Table of Content

15 September 2024, Volume 53 Issue 9

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Invited

Research Progress on Theoretical Design of Nonlinear Optical Materials via Data-Driven Approach

CHU Dongdong, YANG Zhihua, PAN Shilie

2024, 53(9):  1475-1493. 

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Nonlinear optical crystals are the core devices of all-solid-state lasers, and have extensive and important applications in information technology and national security. With the development of high-performance computing, the “top-down” computer-aided design methods have gradually become an important part of nonlinear optical materials design. In addition, the large-scale structural and properties information obtained based on high-throughput computing provides a solid data foundation for data mining and machine learning algorithm training, accelerating the development of the fourth paradigm of material design. This paper starts with the computational design of nonlinear optical materials, and then, discusses the new paradigm of data-driven nonlinear optical materials theoretical design. Finally, the recent research progress of our team in high-throughput screening, crystal structure prediction, and machine learning accelerated nonlinear optical materials are reviewed.

Review

Progress and Prospect of Molecular Beam Epitaxy Equipment at Home and Abroad

CHEN Fengwu, LYU Wenli, GONG Xin, XUE Yong, GONG Xiaoliang

2024, 53(9):  1494-1503. 

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Molecular beam epitaxy (MBE) is an ultra-high vacuum, ultra-high precision and uniformity thin film deposition process by which to fabricate epitaxial films of solid-state microwave RF devices, semiconductor lasers and detectors, etc, and plays a fundamental role in developing compound semiconductor materials for electronics and optics. The article briefly introduces technical characteristics of the MBE equipment. Then historical development and current status of world-renowned MBE manufacturers such as Riber, Veeco, and DCA, and localization progress of MBE equipment from domestic manufacturers such as CETC48, SKY and FERMI are elaborated. Finally, future trends of MBE are expected, pointing out that it is certainly timely for substitution. To seize the opportunities and overcome the challenges, we need to promote technological innovation and industrial application of MBE equipment quickly and to provide important supports for China's scientific and technological self-reliance and self-improvement.

Research Articles

Spectral Analysis and Thermal Properties of Nd∶GdYAG Laser Crystal

DOU Renqin, LIU Yao, LUO Jianqiao, WANG Xiaofei, LIU Wenpeng, ZHANG Qingli

2024, 53(9):  1504-1511. 

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The adsorption and fluorescence spectra of the grown Nd∶GdYAG were measured. The spectral parameters, such as oscillator strength, line strength, intensity parameter Ω_t, transition probability between ⁴F_3/2→⁴I_J levels, radiation lifetime, and fluorescence branching ratio, were calculated with Judd-Ofelt theory. The calculated Ω_t are Ω₂=(0.813±0.200)×10^-20 cm², Ω₄=(3.381±0.187)×10^-20 cm², Ω₆=(5.135±0.278)×10^-20 cm², respectively. Compared with Nd-doped YAG, LuAG, YVO₄, and other crystals, Nd∶GdYAG crystal has a larger Ω₂, showing that the addition of Gd³⁺increases the disorder of the host. The absorption cross-section and refractive index in the range of 300~1 200 nm were calculated and fitted. The absorption cross-section at 808 nm is 5.0×10^-20 cm². The refractive index at 1 064 nm is 1.80. The measured fluorescence lifetime of ⁴F_3/2 level is 228 μs, which is close to the calculated radiation lifetime of 240 μs. The emission cross-section at 1 064 nm is 1.23×10^-19 cm², which is close to that of Nd∶YAG crystal. Addition, at room temperature, the thermal conductivity of Nd∶GdYAG crystal is 5.992 W/(m·K), which is slightly smaller than that of Nd∶YAG and Nd∶GGG, but larger than that of Nd∶YVO₄ crystal. The results show that Nd∶GdYAG is a promising new laser crystal material.

A 561 nm Fundamental Mode Laser Based on a Compact Nd∶YAG/PPMgLN Module

WU Qiulin, FENG Xinkai, CHEN Huaixi, CHEN Jiaying, MA Cuiping, LIANG Wanguo

2024, 53(9):  1512-1518. 

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In this paper, a nonlinear crystal corner-cutting method is proposed to change the laser mode distribution on the output face of the PPMgLN crystal by cutting off a corner of the output face of the PPMgLN crystal in the resonance cavity, so as to realize the stable fundamental mode output of the 561 nm yellow laser. Using the finite-difference eigenmode method, the laser mode distributions at the output end face of various corner-cutting schemes were simulated to discuss the principle of their output fundamental mode, and the change curves of the output power of each scheme with the pump power were measured experimentally. The results show that when the pumping power is 4.8 W, the highest fundamental mode output of 121 mW is realized, with an optical-to-optical conversion efficiency of 2.6%, a central wavelength of 560.95 nm and a full width at half maximum of 0.92 nm, and an instability of less than 1.91% in 3 h. With a smaller structure size compared with the reported experimental results, this experimental result will provide an important reference for compact fundamental mode lasers.

Dissolution Mechanism of Baloxavir Marboxil Single Crystal Based on In-Situ AFM

WANG Hongshuai, WANG Lei, SONG Shuhong, TAO Xutang

2024, 53(9):  1519-1527. 

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The dissolution behavior of the largest exposed crystal face of Baloxavir marboxil Form I crystal, an anti-influenza drug, was investigated by in-situ atomic force microscopy (AFM) at near molecular scale in water. The largest exposed crystal surface is the (020) face, the microstructure features of layered steps and spiral dislocations appear before dissolution. The in-situ AFM tests show that there are two main dissolution mechanisms: step retreat and pit expansion dissolution. The step retreat dissolution mechanism mainly occurs at the crystal faces where growth steps remain, and the dissolution is promoted by gradual retreat of layered steps. There are two forms of pits in pit expansion dissolution mechanism: regular pits and inverted spiral dislocation pits. The formation of inverted spiral dislocation pits is related to the defect initiated-dissolution at the spiral dislocation sites; the regular quadrilateral pits mainly appear at the relatively smooth and perfect crystal faces, because this characteristic crystal surface can only promote the dissolution process through spontaneous pitting nucleation. When the crystal face is dissolved by the regular pit dissolution mechanism, the critical size of the pit-dissolution exists, meaning only pits above a certain size can promote dissolution.

Effect of Aluminum Doping on the Crystal Structure and Properties of Indium Selenide Crystals

ZHENG Quan, LIU Xuechao, WANG Hao, ZHU Xinfeng, PAN Xiuhong, CHEN Kun, DENG Weijie, TANG Meibo, XU Hao, WU Honghui, JIN Min

2024, 53(9):  1528-1535. 

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Indium selenide (InSe) is a novel narrow bandgap (1.3 eV) layered semiconductor with excellent plasticity and electrical properties, and has broad application prospects in new electronic and optoelectronic devices. Undoped and aluminum doped InSe crystals were grown by Bridgman method. The chemical composition and surface morphology of the prepared materials were characterized using energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). This study founds that aluminum doping can regulate the plasticity and optoelectronic properties of InSe crystals. X-ray diffraction (XRD) analysis shows that the crystal has a hexagonal structure, and Raman spectroscopy characterization confirms that the crystal structure is ε-InSe. Nanoindentation measurements indicate that as the aluminum doping content increases, the hardness and modulus of InSe crystal decrease, while the plasticity of the material increases. Hall effect measurement and optical absorption spectrum results indicate that aluminum doping can increase the carrier concentration and bandgap width.

Effects of Electron Irradiation on Defects of 4H-SiC MOS Materials

LIU Shuai, XIONG Huifan, YANG Xia, YANG Deren, PI Xiaodong, SONG Lihui

2024, 53(9):  1536-1541. 

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4H-SiC metal-oxide-semiconductor (MOS)-based devices appear to worse electrical performance when exposed to electron irradiation, owing to the production of material defects. This study demonstrates an analysis of defect evolution of 4H-SiC MOS capacitors with the simplest structure, subjected to a series dose of electron irradiation with 10 MeV electron beam, including 30, 50, 100, 500, 1 000 kGy. Deep level transient spectroscopy (DLTS) test and capacitance-voltage (C-V) measurement were used to obtain defects information among MOS samples pre- and post-irradiation. DLTS results present that a low dose of irradiation causes no evident impact on defect evolution near and at the 4H-SiC/SiO₂ interface, whereas a high dose of irradiation makes a defect configuration of carbon interstitial dimer defect evolve into another more stable one at a deeper energy level. C-V curves show that different irradiation doses lead to different negative shift degrees of flat-band voltage. This is considered to be resulted from multiple factors, including oxygen vacancies in the SiO₂ layer and defects near and at the 4H-SiC/SiO₂ interface. This work might be helpful for the development and optimization of 4H-SiC MOS fabrication with respect to anti-irradiation performance.

Regulation of AlN Crystal Growth Mode by PVT Method

QIN Zuoyan, JIN Lei, LI Wenliang, TAN Jun, HE Guangze, WU Honglei

2024, 53(9):  1542-1549. 

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The generation of sub-grains during the preparation of AlN crystals by physical vapor transport (PVT) method can reduce crystal quality, and even lead to the development of polycrystallization. In this paper, the generation and evolution of sub-grains were studied by adjusting the thermodynamic and kinetic growth conditions, and effective suppression methods were proposed to regulate crystal growth mode. The experimental results show that the large temperature fluctuation leads to the large fluctuation of the gaseous substances supersaturation on the crystal surface. It promotes the formation probability of high-index facets, which are difficult to achieve perfect coalescence due to non-uniformity. The influence of the transport path of gaseous substances on the crystal growth mode under the condition of a stable temperature field was also studied. The experimental and simulation results show that during the crystal growth under the traditional crucible structure, the transmission path of gaseous substances migrates from the edge to the center on the crystal surface, which is opposite to the direction of the growth step. The crystal surface is prone to forming step clusters and evolving into Stranski-Krastanov growth mode. A novel crucible was designed to enable the migration of gaseous substances along the crystal growth step direction, which met the basic conditions of layer-by-layer growth. The experimental results of growth temperature from 2 200 ℃ to 2 300 ℃ show that as the decrease of temperature, crystal growth exhibits c-axis dominant growth, and lateral expansion capability decreases. As the temperature increases, the lateral expansion capability increases, but the probability of the formation of high-index crystal facets increases continuously. When the temperature is about 2 250 ℃, the two reach a balance, which is suitable for the suppression and elimination of sub-grains. Combined with BCF theory analysis, reducing the supersaturation enhances the two-dimensional tiling ability of screw dislocation-driven growth, and increases the growth step width, which is conducive to dispersing sub-grain boundaries into step flow. The optimized experimental results show that the Stranski-Krastanov growth mode gradually changes to a screw dislocation-driven growth mode, and the sub-grains are gradually annihilated. The high-quality AlN crystals were obtained, with an X-ray single crystal rocking curve full width at half maximum values of 58″ on AlN (0002) surface, a Raman spectrum E₂ (High) full width at half maximum value of 3.3 cm^-1, and a dislocation density on the crystal surface of 2.87×10³ cm^-2.

CsBa₂ScB₈O₁₆: the First Rare-Earth Borate Simultaneously Containing Zero-Dimensional [B₃O₆] Units and One-Dimensional B—O Chains

JIAO Sihui, WU Hongping, YU Hongwei

2024, 53(9):  1550-1559. 

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The first rare-earth borate crystal CsBa₂ScB₈O₁₆ with both zero-dimensional [B₃O₆] units and one-dimensional B—O chain structures has been synthesized by the high-temperature solution method. It crystallizes in the triclinic crystal system with the P1 space group, with lattice parameters of a=6.698 5 Å, b=7.216 Å, c=14.798 Å, α=97.563°, β=95.226°, γ=95.546°, Z=2. In this compound, [BO₃] and [B₄O₉] units are connected by sharing oxygen atoms to form a one-dimensional chain [B₅O₁₀]_∞. Octahedrally coordinated [Sc(1)O₆] groups and the one-dimensional chain [B₅O₁₀]_∞ are further connected by sharing oxygen atoms to form two-dimensional layer [Sc(1)(B₄O₉)]_∞. Interlayers are linked by octahedrally coordinated [Sc(2)O₆] groups, which share oxygen atoms to form a three-dimensional Sc—B—O framework. Isolated [B₃O₆] units are filled in the three-dimensional channels with Cs⁺ and Ba²⁺ to balance the charges. In order to further explore the novelty of the structure of CsBa₂ScB₈O₁₆, we compared it with other rare-earth borates containing alkali or alkaline-earth metals, and discuss the effect of the cation-to-boron molar ratio (n(A)/n(B)) on the degree of polymerization of B—O units, as well as the dimensionality of the B—O anion framework. Furthermore, the first-principles calculations, infrared spectrum, UV-vis-NIR diffuse reflectance spectrum and the thermal analysis of the compounds have also been performed. Property measurements show that CsBa₂ScB₈O₁₆ exhibits short UV absorption edge (＜190 nm) and moderate birefringence (0.072@1 064 nm). The optical properties of the compound are mainly contributed by the [B₃O₆], [B₅O₁₀] units, and [ScO₆] octahedra.

Synthesis and Luminescence Properties of Dy³⁺/Eu³⁺ Co-Doped CaLaGa₃O₇ Color Tunable Phosphors

LIU Yunyun, HUANG Chuanxin, WANG Meng, WANG Yan

2024, 53(9):  1560-1567. 

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A series of Eu³⁺ singly- and Dy³⁺/Eu³⁺ co-doped CaLaGa₃O₇ single matrix phosphors were successfully prepared by high-temperature solid-phase method. The phase and luminescence properties of the samples were characterized by X-ray diffraction (XRD) and photoluminescence spectra. The XRD patterns show that all the prepared samples have a tetragonal structure consistent with the matrix crystal, indicating the successful synthesis of that Eu³⁺ singly- and Dy³⁺/Eu³⁺ co-doped CaLaGa₃O₇ phosphors. Under excitation of 393 nm, Eu³⁺∶CaLaGa₃O₇ exhibits characteristic red emission of Eu³⁺ (⁵D₀→⁷F₂), and the luminescence purity is as high as 100%. After introducing Dy³⁺, Dy³⁺/Eu³⁺ co-doped CaLaGa₃O₇ phosphors could be excited not only by 393 nm light but also by 348 nm. Regardless of the excitation wavelength, the emission spectra of Dy³⁺/Eu³⁺∶CaLaGa₃O₇ include both the characteristic red emission of Eu³⁺ and the yellow emission of Dy³⁺ (⁴F_9/2→⁶H_13/2). By analyzing the emission spectra and fluorescence lifetime, it is confirmed that there exists effective energy transfer process between Dy³⁺ and Eu³⁺ in the co-doped phosphors. Further, the corresponding chromaticity coordinates and CCT values were calculated. The results show that the overall chromaticity coordinates shift from the yellow-green region to the yellow-orange region when the excitation wavelength is changed from 348 nm to 393 nm. Therefore, the Dy³⁺/Eu³⁺∶CaLaGa₃O₇ is a tunable luminescent material with good application prospects in displays and solid-state lighting.

Performance of In³⁺ Doped Zn₃Ga₂Ge₂O₁₀∶Cr³⁺ Far-Red Light Emitting Materials for Plant Light Supplement

BAI Qiongyu, WANG Chunhao

2024, 53(9):  1568-1575. 

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Cr³⁺ doped Zn₃Ga₂Ge₂O₁₀∶Cr³⁺ far-red phosphor was synthesized by the high temperature solid state method, and the luminescent properties of Zn₃Ga₂Ge₂O₁₀∶Cr³⁺ was tuned by introducing In³⁺. The crystal structure of Zn₃(Ga_1-xIn_x)₂Ge₂O₁₀∶2%Cr³⁺ was determined by X-ray diffraction(XRD), and the luminescent properties were analysed using room-temperature photoluminescence spectra and thermoluminescence spectra. Zn₃(Ga_1-xIn_x)₂Ge₂O₁₀∶2%Cr³⁺ exhibits a broad emission band, which is composed of two luminescent peaks at 705 and 721 nm from the transitions of ⁴T₂(⁴F)→⁴A₂ and ²E→⁴A₂ respectively. As the In³⁺ doping concentration increases, the emission spectrum of Zn₃(Ga_1-xIn_x)₂Ge₂O₁₀∶2%Cr³⁺ broadens. This broadening is attributed to the changes in the crystal field environment around the Cr³⁺, which leads to an increase in the full width at half maximum (FWHM) of the material's emission spectrum as the crystal field splitting becomes more pronounced. Therefore, Zn₃(Ga_1-xIn_x)₂Ge₂O₁₀∶2%Cr³⁺ phosphors are expected to be applied in the field of plant lighting for their luminescence characteristics matching with the absorption spectrum of phytochrome in plants. Additionally, as the In³⁺ doping concentration increases, the phosphor material exhibits a red long afterlow phenomenon, and its afterglow duration is related to the In³⁺ doping concentration.

Synthesis, Crystal Structure and Fluorescence Properties of Zn(II) Complex Based on Pyrazine Carboxylic Acid Ligand

WU Miao, SONG Juan, ZHOU Yunlong, REN Chuanqing

2024, 53(9):  1576-1582. 

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A zinc complex [Zn₂(Hbppc)(bppc)Cl₃]·0.5H₂O was synthesized under hydrothermal conditions using 4-(2,6-di(pyrazin-2-yl)pyridine-4-yl)-benzoic acid (Hbppc) as ligand and ZnCl₂ as metal source. The complex was characterized by SXRD, PXRD, IR, FT-IR, etc. X-ray single crystal diffraction shows that the complex crystallized in the orthorhombic, Pbca space group, with a zero-dimensional structure. Moreover, the complex has a two-nuclear structure, and the binuclear units are further connected by hydrogen bonds to form 2D supramolecular network structure. Hirshfeld surface analysis of the complex was performed by Crystal Explorer 21. In addition, fluorescence analysis of ligands and the complex were performed, and the results show that the fluorescence of the complex is significantly enhanced compared with that of the free ligand. Gaussianview 5.0 and Gaussian 09W were used to calculate the frontier molecular orbital energy of ligand and complex, and to explore the mechanism of fluorescence enhancement.

Synthesis, Characterization and Quantum Chemical Calculation of Cobalt Coordination Polymer with 4,4′-bipy Bridge

SHI Yiwei, YANG Ruijie, ZHANG Yingchun, WANG Xin, WANG Min, SONG Zhiguo

2024, 53(9):  1583-1590. 

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A novel structure cobalt coordination polymer of {[Co(4,4′-bipy)(H₂O)₄]·(p-CH₃C₆H₄SO₃)₂}_n was prepared by solvothermal method with sodium p-toluenesulfonate as the main ligand and 4,4′-bipy as the auxiliary ligand. The cobalt coordination polymer was characterized by infrared spectroscopy, X-ray single crystal diffraction, thermogravimetric analysis and X-ray powder diffraction. The results show that {[Co(4,4′-bipy)(H₂O)₄]·(p-CH₃C₆H₄SO₃)₂}_n belongs to monoclinic system, P2₁/c space group; cell parameters of a=11.319 1(14)Å, b=8.062 6(11)Å, c=14.936(2)Å, α=90°, β=92.423(4)°, γ=90°, V=1 361.9(3)ų, Z=2. The central metal Co(Ⅱ) ion is a hexagonal octahedral structure with slightly distorted coordination. It forms a one-dimensional infinite chain through the bridging of N atoms in 4,4′-bipy. The interlayer is further expanded into a three-dimensional supramolecular structure through the hydrogen bonding between the coordination water molecule and p-methylbenzenesulfonic acid. The [Co(4,4′-bipy)₂(H₂O)₄]·(p-CH₃C₆H₄SO₃) structural unit in the cobalt coordination polymer was quantum chemically calculated by Gaussian 09 program, and the optimal configuration was obtained. The atomic charge distribution and the composition of the front occupied orbital well support the coordination environment of the crystal structure. Finally, the electrochemical impedance test shows that the resistance of the coordination polymer is small and the conductivity is good, which provides a certain theoretical basis for its electrochemical application.

Synthesis, Crystal Structure and Photocatalytic Properties of Nanosized La³⁺-Substituted Arsenotungstate Cluster

YANG Ling, SU Binbin, WANG Hongsheng, LI Jinzhao, LI Yesheng, CHEN Rui

2024, 53(9):  1591-1598. 

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Based on the principle of molecular design and self-assembly, a novel rare earth based arsenotungstate was obtained by introducing rare earth La^Ⅲ ions into the lacunary polyoxotungstates clusters with vacancy structure by one-pot method with Na₂WO₄·2H₂O, NaAsO₂ and LaCl₃·6H₂O as the main materials. The structure and composition of this complex was confirmed by single-crystal X-ray diffraction, X-ray powder diffraction (PXRD), infrared spectroscopy (IR) and so on. The single crystal X-ray diffraction results show that the complex is in the monoclinic system, C2/c space group, and with the cell parameters of a=3.595 56(14) nm, b=1.222 48(4) nm, c=2.247 34(9) nm, β = 117.117 0(10)°, V=8.792 3(6) nm³, Z=4. The molecular formula of this compound is [(CH₃)₂NH₂]₈H_3.56[{LaO(H₂O)₂}{WO(H₂O)}{W_0.24(H₂O)₂}{AsW₉O₃₃}₂]. And the polyoxoanion [{LaO(H₂O)₂}{WO(H₂O)}{W_0.24(H₂O)₂}{AsW₉O₃₃}₂]^11.56- shows a novel sandwich type structure, which can be simply described as two trilacunary Keggin type{AsW₉O₃₃} units are linked by a {LaO(H₂O)₂} segment, a {WO(H₂O)} segment and a {W_0.24(H₂O)₂} segment. Catalytic degradation property of this compound for Rhodamine-B was further inverstigated. The results demonstrate that the compound shows good photocatalytic activity under the condition of 300 W Hg lamp irradiation, and the degradation efficiency reaches to 74%.

A Novel Three-Dimensional Ni (II) Complex: Synthesis, Crystal Structure and Detection for Fe³⁺, CrO^2-₄ and Cr₂O^2-₇ in Water

AN Hangyi, HUANG Yanxi, WANG Airong, WANG Xiaoli, LI Jiaming, SHI Zhongfeng

2024, 53(9):  1599-1607. 

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A novel Ni (II) coordination polymer [Ni(pdc)(bib)(H₂O)]_n(Ni-CP) was synthesised by solvothermal method with 3,5-pyridyl dicarboxylic acid (3,5-H₂pdc), 1, 4-bis (1-imidazolyl) benzene (bib) and Ni(NO₃)₂, and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric, IR spectroscopic and fluorescence spectroscopy analysis. The results show that Ni-CP crystallized as a monoclinic system with C2/c space group. The asymmetric unit of Ni-CP was comprised of one Ni(II), two half bib ligands, one completely deprotonated 3,5-pdc^2- ligands and one coordinated water molecule. The environment around central Ni(II) can be described as irregular hexacoordination octahedral geometry of NiO₃N₃. The bib and 3,5-pdc^2- ligands were bridged by the bidentate coordination mode in the μ₂-η¹∶η¹ fashion and the tridentate coordination mode in the μ₃-η¹∶η¹∶η¹ fashion to form a three-dimensional network framework. From a topological point of view, the two-dimensional frame structure can be simplified to a 3-connected topology with a Schläfli symbol (4·8²). We consider the 3,5-pdc^2- ligands and Ni(II) as nodes and the bib ligands as connectors, forming a three-dimensional structure can be simplified to a 3,5-connected double nodes with topological symbols (4·6·8)(4·6²·8⁷). The porosity of Ni-CP is 17.4%. Ni-CP could selectively detect Fe³⁺, CrO^2-₄ and Cr₂O^2-₇ with detection limits of 4.275×10^-5, 2.681×10^-5, 2.681×10^-5 mol/L, respectively, and have a high quenching rate.

Study of Gas-Phase Parasitic Reaction Pathways for ZnO Thin Film Grown by MOCVD

WU Rui, HU Yang, TANG Rongfen, YANG Qian, WANG Xu, WU Yiyi, NIE Dengpan, WANG Huanjiang

2024, 53(9):  1608-1619. 

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This study utilized density functional theory (DFT) in quantum chemistry to investigate the gas-phase parasitic reaction mechanism between diethylzinc (DEZn) and tert-butanol (t-BuOH) during the metal-organic chemical vapor deposition (MOCVD) growth process of ZnO thin films. By calculating the Gibbs free energy changes along various reaction pathways at different temperatures, a comprehensive thermodynamic evaluation of key intermediates (HOZnOBu^t, H(ZnO)₂Bu^t, HZnOH), as well as the formation of dimers (Zn₂O₂H₄, Zn₂O₄H₄, Zn₄O₄H₄), and trimers (Zn₃O₆H₆) was performed. The main objective was to identify potential pathways and products that could lead to the formation of nanoparticles, which might impede ZnO thin film growth. Research has shown that under high-temperature deposition conditions (673.15 K<T<713.15 K), the intermediate product H(ZnO)₂Bu^t resulting from the thermal decomposition of DEZn readily reacts with H₂O to form (ZnOH)₂, supporting ZnO thin film growth. However, these intermediates can also undergo polymerization elimination reactions to generate dimers and trimers, serving as crucial precursors for nanoparticle formation. Notably, the most favorable pathway involved the formation of Zn₂O₄H₄ through the polymerization of (HOZnOBu^t)₂ followed by the elimination of C₄H₈. Therefore, the dimer Zn₂O₄H₄ emerged as a crucial precursor for nanoparticle formation.

First-Principles Study on the Effect of VI Group Elements Modification on the Electronic Properties of Two-Dimensional AlN

MO Qiuyan, OU Manlin, ZHANG Song, JING Tao, WU Jiayin

2024, 53(9):  1620-1628. 

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Effect of VI group elements (O, S, Se, Te) modification on the electronic properties of two-dimensional AlN were investigated by first-principles calculation method using density functional theory. The calculation results indicate that after O modification, the energy bands of the two-dimensional AlN system undergo splitting, thereby transforming into magnetic materials. After modification with S, Se and Te, the electron density of states curves of the two-dimensional AlN exhibit complete spin up and spin down symmetry, forming a non-magnetic structure. From the density of states graph, it can be seen that the density of states near the Fermi level is mainly contributed by the p-state electrons of the modified atom and the p-state electrons of the N atom. The bottom of the conduction band gradually moves towards the lower energy region, causing the absorption wavelength threshold of two-dimensional AlN to shift from the ultraviolet region to visible light. Therefore, the modified two-dimensional AlN improves its photocatalytic efficiency and has the potential to be used in the visible light responsive optoelectronic and spin electronic devices.

Optimization of Electronic Transport Model and Device Performance in Tin Dioxide-Based Dye-Sensitized Solar Cells

CHENG Youliang, DU Huibin, ZHANG Zhongbao, WANG Kai

2024, 53(9):  1629-1639. 

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For dye-sensitized solar cells (DSSC), the material properties and design parameters of their photoanodes have a more significant impact on the performance of DSSCs. In order to investigate this issue in depth, this paper adopts numerical simulation to explore the detailed impact of change in the photoanode structure on the performance of DSSC. However, the current mathematical model is not comprehensive enough and the prediction accuracy is low. Therefore, based on the theory of photoelectron transfer and Lambert Beer's law, this paper introduces the influence of porosity on electron diffusion coefficient into the mathematical model of DSSC using constant stacking method and variable stacking method, and establishes a more comprehensive and accurate electron transfer model. This model can deeply analyze the impact of changes in the structure parameters of the photoanode on the performance of DSSC. The performance of DSSC under different pore volumes, electron lifetime, SnO₂ coating thickness, and specific surface area were simulated through numerical simulation. The results show that as the pore volume of SnO₂ thin films increases, the short-circuit current density of solar cells gradually decreases, while the open circuit voltage shows an increasing trend, leading to a gradual decrease in photoelectric conversion efficiency. When the pore volume reaches 0.10 cm³/g, its photoelectric conversion efficiency reaches 5.16%. Therefore, while ensuring the rigidity of the battery, reducing the pore volume of SnO₂ as much as possible is beneficial for improving the absorption coefficient and diffusion coefficient. The improvement of these two parameters is conducive to the overall performance of DSSC. At the same time, the extension of electron lifetime will bring about an increase in the short-circuit current density and open circuit voltage of solar cells, thereby improving the photoelectric conversion efficiency. When the electron lifetime reaches 200 ms, its photoelectric conversion efficiency reaches 5.82%. This study provides strong theoretical guidance for optimizing the photoanode structure and improving the photoelectric performance of DSSC through detailed numerical simulation analysis, which helps to further promote the research and application of dye sensitized solar cells.

Effect of Sulfur-Rich Precursor Solution on Photovoltaic Performance of CuPbSbS₃ Solar Cells

ZHAO Ya, ZHUANG Zhong, WEI Mengyuan, JIANG Qingsong, YANG Xiao, XUN Wei, LIU Yuhao

2024, 53(9):  1640-1647. 

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Owing to the excellent optoelectronic characteristics, such as high absorption coefficient and suitable bandgap, CuPbSbS₃ semiconductor materials have a wide application prospect in solar cells. In this paper, CuPbSbS₃ films were deposited in the annealing process of tube furnace through butyldithiocarbamic acid (BDCA) solution method. CuPbSbS₃ film is regulated deposited by adjusting the proportion of CS₂ in BDCA solution. The effect of the proportion of CS₂ in BDCA solution on the surface morphology and crystal structure of CuPbSbS₃ films was analyzed by scanning electron microscopy and X-ray diffractometer. The results indicate that deposited CuPbSbS₃ film exhibits good crystalline morphology by fixing the volume ratio of ethanol, n-butylamine, and carbon disulfide of 7.4∶9.6∶6. Then, solar cells with the structure of FTO/SnO₂/CuPbSbS₃/Spiro-OMeTAD/Ag were fabricated. The interfacial charge transport kinetics of CuPbSbS₃ solar cells were further investigated by Mott-Schottky curves, Nyquist impedance spectra, dark current density-voltage curves, and current-voltage curves of symmetrical devices in the dark state. The results from the above electrical measurements demonstrate that the defect recombination center density and charge transport resistance of the deposited CuPbSbS₃ films is effectively reduced, decreasing the non-radiative recombination of photogenerated carriers and improving the carrier transport ability. Finally, the CuPbSbS₃ solar cell shows a photoelectric conversion efficiency of 0.81% (a short-circuit current density of 9.08 mA·cm^-2 and an open-circuit voltage of 250 mV). The relevant research results provide an experimental basis for the fabrication of high-quality CuPbSbS₃ films.

Effects of Chamber Materials on the Preparation of Graphene on the Oxidized Copper Foils Substrate

SHEN Xi, SHI Yonggui, WAN Yuhui, FU Ying, MA Jiaheng, YANG Haodong, WANG Yijia

2024, 53(9):  1648-1654. 

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Graphene prepared by the traditional chemical vapor deposition are generally subjected to small domain area and multiple grain boundary defects, which seriously restricts the performance and application of large-area graphene. In this study, the low-pressure chemical vapor deposition technology was used to prepare graphene on the oxidized copper foils substrate in the restricted growth chambers. The growth behavior of the graphene on two kinds of restricted growth chambers (quartz and corundum) were studied. The effects of the quartz restricted growth chamber and the corundum restricted growth chamber on the nucleation and growth of graphene on the oxidized copper foils under different methane flow rates and growth time were compared. The results indicates that, compared to the quartz restricted growth chamber, although the domain sizes of graphene on the oxidized copper foils substrate in the restricted growth chamber of corundum are smaller, there are fewer deposited impurity particles on the surface of the oxidized copper foils substrate, resulting in lower nucleation density and higher crystal quality of graphene, which is more conducive to the preparation large-sized and high-quality graphene.