Table of Content

15 December 2020, Volume 49 Issue 12

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Research Progress in Antimonide-Based Type-II Superlattice Multi-Color Infrared Detectors

JIANG Dongwei, XU Yingqiang, WANG Guowei, NIU Zhichuan

2020, 49(12):  2211-2220. 

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In recent years, Type-Ⅱ InAs/GaSb superlattice infrared detectors have experienced significant developments in material growth quality, device structural designs, and imaging applications. Especially for multi-color infrared detection, type-Ⅱ superlattice has several fundamental properties such as tunable band gap, low dark current, high quantum efficiency, high uniformity, and low cost, that makes it the preferred material for the third-generation infrared detection technology. In this paper, recent advances in antimonide multi-color detectors at the Center for Antimonide Narrow-Bandgap Semiconductors have been reported. Development of a variety of high-performance multi-color infrared detectors with low noise, high quantum efficiency and low optical crosstalk, such as short/mid, short/long, mid/long, long/long, and mid/long/very long multi-color infrared detectors were successfully realized.

Progress in MBE Growth of HgCdTe at Kunming Institute of Physics

KONG Jincheng, LI Yanhui, YANG Chunzhang, YANG Jin, QIN Gang, CHEN Weiye, CHEN Xiaoxuan, REN Yang, WANG Shanli, HU Xu, WANG Xiangqian, LI Xiongjun, ZHAO Jun

2020, 49(12):  2221-2229. 

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HgCdTe(MCT) has dominated the high performance end of the IR detector market for decades. Owing to many merits, including the possibility of using low cost alternative substrates such as Ge and Si, precisely energy band structure control, and device structure grown, molecular beam epitaxy(MBE) growth of MCT has become the main tool for fabricating third generation IR focal plane arrays(FPA). Recent progress in MBE growth of MCT at Kunming Institute of Physics (KIP) is reported, including results in structure design, crystalline quality control, surface macro-defect control, cut-off wavelength and thickness uniformity control, doping control. For MCT on alternative and CdZnTe substrate, the maximum size are 4-inch(10.16 cm) and 2.5 cm×2.5 cm, the EPD are around 1×10⁶ cm^-2 and in the range of (3~30)×10⁴ cm^-2, the macro-defect density are around 30 cm^-2 and between (1~3)×10² cm^-2, respectively. Single color MWIR 2 048×2 048 detector, SWIR 2 048×2 048 detector, dual-band S-MWIR 640×512 detector, and dual-band M-MWIR 320×256 FPA detector are fabricated and demonstrated using MBE MCT.

Development and Application of InSb Crystal

BAI Wei, ZHAO Chao, LIU Ming

2020, 49(12):  2230-2243. 

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Indium antimonide (InSb) crystal has became a hot spot in the field of semiconductor materials due to its unique physicochemical properties and excellent process compatibility since it is discovered. In recent years, as its application prospect in the field of infrared detection, it is widely concerned and valued by many research institution all over the world, and the technology has developed rapidly. At present, InSb crystal is the first choice for the preparation of high-performance medium wave infrared detector, which has great application prospect and commercial demand. The rapid development of infrared detector based on InSb crystal have greatly improved the performance of the infrared system and it promoted the infrared technology wide application in military and civil fields. This paper mainly introduce the properties of InSb crystal and summarize the research progress of InSb crystal at home and abroad, as well as its application in the field of infrared detection. Finally, the prospect and trend of its development is prospected.

Effect of He Ion Implantation on the Defect Behaviour in Ge

KE Haipeng, OU Xuewen, KE Shaoying

2020, 49(12):  2244-2251. 

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In this study, SRIM software based on the Monte Carlo method is used to simulate the defect behavior in Ge during He ion implantation, which provides theoretical guidance for the preparation of high-quality GOI (Ge on insulator) materials. The effect of the implantation angle, energy, and dose of the He ion on the damage degree and sputtering yield in Ge material was investigated. The results show that, the training effect is not serious when the incident angle is low. The channel effect can be avoided and the DPA in Ge material can be decreased. With the increase of the energy, the project range increases and the sputtering yield decreases. Moreover, the DPA in the Ge near surface decreases with the increase of the energy, indicating the low DPA in the GOI(Germanium-on-Insulator, GOI) material. The increase of ion implantation dose leads to the increase of the damage area and the aggregation of the defects. Moreover, when the dose increases, more He ions aggregate near the project range. This may lead to the decrease of the lift-off temperature of GOI material.

Synthesis, Structure and Properties of InSeI Single Crystals

ZHOU Xuan, CHENG Guofeng, HE Daihua

2020, 49(12):  2252-2255. 

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InSeI single crystals were synthesized by the chemical vapor transport (CVT) method. The crystal is yellow needle-shaped and brittle. X-ray diffraction results at room temperature show the tetragonal system of InSeI, with lattice parameters of a=b=1.864 3(5) nm, c=1.012 0(3) nm, V=3.517 2 nm³, and space group is I4₁/a. The ultraviolet-visible absorption spectrum, photoluminescence spectrum results show that InSeI has a 2.48 eV band gap, under the excitation of a certain band of light, InSeI single crystal has a wide emission peak at about 600 nm, which indicates that the luminescence mode of the crystal is defect state luminescence. The dielectric temperature spectrum indicates that a phase transition happened in the tetragonal structure of InSeI crystals at 440 K.

Influence of Unequal Thickness Electrode on High Frequency Vibrations of Quartz Crystal Plate

WU Rongxing, WANG Xiaoming

2020, 49(12):  2256-2260. 

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Based on Mindlin's first-order plate theory, the high-frequency vibrations of AT cut quartz crystal plate covered with unequal thickness electrode layers was analyzed. The dispersion relation and frequency spectrum of vibration modes including thickness-shear vibration mode, flexural vibration mode, face-shear vibration mode, extension mode and thickness-twist modes were obtained. The research results show that due to unequal thickness of the upper and lower electrode layers, the two originally groups of vibration modes that were previously considered uncoupled are now coupled and must be solved jointly. The computing results show that the frequency of every vibration mode decrease due to the mass effect of the unequal thickness electrode layer. According to the frequency spectrum of high frequency vibration of quartz crystal plate, the optimal length/thickness ratio of quartz crystal plate can be selected as the manufacturing size of resonator. The relationship between the thickness of the electrode layer and the frequency variation can be used to guide the design of the electrode layer thickness of the resonator.

Study on p-Type Doping of Two-Dimensional g-AlN Materials Based on First-Principles

XIAO Wenjun, LIU Tianyun, LIU Xuefei

2020, 49(12):  2261-2267. 

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The realization of n-type and p-type carrier conductivity by doping in semiconductor materials is of great significance in the field of semiconductor devices. Theoretically, the n-type and p-type doping efficiency of semiconductor materials can be explored by calculating charge transfer energy levels and defect formation energy. The structural, magnetic, electronic, defect formation energy and charge transfer energy levels of four potential p-type doped defects in g-AlN (Be_Al, Mg_Al, Ca_Al, Sr_Al) were systematically calculated based on frist-principles and combined with two-dimensional (2D) charged defect calculation method.The results show that all defective systems are deep acceptor energy levels, and it is difficult to provide p-type carriers for the 2D AlN. On the contrary, they will capture the holes in AlN, which will seriously affect the hole conductivity of 2D g-AlN materials. Be_Al has the minimum forming energy in the whole range of electronic chemical potential, so it is easier to be doped into g-AlN, affecting the p-type doping efficiency of g-AlN materials.

Nucleation and Diffusion of In Atom on GaAs(001) Surface

WANG Yi, DING Zhao, WEI Jiemin, YANG Chen, LUO Zijiang, WANG Jihong, GUO Xiang

2020, 49(12):  2268-2273. 

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In recent years, the basic physical properties and potential applications of semiconductor quantum dots, especially InAs quantum dots, have been extensively studied. Many researchers use the structural changes of InAs quantum dots to modulate their photoelectric properties. Various amount of indium (3 ML, 4 ML, 5 ML) were deposited on GaAs(001) surface by droplets epitaxy for investigating the nucleation mechanisms and surface diffusion of indium. As the amount of indium deposition increases, the droplet size (including diameter and height) increases obviously. Not only that, higher deposition amount also leads to higher density of droplets at the same substrate temperature. The critical thickness of indium droplet formation was theoretically calculated as 0.57 ML on the GaAs (001) surface. It is in agreement with experimental result. The mechanism of the formation and morphology evolution of droplets is explained by diffusion and intermixing between the gallium and indium migration. The critical thickness of In droplet obtained in the experiment and the nucleation mechanism of In droplet on GaAs(001) can provide experimental guidance for InAs quantum dots growth.

Preparation and Properties of CuInS₂ Quantum Dot-Sensitized ZnO Based Photoanode

XIA Donglin, GUO Jinhua

2020, 49(12):  2274-2281. 

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Pure ZnO nanorods and Y-doped ZnO nanorods (ZnO∶Y) were prepared on conductive glass (FTO) substrate by two-step method. ZnO/CuInS₂ and ZnO∶Y/CuInS₂ photoanodes were fabricated by successive ionic layer adsorption and reaction (SILAR), respectively. The crystal phase structure, micro-morphology, chemical composition, light absorption performance and solar cell efficiency of different photoanode samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometer(EDS), ultraviolet visible spectrophotometer (UV-Vis) and current density-voltage (J-V) curves and other technical means. The experimental results show that the prepared ZnO nanorods and ZnO∶Y nanorods have a hexagonal wurtzite structure. The optical band gap of the CuInS₂ quantum dot-sensitized ZnO nanorod films reduce from 3.22 eV to 2.98 eV. Compared with ZnO/CuInS₂ photoanode solar cell, the short-circuit current density and photoelectric conversion efficiency of ZnO∶Y/CuInS₂ photoanodes solar cell increase by 6.5% and 50.4%, respectively.

Simulation Study of ZnO(n)/ZnSe(i)/c-Si(p) Heterojunction Solar Cells

LUO Wei, DU Rui

2020, 49(12):  2282-2286. 

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Heterojunction with intrinsic thin-layer (HIT) solar cells have attracted a great deal of interest in the researchers recently due to its advantages of high energy conversion efficiency and low temperature production procedure, however the high cost of raw material, the harsh technical conditions and the defect state control have become the major problems which prevent its further development. The AFORS-HET software is employed to simulate the influence of the absorber layer doping concentration, the defect density and the interface defect density of state on the ZnO(n)/ZnSe(i)/c-Si(p) heterojunction solar cell's performances (the short-circuit current, open-circuit voltage, fill factor and photoelectric conversion efficiency). The optimized result shows that when the doping concentration of the absorber layer is 1×10²¹ cm^-3, the defect density of the ZnO layer and c-Si layer is less than 10¹⁷ cm^-3, and the defect density of the ZnSe/c-Si interface is less than 10²⁵ cm^-3, the photoelectric conversion efficiency of the solar cell with this structure can reach 24.29%.

Numerical Simulation of Monolayer n-Type MoS₂/p-Type c-Si Heterojunction Solar Cells

CHEN Yun, CAI Houdao

2020, 49(12):  2287-2291. 

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Monolayer MoS₂ is a promising semiconductor material for solar energy conversion application because of its excellent optoelectronic properties. In this study, monolayer n-type MoS₂/p-type c-Si heterojunction solar cell was proposed and simulated using AMPS software. The different factors influenced the photovoltaic performance of the solar cell were studied. The simulation results show that the solar cell can achieve the highest conversion efficiency of 22.1% with the electron affinity of n-type MoS₂ is 3.75 eV, the doping concentration of n-type MoS₂ is 10¹⁸ cm^-3, and the doping concentration of p-type c-Si is 10¹⁷ cm^-3. Finally, the influence of interface states at the n-type MoS₂/p-type c-Si heterointerface on the overall performance of solar cell is simulated. It is found that the interface state density over 10¹¹ cm^-2·eV^-1 will seriously affect the photovoltaic performance of solar cell.

Investigation of Low Lattice Thermal Conductivity in Two-Dimensional CdO

LIU Xuefei, LUO Zijiang, LYU Bing

2020, 49(12):  2292-2296. 

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Seeking two-dimensional materials with low lattice thermal conductivity (k_lat)is of great significance to enhance high thermoelectric performance. Based on ab-initio calculations and phonon Boltzmann transport theory, the structure of two-dimensional CdO is optimized and the dynamic stability of monolayer CdO is verified by calculating phonon spectra. The phonon transport properties of monolayer CdO were studied in detail. The results show that the lattice thermal conductivity of monolayer CdO is around 5.7 W/(m·K) at room temperature, which is much lower than that of monolayer graphene, buckled monolayer phosphorene, monolayer black phosphorene, and MoS₂. The percentage contribution of Z-direction acoustic (ZA), transverse acoustic(TA), longitudinal acoustic(LA), Z-direction optical (ZO), transverse optical(TO) and longitudinal optical (LO) branches to k_lat is 73.7%, 13.9%, 3.7%, 2.8%, 4.7% and 1.2%, respectively. The strong scattering among optical-acoustic phonons is found to be responsible for the low thermal conductivity of monolayer CdO. The calculated results could guide the design of CdO-based low-dimensional thermoelectric devices.

Photocatalytic Properties of TmFeO₃ Adsorbed on Carbon Prepared by Hydrothermal Method

ZHANG Mingyuan, ZHANG Yanbin, NIU Yutong, GUO Guibao

2020, 49(12):  2297-2301. 

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The TmFeO₃ nano powder with perovskite type adsorbed on carbon were prepared by hydrothermal method. Their specific surface area, thermal stability, absorption property and physical structure of the crystal were analyzed by X-ray diffraction(XRD), thermal gravimetric-differential thermal analyzer(TG-DTA), ultraviolet visible spectrophotometer(UV-Vis) and gas chromatograph. The photocatalytic properties of TmFeO₃ powder was evaluated by degradation of methyl orange using dysprosium lamp as visible light source. The experimental results show that TmFeO₃ adsorbed on carbon prepared by hydrothermal method has better crystallinity, higher thermal stability, larger specific surface area, larger visible absorption range and better absorptivity. The experimental results of photocatalytic degradation of methyl orange show that the degradation rate of TmFeO₃ adsorbed on carbon methyl orange reaches 88% after light irradiation for 140 min and is 1.5 times of TmFeO₃ prepared by ordinary hydrothermal method.

Synthesis and Photoluminescence Properties of Ba₂YAlO₅∶Eu³⁺, Na⁺ Phosphor

DUAN Huan, CUI Ruirui, DENG Chaoyong

2020, 49(12):  2302-2307. 

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A series of Ba₂YAlO₅∶0.2Eu³⁺, xNa⁺(x=0.01, 0.03, 0.05, 0.10, 0.20, 0.30) phosphors were synthesized successfully by high temperature solid phase method. The effect of Eu³⁺, Na⁺ doping on the crystal structure was studied. Observe the morphology of fluorescent materials with scanning electron microscope. The excitation and emission optical properties of phosphors were observed and analyzed by fluorescence spectrometer. Conducted theoretical research on concentration quenching and energy transfer. Under 613 nm emission, O^2-→Eu³⁺ charge transfer band appears at 270 nm to 290 nm, peaks appear at 395 nm and 465 nm, the peak at 465 nm is the highest, corresponding to the ⁷F₀→⁵D₂ transition. Under 465 nm excitation, it is observed that emission peak is the strongest at 613 nm, corresponding to the ⁵D₀→⁷F₂ transition, and the optimal doping concentration of sodium ion is x=0.03. Theoretical calculation verified that the energy transfer in the host material is between the nearest neighbor ions. Thermal stability test analysis of the luminescent material show that activation energy of thermal quenching is 0.058 eV, and color coordinates of Ba₂YAlO₅∶0.2Eu³⁺, 0.03 Na⁺ phosphors are calculated locate in (0.61, 0.39), which is very close to the standard chromaticity coordinates (0.67, 0.33) stipulated by the International Commission on Lighting.

Kinetic of Photocatalytic Degradation of Gaseous Benzene by One-Dimensional TiO₂ Nanotubes

DU Jingjing, ZHAO Junwei, CHENG Xiaomin, SHI Fei

2020, 49(12):  2308-2312. 

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One-dimensional TiO₂ nanotubes were prepared by hydrothermal method, and also applied to the photocatalytic degradation of gaseous benzene. The effects of the dosage of TiO₂, the area of TiO₂ and the initial concentration of benzene on the photocatalytic performance were discussed, and the degradation kinetics were investigated. The results show that when the catalyst dosage is 0.5 g, the area is 180 cm², and the initial concentration of benzene is 480 mg/m³, the removal rate of benzene is up to 66%. Moreover, with the increase of catalyst dosage and area, the degradation rate of gaseous benzene increases, but the effect is gradually weakened. However, the initial concentration of gaseous benzene has a great influence on the photocatalytic degradation rate, and the process is in accord with the pseudo-first order kinetics law, which can be described by the L-H dynamic model, the kinetic equation of photocatalysis is established as r=0.003 8C_t/(1+0.587C_t).

Synthesis of Erbium Doped g-C₃N₄ Catalyst and Its Photocatalytic Degradation Activity under Red Light

XU Qili, SHEN Chaofeng, HE Changchun, SHI Wei, ZHANG Hui, YIN Yujie, TIAN Jing, ZHANG Ziyue, CHEN Na, WANG Peng

2020, 49(12):  2313-2321. 

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Graphite carbon nitride (g-C₃N₄) has become the hot research material in the field of photocatalysis. In this study, Er-doped g-C₃N₄ was synthesized by methanol-refluxing method using melamine as precursor. The resulting composite photocatalysts were characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), ultraviolet-visible-near infrared reflection spectrophotometer (UV-Vis-NIR Spectrophotometer), infrared spectrum (IR), photoluminescence spectroscopy (PL), N₂-physisorption and confocal laser scanning microscopy (CLMS). Results indicate that the rare-earth metal Er is highly disperse on g-C₃N₄ and it is favor for the introduction of nitrogen vacancies. The addition of Er optimize the energy band structure of g-C₃N₄, enhance the absorption of visible light, improve the electron-hole separation rate, furthermore, it is also found that Er/g-C₃N₄ photocatalyst process strong upconversion ability. The photocatalytic degradation of rhodamine B solution is performed under 660 nm LED red-light irradiation, and the rate constant of the Er/g-C₃N₄ is 2.0 times as high as that of pure g-C₃N₄. It is also found that the superoxide radical is the main active species for catalytic reaction in this system.

Preparation and Photocatalytic Performance of WS₂/MgAl-LDH Composite

MENG Zihui, ZHENG Guoyuan, WANG Jilin, XI Yu, LONG Fei

2020, 49(12):  2322-2330. 

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The WS₂/MgAl-LDH composite was prepared by a two-step hydrothermal method. The analysis of X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscope, transmission electron microscope and X-ray photoelectron spectroscopy show that the WS₂ nanoparticles are synthesized in situ between layers of MgAl-LDH. The composite was used as a catalyst to degrade 150 mg·L^-1 methyl orange solution with pH value of 3.The results show that the degradation rate of methyl orange solution exceeds 80% under simulated visible light irradiation for 75 min, and the cycling performance is excellent. Therefore, WS₂/MgAl-LDH composite is considered a promising photocatalyst.

Preparation and Electrochemical Performance of Flower-Like NiCo-LDH/CB Composite

ZHOU Lingli, LAN Cuiling, XIE Ruigang, YANG Yisong, QIN Fengxiang

2020, 49(12):  2331-2335. 

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The composite of three-dimensional flower-like layered double hydroxides (LDH) with carbon black (CB) was prepared by solvothermal method using ethanol as the solvent. X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM) were used to characterize the structure and morphology of the samples. Cyclic voltammetry, AC impedance, constant current charge and discharge were used to analyze the electrochemical properties of materials. The results show that the prepared NiCo-LDH/CB and NiCo-LDH/CB-D electrodes have specific capacitances of 1 520 F·g^-1 and 2 127 F·g^-1 at a current density of 1 A·g^-1 respectively when used as electrode materials for supercapacitors. Even at the high current density of 7 A·g^-1, their specific capacitance can still reach 1 438 F·g^-1 and 2 011 F·g^-1, and the capacity retention rate is 94.6% and 94.5%. Compared with pure flower-like NiCo-LDH, the introduction of CB significantly improves the electrochemical performance of the material.

Photocatalytic Properties of Core-Shell Structure CdS@C Nanocomposites

ZHANG Kecheng, MA Qiang, WANG Jian, MA Long, LU Qiang, WEI Qilong, WEI Zhiqiang, QIAO Hongxia

2020, 49(12):  2336-2343. 

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CdS@C nanoparticles with different carbon content were successfully prepared by hydrothermal carbonization method, and the phase structure, morphology, optical, photoelectric chemistry and photocatalytic properties of CdS@C were studied. The experimental results show that the shell is successfully prepared as carbon layer, and the hexahedrite structure CdS is used as CdS@C particles in the core. The morphology of CdS@C particles is mainly spherical, with uniform particle size and good dispersion. XPS spectra confirm that the carbon loading on the surface of CdS@C particles mainly existe in the form of amorphous carbon. UV-Vis spectra show that the sensitization of surface carbon in CdS@C nanocrystals increase the visible light response range and narrowed the energy gap. PL show that the luminescence intensity of carbon-coated CdS@C nanoparticles is weaker than that of pure CdS, which effectively inhibited the electron-hole pair recombination. Transient photocurrent response and electrochemical impedance spectroscopy (EIS) indicate that CdS@C nanocomposite have a good optical response and show more efficient photocarrier separation and transfer efficiency. CdS@C nanocomposite exhibites good photocatalytic activity and stability under visible light radiation, and ·O₂^- and h⁺ play major roles in photocatalysis.

Electrochemical Performance of Metal Tin Film Anodes Prepared by Electrodeposition

YU Limin, MIAO Chang, LI Rui, TAN Yi, XIAO Wei

2020, 49(12):  2344-2349. 

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The metal tin films on a copper foil with different morphologies were synthesized by electrodeposition at different current densities. The physical and electrochemical properties were further characterized by scanning electron microscope, X-ray diffraction, galvanostatic discharge-charge test, cyclic voltammetry and electrochemical impedance spectroscopy. The results indicate that the electrodeposited metal tin films prepared at 2 mA/cm² possess the densest surface and highest crystallinity. When assembled into CR2025 coin cells as anode materials, the electrodeposited metal tin film electrode delivers an initial discharge specific capacity of 752 mAh/g with a high initial coulombic efficiency of 81.65% and still can maintain 350 mAh/g after 30 cycles. In addition, the electrodeposited metal tin film electrode exhibits high electronic conductivity and lithium ion diffusion ability, in which the initial charge transfer resistance and lithium ionic diffusion coefficient are 113.3 Ω and 8.968×10^-17 cm²/s, respectively.

Synthesis by Functional-Template Induced Methodology and Photoelectrochemical Performance of Mesoporous Tungsten Trioxide

LI Dong, GAO Caiyun

2020, 49(12):  2350-2357. 

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Mesoporous tungsten trioxide (DDA-WO₃) was prepared using tungstic acid (H₂WO₄) as a tungsten precursor, dodecylamine (DDA) as a surfactant template which has structure guiding function. The specific surface area (57.3 m²·g^-1) of DDA-WO₃ was 2.35 times of 24.5 m²·g^-1for WO₃ (H₂WO₄-WO₃) prepared without DDA. X-ray diffraction (XRD) result of the DDA-WO₃ calcined at 400 ℃ indicates that a crystalline framework with disordered arrangement of pores. The crystallinity of DDA-WO₃ calcined at 400~550 ℃ is higher than each of H₂WO₄-WO₃. DDA-WO₃/FTO (SnO₂∶F) calcined at 400 ℃ generates photoanodic current density of 0.18 mA·cm^-2 at 1.0 V versus Ag/AgCl, which is about 3 times higher than that of the H₂WO₄-WO₃/FTO(0.06 mA·cm^-2). The enhanced photoelectrochemical (PEC) performance of DDA-WO₃/FTO suggests that the higher specific surface area of mesoporous structure is a dominant factor for the PEC performance rather than insufficient crystallinity. DDA-WO₃/FTO calcined at 500 ℃ still exhibites excellent PEC performance than H₂WO₄-WO₃/FTO due to higher crystallinity, although the degradation of the mesostructure at higher temperature.

Process Optimization for Fabrication of Self-Supporting Silicon Nitride Film Structure

WANG Fuxiong, XIE Wanyi

2020, 49(12):  2358-2364. 

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Generally, the self-supporting silicon nitride film structure is based on micro-nano fabrication technology. Fabrication of self-supporting silicon nitride film structure was studied in this paper, in which parameters of dry etching and anisotropic wet etching were optimized to enhance the quality of self-supporting film structure. Dry etching process included reaction gas ratio and etching time, anisotropic wet etching process involved etchant concentration and etching temperature. First, the experiments were conducted with different parameters. Then the surface morphology of the films fabricated in these experiments were observed by optical microscope, during which the ideal process condition was obtained by comparing the results. It was found that the addition of oxygen to the reaction gas can improve the effect of dry etching, and the best ratio of etching gas is V(SF₆)∶V(CHF₃)∶V(O₂)=6∶37∶3, with 2 min etching time. In wet drying, etching with a mass fraction 25% etchant can achieve the maximum etching rate and ideal surface morphology of silicon nitride film.

Preparation and Thermal Properties of Stearic Acid/Intercalated Kaolinite Composite Phase Change Material

ZHANG Meng, ZHAO Bingxin, WANG Juan, CHENG Hongfei

2020, 49(12):  2365-2370. 

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Kaolinite (K) is a common clay mineral with inherent advantages such as low cost, flame retardant, and multilayer structure. In this paper, a vacuum impregnation method was used to adsorb stearic acid (SA) into dimethyl sulfoxide (DMSO) and intercalated kaolinite (IKL) pores to prepare a composite phase change material for heat storage. Thermal properties, structure and composition of the prepared composite were tested by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), thermal gravimetric(TG), differential scanning calorimety (DSC), scanning electron microscope (SEM), and Brunauer-Emmet-Tellerare (BET). The mass ratio of SA adsorbed into IKL without leakage is as high as 32.3%, ascribed to the expansion of kaolinite interlayer. The latent heat of melting and freezing is 43.36 J/g and 43.16 J/g, and the melting and freezing temperatures is 51.9 ℃ and 51.7 ℃. In addition, the composite phase change material has excellent thermal stability. Due to the high adsorption capacity, high latent heat, good thermal stability, as well as low cost, SA/IKL composite phase change material has potential application value in practical applications.

Magnetron Sputtering Deposition and Properties of High Borosilicate Glass Films

SHI Boyuan, ZHANG Qinyu, JIANG Hong, WEN Feng, MA Yanping

2020, 49(12):  2371-2375. 

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Hig borosilicate glass films were prepared by RF magnetron sputtering on high borosilicate glass substrate using high borosilicate glass as sputtering target. The properties differences of high borosilicate glass prepared by magnetron sputtering and melting were discussed and the sputtering power on film quality was particularly addressed. The phase structure, composition, deposition rate, light transmittance, nano hardness and Young's modulus of the films were characterized and analyzed by XRD, FT-IR, XPS, SEM, stylus profiler, UV-Vis spectrophotometer, and nano indentation instrument. The results show that the high borosilicate glass thin film prepared in this experiment shows amorphous structure. When the working pressure is 0.6 Pa, the deposition rate increases with the sputtering power. By comparing transmittance of the films prepared using different sputtering powers, it is found that high borosilicate glass films do not obviously influence the transmittance of substrate, with a loss of visible light transmittance being 2% at the sputtering power of 150 W. At different sputtering powers, the nano-hardness and Young's modulus of the films first increase and then decrease with the sputtering powers, these properties reaches the peak values at 120 W, respectively increased by 3% and 3.5% with respect to the base glass substrate.

Research Progress on Preparation of Gallium Oxide Nanomaterials and Its Application in Photoelectric Detection

ZHUANG Wenchang, ZHANG Jie, LI Qintang, ZHU Wenyou, JIA Zhitai

2020, 49(12):  2376-2382. 

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In recent years, the nanostructures of semiconductor materials has attracted wide attention because of its unique and novel size-related characteristics, especially nano-metal oxides. Gallium oxide nanomaterials have excellent photoelectric properties, gas sensing properties, pressure resistance and low loss properties, which bring new opportunities to many research fields such as materials science, electronics and chemistry. In this paper,the preparation methods of nano gallium oxide are reviewed, and its application in photoelectric detection is prospected.

Research Progress on Gd-Based Coordination Polymer Molecular Magnetic Refrigeration Materials

HU Peng, ZHU Xiaoming, WANG Juntao, LI Zeyu, JI Liudi

2020, 49(12):  2383-2388. 

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As a high-efficiency, energy-saving, and environmentally friendly new refrigeration technology, magnetic refrigeration has broad application prospects in many fields such as gas liquefaction, high-energy physics, and superconducting technology. Gd-based coordination polymer molecular magnetic refrigeration materials have attracted much attention not only because of fascinating structure and excellent magnetothermal effect, but also good physical and chemical stability. In this review, the research progress of Gd-based coordination polymer molecular magnetic refrigeration materials in recent years is mainly summarized in terms of synthesis strategy, structure and performance. The structure-activity relationship and the effective methods to improve magnetothermal effect are also discussed, and the future development and problems are prospected.

Research Progress on Synthesis of Perovskite Single Crystal

ZHANG Hanhong, YE Shuai, ZHANG Fan

2020, 49(12):  2389-2397. 

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The excellent photoelectric properties of perovskite materials make perovskite solar cells one of the fastest growing photovoltaic technologies. Recent studies have found that single crystal perovskite films without grain boundaries have lower defect density, higher carrier mobility, longer carrier recombination life, higher stability and wider range of light absorption. Therefore, it is expected to prepare more efficient and stable perovskite solar cells. This article briefly introduces the basic structure and development history of single crystal perovskite solar cells, and focuses on the preparation methods of single crystal perovskite films and bulk single crystal perovskites. Beside, the efficiency of single crystal perovskite solar cells prepared by different methods are compared. Finally, the current problems and future development of single crystal perovskite solar cells are briefly analyzed and prospected.

Review of Phase Change Memory and Its Application in Neuromorphic Computation

DU Lingling, ZHOU Xiying, LI Xiao

2020, 49(12):  2398-2405. 

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With the rise of artificial intelligence and the explosive demand for data storage and computing, the improvement of memory and the efficient storage and computing efficiency similar to that of human brain are urgently needed. Therefore, it is necessary to study phase change memory and its application in neuromorphic computation. The change of resistance caused by the excitation of phase change materials (PCMs) can be used to build the spike neural network and realize the simulation of neural morphological computing system. This paper introduces the physical mechanism of phase change memory, including the phase change principle and main performance characteristics of phase change materials, and focuses on the research progress and application of phase change memory, so as to provide reference for the future development direction of this field.