In order to realize the monolithic integration of Ⅲ-V devices on silicon platform, the heteroepitaxy of Ⅲ-V semiconductor on silicon substrate has been widely studied in recent years. Due to the large lattice mismatch and different lattice structure between Ⅲ-V semiconductor and Si, there are many mismatches and antiphase domains in Ⅲ-V semiconductor grown on Si, which have a serious impact on device performance. However, the diatomic steps on Si (111) surface can avoid the formation of antiphase domains. In this work, GaAs (111) films were grown on Si (111) substrate by molecular beam epitaxy, and Al/AlAs was used as intermediate layer for the first time. A series of samples were grown to optimize the growth conditions of Al/AlAs interlayer and it is shown that Al/AlAs interlayers have positive effect on the quality of subsequent GaAs films. On this basis of the Al/AlAs interlayers, the GaAs films were grown by two-step method and the growth conditions were optimized. The results show that Al/AlAs interlayers provide a template for the epitaxial growth of GaAs and release the mismatch strain between GaAs and Si to a certain extent, so that the crystal quality of GaAs films can be improved. All of the above-mentioned work can provide new ideas and pathways for the growth of Ⅲ-V semiconductor on silicon.

The waveguide structure made of lithium niobate crystal (LiNbO3, LN) can further improve the device integration. It has been widely used in electro-optical modulator, frequency conversion, acousto-optic Q-switching and other optoelectronic devices. It has important application prospects in optical fiber communication, photoelectric sensing, lidar, aerospace and other fields. The LN waveguide made by traditional Ti diffusion method has poor resistance to photorefractive damage in short wave applications. The LN waveguide made by annealing proton exchange method only support TM mode (transverse magnetic mode) single polarization transmission, and its application field is limited. In this paper, a new Zn diffusion method is proposed to fabricate magnesium doped LN ridge waveguide. By establishing the diffusion model and simulation of the waveguide, the technological conditions were explored and tested. The lowest transmission loss of LN waveguide is 0.86 dB/cm, and the photorefractive damage threshold can reach 184 kW/cm2. It will provide a better preparation way for the research and development of high power lithium niobate waveguide integrated optoelectronic devices.

In this paper, a trapezoidal periodically poled magnesium doped lithium niobate (PPMgLN) waveguide was designed, and its acceptable bandwidth of the pump source during frequency doubling (SHG) process can be widened by introducing a temperature gradient along the propagation direction. The effective refractive index of the waveguide was calculated and the dimension of the waveguide was designed by the finite difference beam propagation method. The results show that, by changing the temperature at different positions of the trapezoidal waveguide to form a temperature gradient, the wavelength receiving bandwidth of the pump light source can be widened. The maximum receiving bandwidth of the PPMgLN waveguide pump light source designed in this paper is C-band, which range is from 1 530 nm to 1 565 nm. The waveguide can double the frequency of C-band, and the output band bandwidth is 765 nm to 782.5 nm, and the temperature tuning range is from 30 ℃ to 150 ℃.

Acoustic barriers with Helmholtz resonant structures have potential in controlling traffic road noise. In order to effectively improve the noise control in a specific frequency band, a Helmholtz composite resonator structure with four secondary resonators is designed in this paper. Firstly, the finite element method is used to calculate and analyze the resonator model, and the band gap structure and sound transmission loss curve of the resonator are obtained. Secondly, the equivalent circuit of Helmholtz resonator is established by acoustic-electric analogy method, and the generation mechanism of band gap is analyzed. Finally, the influence of structural parameters on the band gap of Helmholtz resonator is discussed, and the mechanism of these parameters on the lower limit of the first band gap is analyzed. The results show that the sound wave has interaction and cavity resonance effect among the Helmholtz cavity elements at the same time. The first band gap in the range of 432.43 Hz to 663.98 Hz can be obtained when the lattice constant is 60 mm, which is lower than the initial frequency of the band gap of the opening ring. The sound insulation in most frequency ranges reaches more than 10 dB, and the maximum sound insulation exceeds 90 dB, which shows better intermediate frequency sound insulation characteristics. The maximum error between the equivalent circuit model and the calculated value of the finite element method does not exceed 10% and the average error is less than 5%, the established equivalent model is reasonable. The structure parameters have a great influence on the band gap by affecting the volume of gas in the cavity.

In this paper, Fe2+∶ZnSe laser crystal with a size of 22 mm×4 mm was obtained by double temperature zone thermal diffusion doping method using CVD ZnSe wafer as the host material and FeSe powder as the dopant. SIMS show that iron ion concentration on the surface of the crystal sample is 3.43×1018 cm-3, and the valence state of iron in the crystal sample was analyzed by XPS. The transmission spectra of Fe2+∶ZnSe laser crystals were tested by UV/Vis/NIR spectrophotometer and Fourier transform infrared spectrometer, presenting that there is an obvious Fe2+ absorption peak at 3.0 μm with the peak transmittance of 5.5%. Fe2+∶ZnSe crystal with a size of 10 mm×10 mm×4 mm was pumped by Cr, Er∶YAG laser with a wavelength of 2.93 μm at 77 K, obtaining a mid-infrared laser output of 191 mJ and a center wavelength of 4.04 μm with the light-to-light conversion efficiency of 13.84%.

A gadolinium-scandium-aluminum garnet single crystal (Gd3Sc2Al3O12, GSAG) co-doped with 2%Dy3+ and 1% Tb3+ (atomic number fraction) was grown by Czochralski method. The morphology of etched defect on the crystal surface of (111) plane was studied and the mechanism for the formation of the defects was discussed. Besides, the Vickers hardness and Mohs hardness of the (111) plane were also characterized and calculated. On the condition of 0.2 kgf loading and 10 s keeping time, the Vickers hardness for the (111) plane is 1 267 kg/mm2, corresponding to the Mohs hardness of 7.3. The results have reference value for revealing the origin of defects in mixed garnet crystals and exploring the growth technics for high quality crystals.

Synthesis conditions of Aurivillius structure Bi2MoxW1-xO6 series and the composition range of solid solution were explored by solid phase reaction method, and the flux growth system of Bi2MoxW1-xO6 crystal was explored. The structure, variable temperature dielectric property and resistivity of the crystal were measured and analyzed. Due to their large spontaneous polarization and high Curie temperatures, ferroelectric Aurivillius Bi2MoxW1-xO6 have attracted tremendous research attention in petroleum mining industries, communication equipments, meidcal ultrsonic diagnostics, structural health monitoring, et al. In this study, the composition variation range of n(Mo)∶n(W) ratio in Bi2MoxW1-xO6 solid solution were studied in detail through changing the sintering temperature and dewelling time. According to the synthetic results, the proportion(x) of Mo in the solid solution can be continuously tuned in the range of 0 to 1, and the pure ferroelectric phase of Bi2MoxW1-xO6 can be synthesized under different temperatures in the range of 500 ℃ to 870 ℃. Growth of the Bi2MoxW1-xO6 single crystals through the high temperature solution method were also explored systematically. By employing Li2B4O7-Bi2O3 (molar ratio 2∶1) as a flux, centimeter-sized Bi2WO6 single domain crystals were grown with the thickness of about 2 mm and the maximum dimension reaching as large as 40 mm. Centimeter-sized single domain crystals of Bi2Mo0.15W0.85O6 with the thickness of about 1 mm were also grown in n(Bi2O3)∶n(MoO3)∶n(WO3)∶n(Li2B4O7)=1∶1∶1∶1 (molar ratio) flux system. Structural refinement reveals that Bi2Mo0.15W0.85O6 crystallizes into the orthorhombic system, Aba2 (No.41) space group. Variable temperature dielectric measurements show that the dielectric constant ε33 increases from 70 of Bi2WO6 crystal to 102, and the temperature at which the dielectric relaxation occurs decreases from 430 ℃ of Bi2WO6 crystal to around 330 ℃. The temperature varying resistivity shows that the resistivity of Bi2WO6 and Bi2Mo0.15W0.85O6 crystals both decrease with the increase of temperature. Below 100 ℃, the resistivity of Bi2WO6 is higher than that of Bi2Mo0.15W0.85O6 crystal, and with the increase of temperature, the difference of resistivity between the two crystals is gradually narrowing.

Molybdenum disulfide (MoS2) has good thermal and chemical stability and relatively high mobility in the environment. It has been used in the applications of gas sensors, photodetectors and field effect transistors. Oxygen-doped molybdenum disulfide (MoS2-xOx) generated by oxygen-assisted technology can not only regulate the size of MoS2 single crystal, but also improve the photoluminescence intensity of MoS2 single crystal. MoS2-xOx films were prepared and their optical properties were investigated in this paper. First, radio frequency reactive magnetron sputtering technology was used to prepare the precursors of MoS2-xOx films; next, the precursors in natural environment for 60 d were oxidized; finally, the MoS2-xOx films after a thermal annealing process were obtained. Herein, the angle between the sputtering plume and the glass substrate was specifically varied. The optical properties of MoS2-xOx films were investigated. X-ray photoelectron spectroscopy was used to analyze the elements and valence states of the samples. Scanning electron microscopy results show that the surface morphology is optimal at an angle of 45° (θ=45°) between the sputtering plume and the substrate. UV-Vis spectrophotometry results show that the optical band gap of the MoS2-xOx films decreasing as the thickness and oxygen content increasing. COMSOL Multiphysics software was utilized to simulate the transmittance of MoS2-xOx films, and the theoretical and experimental results agree well. The results of this paper will provide experimental data reference for the application of MoS2-xOx in the field of optical devices.

CdZnTe thin films were prepared on ITO glass by magnetron sputtering method to explore the effect of mechanical grinding and polishing on the resistive switching characteristics of CdZnTe thin films. Through the analysis of experimental results such as XRD patterns, Raman spectroscopy, AFM micrograph, etc., the physical mechanism of mechanical grinding and polishing affecting the resistive switching characteristics of CdZnTe thin film was elucidated. The results show that the thin films prepared by magnetron sputtering are sphalerite structures with F43m space group. Mechanical grinding and polishing improves the crystallization quality of CdZnTe thin films; the roughness (Ra) of CdZnTe film decreases from 3.42 nm to 1.73 nm after grinding and polishing. Transmittance of CdZnTe thin film after grinding and polishing and the vibration peak of CdTe-like phonon peaks at 162 cm-1 were enhanced. After grinding and polishing, the resistive switching ratio of CdZnTe thin film increases from 1.2 to 4.9. The reason why mechanical grinding and polishing improves the quality and resistive switching characteristics of CdZnTe thin films may be that CdZnTe thin films are recrystallize during the grinding process.

Since the discovery of graphene, various two-dimensional materials with novel properties have attracted more and more attention. Janus two-dimensional materials have asymmetric surface properties. These special structures often have peculiar electrical, magnetic and optical properties, which have become a research hotspot in the field of material science in recent years. In this paper, the structures of Janus two-dimensional materials CrXX’(X/X’=S, Se, Te)(CrSSe, CrSTe, CrSeTe) were built, their electronic, magnetic, optical properties were studied, and the effect of biaxial strain on above properties was studied. In terms of electronic structure, the results show that CrSSe, CrSTe and CrSeTe are metallic and excellent conductors of electrons. Biaxial strain does not change their metallicity, which means their electronic structure has good robustness. In terms of magnetic properties, due to the contribution of unpaired electrons in the 3d orbital of Cr atom, CrXX’(X/X’=S, Se, Te) have long range magnetic ordering. By applying tensile strain, their magnetic moments increase, and by applying compressive strain, their magnetic moments decrease. In addition, CrXX’(X/X’=S, Se, Te) have higher Curie temperature. The Curie temperature of CrSSe is 165 K, that of CrSeTe is 195 K, and that of CrSTe is 310 K, which is above the room temperature. For optical properties, the results show that CrXX’(X/X’=S, Se, Te) have excellent absorption capacity of visible and ultraviolet light, which is about 50% higher than that of typical light absorption material graphene. Their light absorption coefficients can be adjusted by applying strain, compressive strain and tensile strain can move the absorption spectrum to short wave and long wave respectively. In conclusion, this work provides theoretical guidance for the further study of the application of two-dimensional monolayer CrXX’(X/X’=S, Se, Te) in the field of new room temperature spintronic devices.

The electronic structures and magnetic properties of the bulk Fe2Ge and its (001) surfaces were calculated by the pseudo-potential plane wave method based on the first-principle of density functional theory. Here, two types of the terminated (001) surfaces were considered: Ge(Ⅰ)-(001) surface and Ge(Ⅱ)-(001) surface. For the electronic structures, the different types of the Fe2Ge (001) surfaces all show metallic characteristics, which are in agreement with the bulk counterpart. For the magnetism, the Ge atoms are ferromagnetic spin ordering in the bulk and Ge(Ⅱ)-(001) surface, while the Ge atoms are ferrimagnetic spin ordering in the first layer of the Ge(Ⅰ)-(001) surface. Moreover, the spin magnetic moment of the Ge atoms in the Ge(Ⅱ)-(001) surface are better than those of the bulk and Ge(Ⅰ)-(001) surface. These results are related to the hybridization between the Fe d and Ge p states, which were discussed by analyzing their density of states.

Cu foils play an important role in preparing high quality of graphene films by chemical vapor deposition. For the commonly used commercial Cu foil, the nucleation density of graphene is high due to the associated defects in the manufacturing process of Cu foil. In this work, different substrates containing polished aluminum plate, polished stainless steel plate, glass ceramics, and SiO2/Si were selected as substrates to prepare distinct Cu foils with different roughness by thermal evaporation method. Then the growth conditions of high flatness graphene films and the effect of Cu foils on graphene films were discussed in detail. The results show that Cu foils are predominantly (111) orientation, and keep the surface with nanometer-level flatness after separation from substrates. After the growth of graphene, the nucleation density of Cu foil peeled from SiO2/Si is the lowest among these four kinds of substrates. At the same time, its crystal structure has almost no change and has good crystallinity. There are nearly no Cu grain boundary defects on the surface of the Cu foil peeled from SiO2/Si. When the pressure is 3 000 Pa and the flow rates of hydrogen and methane are 300 mL/min and 0.5 mL/min, respectively, a graphene single crystal domain with a lateral dimension of about 1 mm can be obtained.

Carbon nanotubes, as a successful conducting agent for power lithium ion cathode, have been applied in a large scale. Among the production of carbon nanotubes, the purification of carbon nanotubes is an important step for the application in lithium ion power battery. In this paper, physical purification, instead of chemical purification, of as-carbon nanotube soot in an Acheson furnace was investigated. The carbon nanotubes were first purified in an Acheson furnace at 3 000 ℃ and 2 800 ℃ respectively. Then, metal content, burning residue content of these purified carbon nanotubes were measured with ICP, EDS, and thermos-gravimetric analysis (TGA). And their resistivity were detected with a four-probe film resistance instrument. The micro structure and surface characteristics of these carbon nanotubes purified at different temperatures were characterized by SEM, XRD, FT-IR. The results show that the carbon nanotubes purified respectively at different high temperatures in Acheson furnace can be effectively reduced in metal content and burning residues, and these carbon nanotubes, as conductive agent can meet the requirements of power battery. Compared with the non-purified carbon nanotubes, the resistivity of carbon nanotubes purified at 3 000 ℃ decreases significantly and the crystallization degree of graphite increases, while the resistivity of carbon nanotubes purified at 2 800 ℃ increases slightly, the degree of graphite crystallization did not change much, and the quantity of their surface functional groups decreases.

A series of novel Sr7-xSb2O12∶xDy3+(x=0~0.35) (mole percentage) phosphors were obtained by high temperature solid-state reaction. Its phase structure, luminescence properties, thermal stability and fluorescent decay lifetime were investigated. The characteristic emissions centered at 482 nm and 576 nm of Sr7-xSb2O12∶xDy3+ were observed under the excitation light of 350 nm. When x=0.056, the Dy3+ concentration quench, and the Sr6.944Sb2O12∶0.056Dy3+CIE chromaticity coordinates are (0.340 8, 0.349 3). The quenching mechanism is attributed to the dipole-dipole interaction between Dy3+. When x=0.14, the phosphors can emit white light with color coordinates (0.310 9, 0.314 0). In addition, the luminescence intensity of Sr7-xSb2O12∶xDy3+ at 453 K is about 83.3% of that at room temperature, showing good thermal stability. The above research results suggest that the Sr7-xSb2O12∶xDy3+ phosphor is expected to be used in UV-excited white light emitting diode.

In order to improve the photoelectric conversion efficiency of n-type interdigitated back contact (IBC) solar cells, the selective emitter structure was prepared by screen printing boron paste and high temperature diffusion, the effects of boron diffusion and screen printing on the passivation and contact properties of the cells were studied. The experimental results show that when the deposition time and annealing time of boron diffusion remain unchanged, the BBr3 flow rate is 100 mL/min, the deposition temperature is 830 ℃, and the annealing temperature is 920 ℃, the implied open circuit voltage of light doping emitter (p+) reaches 710 mV, and the dark saturation current density reaches 12.2 fA/cm2. When the consumption of the locally printed boron paste at the emitter is 220 mg, after high temperature annealing on boron diffusion, the implied open circuit voltage of heavily doping emitter (p++) remains at about 683 mV, the sheet resistance is only 46 Ω/□, and the metal contact resistance is 2.3 mΩ·cm2. The highest photoelectric conversion efficiency and average photoelectric conversion efficiency of IBC cells prepared by this process are 24.40% and 24.32%, compared with the IBC cells before optimization, the conversion efficiency is improved by 0.28 percentage points.

In this paper, organic-inorganic hybrid perovskite (MAPbI3) optical absorption layer thin film with different thickness was prepared by controlling the concentration of PbI2(DMSO) solution by two-step method, and a large area perovskite solar cell based on carbon electrode hole-free transport layer was assembled. The crystal phase, optical absorption properties, surface morphology and elemental composition of MAPbI3 optical absorption layer films with different thickness were analyzed, and the photovoltaic performance of perovskite solar cells prepared based on MAPbI3 film were further tested. The results show that the thickness of MAPbI3 photoabsorption layer is positively correlated with the concentration of PbI2(DMSO). The thickness of MAPbI3 optical absorption layer prepared by 1.3 mol/L PbI2 solution is about 350 nm, which has good crystallinity and optical absorption intensity, and the surface of the film is compact and smooth without obvious defects. Finally, the perovskite solar cell based on 350 nm MAPbI3 optical absorption layer achieves 8.48% photoelectric conversion efficiency.

In our group, the organic compounds 2, 5-dibromoterephthalic acid (H2L1) and 2, 2′-bipyridine (L2) were used as biligands to react with zinc sulfate heptahydrate (ZnSO4·7H2O) and cobalt nitrate hexahydrate (Co(NO3)2·6H2O), respectively, using solvothermal method to obtain a zinc complex ［Zn(L1)(L2)(H2O)］n (1) and a cobalt complex ［Co(L1)(L2)(H2O)］n (2). The structural characterization and properties measurement were performed by single crystal X-ray diffraction, elemental analysis, infrared spectroscopy, ultraviolet spectroscopy, fluorescence spectroscopy, thermogravimetric analysis and other tests. The results show that complex 1 is a monoclinic crystal system with one-dimensional chain structure formed by the coordination of Zn2+ linking L2-1 and L2, each chain forming a three-dimensional network structure by regular stacking under intermolecular hydrogen bonding and π…π conjugation. Complex 2 is a triclinic crystal system with Co1 and Co1i ions linked by carboxylic acid oxygen atoms O4 and O4i on H2L1 to form a bidentate chelated ligand structural unit. A two-dimensional lattice structure is formed with Co2+ ligands connecting L2-1 and L2, and the layers are regularly stacked under O-H…O intermolecular hydrogen bonding and van der Waals forces to form a three-dimensional network structure. Both complexes 1 and 2 contain aromatic heterocycles, carboxyl heterocycles and nitrogen heterocycles, they have good fluorescence property and thermal stability, the maximum emission wavelengths of complex 1 and complex 2 are 345 nm and 333 nm, respectively.

The nickel (Ⅱ) complex ［Ni(PCPA)2(phen)H2O］ was synthesized by solvent evaporation method, with p-chlorophenylacetic acid(PCPA), 1, 10-phenanthroline(phen) and nickel sulfate hexahydrate as main raw materials. The crystal structure of the metal-organic complex was determined by single crystal X-ray diffraction method. The results show that complex crystallizes in the monoclinic space group P21/n with each asymmetric unit consisting of one Ni(Ⅱ) ion, two p-chlorophenylacetic acid ligands and one 1, 10-phenanthroline ligand.Fluorescence spectrum analysis shows that the excitation peak of complex is 336 nm, emission peak of complex is 393 nm. The thermal stability study shows that the complex is stable at room temperature. The magnetic measurement result shows that intramolecular antiferromagnetic interaction is observed in complex.

In this paper, the nano-p-CuO/n-T-ZnOw composite catalysts were prepared by chemical deposition method, and the effects of polyethylene glycol-600 (PEG-600) concentration in the synthesis system on the phase, microstructure and photocatalytic activity of samples were discussed. The results show that PEG-600 plays an important role in the deposition of CuO nanoparticles on the surface of T-ZnOw in the synthesis system, with the increase of PEG-600 concentration, the denser p-CuO nanoparticles deposited on the surface of n-T-ZnOw. All the compounds exhibit excellent photocatalytic activity in decomposing of methylene blue (MB) and methyl orange (MO) under UV light than that of T-ZnOw, the photocatalytic activity of the samples increase with the increasing of PEG-600 concentration up to 0.6 mol/L, while it decreases when further increasing the PEG-600 concentration. This study is expected to provide a reference for the facile and low-cost preparation of high-performance of nano-p-CuO/n-T-ZnOw composite catalysts.

In this work, novel lead-free relaxor ferroelectric (1-x)［0.9BaTiO3-0.1Bi(Mg0.25Ta0.5)O3］-xBi0.5Na0.5TiO3ceramics were synthesized via composite strategy using the traditional solid-state process. Results indicate that the incorporation of Bi0.5Na0.5TiO3 with a high Curie temperature could not only significantly enhance the energy storage density, but also improve the temperature stability. As BNT concentration rose, the nano-scale polarization mismatch dominated by Bi-O coupling was established and enhanced, significantly compensating for the reduction of macroscopic polarization due to the addition of Bi(Mg0.25Ta0.5)O3, leading to elevate saturation polarization and improve temperature stability. The ceramics which x is 0.2 show optimal energy storage features with a high energy storage density of 4.01 J/cm3 in the electric field of 245 kV/cm combined with a relatively high energy storage efficiency of 84.86%. Moreover, excellent temperature stabilities were noticed with the change rate of energy storage density is less than 5% and energy storage efficiency is less than 6% over a broad temperature range (20~170 ℃).

As the representative of the third generation semiconductor materials, SiC has excellent physical and chemical properties. With the development of materials and applications, SiC substrates are increasingly important in aerospace power supply, electric vehicles, smart power grids, rail transit, industrial motors and other fields. Compared with the first generation of semiconductor materials such as Si and the second generation of semiconductor materials such as GaAs, the quality of SiC substrate which has a lot of room for improvement, is the current research and development and industry hot spot. The detection and reduction of SiC single crystal defects, especially one-dimensional dislocation defects, is an important research content in the last ten years. This review focuses on the formation of dislocation in SiC, dislocation detection techniques, methods of reducing dislocation density and the optimization level of dislocation in SiC single crystal in recent years. Finally, the paper puts forward the direction of SiC's further breakthrough and development.

Porous silicon has the characteristics of large specific surface area and good luminescent properties. At present, the research on porous silicon has been involved in the fields of biological and chemical sensors, drug delivery, photocatalysis, energy and so on. The pore of porous silicon can effectively reduce the volume expansion in the process of silicon lithiation, shorten the distance of lithium ion diffusion from electrolyte to silicon, and promote the charge-discharge process at high current density. Therefore, porous silicon has been widely studied and developed in the field of energy storage. However, some challenges still exist, such as preparation cost, etching mechanism, regulation of porous structure, and electrochemical performance of porous silicon, which cannot meet the requirements of commercial application. The current research on the preparation methods of porous silicon at home and abroad is reviewed in this paper, and the application of porous silicon in lithium ion battery is introduced in detail. Finally, the development of porous silicon materials in energy storage field is prospected.