Table of Content

15 February 2021, Volume 50 Issue 2

Previous Issue    Next Issue

Invited

Development of Zinc Oxide: Bulk Crystal Growth, Arbitrary Regulation of Carrier Concentration and Practical Applications

HUANG Feng, ZHENG Wei, WANG Mengye, HE Jiaqing, CHENG Lu, LI Titao, XU Cunhua, DAI Yejing, LI Yuqiang

2021, 50(2):  209-243. 

Asbtract ( 334 )   PDF (7018KB) ( 289 )  

References | Related Articles | Metrics

Zinc oxide (ZnO) possesses a long history. It was initially predicted to be used in the fields of piezoelectrics and nonlinear optics because of its non-centrosymmetric microstructure. And it is an important wide-bandgap semiconductor material that has received extensive attention in the semiconductor field due to its direct wide band gap (E_g~3.3 eV at 300 K) and large exciton binding energy (~60 meV). However, in practical applications, ZnO has encountered some bottlenecks in all above-mentioned fields. For example, in the field of piezoelectrics, ZnO was originally thought to be an insulator, but it shows unexpected conductivity. In the field of nonlinear optics, the refractive index difference of ZnO is very poor, so it is difficult to obtain good phase matching. In the field of semiconductor, it is difficult to obtain p-type ZnO with high carrier concentration, high mobility, and high thermal stability at the same time. This article mainly summarizes the application prospects and corresponding bottlenecks of ZnO in the above-mentioned fields. And a theory that can be understood by both semiconductor physicists and materials scientists is proposed. Specifically, chemical composition complete expression (CCCE) uniquely determines the conduction type of materials. As a novel knowledge, this connects the two concepts of CCCE and carrier type, which makes a great breakthrough in understanding and forms a new paradigm for materials science research. Under this guidance, n-type ZnO single crystals with high insulation and high thermal stability, Al∶ZnO thin films with high mobility were successfully manufactured. And it provides a new idea for the preparation of p-type ZnO with high carrier concentration, high mobility and high thermal stability. Recently, the native ZnO bulk crystal has been found to have a new possibility of breaking the bottleneck of MIR transparent conductivity. ZnO∶Ga crystal scintillators are also identified as promising ultrafast inorganic scintillators. It is speculated that these two fields would achieve progress in practical applications.

Research Articles

Growth and Defects of Large Size Nd,Ce∶YAG Laser Crystal

GUO Yongwen, HUANG Jinqiang, QUAN Jiliang

2021, 50(2):  244-247. 

Asbtract ( 175 )   PDF (2266KB) ( 139 )  

References | Related Articles | Metrics

Compared with the traditional Nd∶YAG, the co-doped Nd,Ce∶YAG crystal has the advantages of high output energy and low laser oscillation threshold. In recent years, the development of high energy efficiency solid-state lasers requires more and more large size and high-quality Nd,Ce∶YAG crystals. When large size Nd,Ce∶YAG is grown by Czochralski method, inclusion and cracking defects are very easy to occur. In this paper, the reason of the defects formation during the crystal growth were analyzed by combining theory with practice, and the solutions were put forward. Finally, high-quality Nd,Ce∶YAG single crystal with a diameter of 50 mm and an equal length of 150 mm was successfully grown. The results can provide direction and guidance for the quality improvement of mass production of large size Nd,Ce∶YAG crystals.

Czochralski Growth of Large Size YVO₄ Crystal with Autocontrolled Diameter

ZENG Xianlin, CHEN Wei, ZHANG Xing, CHEN Qiuhua

2021, 50(2):  248-252. 

Asbtract ( 134 )   PDF (3143KB) ( 129 )  

References | Related Articles | Metrics

This paper presents a research on the Czochralski growth of large size YVO₄ crystal with autocontrolled diameter. The large size YVO₄ single crystal was successfully grown by the Czochralski process with modified up-weighing method. In the Czochralski growth process of large size YVO₄ crystals, the slope integral mode was used in the shoulder expanding part, transition from slope integration to diameter integration mode was used in the shoulder turning part, and the diameter integral mode was used in the growth of the equal diameter part. The automatic growth of YVO₄ crystal has been realized by the subsection controlling procedure described above. The reliability of the automatic growth process of YVO₄ crystal was verified with four 50 mode automatic furnaces in a duration of one year. The technical goal of grown crystals was preset as follows: a crystal diameter of more than 40 mm, a length with the equal diameter part of more than 30 mm, and more than 80% production of B-grade quality crystals. A total of 138 crystal boules were grown by the Czochralski process with autocontrolling mode. The statistic data was summerized as 99.3% crystal boules with the standard diameter, 53.6% crystal boules with the standard length, and 88.4% yield of crystal growth. The technological factors concerning of the yield of crystal boules with the standard length of equal diameter part were also discussed.

Influence of Cooling Rate on the Growth of 4-N,N Dimethylamino-4′-N′- Methyl-Stilbazoliumtosylate (DAST) Single Crystal

MENG Huan, YANG Ruixia, WANG Jian, WANG Zenghua, MA Lin

2021, 50(2):  253-259. 

Asbtract ( 113 )   PDF (2695KB) ( 51 )  

References | Related Articles | Metrics

High quality 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST) crystals were grown by seed crystal method through adjusting cooling rate. The influence of cooling rate on crystal quality, optical properties and terahertz(THz) output characteristics of DAST crystals were explored. Additionally, the structure and purity of raw materials were characterized by applying nuclear magnetic resonance analysis method. X-ray diffraction rocking curve measurement of (001) plane of the as-grown crystals was measured by X-ray diffractometer. A best full-width at half-maximum (FWHM) narrowed as 57.6″ was obtained at the cooling rate of 0.1 ℃/d. Optical transmittance of the crystals grown under these conditions is 65% in the wavelength range of 780 nm to 1 576 nm. Moreover, using the differential frequency method wideband tunable terahertz waves in the range of 0.1 THz to 20 THz were generated from DAST crystals. At 18.8 THz, the maximum output energy of the terahertz wave is 0.477 μJ/pulse, and the corresponding energy conversion efficiency is 5.31×10^-5.

Surface Acoustic Waves Properties of 0.24PIN-0.47PMN-0.29PT Relaxor Ferroelectric Single Crystals

LI Xiuming, WU Guangtao, ZHANG Rui

2021, 50(2):  260-265. 

Asbtract ( 93 )   PDF (1417KB) ( 33 )  

References | Related Articles | Metrics

With the rapid development of the information technology, the requirements for surface acoustic wave devices are also increased. In order to find substrate materials with excellent surface acoustic wave performances, a detail theoretical analysis was conducted on the surface acoustic wave properties in 0.24PIN-0.47PMN-0.29PT single crystals along [001]_c and [011]_c at room temperature using the partial wave method. The relaxor ferroelectric single crystals xPb(In_1/2Nb_1/2)O₃-yPb(Mg_1/3Nb_2/3)O₃-(1-x-y)PbTiO₃ with compositions near the morphotropic phase boundary have comparably large piezoelectric and electromechanical properties and much higher Curie temperature. From the complete sets of elastic, piezoelectric and dielectric properties of [001]_c and [011]_c poled 0.24PIN-0.47PMN-0.29PT single crystals, the orientational dependence of surface acoustic wave phase velocities, electromechanical coupling coefficients and power flow angles was calculated by the Christoffel equation with semi-infinite boundary conditions. The results indicate that 0.24PIN-0.47PMN-0.29PT single crystals along [011]_c has better surface acoustic wave properties than the 0.24PIN-0.47PMN-0.29PT single crystals along [001]_c. It is very apparent that the surface acoustic wave electromechanical coupling coefficient for 0.24PIN-0.47PMN-0.29PT single crystal along [011]_c is dramatically higher compared to along [001]_c single crystal. Also, maximum power flow angle for 0.24PIN-0.47PMN-0.29PT single crystals along [011]_c is apparently bigger than 0.24PIN-0.47PMN-0.29PT single crystals along [001]_c. Therefore, the 0.24PIN-0.47PMN-0.29PT single crystal along [011]_c with excellent surface acoustic wave properties and temperature stability is very suitable in making surface acoustic wave devices.

First-Principles Study on Properties of S-La Co-Doped ZnO

ZHAO Xudong, CUI Ruirui, DENG Chaoyong

2021, 50(2):  266-272. 

Asbtract ( 69 )   PDF (3009KB) ( 43 )  

References | Related Articles | Metrics

The band structure, density of states and optical properties of pure ZnO, S single-doped, La single-doped and S-La co-doped ZnO were studied by first-principles method based on the generalized gradient approximation. After ZnO doped with S, the valence band and conduction band transfer to low energy at the same time, which leads to the reduction of band gap. The band gap of ZnO doped with La reduces because of the impurity energy level at the base of the conduction band. The localization of S-La co-doped ZnO results in the weakening of La localization, which indicates that the donor energy level of La becomes shallower due to the influence of S 3p state, thus reducing the band gap. After doping, the band gap of ZnO decreases obviously, which increases the absorption ability of ZnO in visible light region, and further produces more photo-electric charge carriers to improve the photocatalytic activity of ZnO. Compared with pure ZnO, the doped ZnO has lower absorption coefficient and reflection coefficient, and stronger transmission ability, which provides a potential theoretical basis for the application of ZnO as transparent conductive oxide in solar cells.

First-Principles Calculations of P and As Doped Mn₄Si₇

ZHONG Yi, ZHANG Jinmin, WANG Li, HE Teng, XIAO Qingquan, XIE Quan

2021, 50(2):  273-277. 

Asbtract ( 61 )   PDF (1515KB) ( 54 )  

References | Related Articles | Metrics

The electronic structure and optical properties of intrinsic and P, As doped Mn₄Si₇ were calculated with the fisrt-principles calculation method. The result shows that the intrinsic Mn₄Si₇ is an indirect semiconductor material with a gap of 0.810 eV, the P doped Mn₄Si₇ band gap increases to 0.839 eV, and the As doped Mn₄Si₇ band gap decreases to 0.752 eV. Doping causes a shift to the low energy region, and causes an increase of the real part of dielectric function notably in the low energy region and an increase of the imaginary part in almost all region, imaginary part decreases to zero after 8 eV. Besides, doping obviously increases the extinction coefficient, absorption coefficient reflection coefficient and photoconductivity in the high energy region, and improves the optical properties of the Mn₄Si₇.

First-Principles Study on Electronic and Optical Properties of Fe Doped α-Bi₂O₃

XIONG Zhihui, LI Zhixi, YIN Yaqing, PU Chaobo, ZENG Tixian, AN Xinyou

2021, 50(2):  278-282. 

Asbtract ( 76 )   PDF (1684KB) ( 29 )  

References | Related Articles | Metrics

The electronic structure and optical properties of Fe doped α-Bi₂O₃ were studied by using the first-principles hybrid functional HSE06 method. The calculation results show that Fe doped α-Bi₂O₃ has a small structural deformation, the intrinsic α-Bi₂O₃ has a band gap of 2.69 eV, and Fe doping reduces the band gap of α-Bi₂O₃(about 2.34 eV). The optical properties show that the absorption range of visible light of α-Bi₂O₃ is extended by Fe doping, that is, absorption spectrum redshifts, and the optical properties change mainly in the low energy range. Therefore, it provides a theoretical basis for the application of Fe doped α-Bi₂O₃ in the field of photocatalysis.

Diffusion and Nucleation of Aluminum Droplet on GaAs(001) Surface during Molecular Beam Epitaxy Growth

JIANG Chong, WANG Yi, DING Zhao, HUANG Yanbin, LUO Zijiang, LI Zhihong, LI Ershi, GUO Xiang

2021, 50(2):  283-289. 

Asbtract ( 74 )   PDF (2320KB) ( 31 )  

References | Related Articles | Metrics

The properties of quantum dots are mainly controlled by their density and size parameters, and the nucleation motion of atoms on the substrate determines the density, diameter, height and other parameters of quantum dots. Therefore, studying the diffusion and nucleation process of atoms is important for self-assembly preparation of quantum dots. A study was conducted on the nucleation process of aluminum droplets on GaAs(001) surface during molecular beam epitaxial growth, which leads to the finding that the influencing factors in the nucleation process include the substrate temperature and the deposition rate when other conditions are unchanged. According to the classical nucleation theory, the spatial distribution and geometric structure evolution of the aluminum droplet on the surface of GaAs(001) were analyzed, and the relation equation of the metal aluminum droplet density on the surface with the substrate temperature and the metal aluminum deposition rate was deduced. In the meantime, the minimum atomic number for the three states of the extreme incomplete state, the initially incomplete state and the complete state are calculated to be 1, 2 and 5, respectively.

Direct Evidence of Spatially Indirect Charged Exciton Transition Photoluminescence in N-doped ZnSe/BeTe Type-Ⅱ Quantum Wells

QU Shangda, JI Ziwu

2021, 50(2):  290-295. 

Asbtract ( 71 )   PDF (1440KB) ( 20 )  

References | Related Articles | Metrics

Applied electric field dependence of spatially indirect luminescence spectra of N-doped ZnSe/BeTe/ZnSe type-Ⅱ quantum wells was studied. Experimental results indicate that each of the luminescence spectra exhibits a main luminescence peak with a lower linear polarization degree. This phenomenon can be attributed to the equalizing potential of both wells, which is due to the screening of the built-in electric field caused by the doped electrons in the structure. Meanwhile, each of the luminescence spectra exhibits an asymmetry peak with an inverse-Boltzmann line-shape, and the line-shape and linear polarization degree remain unchanged within the entire voltage range. However, the integrated luminescence intensity depends strikingly on various external voltages: with changing the positive gate voltage (in the range of +7 V to 0 V), the integrated luminescence intensity almost maintains a constant, but with increasing negative gate voltage (-1 V to -7 V), the integrated luminescence intensity reduces significantly. These behaviors indicate that the spatially indirect luminescence spectra show a characteristic feature for a negatively charged exciton transition. The constant integrated luminescence intensity is explained as screening of the applied electric field with the doped layer, while the significantly reduced integrated luminescence intensity is ascribed to excitation of doping electrons by applied electric field (leading to a decrease in the electron concentration in the region excited by laser), thus resulting in a reduction in the number of negatively charged exciton. In addition, the possible particle configuration of the spatially indirect negatively charged exciton was also explored.

Effects of Substrate Heating Temperature and Post-Annealing Temperature on the Preparation of β-Ga₂O₃ Thin Films by Magnetron Sputtering

GAO Cancan, JI Kaidi, MA Kui, YANG Fashun

2021, 50(2):  296-301. 

Asbtract ( 72 )   PDF (4712KB) ( 44 )  

References | Related Articles | Metrics

As a member of wide band gap semiconductor materials, β-Ga₂O₃ with stable structure has a wider band gap and higher Baligar value than SiC and GaN, which has attracted extensive attention of researchers in recent years. In this paper, β-Ga₂O₃ thin films were grown on C-plane sapphire substrates by RF magnetron sputtering, and the influence of the substrate heating temperature during the sputtering process was explored. After sputtering, the quality of gallium oxide thin films was improved by high temperature annealing treatment. The effect of substrate heating temperature and post-annealing temperature on the crystal structure and surface morphology of gallium oxide films were studied. The crystal structure and surface morphology of β-Ga₂O₃ thin films were characterized by X-ray diffraction(XRD) and atomic force microscopy(AFM). The experimental results show that with the increase of substrate heating temperature, the surface roughness of β-Ga₂O₃ film decreases gradually, and the crystal quality of the film is significantly improved. After annealing in oxygen atmosphere, the appropriate post-annealing temperature is conducive to recrystallization of gallium oxide thin film, increase the grain size, effectively repair the surface state and point defects of the thin film, and improve the crystal quality of the film obvious advantages.

Influence of Hydrogen Impurities in the Subsurface of CVD Diamond Films on Surface Activation Reaction

JIAN Xiaogang, TANG Jinyao, MA Qianli, HU Jibo, YIN Mingrui

2021, 50(2):  302-309. 

Asbtract ( 85 )   PDF (4522KB) ( 36 )  

References | Related Articles | Metrics

Density functional theory (DFT) plane wave pseudopotential method was used to study the structural changes of diamond when hydrogen impurities were located at three different sites in the subsurface of hydrogen terminated diamond films, and the difficulty of hydrogen atom adsorption on the three kinds of diamond films. Meanwhile, the transition state search of surface activation reaction was carried out. All work is to explore the influence of hydrogen impurities in the subsurface of diamond films on surface activation during chemical vapor deposition(CVD). The results show that: during the growth process, the structure of diamond near hydrogen impurities in subsurface is distorted, and the surface structure of diamond has an effect on the degree of distortion. The adsorption energy of hydrogen atom on the three kinds of diamond films containing hydrogen impurities are little different from that of ideal diamond film. However, the energy barrier of the active sites generated is lower than that of the ideal diamond films, which is related to the phenomenon that the hydrogen impurities in the subsurface make the diamond films have P-type semiconductor characteristics. The results show that the formation rate of surface active sites can increases as hydrogen impurities entering the subsurface of the film in hydrogen rich reaction atmosphere.

Microstructure and Properties of Cadmium Sulfide Thin Films Prepared by Chemical Bath Deposition

ZHANG Xiaoyong, ZHANG Yanchun, ZHANG Xiaoyu, ZHANG Sen

2021, 50(2):  310-317. 

Asbtract ( 98 )   PDF (5618KB) ( 43 )  

References | Related Articles | Metrics

CdS thin films for the buffer layer of Cu(In,Ga)Se₂ solar cells were prepared by chemical bath deposition at different ammonia dosages. The initial concentration, pH value and ion product of the reaction particles in the mixed solution were calculated according to the chemical equilibrium kinetics. The film thickness, surface morphology, crystal structure, external quantum efficiency and photoelectric conversion efficiency of the samples were analyzed by step tester, SEM, XRD, EQE and IV tester. The results show that with the increase of ammonia amount, the homogeneous reaction rate reduces because the free Cd²⁺ concentration decreases, and the heterogeneous reaction rate increases because the Cd(OH)₂(NH₃)_n density adsorbed on the substrate surface increases; the crystal structure of CdS thin films changes from cubic phase to hexagonal phase because the cubic phase is formed by the homogeneous reaction, and the hexagonal CdS thin film is formed by the heterogeneous reaction; the surface morphology changes from loose porous structure formed by physical adsorption of large round particles to uniform and dense thin film grown by liquid phase epitaxy, the grain shape changes from willow catkins to granular, the grain size gradually increases, the particle size distribution is more uniform, and the film surface is smoother; the electrical parameters such as EQE, V_oc,J_sc, FF and R_s are optimized, and the photoelectric conversion efficiency increases from 7.64% to 13.60%.

Preparation of Reduced Graphene Oxide/TiO₂ Nanowires Composite Film and Its Adsorption Performance for Cu²⁺

LIN Xiaoxia, LI Hui, FU Degang

2021, 50(2):  318-324. 

Asbtract ( 56 )   PDF (4906KB) ( 19 )  

References | Related Articles | Metrics

The composite film of reduced graphene oxide/TiO₂ nanowires(rGO/TiO₂ NWs) was prepared by two-step hydrothermal method united vacuum filtration using graphene and self-prepared TiO₂ powder as raw materials. The sample was characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffractometer (XRD) and Raman spectroscopy. The results show that reduced graphene oxide and TiO₂ NWs are successfully compounded, and the dispersion of TiO₂ NWs are good. The adsorption experiments of Cu²⁺ show that the proportion of TiO₂ NWs in the composite, pH values are the important factors affecting the Cu²⁺ adsorption, the adsorption of Cu²⁺on the composite should be studied near neutral environment with pH=6.0. While containing 50% TiO₂ NWs, the adsorption capacity of the composite film for Cu²⁺ is 4 times of rGO film. The composite film has good adsorption stability, and the adsorption rate still retains 91% of the original adsorption after 5 times of reuse.

Luminescent Properties of LuGG∶Ce Nanophosphor Synthesized via Co-Precipitation Method

LIU Wenpeng, REN Hao, LI Hongyuan, DING Shoujun, ZHANG Qingli

2021, 50(2):  325-330. 

Asbtract ( 96 )   PDF (2882KB) ( 45 )  

References | Related Articles | Metrics

Ce³⁺ doped Lu₃Ga₅O₁₂ (LuGG∶Ce) nanophosphor was synthesized via co-precipitation method. Its structured parameters were obtained by Rietveld refinement method. The morphology of the as-synthesized nanophosphor was determined with Scanning Electron Microscope (SEM). Under 365 nm excitation, the emission spectrum exhibits an asymmetry broad band with central wavelength at 438 nm and this broad band can be deconvolved into two peaks with wavelength centers at around 426 nm and 470 nm, respectively. The chromaticity coordinate of LuGG∶Ce is (0.176 9, 0.180 3), which corresponds to blue light emission. The results show LuGG∶Ce is suitable for realizing blue light emission under UV excitation and thus has potential applications in the fields of UV-excited white light emitting diodes(LEDs).

Synthesis and Crystal Structure of Mono-, Binuclear Copper(Ⅱ) Ternary Complexes Based on 5-Sulfosalicylic Acid

YANG Lining, CHENG Zhao, MIAO Yanqing, LIANG Lingling

2021, 50(2):  331-337. 

Asbtract ( 74 )   PDF (2058KB) ( 45 )  

References | Related Articles | Metrics

Mono- and binuclear structure of ternary complexes of Cu(Ⅱ):[Cu(H₂biim)(Hssal) (H₂O)₂]·H₂O(1) and {[Cu(MeHbiim)(Hssal)(H₂O)]·0.5H₂O}₂ (2) (H₃ssal=5-sulfonylsalicylic acid, H₂biim=2,2′-diimidazole, MeHbiim=N-methyl-2,2′-diimidazole) were synthesized using 5-sulfosalicylic acid and imidazole derivatives as the ligands. The structures were characterized by elemental analysis, IR, UV-Vis, single crystal X-ray diffraction and TG analysis. X-ray crystallographic studies show that complex 1 belongs to monoclinic, P2₁/C space group. Each Cu (Ⅱ) ion is coordinated with one 5-sulfosalicylic acid anion, two water molecules and one biimidazole molecule to form five-coordinated mononuclear structural unit of distorted square pyramidal configuration. Binuclear Cu(II) complex 2 exhibits orthorhombic, P2(1)2(1)2(1) space group. One Cu(II) ion of binuclear structural unit is five-coordinated with geometry of square pyramid same as complex 1 and another Cu(II) ion is four-coordinated with geometry of quadrilateral plane. Compared to complex 1, 5-sulfonyl salicylic acid anion acted as a μ₂ bis-monodentate bridging ligand in complex 2. The fluorescence spectrum analysis shows that the complex 2 has good fluorescence property.

Crystal Structure and Density Functional Theory of 2,2-Bis(4-Chloro-2-Fluorobenzyl) Diethyl Malonate

REN Qian, LIU Ye, GAO Ting, ZHOU Zhixu, ZHAO Chunshen, CHAI Huifang

2021, 50(2):  338-344. 

Asbtract ( 63 )   PDF (2624KB) ( 27 )  

References | Related Articles | Metrics

The title compound is an important fine chemical intermediate, which can be used to prepare kinds of pyrimidines and pyrazoles products. This compound was characterized by IR, MS, ¹H NMR,¹³C NMR and X-ray single crystal diffraction, and the most stable crystal structure, HOMO and LUMO energy were calculated by using density functional theory (DFT) in B3LYP/6-311G(d, p) mode. The results show that the molecular structure optimized by DFT is consistent with the crystal structure determined by X-ray single crystal diffraction. The compound belongs to the monoclinic P2(1)/n space group, its crystallographic parameters are as follows: a=1.563 9(10) nm, b=0.778 6(4) nm, c=1.838 2(10) nm, Z=4, ρ_c=1.345 g·cm^-3, R=0.047 7, R_w=0.138 7.

Synthesis, Crystal Structure and Luminescence Properties of [(Epy)₂][MnBr₂I₂] Complex

YANG Chenyue, LI Lingyan, LI Man, SHEN Yiming, PAN Shangke, PAN Jianguo

2021, 50(2):  345-352. 

Asbtract ( 89 )   PDF (2899KB) ( 39 )  

References | Related Articles | Metrics

A zero-dimensional luminescent material [(Epy)₂][MnBr₂I₂] was synthesized using N-ethylpyridine iodized salt (Epy)I and manganese bromide tetrahydrate (MnBr₂·4H₂O) as raw material at room temperature. The complex was tested by element content analysis, infrared spectrum, single crystal X-ray diffraction, powder X-ray diffraction, UV-visible absorption spectrum, photoluminescence spectrum X-ray excitation emission spectrum and so on. The single crystal X-ray diffraction results show that the complex is monoclinic, space group of C2/c, and the central Mn(Ⅱ) has a tetrahedron configuration. The crystal cell parameters are a=2.825 5(6) nm, b=0.839 71(17) nm, and c=1.836 0(4) nm. Under the UV light (λ_ex=332 nm), the complex emits green light at 528 nm, corresponding to the tetrahedron Mn(Ⅱ) complex of ⁴T₁(G) →⁶A₁ radiation characteristics of the transition. Moreover, the fluorescence lifetime is 58.85 μs and the corresponding fluorescence quantum yield is 58.29%. X-ray excitation spectrum shows that the complex has high luminescence intensity, and it has certain X-ray fluorescence properties.

Research on Transverse Silicon Controlled Rectifier Discharge Transistor with Bidirectional Low Trigger Voltage

JIANG Gang, DENG Xucong, ZHAO Ming

2021, 50(2):  353-360. 

Asbtract ( 65 )   PDF (2225KB) ( 22 )  

References | Related Articles | Metrics

According to the requirements of the electrical parameters of trigger voltage V_S, switching current I_S, hold current I_H and V_S, I_H high and low temperature rate of change, the Silvaco-TCAD semiconductor device simulation software was used to complete the design of the transverse silicon controlled rectifier (SCR) discharge transistor with bidirectional low trigger voltage. The N^- substrate, parasitic PNP transistor P^- collector region, parasitic NPN transistor P^- base region, N⁺ cathode region, N⁺ trigger region, parasitic PNP transistor P^- collector region and parasitic NPN transistor P^- base region spacing, parasitic NPN transistor base surface width are important structural parameters of the transverse SCR discharge transistor with bidirectional low trigger voltage, which have a significant impact on the triggering characteristics of the device. The effects of the above structural parameters on the output I-V characteristics and the resistance to transient current burn down of the device were analyzed in detail.According to the structure parameters of the device, the layout is drawn, and the process scheme of transverse SCR discharge transistor with bidirectional low trigger voltage was developed and trial-produced.Through the actual flow sheet, the key technology was solved, the V_S, I_S, I_H, and V_S, I_H high and low temperature change rate of the developed sample sheet can fully meet the requirements of the electrical parameters.

Design of Follow-Up Heater for Czochralski Single Crystal Furnace

ZHANG Xiya, GAO Dedong, WANG Shan, GUO Bing, SONG Shenghong

2021, 50(2):  361-367. 

Asbtract ( 171 )   PDF (2141KB) ( 120 )  

References | Related Articles | Metrics

Single crystal furnace is a kind of equipment which uses graphite thermal field to melt polysilicon materials in the inert gas environment dominated by high-purity argon, and grows single crystal silicon by Czochralski method. In the process of solar single crystal silicon drawing, how to improve the speed and quality of drawing crystals and reduce the energy consumption of equipment has always been the eternal pursuit of single crystal silicon manufacturers. From the perspective of mechanical structure, this paper analyzes the decrease of crystal drawing speed and extra energy consumption caused by rising crucible in single crystal furnace. On the basis of this problem, a method for optimizing the structure of single crystal furnace with crucible rising in the process of crystal drawing was proposed, and through the finite element simulation, the thermal field of the crystal and the melt before and after the optimization of the single crystal furnace and the heater power during the crystal drawing process were analyzed. The simulation analysis shows that the optimizing single crystal furnace can not only improve the stability and speed of crystal drawing process, so as to further improve the quality and output of single crystal furnace, but can also effectively reduce the energy consumption of single crystal furnace.

CNTs-Pt Formaldehyde Sensor and CNTs-Au Glucose Sensor

ZHANG Xunhai, WANG Chaohui, LIN Wei, LI Xiaosheng, ZHANG Yong

2021, 50(2):  368-374. 

Asbtract ( 62 )   PDF (7525KB) ( 17 )  

References | Related Articles | Metrics

Carbon nanotubes (CNTs) were prepared by CH₄ pyrolysis using chemical vapor deposition (CVD) technique. And then spinning disc processor (SDP) self-assembly technique was used to modify the CNTs with nano Pt and nano Au through electrodeposition processes. Subsequently, CNTs-Pt/GCE electrode and CNTs-Au modified electrode were prepared by electrochemical deposition of platinum particles on CNTs-modified glassy carbon electrode (GCE) and immobilization of glucose oxidase on Au electrode via electrostatic effect, respectively. Finally, the electrochemical behavior of glucose on CNTs-Au electrode and formaldehyde on CNTs-Pt/GCE electrode was investigated by cyclic voltammetry (CV) method in a three-electrode system. The electrochemical test results show that Au nanoparticles and CNTs could effectively increase the specific surface area of the electrode and increase its electron transfer rate. Therefore, CNTs-Au biosensor has good repeatability, stability and rapid glucose detection response, which could be used for the detection of serum glucose concentration in clinical practice. In addition, due to the high dispersion of Pt nano particles and the synergistic effect of CNTs and Pt nano particles, the active sites on the electrode surface are enhanced, so the CNTs-Pt/GCE electrode exhibits high sensitivity and good reproducibility in the detection process of formaldehyde. The above results shows that this work has a very good potential for practical application.

Affecting Analysis of Multi-Factors on Soybean Urease-Induced Calcium Carbonate Precipitation

YUAN Hua, LIU Kang, YUAN Yaonan, FENG Jiaxing

2021, 50(2):  375-380. 

Asbtract ( 83 )   PDF (3900KB) ( 23 )  

References | Related Articles | Metrics

The effects of multiple influencing factors on soybean urease-induced calcium carbonate precipitation (SICP) were explored to select the main influencing factors and provided their optimal ranges. Firstly, the influence of urease concentration and temperature on urease activity were analyzed. After that, based on orthogonal test design, 25 test conditions of SICP aqueous solution tests were conducted, and the variation law of Ca²⁺ utilization ratio was studied through the combination of different factors. Also the morphology of CaCO₃ was observed with SEM in diverse test conditions. The results show that low temperature delivers benefits to urease preservation and its activity exertion, urease activity can be preserved over 21 d with 5 ℃. At the same temperature, the greater the urease concentration is, the higher the initial activity of urease boasts and the shorter the time required for complete inactivation of urease. The pH value and the volume ratio of urease to cementation solution are the main factors affecting the Ca²⁺ utilization ratio. In order to achieve a higher Ca²⁺ utilization ratio, the optimum volume ratio of urease to cementation solution could be 1 while the optimal concentration ratio of CaCl₂ to urea is 1.5, and the best Ca²⁺ concentration is 1 mol/L. More hexahedral CaCO₃ is produced, when the urease concentration is low, and the shape of precipitated CaCO₃ turns into spherical as the urease concentration increases. Aspartic acid which is rich in soybeans, is an significant factor in controlling the form of CaCO₃.

Reviews

Research Progress of GaAs Based 980 nm High Power Semiconductor Lasers

HU Xueying, DONG Hailiang, JIA Zhigang, ZHANG Aiqin, LIANG Jian, XU Bingshe

2021, 50(2):  381-390. 

Asbtract ( 120 )   PDF (3320KB) ( 85 )  

References | Related Articles | Metrics

980 nm GaAs based semiconductor lasers have important applications in the fields of materials processing, communication, medical treatment and so on. The conversion efficiency, output power and reliability of GaAs based semiconductor lasers have been improved because of the emergence of strain quantum well. Historical development of GaAs based quantum well laser are reviewed and epitaxial structure design, chip design and chip encapsulation design are introduced in this paper. More importantly, the problems of effect on optical-electrical performances, heat-sink cooling and practical application are discussed emphatically for high power GaAs based quantum well laser. The proposed solutions and achievements are discussed based on the above problems, the shortcomings and improvement directions of each solution are pointed out. Finally, the development status of high power semiconductor lasers is summarized and the development direction is prospected.

Research Progress of BAs Crystal Growth

LIU Jingming, ZHAO Youwen

2021, 50(2):  391-396. 

Asbtract ( 201 )   PDF (2438KB) ( 139 )  

References | Related Articles | Metrics

Cubic boron arsenide (BAs) belongs to Ⅲ-V compound semiconductor with indirect band gap and zin-blende FCC structure. First-principles calculations based on four-phonon scattering indicate that zinc-blende BAs has an unusually high room-temperature thermal conductivity which is second only to that of diamond. BAs single crystal demonstrates broad application prospects in electronics thermal management due to the unusually high thermal conductivity, and it becomes one of hotpots in the field of compound semiconductor materials. Great progress has been made in the growth of cubic BAs single crystal for the past few years. Ultrahigh thermal conductivity of 1 300 W·m^-1·K^-1 at room temperature is experimentally observed in high-quality BAs single crystal with millimeter-sized synthesized by chemical vapor transport (CVT) growth method. Undoped BAs is p-type conducting due to the existence of the intrinsic acceptor defects. The application prospects, crystal structure, material properties and crystal growth method of cubic BAs are introduced. The research progress in crystal growth is reviewed, the technical challenges of crystal growth is described, and development prospects are also analyzed.

Research Progress in Molecular Dynamics Simulation of SiO₂ Aerogels

YANG Yun, SHI Xinyue, WU Hongya, QIN Shengjian, ZHANG Guanglei

2021, 50(2):  397-406. 

Asbtract ( 72 )   PDF (1859KB) ( 29 )  

References | Related Articles | Metrics

Silica aerogels are nanoporous materials with three-dimensional framework network structure. Silica aerogels have many unique properties such as high porosity, low density, low thermal conductivity and acoustical insulation properties. However, due to the poor mechanical performance of silica aerogels such as brittleness and high temperature instability, the large-scale commercial application of silica aerogels is limited. The thermodynamic properties of silica aerogels are related to their three-dimensional ligament network and pore structure. Exploring the relationship between microstructure evolution and macroscopic properties of silica aerogels is essential for improving their thermodynamic properties. Molecular dynamics (MD) simulations are an appropriate tool for the study of mechanical properties from the atomistic level. Based on the accurate potential, MD simulations have correctly predicted the power law that relates thermal conductivity and density. MD simulations also analyze aerogel structure from the atomistic level and predict their thermodynamic performance. The interatomic potential, pore structure generation, structural characterization, mechanical properties and thermal conductivity of the silica aerogels from the aspect of MD simulations are summarized. This work contributes to explaining the relationship between the structure and properties of silica aerogels from the atomistic level, which can provide a theoretical guidance for designing silica aerogels in terms of composition and structure.