Table of Content

15 June 2021, Volume 50 Issue 6

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Research Articles

Design of Thermal Field for 6-Inch Low Dislocation Germanium Single Crystal Growth

CHEN Chen, ZHAO Kun, HAN Huanpeng

2021, 50(6):  979-986. 

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Germanium wafer have been widely used as substrate in space solar cells. In recent years, after the demand for germanium wafer for germanium-based space solar cells increase from 4 inch to 6 inch, the growth of low-dislocation germanium crystals becomes more difficult. This paper designed a double heaters thermal field system suitable for 6 inch low dislocation germanium single crystal by the Cz method, the thermal field distribution in the case of different shapes of main heaters was simulated. The research found that: the thermal field structure of the gradual main heater with the gradual length of L/h=1/2 and the gradual rate ɑ of 65° can obtain the best thermal field distribution, which is conductive to the growth of low dislocation density. It has been verified that the thermal stress of germanium single crystal is reduced, and the dislocation density can be controlled within 310 cm^-2 to 450 cm^-2.

Design and Research on Descended Heat Shield of the Single Crystal Furnace

ZHANG Xiya, GAO Dedong, WANG Shan, PENG Xin, LIN Guangwei, GAO Junwei

2021, 50(6):  987-995. 

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Photovoltaic power generation has been widely adopted for its advantages such as green, renewable, high energy quality and not restricted by the geographical distribution of resources. Monocrystalline silicon has gradually surpassed the market share of polycrystalline silicon photovoltaic cells with the advantages of low attenuation rate and high conversion efficiency. However, cost issues and productivity issues have been restricting the development of the monocrystalline silicon solar industry. This paper proposes a thermal shield structure of a Czochralski single crystal furnace that drops with the drop of silicon liquid level during crystal growth. To solve the problems of lower crystal pulling speed and stability, as well as the increase of crystal pulling energy consumption caused by the rise of the crucible during the crystal pulling process, taking the CL120-97 single crystal furnace thermal field as the research object, the finite element simulation was used to analyze the flow field of argon gas and the thermal field of the crystal and melt before and after the optimization of the single crystal furnace. The analysis and simulation results show that the optimized single crystal furnace can not only improve the pulling speed and quality of the single crystal, but also effectively reduce the energy consumption of the single crystal furnace.

Optical Properties of LPE-GaN Grown in Different Polar Directions

REN Yujiao, LIU Zongliang, GU Hong, DONG Xiaoming, GAO Xiaodong, SI Zhiwei, XU Ke

2021, 50(6):  996-1001. 

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The polarization effect in gallium nitride (GaN) will reduce the efficiency of light-emitting diodes (LEDs), so the research on non-polar and semi-polar bulk GaN has received extensive attention. The purpose of our research is to optimize the growth of bulk GaN by exploring the luminescence characteristics between different polar directions of GaN and the fundamental mechanism of impurity doping. In this paper, the bulk GaN single crystals with different polar directions grown laterally by the Na-flux method are used as the research object. The optical properties and impurity distribution characteristics of bulk GaN with different polar directions were compared, and the origin of yellow luminescence (YL) band of bulk GaN and its influencing factors were discussed. At the beginning, the optical properties of GaN bulk single crystals with different polar directions by liquid phase epitaxy (LPE) were studied by cathodoluminescence (CL) and photoluminescence (PL). The experimental results show that optical properties of bulk GaN with different growth polar directions are different. The CL and PL characteristics of [1122] and [1120] GaN grown in the lateral direction are similar, but the spectra of [0001] GaN is quite different. The impurity peak of the photoluminescence contains two shoulder peaks, peak 1 (2.2 eV) and peak 2 (2.6 eV), which accounted for different proportions in different polar directions. We speculate that they are related to the C_NO_N complex and the 0/+ energy of C_N defect respectively. Then through time of flight secondary ion mass spectrometer (TOF-SIMS) element analysis, the distribution of C impurity is relatively uniform. There is a big difference in the distribution of oxygen impurity. In the [1122] GaN region, the oxygen impurity content gradually increases along the growth direction. Combined with the increase in the intensity of the peak 1 at 2.2 eV in the PL spectra, this phenomenon further proves that there is a positive correlation between the intensity of the 2.2 eV peak and the oxygen impurity.

Numerical Simulation Study on Growth Rate and Gas Reaction Path of AlN-MOCVD with Close-Coupled Showerhead Reactor

WAN Xu, ZUO Ran

2021, 50(6):  1002-1009. 

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By numerical simulation and combining reaction kinetics and gas transport process, the effects of gas flow rate (NH₃ and H₂), inlet temperature, pressure and chamber height on the growth rate and gas reaction path of AlN-MOCVD with close-coupled showerhead reactor were studied. It is found that the concentrations of AlN film precursor and nanoparticle precursor determine the growth rate and the gas reaction path. Under the conditions of low Ⅴ/Ⅲ ratio(2 000), high H₂ flow rate (12 L/min), high inlet temperature(700 K), low pressure(2 kPa) and low chamber height(5 mm), the reaction is dominated by both the adduct path and the pyrolysis path, and the growth rate is relatively high. On the contrary conditions, the reaction is dominated by the adduct path and the growth rate is rather low. There are different reasons for the effects of the above parameters on the reaction path, such as, the high NH₃ flow rate brings the precursor out of the growth zone and the high H₂ flow dilutes the reaction precursors in the growing region; the low pressure and low chamber height reduce the particle collision frequency and residence time, and weaken the parasitic response; the inlet temperature causes a change in the temperature gradient.

Preparation of CVD Diamond Window for High Power CO₂ Laser

AN Xiaoming, GE Xingang, LIU Xiaochen, LI Yifeng, JIANG Long, LUO Haihan

2021, 50(6):  1010-1015. 

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CVD diamond window which can be used in high power CO₂ laser was prepared. Firstly, a 2 inch diameter diamond self-supporting film was deposited by a circumferential antenna ellipsoidal cavity type MPCVD reactor. Then both sides of the film were polished, and the film was cut into rectangular samples by laser. An antireflective film with the central wavelength of 10.6 μm was prepared on the surface of the sample by vacuum evaporation. Finally, the diamond optical window was prepared. In this study, the infrared transmittance before and after coating, thermal conductivity and burst strength of diamond substrate were respectively measured by Fourier transform infrared spectroscopy, thermal conductivity meter and pressure blasting test stand. Using a self-built optical platform, the laser power density that the CVD diamond substrate antireflection coating can withstand was tested. The results show that the transmittance of CVD diamond substrate at 10.6 μm is 70.9%, the absorption coefficient calculated by spectrum is 0.06 cm^-1, the thermal conductivity is more than 19.5 W/(cm·K), the burst strength is more than 5.62 MPa, the transmittance with coating is 99.2%, and the laser power density that the AR coating can withstand>995 W/mm².

Effect of ZrO₂ on the Densification and Optical Properties of Ho∶(Y_0.7Sc_0.3)₂O₃ Laser Ceramics

BAI Yuchen, ZHANG Junyu, ZHAO Hongyang, ZHAO Jin, ZHANG Jian, WANG Shiwei

2021, 50(6):  1016-1022. 

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2 μm laser is one of the most important eye-safe lasers, and has important potential and practical applications in military and civilian fields such as medical treatment, materials processing, infrared detection/IR-counter measurement, and atmospheric environment monitoring. Due to their broad absorption and emission band in 2 μm range, high thermal conductivity, and low phonon energy, Ho³⁺ doped sesquioxide ceramic materials are important type of 2 μm laser materials. In addition, through forming the solid solution, much wider absorption and emission band can even be achieved, which give them the possibility to be the excellent mid-infrared solid-state laser materials. In this work, vacuum pressureless sintering combined with hot isostatic pressing sintering treatment was applied to prepare the 0.5%Ho∶(Y_0.7Sc_0.3)₂O₃ transparent ceramics by using commercial available Y₂O₃, Sc₂O₃ and Ho₂O₃ powders as the starting materials. By adding ZrO₂ as the sintering aid, grain growth of the Ho∶(Y_0.7Sc_0.3)₂O₃ ceramic at high sintering temperature was effectively inhibited. The effect of ZrO₂ doping ranged from 0~1.0% on the densification process, its further effect on the optical properties of Ho∶(Y_0.7Sc_0.3)₂O₃ laser ceramics was studied thoroughly. After pre-sintered at 1 690 ℃ for 4 h in vacuum and then hot isostatic sintered at 1 600 ℃/190 MPa for 3 h, the transmittance of 1.0%ZrO₂ doped Ho∶(Y_0.7Sc_0.3)₂O₃ ceramic reaches 79.1% at 1 100 nm (4.4 mm in thickness), which is close to its theoretic value.

First-Principle Study of Er-Doped Diamond Defects

TAN Xin, ZHANG Bochen, REN Yuan, CHEN Chengbin, LIU Yuefei

2021, 50(6):  1023-1028. 

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In this paper, the electronic structure, energy transition, and the effect of co-doping of N and B atoms on Er-doped diamond defects were investigated based on first-principles calculations. First, the defect formation energy and binding energy calculations are performed for Er-doped diamond. The results show that the stable structure of diamond ErV defects is a structure with one vacancy around the Er atom, and the stable valence of +3 valence. The electronic structure of the diamond defect is calculated using this stable structure, and its energy band and energy level structures are obtained. A zero-phonon line (ZPL) of 0.807 eV and emission wavelength of 1 536.289 nm are predicted for the ErV defect. Finally, the calculation of the co-doping of N and B atoms shows that the doping of N and B atoms can reduce the formation energy and increase the structural stability. Er doped diamond makes it emit light in the near infrared spectrum, which provides a theoretical basis for the application of Er diamond color center.

First-Principle Study on Electronic Structure and Optical Properties of Sr₂MoBO₆ (B=Os,Re,W)

ZHANG Qi, HAO Jiuyuan, ZHANG Min, LI Rui, ZU Ningning

2021, 50(6):  1029-1035. 

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Double perovskite oxides Sr₂MoBO₆ (B=Os,Re,W) have been predicted to be half metals with high magnetic ordering temperature. In this work, the electronic structure and optical properties of Sr₂MoBO₆ were calculated by first-principles method, and the intrinsic relationships between them were also discussed. From the energy band structure, Sr₂MoOsO₆ and Sr₂MoWO₆ are half metals, and Sr₂MoReO₆ is a normal metal. The imaginary part ε₂(ω) of the complex dielectric function of Sr₂MoBO₆ all have obvious dielectric peaks in the visible region due to the transition process between B 5d and Mo 4d. Further, the three compounds all have a wide absorption spectrum and a high absorption coefficient. Among them, the absorption spectra of Sr₂MoReO₆ and Sr₂MoWO₆ stretch across the whole visible region and even extend to the infrared band. The highest absorption coefficient of Sr₂MoReO₆ in the visible region is 41.86×10⁴ cm^-1, and one of the absorption peaks is located at 886 nm. The absorption peak of Sr₂MoWO₆ is at 780 nm and the peak absorption coefficient is 41.62×10⁴ cm^-1. In addition, Sr₂MoBO₆ have high reflectivity in the whole range of visible region. The peak reflectivity of Sr₂MoWO₆ can reach up to 0.55. The response of Sr₂MoBO₆ to visible light indicates that they have a wide application prospect in the field of optoelectronic devices.

Hydrothermal Synthesis of Cs_xWO₃ Nanorods and Their Infrared Absorption Properties

XIONG Yuanpeng, LI Ruixing, ZHANG Yue, KONG Fandong, ZHONG Qi

2021, 50(6):  1036-1043. 

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Cs_xWO₃ nanrods have attracted extensive attention due to their excellent near-infrared absorption properties. However, the Cs_xWO₃ nanorods synthesized via hydrothermal method are easy to form equiaxed nanoparticles, and the reaction temperature is high, followed by post-treatment. The Cs_0.2WO₃ nanorods with diameter and length of 10~20 nm and 100~250 nm were successfully hydrothermal synthesized via using ammonium tungstate ((NH₄)₆ W₇O₂₄·6H₂O), cesium chloride (CsCl), hydrochloride acid (HCl), oleylamine (C₁₈H₃₇N) as reactants in this paper. The effects of solvents, reaction route and amount of HCl on the phase and morphology of Cs_0.2WO₃ nanorods were investigated, followed by the discussion of the formation mechanism of Cs_0.2WO₃ nanorods and the test of infrared absorption properties of Cs_0.2WO₃ nanorods. The results show adding excess or little HCl are harmful for the synthesis of Cs_0.2WO₃. Changing the addition order of HCl and CsCl, following the decrease of reaction rate among (NH₄)₆ W₇O₂₄, CsCl and HCl, is benefit for the formation of Cs_0.2WO₃ nanorods. The infrared absorption test show Cs_0.2WO₃ nanorods are better than equiaxed Cs_0.2WO₃ nanoparticles.

Synthesis, Structure and Luminescent Properties of a Cd(Ⅱ) Coordination Compound

LIU Yirui, DUAN Minna, GU Xixuan, GAO Yanhong, HE Yong, SONG Juan

2021, 50(6):  1044-1048. 

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Cadmium complexes are widely used in the fields of optics, medicine, chemistry and so on because of their unique structure and properties.Hydrothermal method is one of the most convenient and effective methods to synthesize complex at present because of its solvent cleaning and simple operation. A compound [Cd₂(L)₂(bdc)(H₂O)₄](bdc) was hydrothermally synthesized using 2,6-di(pyrazin-2-yl)-4,4′-bipyridine(L), terephthalic acid and CdCl₂·2.5H₂O as raw materials, the structure and luminescent properties of the complexes were characterized by single crystal X-ray diffraction and infrared spectroscopy. The experimental results show that the [Cd₂(L)₂(bdc)(H₂O)₄](bdc) belongs to the triclinic system, P1 space group, a=1.002 78(17) nm, b=1.044 25(17) nm, c=1.274 8(2) nm, β=78.559(2)°, and has good fluorescence.

Synthesis and Properties of a Novel Cadmium(Ⅱ) Complex-Based Luminescent Probe

XU Heng, GUI Naicheng, YAN Da, XIONG Zhi, HUANG Rongyi

2021, 50(6):  1049-1055. 

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A new one-dimensional chain-like complex, [Cd(8-aql)₂(1,5-nd)]₂·H₂O (1)(8-aql=8-aminoquinoline, 1,5-nd=1,5-naphthalene disulfonic acidroot) was synthesized using 8-aminoquinoline and 1,5-naphthalene disulfonic acid salt as ligands and NaN₃ as pH regulator by hydrothermal reaction. And it was characterized by elemental analysis, FT-IR and single crystal X-ray diffraction. Complex 1 crystallizes in the monoclinic system with P2₁/n space group, and its asymmetric unit includes half of one Cd(Ⅱ), one 8-aql, half of one 1,5-nd and one free water molecule. In complex 1, the Cd²⁺ has a distorted octahedral coordination geometry coordinated by six atoms. Meanwhile, complex 1 shows high thermal stability under 110 ℃ and displays green fluorescence at 510 nm in the solid state. The emission peak is attributed to π^*-π of ligand due to the outermost electron of Cd²⁺ is d¹⁰. The fluorescence properties of the complex in common solvents were discussed. The experimental results show that all wavelengths of the suspension fluorescent are 10 nm to 50 nm red or blue shift and the fluorescence intensity changes obviously. The complex can be used as a fluorescent probe to detect nitrobenzene in low concentration: the linear regression equation shows that the fluorescence intensity has a good linear relationship with the concentration of nitrobenzene in the range of 6.5×10^-5 mol·L^-1 to 9.5×10^-2 mol· L^-1, and the lowest detection limit of nitrobenzene is 8.73×10^-5 mol·L^-1 according to the calculation formula of detection limit. Therefore, it can be considered that complex 1 is a potential fluorescent probe for the detection of environmental pollutants nitrobenzene with high sensitivity, low detection limit and wide linear detection range.

Effect of Post Annealing Atmosphere on β-Ga₂O₃ Thin Films Prepared by Magnetron Sputtering

JI Kaidi, GAO Cancan, YANG Fashun, XIONG Qian, MA Kui

2021, 50(6):  1056-1061. 

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In recent years, β-Ga₂O₃ has attracted more and more attention as a wide band gap semiconductor material. A large number of researchers all over the world have carried out a lot of studies in preparation, doping and etching of β-Ga₂O₃. Radio frequency magnetron sputtering is one of the most popular methods for preparing β-Ga₂O₃ thin film. And post annealing is usually used to improve the quality of the film. In this paper, effects of annealing temperature and annealing atmosphere on β-Ga₂O₃ thin films on C-plane sapphire substrate prepared by radio frequency magnetron sputtering were investigated. Testing results of XRD and AFM indicate that under nitrogen atmosphere, the quality of β-Ga₂O₃ films annealed at 1 000 ℃ is better. At the same temperature, oxygen atmosphere annealing is better than nitrogen atmosphere annealing to improve the crystallization properties and reduce the surface roughness of the films. And under oxygen atmosphere, the quality of films annealed at 1 000 ℃ is better than that annealed at 900 ℃.

Preparation of NiCoSe₄ Film and Its Application in Dye-Sensitized Solar Cells

GE Xuehao, WU Jing, XING Dongliang, PAN Wenjing, ZHANG Yulin, JIANG Qingsong

2021, 50(6):  1062-1069. 

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Counter electrode is considered as a key component of dye-sensitized solar cells. Counter electrode, especially selenide counter electrode, has always been the focus of research. Nickel cobalt selenide film was prepared through the potentiostatic deposition-solvothermal-selenization process, and directly applied to dye-sensitized solar cells. Through the analysis of phase, morphology, and surface element valence state, NiCoSe₄ film has been successfully synthesized on fluorine doped tin oxide (FTO) glass. NiCoSe₄ film displays the sheet-like porous structure composed of nanoparticles. The results from electrochemical measurement demonstrate that NiCoSe₄ film shows high electrocatalytic activity in electrolyte based on I^-/I^-₃ redox pair. Dye-sensitized solar cell with NiCoSe₄ film exhibits high photovoltaic performance. The corresponding photoelectric conversion efficiency is up to 7.84%, which is higher than that of platinum-based solar cells (6.95%).

Flatband Potentials for Nanostructured SrTiO₃ Film Electrodes in Nonaqueous Solvents

ZHANG Huihui, KOU Huizhi, WANG Haibo

2021, 50(6):  1070-1075. 

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Transparent nanostructured SrTiO₃ film electrodes were prepared on conduction substrates and characterized by XRD, TEM and SEM. The flatband potential (E_fb) of a nanostructured SrTiO₃ electrode was determined with spectroelectrochemical measurement in a range of nonaqueous solvents (acetonitrile, tetrahydrofuran, methanol and ethanol). The results show that E_fb is significantly more positive for water and nonaqueous protic solvents (methanol and ethanol) than for nonaqueous aprotic solvents (acetonitrile and tetrahydrofuran) due to establishment of a proton adsorption-desorption equilibrium. Further, addition of Li⁺ has no significant effect on E_fb in water and nonaqueous protic solvents, but in nonaqueous aprotic solvents, the E_fb shifts to more positive values following the increase of added Li⁺ concentration.

Crystal Structure, Luminescent Properties and Antibacterial Activity of Silver(I) Coordination Polymer with Pyrazine Schiff-Base Derivative Ligand

LIAO Yanzhi, GUO Juner, FENG Ansheng, LAI Mincheng, YANG Chaojie, XU Xiaoyun, YOU Ao

2021, 50(6):  1076-1081. 

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Pyrazine Schiff base derivative N-[1-(pyrazin-2-yl)ethylidene] isonicotinohydrazide(L) was obtained by the reaction of 2-acetylpyrazine and isoniazid in anhydrous ethanol. A coordination polymer {[Ag₃L₂(NO₃)₂]CH₃CN}_n was synthesized by diffusion method with the ligand and silver nitrate as raw materials, and its structure and properties were analyzed and characterized by X-ray single crystal diffraction, elemental analysis, IR, and fluorescence spectra. The results of single crystal diffraction analysis show that the complex belongs to monoclinic crystal system, P2₁/c space group, and the crystal cell parameters are a=0.611 70(10) nm, b=1.347 08(3) nm, c=2.018 69(4) nm, V=1.661 06(6) nm³, Z=2, Mr=970.19, Dc=1.940 g/cm³. The ligand molecules form a two-dimensional reticular structure with silver ions as the connecting point. Fluorescence spectrum analysis shows that both the ligand and the complex have better luminescent performance, and the fluorescence intensity of the complex is better than that of the ligand. The antibacterial activity indicates that the complex has good specificity to S. albus, S. luteus, and B. subtilis which has good prospects for medical application.

Sintering Process and Electrical Magnetic Properties of Ordered Room Temperature Ferromagnetism Sr₃YCo₄O_10.5+δ Polycrystals

HUO Guangpeng, ZHANG Xiaodong, SONG Hongyuan, HUI Yuyu, DU Xiaoli, CHEN Liangwei, YU Lan

2021, 50(6):  1082-1088. 

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Sr₃YCo₄O_10.5+δ polycrystalline bulks were prepared by the solid state reaction of 7 processes with different sintering temperatures (950~1 180 ℃), sintering time and sintering times. Based on thermal analysis, XRD and SEM, order phase transition and optimal sintering process (1 180 ℃/24 h+1 180 ℃/24 h) were determined, then electrical magnetic properties of polycrystals were inverstigated. The results show that the tetragonal Sr₃YCo₄O_10.5 fully crystallized at 964 ℃ and formed the ordering Sr₃YCo₄O_10.5+δ by absorbs oxygen (δ) at 1 042 ℃. Samples sintered at 1 100 ℃ and 1 180 ℃ show superstructure peaks of (103) and (215), which verifies the order of polycrystalline structure. The bulks exhibit semiconductor behavior, secondary sintering improve the lattice integrity, grain growth and resistivity is only 0.06 Ω·cm at 300 K, Curie temperature (T_c)~335 K. Hopkinson peak on the zero field colded (ZFC) curve from the fact that the frozen magnetic moments at low temperature turn to the direction of the magnetic field as the temperature rises, the magnetization reaches the maximum at 298 K, and then decreases under the thermal disturbance. Room temperature ferromagnetism originates from the e_g orbitals ordering of the middle spin or high spin state Co³⁺ caused by the ordered structure.

Surface Structure and Properties of Ti/Au Composite Electrode on CdZnTe (111)B Surface

TAO Siqi, ZHANG Jijun, WANG Shulei, QIN Meiqi, QIU Panhui, SONG Xiaolong

2021, 50(6):  1089-1095. 

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In recent years, detectors made from cadmium zinc telluride (CdZnTe) have become a research focal point, and proper contact characteristics have become a key issue for improving the performance of the detector. This paper mainly discusses the ohmic contact performance of Ti/Au composite electrode on the weak n-type CdZnTe crystal (111)B surface, preparation of Ti/Au composite electrode by two-step deposition process.Through AFM, FIB/TEM, XPS, I-V and other test methods, the interface structure, chemical composition and electrical properties of the interface between the electrode and CdZnTe were studied. The results show that the introduction of the Ti transition layer can reduce and improve the damage layer formed during the wafer polishing process, and increase the ohmic characteristics between the electrode and the crystal. Compared with the Cr/Au composite electrode on the CdZnTe (111)B surface, the Ti/Au composite electrode has a lower roughness, a smoother contact interface, and a lower thickness of the lattice mismatch layer. The Ti intermediate layer promotes the interdiffusion phenomenon of the gold/half interface, which is beneficial to increase the adhesion and reduce the Schottky barrier, and the presence of oxygen is not observed at the interface between the Ti/Au composite electrode and the CdZnTe contact.The I-V test shows that the Ti/Au composite electrode has better ohmic characteristics and lower Schottky barrier.

Effect of the Compound Surfactant of Sodium Dodecylbenzene Sulfonate and Polyvinylpyrrolidone on the Surface Texturing of Monocrystalline Silicon

ZHANG Jiahua, KANG Qiao, HUANG Shihua

2021, 50(6):  1096-1103. 

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In this paper, a compound solution of sodium dodecylbenzene sulfonate (SDBS) and polyvinylpyrrolidone (PVP) was used as a texturing additive to replace the isopropyl alcohol (IPA) commonly used at in monocrystalline silicon texturing process. It not only reduces the reflectivity of the texturing surface and shortens the time for texturing, but also has the characteristics of low cost and no need for regular supplementation during the texturing process. The ratio, concentration, reaction time, and reaction temperature of SDBS and PVP compound additives on the effect of monocrystalline silicon texturing were investigated. The average reflectance in the wavelength range of 400 nm to 1 000 nm is 9.8% when monocrystalline silicon is textured with the mixing volume ratio of SDBS and PVP of 1∶4, the concentration of compound additives of 0.26%(mass fraction), the texturing temperature of 80 ℃, and the texturing time of 15 min. Compared with the traditional alkali alcohol texturing liquid, this compound additive not only reduces the reflectivity of the texturing surface by about 2% and shortens the texturing time by 25 min, but also has the advantages of low cost and no need to replenish the texturing liquid regularly during the texturing process.At the same time, based on the unique solubilizing and dispersing properties of surfactants, it can effectively improve the cleanliness of the silicon wafer surface. The article also found that by controlling the ratio of PVP and SDBS, the size of the texture can be changed to a certain extent. Therefore, the compound surfactant is a kind of industrial monocrystalline silicon texturing additive with great development potential.

Regulation of Gypsum Crystalline and Morphology in Ca(H₂PO₄)₂-H₃PO₄-K₂SO₄ System

WU Qin, YANG Lin, YI Yun, GENG Pinglan, CAO Jianxin

2021, 50(6):  1104-1111. 

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In order to make the resource utilization of gypsum in the process of preparing KH₂PO₄ from Ca(H₂PO₄)₂, the Ca(H₂PO₄)₂ solution prepared by the reaction of H₃PO₄ and CaCO₃ was mixed with K₂SO₄ solution. Then the regulation of gypsum crystalline and morphology in Ca(H₂PO₄)₂-H₃PO₄-K₂SO₄ system was studied. The results show that the short columnar α-CaSO₄·0.5H₂O can be obtained from Ca(H₂PO₄)₂-H₃PO₄-K₂SO₄ system by changing the reaction condition,including reaction time, reaction temperature, SO^2-₄ excess coefficient (ξ) and CaO content. The α-CaSO₄·0.5H₂O is formed at temperatures above 95 ℃ and CaO content of 3.0% to 5.0%(mass fraction, the same below), while CaSO₄·2H₂O is formed at low temperatures and CaO content of 5.5%. Meanwhile, with the increase of CaO content in the range of 3.0% to 5.0%, the aspect ratio of α-CaSO₄·0.5H₂O decreases. As the reaction time is longer than 20 min and the SO^2-₄ excess coefficient is greater than 1.4, K₂SO₄(CaSO₄)₅·H₂O is easily formed, resulting in the increase of surface defects of gypsum crystals. Under the conditions of reaction time of 5 min, reaction temperature of 95 ℃, SO^2-₄ excess coefficient of 1.2 and CaO content of 5.0%, a short columnar α-CaSO₄·0.5H₂O crystals with length of 42 μm to 70 μm and diameter of 13 μm to 24 μm are prepared, the flexural strength and compressive strength of which are 5.61 MPa and 33.74 MPa, respectively. The yield of potassium and decalcification rate of the filtrate are 94.23% and 83.80%, respectively.

Influencing Factors and Mechanism of Calcium Carbonate Whiskers Prepared from Calcite

YU Yajie, ZHENG Qiang, LIU Haili, XING Run, LI Xue

2021, 50(6):  1112-1122. 

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Calcite was used as raw material, the prepared heavy magnesium water (Mg(HCO₃)₂) and the intermediate product calcium chloride were used to prepare aragonite calcium carbonate whiskers, and the products were characterized by SEM, XRD and EDS. The effects of reaction temperature, reaction time, concentration ratio of magnesium to calcium, concentration of heavy magnesium water and stirring speed on the morphology of calcium carbonate whiskers during the reaction of heavy magnesium water and calcium chloride were explored. The best process conditions are obtained through single factor experiments: temperature of 40 ℃; reaction time of 2 h; magnesium-calcium concentration ratio of 6∶1; heavy magnesium water concentration of 0.14 mol/L; stirring speed of 150 r/min. Under these conditions, aragonite calcium carbonate whiskers with a length of 40~65 μm, a diameter of 0.6~1.5 μm, and an aspect ratio of 25~45 were prepared.

Effect of Fe³⁺ Doping on the Color Performance of CuCr₂O₄ Black Pigment

BAI Mingmin, LI Weixin, WANG Shaohua, LI Xinwei, WANG Qinyu, WANG Yongqing

2021, 50(6):  1123-1130. 

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In order to improve the color performance of CuCr₂O₄ black pigment, CuCr_2-xFe_xO₄ (x=0,0.04,0.05,0.06,0.07) were prepared by co-precipitation method. The samples were characterized by TG-DTA, XRD, SEM, Raman, XPS, UV-Vis and chromaticity values. The results show that the substitution of Fe³⁺ for Cr³⁺ in CuCr₂O₄, and the valence state of Fe is trivalent. There are no impurity phases. The CuCr_2-xFe_xO₄ has well-defined spinel structure, fine grain and good dispersion. The Fe³⁺ substitution decreases the band gap of pigments from 1.25 eV to 1.08 eV, attributes to 2p(O^2-)→3d(Fe³⁺) charge transform and d-d(⁶A_1g→⁴T_1g, ⁶A_1g→⁴T_2g) charge transform in Fe³⁺, which increases absorption in visible light(380 nm to 780 nm), decrease L^* value and shows good blackness. The CuCr_1.95Fe_0.05O₄ has the optimal chromaticity values which are L^*=17.63, a^*=-0.77, b^*=-1.61.

Scallop Pattern Reduction of Through Silicon Via by Multiple Thermal Oxidation

WANG Shuo, YANG Fashun, MA Kui

2021, 50(6):  1131-1137. 

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Through silicon via (TSV) is a very important part of three-dimensional integrated systems. At present, BOSCH etching technology is usually used for etching of through silicon via. Because etching and passivation are carried out alternately, this dry etching process will inevitably form scallop pattern in the inner sidewall of through silicon via, and its scale is generally from ~10 nm to ~100 nm. Scallop pattern will lead to the unsmooth interface between layers inside through silicon via, which will seriously affect the performance of through silicon via and the reliability of three-dimensional integrated systems. During high temperature thermal oxidation, the higher oxygen flow rate can ensure that the oxygen concentration in the via is nearly uniform, and the growth rate of SiO₂ in the scallop ridge bulge is relatively faster. The scallop pattern on the inner wall of through silicon via can be effectively reduced by alternating high temperature oxidation and etching SiO₂. For through silicon via with a ratio of depth to width of 8∶1, after four times of high temperature thermal oxidation (the process conditions of each oxidation process are T=1 150 ℃, t=10 min, and the oxidizing environment is wet oxygen) and four times etching SiO₂, the maximum scallop ripple decreases from 400 nm to 90 nm. The experimental results show that the effect of this method is very obvious.

Reviews

Research Progress and Application of Boron-Doped Diamond Film

ZHENG Yu, ZHANG Yi, TONG Yaqi, XUAN Zhenwu

2021, 50(6):  1138-1148. 

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On the basis of maintaining the excellent properties of diamond, such as high hardness, high stability and good biocompatibility, boron-doped diamond has the characteristics of semiconductor and even low temperature superconductivity, as well as wide electrochemical potential window and low background current. At present, boron-doped diamond film is recognized as an excellent electrochemical electrode material. In order to optimize the performance of boron doped diamond film and expand its application space, a lot of researches focus on boron doping, micro-morphology control of boron-doped diamond film, and surface modification of boron-doped diamond film, and so on. Based on the understanding of the structure of boron-doped diamond, this paper reviews the research progress of its electrical and electrochemical properties, and expounds its main preparation methods. This paper also analyze the application status and prospect of boron-doped diamond film as electrodes in sterilization, wastewater treatment, supercapacitors, biosensors and other fields.

Application and Analysis of Fluxes in Silicate Phosphors

WANG Ming, WANG Lianlian, LI Linfeng, LUO Xinyu, LIU Yang, ZHAO Ran, YANG Xiaoli

2021, 50(6):  1149-1157. 

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Silicate based phosphors for white LED have many advantages, such as abundant raw materials, low cost, simple synthesis process, composition diversity, adjustable luminescence, and so on. And it is extensively investigated in recent years. Fluxes play an important role in the preparation of silicate phosphor. This paper introduces the use of fluxes in silicate phosphor system. The type and amount of fluxes have some influence on the crystal phase, luminous intensity and morphology of phosphor. The results show that adding different fluxes and the different amount of fluxes can make silicate phosphors form different types of crystal phase. The fluxes cation around the activator ions causes the number of luminescence centers to change, which can change the shape of the emission spectrum and greatly improve the luminous intensity, but excessive fluxes will reduce the luminous intensity of the phosphors. The effect of flux on the surface morphology of phosphor is obvious. Appropriate flux can refine the grain, make the grain size uniform and spheroidize, but excessive flux will make the sample agglomerate. The key on the synthesis of high performance phosphors is to strengthen the study on the mechanism of flux in the preparation of phosphors, and to select the appropriate flux and its dosage.

Research Progress on Efficient and Clean Recycling Technology of Spent Ternary Lithium Battery Cathode Materials

WANG Haoyi, ZOU Yulin, MENG Qi, XIA Guanghui, LIN Yan, ZHANG Yingjie

2021, 50(6):  1158-1169. 

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Lithium-ion batteries have been widely used in various fields due to their high energy density, good cycle performance and low self-discharge. In recent years, the number of spent ternary lithium-ion batteries have increased dramatically. From the perspective of environmental protection and resource conservation, it is necessary to carry out green and efficient processes to recycle and regenerate spent lithium-ion batteries. This article reviews the research status of the recycling technology for spent ternary lithium-ion batteries, and point out recycling lithium-ion batteries should be in accordance of their characteristics and states. The hydrometallurgical processes including leaching and regeneration of cathode materials for spent lithium-ion batteries are introduced in detail, as well as the process of physical repair and regeneration of some spent cathode materials, and then their advantages and existing problems are illustrated. In the end, the prospect and development direction of the recycling of spent lithium-ion batteries are prospected.

Research Progress of Key Materials for Lithium Carbon Dioxide Batteries

GU Yang, WANG Zhen, WU Hongkun, XIAO Jie, ZENG Xiaoyuan

2021, 50(6):  1170-1179. 

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Rechargeable lithium-carbon dioxide batteries provide a new method for CO₂ capture and energy storage. Although the technology has made great progress from the beginning of its development to today, they still face many limitations and challenges in practical applications. Among them, although the research on the charging and discharging mechanism has made remarkable achievements, there are still some controversies. At present, most of the researches on lithium-carbon dioxide batteries focus on the preparation of cathode catalysts, such as carbon-based catalysts, noble metal-based catalysts, transition metal-based catalysts, and soluble catalysts, in terms of improving battery performance. Although the above-mentioned catalysts have significantly improved battery performance, there are few catalysts that can simultaneously meet the requirements of low price, simple preparation method and excellent catalytic performance. This is also one of the factors restricting the practical application of lithium-carbon dioxide batteries. Since the lithium-carbon dioxide battery is a semi-open system, the liquid electrolyte has problems such as leakage, evaporation, and lithium dendrites, which leads to a decrease in battery safety and performance. The use of quasi-solid electrolytes can effectively solve the above-mentioned problems and provide the possibility for the realization of flexible wearable lithium-carbon dioxide batteries. This article summarizes the research progress of key materials for lithium-carbon dioxide batteries, and introduces the charging and discharging mechanism of lithium-carbon dioxide batteries, cathode catalysts, solid electrolytes, and anode lithium protection. The current development status, challenges and development trend has been summarized. It provides a reference for the devel opment of high-efficiency and reversible lithium-carbon dioxide batteries.