system increases with the increase of Li coverage, while that of Ca-decorated system is high only in lower Ca coverage. Moreover, Li/Ca co-decoration can effectively increase the hydrogen storage capacity of the system, its hydrogen storage mass density is 5.00% (mass fraction). Finally, the influence of temperature and pressure on the stability of hydrogen adsorption system is studied.

Synthesis and Fluorescent Properties of Metal-Organic Frameworks Based on 4,4'-Azobenzoic Acid

YU Zhong, WANG Yuxue, DAI Ping, HAN Jing, WANG Yan, ZHANG Xu

2023, 52(11):  2024-2033. 

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Using pyrazine and 4,4'-bipyrine as co-ligand, respectively, two metal-organic frameworks (MOFs) were synthesized by complexzation of Cd²⁺ and Zn²⁺ with 4,4'-azobenzoic acid (H₂(4,4'-azo)). X-ray single crystal diffraction shows that their crystal structures are as same as those of the previously published [Cd(4,4'-azo)(H₂O)]_n (1) and [Zn(4,4'-azo)(H₂O)₂]_n (2) where the co-ligands are not involved into the structures. Varying the co-ligand to 1,3-bi(tetrapyridyl)propane (bpp) with larger size and metal ions to Co²⁺, a co-crystal [H₂(4,4'-azo)(bpp)]_n (3) was isolated successfully, which is monoclinic, space group of C2/c with crystal cell parameters a=3.216 8(19) nm, b=0.475 5(3) nm and c=1.873 2(14) nm. The thermal stabilities of the three compounds were investigated by thermal gravimetric analyzer and the fluorescence of two MOFs were examined by fluorescence spectrometer, respectively. Both 1 and 2 display excellent thermal stabilities. Especially, 2 keeps stable up to 247 ℃. UV-Vis spectra and fluorescence spectra of 1 and 2 are different, which are ascribed to that 1 is a 3D network formed by 4,4'-azo bi-dentated coordinating with two Cd²⁺ whereas 2 is a 1D zig-zag chain constructed by 4,4'-azo mono-dentated coordinating with Zn²⁺. In addition to the ligand emission at 359 nm, 2 exhibits a new enhanced emission at 420 nm due to the ligand to metal charge transfer (LMCT) upon Zn²⁺ coordination with 4,4'-azo.

Synthesis and Electrocatalytic Performance of a Polyoxometalate-Based Supramolecular Compound Constructed with Reduced Phosphomolybdate

LIU Xiaohui, LI Hui, XU Na

2023, 52(11):  2034-2040. 

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A supramolecular compound composed of reduced phosphopolybdate and Fe^II was synthesized by hydrothermal method with sodium molybdate, ferric nitrate, phosphoric acid and triethylenetetramine as raw materials. The chemical formula of the compound is [C₈H₂₄N₄]_1.5[C₆H₂₂N₄]_1.5{Fe[Mo₆O₁₂(OH)₃(PO₄)₃(HPO₄)]₂}·5H₂O (1). Single crystal X-ray diffraction, powder X-ray diffraction (PXRD) and infrared spectroscopy (FT-IR) characterizations show that compound 1 is composed of {Fe[P₄Mo^V₆O₃₁]₂}^22- (denoted by {Fe(P₄Mo₆)₂}), protomated triethyltetramine and protomated N, N′-bis(aminoethyl)-piperazine in a three-dimensional supramolecular structure through hydrogen bond interactions. The results of electrocatalytic performance measurement show that compound 1 has good electrochemical sensing performance and low limit of detection (LOD) for chromium ion (Cr^Ⅵ), iron ion (Fe^Ⅲ), potassium bromate (KBrO₃) and ascorbic acid (AA).

Synthesis of Eu(Ⅲ) Functionalized Metal-Organic Framework and Fluorescence Sensing for 1-Naphthol

LIANG Jiali, HU Bing, LI Runyu, LIU Lirong, JIANG Linjin, SUN Jingwen

2023, 52(11):  2041-2049. 

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A metal-organic framework complex {[Zn₂(OH)(TZI)·2H₂O]·6DMF}_n (1) (TZI=5-tetrazolylisophthalic acid) was successfully isolated under solvothermal conditions. The structure of the complex was characterized by single crystal X-ray diffraction, elemental analysis, infrared spectroscopy, thermogravimetric analysis, powder X-ray diffraction. Single crystal X-ray diffraction study reveals that 1 displays a 3D structure with channels, where exist uncoordinated carboxylate groups and coordinated water molecules. Subsequently, through post-synthesis method, a Eu(Ⅲ)@1 with red fluorescence emission was obtained by introducing Eu(Ⅲ) into framework of 1. Under 275 nm wavelength excitation, Eu(Ⅲ)@1 possesses two groups of fluorescence emission. In the first group, the wide peak at 418 nm is the fluorescence emission of 1, which origins from the absorption and emission of the organic ligand. While, the second group of five emission peaks is the red characteristic emission peak of Eu(Ⅲ) ion, with main peak of 619 nm. The results of anti-interference experiments of other components in urine show that Eu(Ⅲ)@1 fluorescent probe is very sensitive to the biomarker 1-naphthol, and can lead to red fluorescence quenching (619 nm), accompanies by cyan fluorescence enhancement (465 nm), and has high selectivity for 1-naphthol. Fluorescence titration results show that the detection limits of Eu(Ⅲ)@1 for 1-naphthol based on fluorescence emission peaks at 465 and 619 nm are 6.95 μmol/L and 1.75 mmol/L, respectively.

Preparation and Luminescence Properties of Dy³⁺ Doped Gd₂MgTiO₆ White Phosphor

ZHAO Yan, JIANG Xiaokang, GAO Feng, YIN Hongmei, ZHOU Hengwei

2023, 52(11):  2050-2056. 

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A series of Gd₂MgTiO₆ (GMT) white phosphors doped with different Dy³⁺ concentrations were prepared by the sol-gel method.The GMT:xDy³⁺(x=0.01, 0.03, 0.05, 0.07, 0.09, 0.11) samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and fluorescence spectroscopy. The research results show that the structure of the prepared series of fluorescent powders is monoclinic, and Dy³⁺ was successfully doped into GMT matrix without affecting the original crystal structure. The grain size of the sample is in the micrometer scale. Under near-ultraviolet excitation at 351 nm, the sample exhibits extremely strong blue and yellow light at 483 and 578 nm, respectively. The blue light is attributed to the ⁴F_9/2→⁶H_15/2 energy level transition of Dy³⁺, while the yellow light belongs to the ⁴F_9/2→⁶H_13/2 energy level transition of Dy the continuous increase of Dy³⁺ concentration, there is a significant concentration quenching phenomenon, which is attributed to the interaction between electric dipoles. When x=0.05, the CIE coordinates (0.324 71, 0.359 74) are relatively close to the CIE coordinates of standard white light (0.33, 0.33), indicating that GMT:Dy³⁺ is a single matrix white phosphor with potential application value.

Degradation and Hydrogen Production Performance of ZnO/g-C₃N₄ Composite Photocatalyst

ZHANG Jinfeng, FU Xiaonan, GUO Yefei, LIU Ruijie, LI Yuanyuan

2023, 52(11):  2057-2067. 

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In this paper, ZnO/g-C₃N₄ series composite photocatalysts were prepared by thermal polymerization and hydrothermal method. The structure, morphology and light absorption properties of the prepared samples were characterized and tested. The photocatalytic performance of these samples was evaluated by the photocatalytic degradation of methylene blue (MB) and the photolysis aquatic hydrogen under visible light irradiation. The experimental results indicate that the performances of the ZnO/g-C₃N₄ composite photocatalysts are superior to those of ZnO and g-C₃N₄. Moreover, when the molar ratio of ZnO and g-C₃N₄ is 1:1, the photocatalytic performance of the prepared ZnO/g-C₃N₄ composite samples is the best. On the one hand, the degradation rate of the 1:1 composite sample reaches 94.36% after only 30 min, and the degradation rate is 5.6 and 6.7 times that of ZnO and g-C₃N₄, respectively. On the other hand, the photolysis aquatic hydrogen of the 1:1 sample after 6 h is 11.75 mmol, and the photolysis aquatic hydrogen rate is 7 times that of g-C₃N₄. The results show that the ZnO/g-C₃N₄ composite photocatalyst has excellent performance in pollutant degradation and photolysis aquatic hydrogen. In addition, the photocatalytic degradation and photolysis aquatic hydrogen mechanism of ZnO/g-C₃N₄ series composite photocatalyst are also studied.

Design and Performance Simulation Analysis of High-Q Terahertz Sensors

ZHOU Xinli, SHU Jingyi, ZHAO Haochen, ZHAO Guozhong

2023, 52(11):  2068-2075. 

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This paper presents a design of an asymmetric metal cross unit structure, which consists of two perpendicular coplanar gold bars deposited on a quartz substrate. The conventional metal cross structure commonly suffers from significant radiation losses in LC resonance and dipole resonance, limiting the achievement of high quality factor and high transmittance in metasurface sensors. By breaking the symmetry of the traditional metal cross structure and introducing a Fano-like resonance effect, the transmission peak sensitivity of 218 GHz/RIU and the quality factor of 78.3 are achieved. The physical mechanism of the Fano resonance effect is explored by analyzing the electric field and surface current distribution of the metasurface. Furthermore, the influence of structural parameters on the transmission spectrum of the terahertz sensor is investigated, and the sensing performance of the sensor is optimized by adjusting the structural parameters. Finally, asymmetric metal cross terahertz sensors with different resonance frequencies are designed for the detection of various types of trace amino acid solutions in subsequent applications.

Optimization and Numerical Simulation of Sn-Based CH₃NH₃SnI₃ Perovskite Solar Cell

WANG Chuankun, LU Chengwei, OUYANG Yujie, ZHANG Shengjun, HAO Yanling

2023, 52(11):  2076-2084. 

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With non-toxic nature, wide bandgap, and thermal stability, Sn-based perovskite materials have become a hot topic in the field of perovskite solar cell research. In this paper, the SCAPS-1D software was used to construct the FTO/TiO₂/CH₃NH₃SnI₃/Spiro-OMeTAD/Ag perovskite solar cells and the performances of the constructed cells were calculated. The effects of the thickness of absorption and hole buffer layer, the surface defects between hole buffer layer and absorption layer, and the operating temperature on the device performance were studied, then the device performance was optimized. The photoelectric conversion efficiency of the optimized perovskite solar cell is 30.955%. The theoretical analysis suggests a new approach for enhancing the photoelectric conversion efficiency of perovskite solar cells.