Crystal Research and Technology最新文献

The rapid advancement of terahertz (THz) technology has driven an increasing demand for efficient THz sources and detectors, particularly in applications such as spectroscopy, imaging, and wireless communications. Organic (NLO) crystals, renowned for their high nonlinear coefficients, tunability, and flexible molecular design, have emerged as highly promising materials for THz generation. This article highlights the latest progress in the design, synthesis, and investigation of novel organic NLO crystals demonstrating exceptional THz activity, with a focus on recent breakthroughs in ionic and molecular crystals. The discussion delves into the pivotal roles of crystal packing, molecular engineering, and functional group modification in optimizing nonlinear optical properties. Furthermore, the article explores strategies for performance enhancement through molecular engineering and functional group modification, offering insights into the mechanisms driving these advancements. Based on cutting-edge research on advanced NLO crystals, this study examines future research directions and potential applications, emphasizing the critical need for improved crystal growth techniques, refined theoretical modeling, and enhanced material stability. By providing a comprehensive review of the current state of organic THz optical crystals, this article aims to illuminate the challenges and opportunities within this rapidly evolving field, paving the way for future innovations.

Third-order nonlinear optical behavior, i.e., nonlinear refraction (n₂), absorption coefficient (β), and third-order susceptibility χ⁽³⁾of an organic single crystal guanidinium benzenesulfonate are investigated under the excitation of Q-switched Nd-YAG laser pulsed radiations (532 nm and 1064 nm) by Z-scan method at different intensities. The calculated values of (β), (n₂) and χ⁽³⁾ at 532 nm are from 0.38(cm/GW) to 0.65(cm/GW), −3.36 × 10⁻⁷(cm²/GW) to −5.37 × 10⁻⁷(cm²/GW) and 1.28 × 10⁻¹¹ (esu) to 2.20 × 10⁻¹¹ (esu) at the beam intensities of 0.38 GW/cm² to 0.92 GW/cm² respectively while the values of (β), (n₂) and χ⁽³⁾ at 1064 nm are from 0.45(cm/GW) to 0.65 (cm/GW), −3.36 × 10⁻⁷(cm²/GW) to −5.82 × 10⁻⁷(cm/GW) and 0.38 to 0.92 GW cm⁻² respectively at the beam intensities of 0.52 to 0.93 GW cm⁻². It is seen that crystal possesses a positive absorption coefficient, negative nonlinearity, and RSA, and can be a potential candidate for different practical device applications.

As an interferometric imaging method, digital holography has shown its unique potential in many fields, especially in the mature and diverse fields of crystallography. Compared to early microscopy imaging and X-ray diffraction approach, this technique captures and accurately reproduces the three-dimensional information of the crystal in real time. It offers advantages such as fast imaging, nondestructive testing, and optimized data processing. This review discusses the progress of digital holography in crystallography, covering crystallization, mineral imaging, and microstructure analysis of two-dimensional materials. The reconstruction of copper sulfate pentahydrate and sodium chloride crystallization serves as an example to demonstrate its powerful ability. Particular emphasis is placed on the advancement of optical instruments and the development of image reconstruction approaches. Regarding the solutions to problems such as dataset processing and field of view limitations, this paper summarizes the research results of combining digital holography with deep learning algorithm models and the free field of view method. In addition, the operating principle of the technology is expounded and the future development direction is also prospected.

ZnO nanoparticles co-doped with Fe and Mg, denoted as Zn_0.99-xMg_0.01Fe_xO with various compositions (x = 0.00, 0.01, 0.02, 0.03, 0.04, 0.05, and 0.10), are synthesized using the sol–gel method. The structural, morphological, optical, and blood compatibility of these Zn_0.99-xMg_0.01Fe_xO nanoparticles are investigated. Structural properties are characterized using X-ray diffraction (XRD) while scanning electron microscopy (SEM) is employed to examine the surface morphology. It is determined that all nanoparticles exhibit a single-phase ZnO hexagonal wurtzite structure. SEM images at different magnifications reveal a dense, quasi-spherical, and agglomerated morphology for the (Fe/Mg) co-doped ZnO nanoparticles. The optical properties of the samples are analyzed via a UV spectrophotometer. The energy bandgaps for the nanoparticles are computed and the impact of dopant elements are explored on their optical behavior. The refractive index is determined through five distinct models. Notably, the highest bandgap is observed E_g = 3.23 eV for Zn₀.₉₈Mg₀.₀₁Fe₀.₀₁O and Zn₀.₉₅Mg₀.₀₁Fe₀.₀₄O nanoparticles. Hemolysis tests are conducted to evaluate the blood compatibility of these nanoparticles.

Herein barium oxide thin films are studied as a promising electro-optical system. The deposited films exhibited a polycrystalline tetragonal structure and are composed of a mixture of BaO and BaO₂. The p-type films are highly transparent (80%) with an energy band gap of 3.55 eV containing exponential band tails of widths of 1.22 eV. Analyses using the Drude-Lorentz model demonstrated the films suitability for nonlinear optical applications, with optical conductivity parameters revealing a scattering time constant in the range of 0.4–1.8 fs, a free hole concentration of 10¹⁸−10¹⁹cm⁻³ and drift mobility values of 0.70–3.16 cm² Vs⁻¹. Terahertz cutoff frequency spectra calculations indicated the films capability as efficient terahertz band filters with a cutoff frequency range of 3.2–193.0 THz. Additionally, the nonlinear third-order optical susceptibility increased with decreasing incident photon energy. Applying an AC signal with a driving frequency of 0.01–1.40 GHz across the terminals of Yb/BaO/Ag devices revealed a high cutoff frequency (≈9 GHz) in the microwave frequency domain. These properties highlight the potential of BaO films as nonlinear optical filters and microwave waveguides, positioning them as candidates for gigahertz/terahertz technology applications.

This work proposes that a change in deuterium content can affect some physical and chemical properties in water, even a change of only the ppm level, which is called the “deuterium effect”. To illustrate the deuterium effect, morphology and mechanism studies are conducted on the crystallization process of the magnesium hydroxide reaction in water with different deuterium contents. Magnesium hydroxide is synthesized via the ammonia method and hydrothermal method, and the results revealed that the particle size and crystal morphology of magnesium hydroxide prepared in deuterium-depleted water are significantly different from those of magnesium hydroxide prepared in normal water. By determining the solubility of magnesium chloride in water with deuterium content in the range of 40–165 ppm, the effect of deuterium on water activity is demonstrated. As the deuterium content decreased, the trend of the solubility change is the same as that caused by the increase in temperature. The crystallization behavior and growth morphology of magnesium hydroxide are predicted and analyzed at the microscale. The results of this research preliminarily confirmed the existence of the deuterium effect.

Al─doped ZnO/SnO₂ (Al─ZnO/SnO₂) thin films are prepared using spray pyrolysis followed by an investigation of their microstructural and optical properties. Unlike ZnO, Al─doped ZnO (Al─ZnO), SnO₂ and Al─doped SnO₂ (Al─SnO₂) films, which exhibited polycrystalline structures with distinct peaks, Al─ZnO/SnO₂ films displayed a single sharp peak, indicating strong preferential orientation along the ZnO (100) plane. Scanning electron microscopy revealed spherical aggregates of random polycrystals in ZnO and SnO₂ samples, while Al─ZnO/SnO₂ films have more pores/voids and various nanostructures, including nanorods growing parallel to the substrate. These nanorods provided 1D conductive pathways that closed the open-circuits created by the pores/voids, thereby improving electron transport. The refractive index (n) and extinction coefficient (k) are evaluated using the Cauchy normal dispersion model, and the obtained values are used to determine other linear and nonlinear optical parameters. Al─ZnO/SnO₂ films exhibited low n (≈1.45) and k (≈0) in the visible region, an enhanced band gap (≈3.8 eV), and low Urbach energy (≈84 meV), which minimized light scattering losses, resulting in high visible region transmittance (≈90%). The synergy between high transparency and improved electrical conductivity inferred from the enhanced microstructural and optoelectronic properties makes these films promising candidates for use as transparent conducting electrodes in optoelectronic devices.