Based on the self-assembled equipment, the properties of Ga2O3 films prepared by atomization-assisted chemical vapor deposition (AA-CVD) method were studied. The effects of temperature and pressure difference on the crystal qualities of Ga2O3 thin films were studied by X-ray diffraction. The results show that there is a phase structure conversion process of Ga2O3, upon the temperature improving from 425 ℃ to 650 ℃, the crystalline structure of the thin films transform from amorphous structure, pure α-Ga2O3 crystal structure to α-Ga2O3, β-Ga2O3 two-phase mixed crystal structure. The effects of temperature on the thin films’ surface morphology were characterized by atomic force microscope. When the temperature increases from 475 ℃ to 650 ℃, the root-mean-square roughness of the thin films surface decrease from 26.8 nm to 24.8 nm. At the same time, the single crystal property of the α-Ga2O3 thin film was measured by high resolution X-ray diffraction. The result shows that the thin film sample having a full width at half maximum of only 190.8″ which prepared at the temperature of 475 ℃ and at the pressure difference of 5 Pa, it can prove that the α-Ga2O3 film is a highly crystallized single-crystal materia.

Vapor equilibrium transport method is used to prepare near stoichiometric lithium tantalate crystals with high quality. However, it is difficult to prepare large-thickness crystals by this method due to its low solid diffusion rate. In this paper, based on the diffusion mechanism of lithium tantalate crystal, the diffusion of lithium tantalate crystal was carried out by asymmetric diffusion process with lithium rich atmosphere on one side of the wafer and congruent composition atmosphere on the other side. The composition and domain inversion field were characterized. The results show that the asymmetric diffusion technique provides a channel for the diffusion of anti-tantalum ion and increases the diffusion rate of anti-tantalum ion and lithium ion in the crystal, which is beneficial to the preparation of large-thickness near stoichiometric lithium tantalate crystal.

The development of low afterglow cesium iodide crystal is very important for the application of cesium iodide crystal in modern security check and medical CT equipment. In this paper, low afterglow cesium iodide crystals by co-doping were grown by an improved Bridgman method, with purified raw materials in which impurities influencing crystal afterglow were removed, the scintillation properties of the crystal were studied. The results show that the afterglow value of the crystal obtained by this method is about 0.31%@50 ms, which is much lower than that of conventional cesium iodide crystal.

The effect of growth pressure on the properties of β-Ga2O3 thin films epitaxial on c-plane sapphire substrate with 6° oblique cut angle by plasma-assisted molecular beam epitaxy were systematically studied. All of the epitaxial films present (201) orientated single-crystalline structure with smooth surface morphology. In addition, the crystalline quality and growth rate increase gradually with the increase of the growth pressure, as demonstrated by X-ray diffraction and scanning electron microscopy characterizations. According to the X-ray photoelectron spectroscopy measurement results, the percentage of oxygen vacancy and Ga3+ oxidation states decrease and increase, respectively, with increasing growth pressure, resulting in the increment of atomic ratio of O to Ga. Moreover, through the calculation of Tauc frormula and Urbach tail model, the results show that the optical band gap of the films increase from 4.94 eV to 5.00 eV, while Urbach energy decreases from 0.47 eV to 0.32 eV. These results suggest that the crystal quality and optical property of β-Ga2O3 were improved by increasing the growth pressure.

AlGaN-based materials are ideal for the preparation of ultraviolet (UV) optoelectronic devices as tunable, direct and wide band gap semiconductor materials. In the absence of access to large-size, low-cost homogeneous substrates, heterogeneous epitaxy of high-quality AlN films is the key to facilitate the development of UV optoelectronic devices. In this work, the metal organic chemical vapor deposition (MOCVD) growth pattern of AlN on sapphire substrates was adjusted to generate high density nanoscale holes, and the holes were used to reduce the dislocations of AlN. Based on this, the AlGaN quantum well structure was epitaxially developed. Deep-UV LED films in the 275 nm band were obtained by epitaxy, and a deep-UV LED device with an on voltage of 4.8V and a reverse leakage current of 2.23 μA (at -3.0 V voltage) was fabricated.

The p-type 4H-SiC are ideal materials of substrate for high-power electronic devices. However, p-type 4H-SiC single crystal substrates with high quality, large size and low resistance could not be produced in China due to technological constraints. In this paper, Al doped p-type 4H-SiC single crystal substrates with a diameter of 4-inch were prepared by physical vapor transport (PVT). Dislocation defects were tested by the corrosion of KOH on the substrate. The crystal quality was characterized by high resolution X-ray diffraction (HRXRD), the crystal polytype was determined by Raman spectrum scanning, and the resistivity was measured by non-contact resistivity tester, respectively. It suggest that as-prepared substrates with low overall dislocation density and total resistivity (less than 0.5 Ω·cm) are prepared, meanwhile their crystal quality are good and crystal polytype is stable. Furthermore, the energy band structure and density of states of pristine 4H-SiC and Al doped p-type 4H-SiC were calculated via the first-principles plane wave ultra-soft pseudopotential method. The results show that the gap width decreases and the Fermi level passes through the valence band after the introduction of Al, which is considered as the characteristics of a p-type semiconductor. This elaborate study pave the way for the large-scale production of the p-type 4H-SiC substrate with high quality and low resistance.

Two-dimensional (2D) organic semiconductor crystals are single crystal materials grown by self-assembly using intermolecular van der Waals forces. The intrinsically single crystal properties make it possess excellent electrical properties. More importantly, the enhanced interfacial properties in the 2D limit can greatly tune the device behaviors, providing the possibility to construct multifunctional interfacial devices. In addition, the exposed charge transport channel and few in-plane defects make it possible to study the intrinsic transport properties of organic electrons. At present, great progress has been made in the growth process of two-dimensional organic semiconductor crystals, however, the theoretical study of the self-assembly process of two-dimensional crystal growth is still very scarce. In this work, two-dimensional organic semiconductor crystals were successfully prepared by additive-assisted crystallization technology, the surface morphology and structure of the two-dimensional crystals were comprehensively characterized by polarized light microscopy and atomic force microscopy. For the mechanistic study of crystal growth, the SEM combined with EDS techniques were employed to study structural and compositional characterization of key nucleation interfaces. The results show that the growth material can nucleate stably at the additive interface, and it is calculated that the favorable interface constructed by the additive can reduce the nucleation barrier to 1/5 of that on the SiO2 interface. This work fully demonstrates the key role of the growth interface in crystal growth, and theoretically reveals the regulated behavior of the interface, that provides a reliable idea for the growth process design of two-dimensional organic semiconductor crystals.

In the process of growing 300 mm diameter silicon single crystal by Czochralski method, uniform diameter is the key to obtain high quality silicon single crystal. It is found in production practice that too high pulling speed causes the phenomenon of twisting crystal at uniform diameter growth stage, which leads to the crystal line fracture and then crystalloblast, and it is unfavorable to uniform diameter growth. In this paper, the origin of the twisting crystal in the growth of 300 mm silicon single crystal was analyzed by the combination of numerical simulation and theory analysis. For varying pulling speed, the correlation between crystal diameter and melt temperature distribution was established, the affecting factors on twisting crystal were obtained. The results show that with the increase of pulling speed, the supercooling zone is generated on the free surface of the melt, and continue to expand. The generation of supercooling zone is the main reason leading to twisting crystal. A method for identifying the maximum stable pulling speed is presented based on the numerical simulation of the finite element thermal field, and the method of varying the rotation speed of the crystal is proposed to improve the free surface temperature distribution of the melt, so as to avoid the crystal twisting. The results provide a guidance to the thermal field design of large diameter silicon monocrystalline growth.

In this paper, the energy band structure and properties of Nb doped ZnO with different concentration were calculated based on the first-principle of density functional theory, and the simulation results of intrinsic ZnO, Al doped ZnO (AZO) and Nb doped ZnO (NZO) were compared and analyzed. The results show that: (1) the band gap values of NZO and AZO are lower than that of intrinsic ZnO, and the band gap values of NZO with the same concentration of 6.25% are lower than that of AZO. With the increase of Nb doping concentration, the conduction band bottom and the peak density of states of NZO decrease obviously, and Nb-4d electrons occupy the main quantum states of Fermi level. (2) With the increase of doping concentration, the absorption peaks and dielectric function peaks of NZO and AZO decrease, and move to the low energy region. Among them, the absorption peaks of NZO move more obviously to the low energy region, and the imaginary part of dielectric function has new peaks at 0.42 eV and 34.29 eV respectively, which is mainly due to the transition of Nb-4d and Nb-5p electronic energy levels in the valence band. The static dielectric constant of NZO with the same concentration of 6.25% is greater than that of AZO, which indicates that NZO has stronger polarization ability, and NZO can improve the photoelectric properties of ZnO more effectively. With the increase of Nb doping concentration, the absorption coefficient and the imaginary part strength of dielectric function of NZO increase and move to the high energy region. The theoretical simulation results of NZO provide a theoretical reference for the experimental research and practical application of high valence element Nb doped ZnO.

Researchers have drawn attention to monolayer g-ZnO because of its broad absorption spectrum, but carrier recombination is an unavoidable problem for monolayer g-ZnO as a photocatalyst. How to reduce electron hole pair recombination rate and improve visible light utilization by monolayer g-ZnO are worth investigating, and builting heterojunctions and biaxial strain on them is a viable approach. As a result, this paper uses the first-principles method to investigate how biaxial strain affects the electronic structure and optical properties of g-ZnO/WS2 heterojunctions. The results show that the band gap of the g-ZnO/WS2 heterojunction is 1.646 eV, which reduces the recombination rate of photogenerated carriers due to the built-in electric field generated inside the heterojunction system. The edge of the heterojunction optical absorption spectrum, on the other hand, expands to the visible region. With the exception of the compressive strain (-2.5%) system, the absorption band edges of all strained systems show red-shift. With strain applied to the heterojunction increases, the degree of red-shift and the ability to bind charge of it increases. With the stronger strain on the heterojunction, the capacity of the hindrance of photogenerated electron-carriers recombination is stronger than that of the unstrained system. Moreover, its photocatalytic capability is also better than that of the unstrained system. The results show that the builting g-ZnO/WS2 heterojunction and biaxial strain on them have significant modulating effects on the electronic structure and optical properties of the heterojunction, making it useful for applications such as narrow-band, infrared and visible semiconductor devices, photocatalytic materials, and so on.

To solve the problem of low-frequency noise in aircraft cabin, a Helmholtz periodic structure with double labyrinth tubes was proposed in this paper. The design of labyrinth tubes greatly increases the length of tubes of Helmholtz resonator, reducing the lower limit of low-frequency band gap. The design of double opening tubes can increase the region of local resonance of the phononic crystal, therefore, the number of low-frequency band gaps increases. Firstly, the band structure and sound insulation characteristics of the structure in the frequency range from 0 Hz to 500 Hz were characterized by finite element method (FEM). It is found that the structure has multiple complete low-frequency band gaps in the frequency range from 0 Hz to 500 Hz, showing an excellent low-frequency sound insulation characteristic. Secondly, to reveal the mechanism of band gap, the equivalent circuit model was established by the method of electro-acoustic analogy. Finally, the influence factors of band gaps were analyzed by FEM and equivalent model. It is found that increasing the length of the tubes can effectively reduce the lower limit of the band gap, and a smaller lattice constant is beneficial to widen the band gap. The research in this paper further explores the influence of phononic crystal structure design on band gap and provides a new method for low-frequency noise reduction of aircraft cabin.

A new dinuclear manganese(Ⅱ) complex with bis-pyridine pendant-arms was synthesized by condensation between 3,3′-((ethane-1,2-diylbis((pyridin-2-ylmethyl)azanediyl)) bis(methylene))bis(2-hydroxy-5-methylbenzaldehyde) and 2-hydroxy-1,3-diaminopropane in the presence of manganese(Ⅱ). The complex was determined by X-ray diffraction single crystal structure analysis, and the corresponding formula is ［Mn2(C37H43N6O6)］·(ClO4)2. The results indicate that the complex crystallizes in monoclinic, space group P21/c, with a=1.096 50(19) nm, b=1.419 5(3) nm, c=3.109 4(5) nm, β=108.153(5)°. The crystal structure shows that the two manganese(Ⅱ) ions in the phenolbased macrocyclic dinuclear complex are coordinated with (Namine)2(Nimine)2O3 and (Nimine)2O4 sites, the corresponding geometry around each manganese(Ⅱ) center are decahedron and distorted octahedron. Two manganese(Ⅱ) centers are equivalently bridged by the phenolic oxygens and an acetate radical with the intermetallic separation of 0.331 6 nm. Moreover, the binding ability of the complex toward calf thymus DNA were analyzed by voltammetric and viscosity method, which indicate the bonding mode between them is weak intercalation.

In this paper, a new isopolymolybdate anion ［δ-Mo8O26］4--based complex ［Co(bipbc)(δ-Mo8O26)0.5(H2O)3］ (bipbc=4,4′-bis［(4-carboxypyridino)methyl］biphenyl) was synthesized under hydrothermal conditions. The title complex shows a 1D chain, which consists of the cyclic dinuclear cobalt complexes ［Co2(bipbc)2］4+ and ［δ-Mo8O26］4-clusters, and crystallizes in the monoclinic system, space group P21/n with a=1.147 9 (8) nm, b=1.440 9 (11) nm, c=2.082 9 (16) nm, β=93.469(2)°, V=3.438 8(4) nm3, Z=4, Mr=1 129.18, F(000)=2 204, μ=1.979 mm-1, Dc=2.181 mg·m-3, S=1.019, R1=0.056 2, wR2=0.137 7. The investigations on photocatalytic properties show that the title complex has photocatalytic activities toward the degradation of gentian violet (GV) and methylene blue (MB) under visible, even near-infrared and full spectrum light irradiation.

Two new cobalt diphosphonates with formulae ［Co4(1,4-ndpa)2(4,4′-bpy)2］·5H2O (1) and ［Co(1,4-ndpaH)］·1.5H2O (2) are isolated based on naphthalene scaffold, where 1,4-ndpa4- represents deprotonation of 1,4-naphthalene diphosphonic acid and 4,4′-bpy is 4,4′-bipyridine. The cobalt atoms are four coordinated with distorted tetrahedral geometries in both 1 and 2. Compound 1 displays a three dimensional framework structure containing ladder-like chains made up of corner-sharing tetrahedra {CoNO3} and {PO3C}. These ladder-like chains are then connected with adjacent ladder-like chains through 1,4-ndpa4-and 4,4′-bpy ligands respectively. Lattice water molecules fill the gaps in the skeleton by hydrogen bond. Compound 2 has a different type of chain structure, where the inorganic chains composed of corner-sharing {CoO4} and {PO3C} are cross-linked by only 1,4-ndpaH3- ligands into 3D open framework structures. Magnetic studies reveal that spin-orbit coupling and/or antiferromagnetic interaction of CoII is observed in compound 1.

In recent years, two-dimensional MXene have attracted more attentions owing to their excellent electrochemical performance, resulting their widely used in electrochemical energy storage field. However, traditional electrodes fabrication processes may result in the self-restacking of MXene nanosheets, which may lead to the low electrochemical performance of MXene based electrode materials. It is effective to design a three-dimensional aerogel to suppress the self-restacking of MXene nanosheets and develop high-performance MXene based electrode materials. Ti3C2Tx/rGO hybrid aerogel (A-TGA) with bidirectionally aligned structure through the bidirectional freeze casting and freeze drying method was prepared in this paper, and the mechanical performance of the hybrid aerogel was improved by the mild reduction of graphene oxide (GO). The A-TGA shows excellent mechanical properties and electrical conductivity, so it can be used as the electrode material for supercapacitors, the unique bidirectionally aligned structure provides barrier-free transport channels for electrolyte ions, which can greatly improve the electrochemical properties of A-TGA. The A-TGA shows a specific capacitance of 370 F·g-1 at 1 A·g-1 and delivers an outstanding cycling performance with a capacitance retention up to 94% over 5 000 cycles at 100 mV·s-1 scanning speed.

BixOyBrz photocatalysts display great application potential in the field of organic pharmaceutical wastewater treatment, but the high recombination rate of photogenerated electron-hole pairs limits their application. In this work, Ti3C2 with excellent electron transfer performance was selected as a cocatalyst. Firstly, Ti3C2-Ru cocatalyst was prepared by taking full use of abundant surface Ti vacancy defects and high reduction ability of Ti3C2, then Bi4O5Br2/Ti3C2-Ru composite photocatalysts were prepared by realizing in-situ growth of Bi4O5Br2 on Ti3C2-Ru surface through the ionic bonding force between Ti3C2 surface functional groups and Bi3+. This special structure ensures the directional transfer of electrons from Bi4O5Br2 to Ti3C2 and then to the reaction active site of Ru, thereby the composite catalysts exhibit higher photogenerated carrier separation rate and lower interfacial charge transfer resistance, which effectively inhibit the recombination rate of photogenerated electron-hole pairs. The photocatalytic performance of composite photocatalysts were evaluated by the sulfamethoxazole (SMX) degradation efficiency. The results reveal that the Bi4O5Br2/Ti3C2-Ru composite photocatalysts exhibit excellent photocatalytic performance on SMX degradation. The optimum removal efficiency of SMX reaches 95.1% under 75 min visible-light irradiation, which increase 36.9 percentage points of pure Bi4O5Br2 and 25.3 percentage points of Bi4O5Br2/Ti3C2, respectively. Finally, the underlying photocatalytic mechanism was elucidated based on the radical scavenging experiments and catalyst band structure. This results will provide a novel design idea for the construction of photocatalyst with pharmaceutical wastewater treatment capability.

The development of nickel-rich and low-cobalt cathode materials is currently an effective way to improve the energy density and reduce the cost of lithium-ion batteries. However, as Ni content increases, Ni-rich layered oxides have some problems, such as difficult precursor synthesis, structural instability, and high interfacial activity, which hinder the promotion of Ni-rich layered oxide cathode materials. In this paper, a structurally stable LiNi0.8Mn0.1Co0.1O2 (NCM811) cathode material was prepared by an optimized co-precipitation method, while a fast ionic conductor Li1.5Y0.5Zr1.5(PO4)3 coating was uniformly wrapped on the surface of NCM811 material to overcome the difficulties of interfacial structural instability and electrolyte corrosion. At a high cut-off voltage of 4.5 V, the discharge specific capacity of the modified sample is 214.2 mAh·g-1 at 0.2 C and up to 158.8 mAh·g-1 at 10 C, which is much higher than the 203.7 mAh·g-1 (0.2 C) and 82.7 mAh·g-1 (10 C) of the original sample. Meanwhile, the capacity retention rate of the modified sample after 200 cycles of 1 C at 4.3 V is as high as 84.7%, which is higher than that of the original sample (61.94%).

Germanium monoselenide (GeSe) has been considered to be a promising photovoltaic absorber material due to its excellent photoelectric properties such as suitable band gap, high absorption coefficient and high carrier mobility. In this paper, the thin film solar cells with the proposed structure of metal grid/AZO/i-ZnO/CdS/GeSe/Mo/glass were simulated. The solar cells output performance parameters were investigated and evaluated in response to changes in materials properties of functional layers (such as thickness, carrier concentration and bulk defect density). After optimizing the thickness and doping concentration of CdS buffer layer and GeSe absorber layer, respectively, the solar cells show a conversion efficiency of 27.59%. Finally, the effect of bulk defect density in the absorber layer on the device performance was simulated. These results show that GeSe based thin film solar cells have the potential to become a high efficiency photovoltaic device.

In this paper, Al2O3/Si foam ceramics with porosity up to 96% were prepared by simple and efficient slurry foaming method, and a large number of SiC nanowires were obtained in Al2O3/Si foam ceramics body by simple and convenient burying sintering process of coke. The growth morophology of SiC nanowires were observed and analyzed by controlling sintering temperature. The microstructure, phase composition, specific surface area, porosity, compressive strength and thermal conductivity of foam ceramics were analyzed and characterized by scanning electron microscope (SEM), X-ray diffractometer, BET specific surface area tester and electronic universal testing machine. The results show that the most SiC nanowires are obtained when sintered at 1 450 ℃. It is also observed that the presence of SiC nanowires change the inherent brittle fracture mode of alumina foam ceramics, and SiC nanowires can effectively promote its crack deflection during compression. In this study, a novel foam ceramics were prepared with three-dimensional network structure of nanowires wound on the hole wall, which provides a new method for in-situ growth of SiC nanowires inside the foam ceramics, and the application of foam ceramics in environmental filtration and catalyst carrier is expanded.

Nuclear radiation detection refers to the process of using various nuclear radiation detectors to obtain nuclear radiation information, which has a wide range of applications in the fields of military, civil and scientific research. As the core of nuclear radiation detection, nuclear radiation detectors are mainly divided into gas detectors, scintillator detectors and semiconductor detectors. Compared with gas detectors, both scintillator detectors and semiconductor detectors need crystals as core materials, and the quality of crystals largely determines the upper limit of detector performance. In order to obtain detectors with better performance, a large number of growth explorations have been carried out on single crystals. This paper reviews the latest research progress of single crystals for nuclear radiation detection in recent years, summarizes the current mainstream growth methods， including solution method, melt method and gas phase method, and the main growth methods of different single crystals for nuclear radiation detection are generalized.

Silicon carbide (SiC) is an ideal electronic material for high temperature, high frequency， and high power electronic devices. In last 20 years, with the continous development of epitaxial equipment and process, the film growth rate and quality of SiC have been significantly improved, which leads more and more applications in various industrial fields such as new energy vehicles, photovoltaic industry, high-voltage transmission industry and intelligent power stations. Different from the silicon semiconductor industry, silicon carbide devices must be processed on the epitaxial film. Therefore, silicon carbide epitaxial equipment plays an critical connecting role in the whole industrial chain, and it is also the most complex and difficult to develop equipment in the whole industrial chain. In this paper, the SiC pitaxial mechanism is briefly described. The progress of several important aspects of the SiC-chemical vapor deposition (CVD) equipment, such as reactor chamber, heating system and rotation system etc. are reviewed. The outlook for the future research key areas and direction of SiC is also given.

As one of the important transition metal oxides, Co3O4 possesses an excellent property, which leads to the fact that Co3O4 is widely used in optical, electrical, magnetic, thermal and other fields. The crystals of Co3O4 can be used as heterogeneous catalytic materials and thereby have an irreplaceable position in many reactions. With the continuous study of the catalytic mechanism, it is found that the catalytic reaction process is not only affected by the particle size of the crystal catalyst, but also is sensitive to the crystal facet. Therefore, the study on crystal facet effect of transition metal oxides is of great significance for the in-depth understanding of heterogeneous catalytic reactions and the effective design of high-active catalysts. Co3O4 crystal has spinel structure with a mixed valence state of octahedral coordinated Co3+ and tetrahedral coordinated Co2+, and it shows the obvious crystal facet effect in different catalytic reactions. In this paper, the crystal facet effects of Co3O4 as heterogeneous crystal catalyst in thermal catalysis, photocatalysis, electrocatalysis and peroxidase-like catalysis in recent years are systematically reviewed. In combination with theoretical calculations, the reasons of these crystal facet effects are explained from the atomic structure of different crystal facets of Co3O4. Finally, the general law of crystal facet effect of Co3O4 in the above reactions is summarized, the shortcomings in current study on Co3O4 crystal facet effect are discussed, and the future development trend is reasonably prospected.