Fabrication Of Crystals Research Articles

Simulation and Fabrication of PMN-PT Single Crystals Phased Array Ultrasonic Transducer Based on Alternating and Direct Current Poling

Simulation and Fabrication of PMN-PT Single Crystals Phased Array Ultrasonic Transducer Based on Alternating and Direct Current Poling

Fabrication of bulk single crystals via texture-engineered grain growth

Fabrication of bulk single crystals via texture-engineered grain growth

Modification of the Spectral Absorption Characteristics of ZnGeP2 in the THz and IR Wavelength Ranges Due to Diffusion Doping with Impurity Atoms of Mg, Se, Sn, and Pb

This study demonstrates that diffusion doping of ZGP single crystals with impurity atoms (Mg, Se, Sn, Pb) leads to a decrease in the specific conductivity of the samples. Consequently, this results in reduced absorption in the terahertz frequency range (150–1000 μm). It has been shown that doping ZGP samples with selenium (Se) and lead (Pb) atoms reduces absorption in the infrared region from 0.3–0.6 cm−1 to 0.06–0.09 cm−1. Doping with tin (Sn) leads to a decrease in absorption only in the wavelength region near 2.1 μm from 0.2 cm−1 to 0.05 cm−1. The proposed mechanism for the decrease in infrared absorption is a reduction in zinc vacancies due to doping with impurity atoms. This research lays the groundwork for a technology that produces ZGP crystals with minimal absorption within the 2–8 μm wavelength range, eliminating the need for fast electron beam irradiation technology. This advancement will facilitate the fabrication of ZGP crystals with arbitrary apertures.

Ultra-Fast Fabrication of Mechanical-Water-Responsive Color-Changing Photonic Crystals Elastomers and 3D Complex Devices.

The traditional fabrication of opal-structured photonic crystals is constrained by the rate of solvent evaporation, a process that is not only time-consuming but also labor-intensive. This study introduces a paradigm shift by incorporating silica nanoparticles (SiNPs) with high zeta potentials and hydrogen bonding capabilities into an elastomeric matrix, resulting in a novel non-close-packed structure. This innovation circumvents the limitations of conventional methods by enabling the rapid formation of photonic inks (PI) into vibrant and luminous photonic elastomers (PEs) within seconds. These PEs demonstrate remarkable mechanochromic properties, exhibiting dynamic color changes across the visible spectrum in response to tensile and compressive deformations. Furthermore, the presence of hydroxyl groups endows the PEs with superior water-responsiveness, which can be finely tuned through the ink formulation. The elimination of solvent evaporation dependency facilitates the fabrication of macroscopic photonic crystal devices with complex geometries using digital light processing (DLP)-based 3D printing. This approach ensures exceptional optical performance and high customization potential. The resulting PEs hold significant promise for applications in smart wearables, soft robotics, and advanced human-machine interface technologies.

Distribution of the electrical resistivity of a n-type 4H-SiC crystal

Nitrogen is commonly doped to obtain n-type 4H-SiC crystals, which have been commercialized for the development of power electronics in recent years. Now the uniformity of electrical resistivity becomes an important issue for the growth of n-type 4H-SiC crystals. In this work, the effects of the radial thermal gradient and growth facet on the distribution of the electrical resistivity were investigated for a n-type 4H-SiC crystal with a diameter of 150 mm during its physical-vapor-transport growth. It is found that the resistivity at the center of the crystal is low in the early growth stage. As the crystal grows, the growth facet expands, accompanied by a reduction in the resistivity of this facet. The change in the distribution of the resistivity in the crystal is initially governed by the radial thermal gradient and then influenced by the spiral growth mode of the growth facet. In the non-facet region of the crystal step-flow growth occurs, where the doping of nitrogen is primarily affected by the temperature and C/Si ratio. In the facet region, the volume fraction of nitrogen in the mixture of argon and nitrogen input into the growth system mainly governs the doping of nitrogen during the spiral growth. The insights gained in the current work may help the fabrication of n-type 4H-SiC crystals with uniform resistivity.

Single Crystal Sn-Based Halide Perovskites.

Sn-based halide perovskites are expected to be the best replacement for toxic lead-based counterparts, owing to their similar ionic radii and the optimal band gap for use in solar cells, as well as their versatile use in light-emitting diodes and photodetection applications. Concerns, however, exist about their stability under ambient conditions, an issue that is exacerbated in polycrystalline films because grain boundaries present large concentrations of defects and act as entrance points for oxygen and water, causing Sn oxidation. A current thriving research area in perovskite materials is the fabrication of perovskite single crystals, promising improved optoelectronic properties due to excellent uniformity, reduced defects, and the absence of grain boundaries. This review summarizes the most recent advances in the fabrication of single crystal Sn-based halide perovskites, with emphasis on synthesis methods, compositional engineering, and formation mechanisms, followed by a discussion of various challenges and appropriate strategies for improving their performance in optoelectronic applications.

γ‐Valerolactone Enabling Spontaneously Inhibited Iodide Oxidation for High‐Quality Perovskite Single Crystal Fabrication

AbstractThe iodide precursor oxidation has persistently plagued solution grown iodine‐based perovskite single crystals (IPSCs) that inevitably introduce undesirable triiodide ion (I3−) defects and severely hindering crystal quality, despite IPSCs having garnered remarkable progress in multifarious photoelectronic applications. In this work, the spontaneously inhibited iodide oxidation is discovered in an eco‐friendly solvent, γ‐Valerolactone (GVL), and demonstrates a universal solution approach for fabricating high‐quality IPSCs. Compared to the routine γ‐Butyrolactone (GBL) system, GVL provides a lowered growth temperature and a significantly broadened inverse temperature operation window, thereby improving the theoretical utilization rate of perovskite precursors up to 88.6%. More importantly, due to its higher open‐ring hydrolysis energy, GVL can spontaneously inhibit the iodide precursors oxidation without any additional reductant and therefore effectively prevent the forming I3− defects. Typically, the as‐fabricated MAPbI3 single crystal possesses an extremely low trap density of 3.57 × 108 cm−3 and a high carrier mobility‐lifetime (µτ) product of 2.74 × 10−3 cm2 V−1, which enables its photodetection capabilities to be on a par with the state‐of‐art MAPbI3 single crystal photodetectors. This work paves an efficacious and green pathway for high‐quality IPSC fabrication toward advanced optoelectronic utilizations.

Recent Advances in Perovskite Single-Crystal Thin Film Optoelectronic Devices.

Among novel semiconductors, perovskites have gained significant attention due to their versatility, combining tunable optoelectronic properties with relatively easy fabrication processes. However, certain issues still hinder their widespread use, often related to the presence of defects and traps within the material. Beyond defect passivation in polycrystalline thin films, an alternative approach to enhancing material quality lies in the fabrication of single crystals. This review aims to provide an overview of the promising approaches explored to address specific challenges of perovskites that benefit from the single crystal nature, restricting our analysis to perovskite single crystal thin films (PSC-TF). We will discuss novel fabrication techniques and highlight recent achievements in devices, such as photodetectors, solar cells, and transistors. By examining the fundamental properties already discovered and showcasing the latest advancements, we aim to provide an overview of the perspectives and open challenges for PSC-TF in next-generation optoelectronic devices.

Bio-inspired synergistic humidity-responsive photonic system for security printing and information encryption

The proliferation of counterfeiting necessitates an urgent need for enhanced technique to safeguard the authenticity of sensitive items. Inspired by the elytra of Tmesisternus isabellae beetles, we designed a new synergistic humidity responsive photonic system (SHRPS) for security printing based on high quality photonic paper and active ink. The photonic paper itself is not sensitive to humidity; only the targeted areas activated by the active ink exhibit humidity responsiveness. We investigated factors influencing humidity responsiveness, including monomer composition, pH of active ink, and treatment period. We found the optimal monomer mixture contains 40% acrylic acid, and the active ink pH is 13. We also applied a scalable method to fabricate photonic paper, successfully overcome the challenge of large-scale fabrication of photonic crystals at room temperature. By integrating the perfect pair of SHRPS and inkjet printer, concealed information with various sizes and resolutions can be printed, invisible in ambient humidity and revealed by blowing air, presenting various humidity responsive ability of SHRPS for multilevel information encryption, which opens a new window for security printing system.

3D Printing Photonic Crystals: A Review.

Living organisms in nature possess diverse and vibrant structural colors generated from their intrinsic surface micro/nanostructures. These intricate micro/nanostructures can be harnessed to develop a new generation of colorful materials for various fields such as photonics, information storage, display, and sensing. Recent advancements in the fabrication of photonic crystals have enabled the preparation of structurally colored materials with customized geometries using 3D printing technologies. Here, a comprehensive review of the historical development of fabrication methods for photonic crystals is provided. Diverse 3D printing approaches along with the underlying mechanisms, as well as the regulation methods adopted to generate photonic crystals with structural color, are discussed. This review aims to offer the readers an overview of the state-of-the-art 3D printing techniques for photonic crystals, present a guide and considerations to fabricate photonic crystals leveraging different 3D printing methods.

Evaluation of the optical, photoluminescence, and thermal characteristics of Barium thiourea chloride (BTCL), a metal–organic crystal for photonic applications

The development of crystal fabrication and characterization approaches makes it possible to study novel materials with enhanced linear and nonlinear optical properties. The solution growth method was adopted in the present investigation to create Barium thiourea chloride (BTCL), a metal–organic single crystal. Structural, optical, and thermal characteristics of the BTCL crystals were evaluated by XRD analysis, Fourier transform infrared spectroscopy, UV–Vis spectrometry, photoluminescence, SHG, and thermal analyses. The XRD method was applied to investigate the structural characteristics of the BTCL, which is related to the monoclinic structure. The FT-IR spectral investigation was conducted to observe the vibrational modes in BTCL. The optical measurements showed the transmittance in the near-UV and visible spectrums. Optical characteristics include bandgap, refractive index, extinction coefficient, optical, and electrical conductivities, and dielectric constants were obtained. The PL curve showed two notable emission peaks at 482.5[Formula: see text]nm and 491[Formula: see text]nm. The ability to generate second harmonics was investigated using the Kurtz and Perry method, and the SHG was more than 1.79 times the KDP sample. The thermal behavior of the BTCL was evaluated by TGA/DTA measurements. The Coats–Redfern relation was used to estimate the activation energy of the thermal system and the value was determined to be 9.48[Formula: see text]KJ/mol. The findings indicate that the BTCL crystals possess excellent optical transparency, higher SHG potency, and good thermal stability, which are suitable for use in photonic structures.

Double-edge scan wavefront metrology and its application in crystal diffraction wavefront measurements.

Achieving diffraction-limited performance in fourth-generation synchrotron radiation sources demands monochromator crystals that can preserve the wavefront across an unprecedented extensive range. There is an urgent need for techniques of absolute crystal diffraction wavefront measurement. At the Beijing Synchrotron Radiation Facility (BSRF), a novel edge scan wavefront metrology technique has been developed. This technique employs a double-edge tracking method, making diffraction-limited level absolute crystal diffraction wavefront measurement a reality. The results demonstrate an equivalent diffraction surface slope error below 70 nrad (corresponding to a wavefront phase error of 4.57% λ) r.m.s. within a nearly 6 mm range for a flat crystal in the crystal surface coordinate. The double-edge structure contributes to exceptional measurement precision for slope error reproducibility, achieving levels below 15 nrad (phase error reproducibility < λ/100) even at a first-generation synchrotron radiation source. Currently, the measurement termed double-edge scan (DES) has already been regarded as a critical feedback mechanism in the fabrication of next-generation crystals.

Direct ink writing of woodpile-kind alumina phononic crystals for MHz regime

We report comprehensive work on the fabrication of alumina-based phononic crystals (PhCs) using direct ink writing (DIW), measurement of anisotropic properties, and identification of acoustic bandgaps. Woodpile-structure-kind PhCs of characteristic size 1.1 mm and 10 periods were fabricated from alumina and polyvinyl alcohol (PVA) solution, and processed by freezing under vacuum. Next, the anisotropic elastic constants of alumina were obtained from bulk specimens using resonant ultrasound spectroscopy. Band diagrams and transmission loss were computed using the finite-element method and good correlations were found between the bandgaps estimated by these methods. Multiple partial bandgaps and several local resonances were observed in many directions for frequencies below 2 MHz. This work is the first step toward developing ceramic PhC using additive manufacturing methods for high-temperature applications.

Chromic and dynamic: soft crystals of platinum(II) complexes pave the way for multi-responsive materials.

The development of smart, stimuli-responsive materials has received increased attention in the past decade for their applications as sensing technologies. This commentary discusses a timely topical review by Kato [(2024). IUCrJ, 11, 442-452] on the fabrication of multi-stimuli responsive crystals comprised of luminescent platinum(II) complexes, which exhibit intriguing chromic phenomena in response to stimuli.

Facile fabrication of recyclable robust noncovalent porous crystals from low-symmetry helicene derivative

Porous frameworks constructed via noncovalent interactions show wide potential in molecular separation and gas adsorption. However, it remains a major challenge to prepare these materials from low-symmetry molecular building blocks. Herein, we report a facile strategy to fabricate noncovalent porous crystals through modular self-assembly of a low-symmetry helicene racemate. The P and M enantiomers in the racemate first stack into right- and left-handed triangular prisms, respectively, and subsequently the two types of prisms alternatively stack together into a hexagonal network with one-dimensional channels with a diameter of 14.5 Å. Remarkably, the framework reveals high stability upon heating to 275 °C, majorly due to the abundant π-interactions between the complementarily engaged helicene building blocks. Such porous framework can be readily prepared by fast rotary evaporation, and is easy to recycle and repeatedly reform. The refined porous structure and enriched π-conjugation also favor the selective adsorption of a series of small molecules.

Size-Effect-Based Dimension Compensations in Wet Etching for Micromachined Quartz Crystal Microstructures.

Microfabrication technology with quartz crystals is gaining importance as the miniaturization of quartz MEMS devices is essential to ensure the development of portable and wearable electronics. However, until now, there have been no reports of dimension compensation for quartz device fabrication. Therefore, this paper studied the wet etching process of Z-cut quartz crystal substrates for making deep trench patterns using Au/Cr metal hard masks and proposed the first quartz fabrication dimension compensation strategy. The size effect of various sizes of hard mask patterns on the undercut developed in wet etching was experimentally investigated. Quartz wafers masked with initial vias ranging from 3 μm to 80 μm in width were etched in a buffered oxide etch solution (BOE, HF:NH4F = 3:2) at 80 °C for prolonged etching (>95 min). It was found that a larger hard mask width resulted in a smaller undercut, and a 30 μm difference in hard mask width would result in a 17.2% increase in undercut. In particular, the undercuts were mainly formed in the first 5 min of etching with a relatively high etching rate of 0.7 μm/min (max). Then, the etching rate decreased rapidly to 27%. Furthermore, based on the etching width compensation and etching position compensation, new solutions were proposed for quartz crystal device fabrication. And these two kinds of compensation solutions were used in the fabrication of an ultra-small quartz crystal tuning fork with a resonant frequency of 32.768 kHz. With these approaches, the actual etched size of critical parts of the device only deviated from the designed size by 0.7%. And the pattern position symmetry of the secondary lithography etching process was improved by 96.3% compared to the uncompensated one. It demonstrated significant potential for improving the fabrication accuracy of quartz crystal devices.

Moving Meniscus-Assisted Template-Free Optothermofluidic Nanoparticle Patterning and Its Application in Optothermoconvective Particle Trapping.

Moving meniscus-assisted vertical lifting is a commonly employed particle assembly technique to realize large-area particle patterning for the easy fabrication of colloidal photonic crystals and sensors. Though great success has been achieved for large-area patterning, inscribing desired patterns over the target substrate with precise control over the morphology remains a challenge. The target substrates need to be functionalized (physically or chemically) to realize desired patterns, which increases the complexity and limits their applicability to specific particle-liquid combinations. We demonstrate a new approach for the precise patterning of gold nanoparticles (Au NPs, diameter ∼60 nm) over solid substrates by the synergy of light-induced Marangoni flow and vertical lifting process (moving meniscus), without the requirement of photomasks or templates. The core idea relies on the particle accumulation due to light-induced Marangoni flow near the liquid meniscus in contact with a solid surface (due to plasmonic absorption of the particles) and the controlled lifting of the substrate. We present both the simulation and experimental results of the developed patterning technique. Various patterns such as continuous lines, intermittent lines with varying lengths, patterns with continuously varying widths, cross patterns, etc. are successfully inscribed. Dynamic control over the three-dimensional morphology of the deposited patterns is achieved by varying the lifting velocity, laser irradiation time, and lifting direction during the inscription process. Finally, we show the applicability of the developed plasmonically active surface for the large-area parallel manipulation of nonabsorbing microparticles based on optothermoconvective flow. The major advantage of the developed method compared to the existing light-controlled patterning techniques is its ability to inscribe patterns over large distances (up to several centimeters). We expect that the results presented in this paper will benefit different applications requiring precise particle patterning, such as optical elements, sensors, plasmonic substrates, microfluidic master templates, and electronic circuits.

Directional heat treatment technique to prepare columnar grains in a TiAl alloy: Microstructure evolution and deformation behavior

Directional TiAl alloys show excellent comprehensive mechanical properties at high temperature (HT), and their notable attributes in high-temperature deformation resistance offer them promising application potential as structural materials in the aero engine industry. Directional heat treatment (DHT) is an effective local solid phase transformation technology in alloy processing and microstructure control. The directional Ti47Al2Nb2Cr alloys with columnar grains microstructure were fabricated via multiple DHT technology, where the HT deformation performance and corresponding deformation mechanism were both investigated. Results show that both the length in axial and width in radial are increasing with the increase of DHT time, together with the reduce of columnar grains amount, ultra-large columnar grains of 58.6 mm in length and 4.8 mm in width are even obtained, which makes it possible to realize the directional single crystals fabrication further, and the DHT-TiAl alloy may possess a tensile strength of 611.7 MPa at 800 ℃. For the first time, the mechanism of columnar grain growth is considered from the point of thermodynamics via analyzing the driving force of different DHT regions, which is thought to be greatly related to the temperature gradient, and the rule of preferred orientation choosing for columnar grains growth is discussed as well, then we defined the possible conditions of controlling columnar grains steady growth. Eventually, the detailed deformation mechanism of the multiple-DHT treated TiAl alloy was analyzed by transmission electron microscopy (TEM), which demonstrates that the twin intersections together with stress-induced γ variants within γ matrix, and the well-known long period stacking order (LPSO) structure 6 R and 9 R characterized by periodic stacking fault both found near α2 phase and γ twins/pseudo-twins further improved the plastic deformation accommodation and interface compatibility of DHT-TiAl alloy. This observed microstructure transformation and corresponding mechanical performance improvement demonstrate the potential of DHT technology in microstructure improving and properties strengthening for TiAl alloys during practical manufacturing process.

High-efficiency fabrication of uniform photonic crystals by a vertical deposition method from multiple glass slides of simple moulds and their application in isomer recognitions

Vertical deposition method is a simple, cheap and common method for fabricating photonic crystals (PCs). However, a majority of PCs are obtained based on the traditional vertical deposition method from one glass slide, the method is low efficiency. Herein, it is proposed to efficiently fabricate uniform PCs by an optimized vertical deposition method from double or multiple glass slides of simple moulds. Amounts of SiO2 spheres, distances of two glass slides of moulds, preparation temperatures and different diameters of SiO2 spheres are investigated for obtaining uniform PCs. And different types of PCs (the bottom-middle-top 3D PCs, bilayer 2D PCs and amorphous PCs) are also fabricated based on the optimized vertical deposition method. The above method is a simple, cheap and high-efficiency way for mass production of uniform PCs. Meanwhile, the chemicals with similar refractive indices (isomers and cis-trans isomers) can be easily distinguished under high humidity based on dynamic reflection spectra of the PCs. For example, the difference in the refractive indices of m-xylene and p-xylene is only 0.002, the difference of desorption balance time of PCs is 263 s. The PCs have potential applications in visual detections, isomer recognitions and monitoring of volatilization rates of trace liquids.

Er-doped Cs2AgBiCl6 double perovskite large single crystal for optoelectronics

Double perovskites have shown great potential in addressing the toxicity and instability concerns of lead halide perovskites for practical applications. However, the fabrication of high-quality double perovskite single crystals has remained challenging. Here, large Er-doped Cs2AgBiCl6 single crystals (SCs) with a maximum dimension of 8 mm were successfully prepared using a solution temperature-lowering (STL) method. The photoluminescence (PL) spectra were excited by the lasers with energies below and above the band gap, and the origin of the abnormal PL peaks changing with temperature is explored. The photodetector made from the Er-doped Cs2AgBiCl6 SCs shows a significantly enhanced light responsivity and detectivity in the wavelength range from 370 nm to 660 nm compared with the undoped one, with excellent environmental and radiation stability. It reveals that the Er ions can be successfully doped into double perovskite single crystal, benefiting the application to optoelectronic devices.