Crystal Research and Technology最新文献

As an important III–V semiconductor material for infrared applications, gallium antimonide (GaSb) single crystals require high quality with excellent lattice perfection, making it necessary to establish an ideal thermal field during the liquid encapsulated Czochralski (LEC) growth process. In this study, global transient numerical simulations are carried out to analyze the effects of growth parameters on the temperature distribution, melt convection structure, and solid–liquid interface deflection during the LEC growth of 3-inch-diameter GaSb crystals. Additionally, an innovative bottom heater is introduced to optimize the thermal distribution. The simulation results demonstrate that the number of melt vortices decreases from three to two when the crucible rotation rate is 2 rpm, significantly reducing the solid–liquid interface deflection. A pulling rate of 8 mm/h reduces local overheating at the interface, thereby minimizing deflection and promoting stable growth. The addition of a bottom heater improves the melt temperature distribution, reduces melt flow intensity, and enhances interface flatness. The average etch pit density (EPD) of the 3-inch (100) GaSb substrate is reduced from 2842 to 147 cm⁻² after thermal field optimization, demonstrating a 94.8% reduction in dislocation density. This work establishes a scalable framework for the optimization of compound semiconductor crystal growth.

In this study, the crystal forms P and L of gimeracil are prepared and characterized by various solid-state analysis methods (powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), polarizing microscope (PLM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic vapor sorption (DVS)). The melting point, solubility, crystal habit, and hygroscopicity of the two crystal forms are better understood. By combining the competitive slurry experiment, hot stage microscopy (HSM) experiments, and dynamic method measurements of the solubility curves of two crystal forms in purified water, methanol, ethanol, isopropanol, and n-butanol, the transformation relationship between the two crystal forms is studied. Crystal form L is a thermodynamically stable crystal form relative to crystal form P. At the same time, various methods for preparing crystal forms P and L are studied. Overall, this study provides a reference for crystal forms' transformation relationship and selective control of crystal forms.

Aluminum Nitride (AlN), an ultra-wide bandgap semiconductor, boasts a direct bandgap of 6.2 eV, exceptional thermal conductivity (340 W m⁻¹ K⁻¹), and a high breakdown electric field (15.4 MV cm⁻¹), making it highly attractive for deep ultraviolet optoelectronics and high-frequency power applications. Despite these advantages, the industrial deployment of AlN is impeded by the challenges in producing large, defect-controlled single crystals. The Physical Vapor Transport (PVT) method has emerged as a leading technique for fabricating high-quality AlN crystals. This review systematically examines recent technological breakthroughs in PVT-grown AlN, including both homogeneous and heterogeneous substrate strategies, thermal field and stress management, mechanisms of point defect formation, and the integration of simulation techniques for process optimization. Innovations in temperature gradient control, gas-phase composition, seed crystal orientation, and novel crucible designs have enabled the stable growth of 2–4 inch AlN single crystals with markedly reduced impurity levels. Future research should emphasize the integration of multi-scale modeling with experimental validation to surmount existing growth limitations and accelerate the practical application of AlN in advanced electronic devices.

In this work, the effect of sulfide concentration on the passivation behavior and film chemistry of CoCrFeNiTiMo_0.1 high-entropy alloy (HEA) is systematically investigated by electrochemical measurements and XPS methods. Electrochemical results elucidate that sulfide can tremendously exacerbate the passive film degradation kinetics as reflected by the raised dissolution current. The main reason that sulfide has a detrimental influence on the passivation behavior and the anti-corrosion behavior is also discussed in detail. The sulfide can exhibit preferential adsorption in the passive film, which can prevent the passivation process by competitively occupying the coordination sites for hydroxyl ion adsorption that are hydroxylation precursors. Moreover, due to the adsorbed responses, the composition, thickness, defect density, and compactness of the passive film are altered, triggering in distinct differences in the structural changes of the passive film. This results in a significantly aggravating effect on its corrosion behavior consequently.

Fluorene (C₁₃H₁₀) single crystals (4 ×3 × 0.5 mm³) were grown via slow evaporation at room temperature to evaluate their potential for organic scintillator applications. Powder X-ray diffraction (PXRD) confirmed an orthorhombic crystal system. Ultravioletvisible (UVVis) spectroscopy showed a 3.7 eV optical band gap, 330 nm cutoff, and 52–70% transmittance. Proton nuclear magnetic resonance (¹H NMR) validated aromatic and methylene environments. Thermal analysis (TGA/DTA) revealed stability up to 113 °C, with defined melting and decomposition points. Photoluminescence (PL) exhibited blue emission at 428 nm under 330 nm excitation. Fourier-transform infrared (FTIR) and Raman spectroscopy identified functional groups and vibrational modes. Fluorescence lifetimes measured by time-correlated single photon counting (TCSPC) were 1.1 ns (prompt) and 5.1 ns (delayed), supporting fast response behavior. Density functional theory (DFT) with the B3LYP/6−311G++ basis set and time-dependent DFT (TD-DFT) described the optimized structure, HOMOLUMO gap, electrostatic potential, and excited states. Hirshfeld surface analysis showed dominant H···H interactions (54.3%), indicating efficient packing and energy transfer. Overall, fluorene exhibits desirable optical, thermal, and electronic properties, making it a promising material for organic scintillation detectors.

Quantum dots (QDs) are semiconductor nanocrystals with superior quantum efficiency, narrow emission linewidths, and tunable bandgaps, making them valuable in optoelectronics. However, their commercialization is hindered by instability under stress and environmental concerns related to heavy metal leaching. To address these issues, advanced encapsulation strategies, particularly using inorganic glass matrices (silicate, phosphate, borate), are crucial. This review examines the structure-property relationships between these matrices and QD variants (perovskite, chalcogenide). It highlights how glass host engineering through network modifiers and phase separation control affects QD growth, defect passivation, and stability. Host-guest interactions at the glass-QD interface enhance photoluminescence quantum yield (15–40%), narrow emission linewidths, and improve thermal quenching resistance (30–50% efficiency retention at 150 °C). These advancements enable emerging applications in solid-state lighting, mini-LED backlights, and X-ray detectors. This analysis provides insights into glass-mediated QD engineering and paves the way for eco-friendly photonic materials.

This article focuses on the growth and analysis of bulk-size glycine zinc sulphate pentahydrate (GZS) single crystal. The structure of the compound is initially analyzed by single-crystal X-ray diffraction. Hirshfeld surface (HS) is analyzed to visualize the distribution of electron density in the GZS crystalline structure. The laser damage threshold (LDT) of GZS is measured using a nanosecond pulsed laser at 1064 nm. Thereafter, the thermal behaviors are examined through thermogravimetric analysis at different heating rates. The activation energy calculations are performed through the Coats-Redfern method. To see the response of GZS crystal under shock wave application, changes in the crystalline quality and optical transmittance are noted. Rocking curve is recorded and FWHM values are calculated to examine the defect behavior due to shock and it is correlated to the transmittance spectra obtained through UV–vis spectroscopy. Bandgap are calculated by Tauc's plot to see the phase stability of the compound under shock wave treatment.

The magneto-optical Kerr effect (MOKE) reflects the spin-orbit coupling in magnetic materials, so it can become a fundamentally important tool for studying the electronic structure of materials. Here the MOKE, and the ultrafast demagnetization process is presented for Bi and Mn-doped Y₃Fe₅O₁₂ films with perpendicular magnetic anisotropy. The structural characterization indicated horizontal dipping has a large growth rate compared to vertical dipping, which will reduce cracks and improve the crystal quality. By analyzing the MOKE signals in different magnetic field directions and comparing them with the theoretical equations, it can be found that the quadratic MOKE values of YIG samples originate from the large perpendicular magnetic anisotropy previously described in YIG samples. Time-resolved MOKE measurements show that with increasing Bi³⁺ content, the spin-orbit coupling is enhanced, which results in the spin-lattice relaxation time constants becoming smaller, and the magnetization recovery processes are accelerated.

The transformation between aragonite and calcite, the two most common CaCO₃ polymorphs, is encountered both in geological and biological (nacre-like) minerals. Recently, the origin of the new polymorph hexaragonite at room temperature and pressure and analysed in detail the homoepitaxy as a new physical phenomenon for both structures is discussed. Here, at first distinguishing epitaxy from topotaxy, which rules the main mechanisms of calcite-aragonite transitions. Then, attempt to move from qualitative to quantitative descriptions of these transitions. Hence, it will deal with 2D (epitaxy) and 3D (topotaxy) conversions in the polymorphic system, in order to gain insight into their differences, resulting from literature experiments and calculation constraints.