Growth Of Single Crystals Research Articles

Growth, structure and optical characterization of new Pr3+-doped LaGaGe2O7 and LaGa0.6Al0.4Ge2O7 single crystals

In this work, a new crystal belonging to the germanate family: LaGaGe2O7 (or LGGO) doped with trivalent Praseodymium (Pr) ion is studied. We report the first single crystal growth of this material using the Czochralski method. The spectroscopic properties including absorption and emission cross-sections of praseodymium in this new matrix are measured, as well as the refractive index along the dielectric axes. This material exhibits very high emission cross sections of 38, 20, and 16 10−20 cm2 at 746 nm, 646 nm and 620 nm, respectively. Some persistent luminescence is observed in Pr:LGGO after UV irradiation at 254 nm. To reduce the phenomenon, the solid solution LaGa1-xAlxGe2O7 (0 ≤ x ≤ 1) is considered. Thermoluminescence experiments show that a substitution of 40 % of gallium by aluminium in the crystal structure allows to suppress this persistent luminescence phenomenon.

Growth of KNbO3 Single Crystals by the Flux Method Using KBO2 as a Flux

KNbO3 single crystals are grown by the self-flux method using K2CO3 as a flux, but often suffer from discolouration. In this work, KNbO3 single crystals were grown by the flux method using KBO2 as a flux. KNbO3 powder was prepared by the solid-state reaction of K2CO3 and Nb2O5. KBO2 was fabricated by the reaction of K2B4O7·4H2O and K2CO3. Single crystals of KNbO3 were grown in a Pt crucible and the structure and dielectric properties of the single crystals were investigated. X-ray diffraction showed the KNbO3 single crystals to have an orthorhombic Cmm2 perovskite unit cell at room temperature. The existence of ferroelastic domains was revealed by transmission electron microscopy. Electron probe microanalysis showed the single crystals to be stoichiometric and contain small amounts of B. Differential thermal analysis, Raman scattering and impedance spectroscopy were used to study the phase transitions. KBO2 may be a suitable flux for the growth of KNbO3 single crystals.

Mg-Defect Compensation to Realize High Performance at Room Temperature in Mg3Bi2-Based Thermoelectric Single Crystals.

Mg3Bi2-based materials are a very promising substitute for current commercial Bi2Te3 thermoelectric alloys. The successful growth of Mg3Bi2-based single crystals with high room-temperature performance is especially significant for practical applications. Previous studies indicated that the effective suppression of Mg defects in Mg3Bi2-based materials was crucial for high performance, which was usually realized by applying excessive Mg during syntheses. However, utilization of excessive Mg generates Mg-rich phases between the crystalline boundaries and is unfavorable for the long-term stability of the materials. Here, bulk single crystals with a low-content Mg component such as Mg3.1Bi1.49Sb0.5Te0.01 were successfully grown. For compensating Mg defects, Li was chosen as the additional electron dopant. The results indicate that Li is a very effective electron compensator when low-concentration doping is applied. For high-concentration doping, Mg atoms in the lattice are substituted by Li, leading to decreased electron concentration again. This strategy is very significant for improving the room-temperature performance of Mg3Bi2-based materials. As a result, a record-high figure of merit of 1.05 at 300 K is achieved for Mg3+xLi0.003Bi1.49Sb0.5Te0.01 single crystals.

Single crystal growth and transport properties of narrow-bandgap semiconductor RhP2

Abstract We report the growth of high-quality single crystals of RhP2, and systematically study its structure and physical properties by transport, magnetism, and heat capacity measurements. Single-crystal x-ray diffraction reveals that RhP2 adopts a monoclinic structure with the cell parameters a = 5.7347(10) Å, b = 5.7804(11) Å, and c = 5.8222(11) Å, space group P21/c (No. 14). The electrical resistivity ρ(T) measurements indicate that RhP2 exhibits narrow-bandgap behavior with the activation energies of 223.1 meV and 27.4 meV for two distinct regions, respectively. The temperature-dependent Hall effect measurements show electron domain transport behavior with a low charge carrier concentration. We find that RhP2 has a high mobility μ e ∼ 210 cm2⋅V−1⋅s−1 with carrier concentrations n e ∼ 3.3 × 1018 cm−3 at 300 K with a narrow-bandgap feature. The high mobility μ e reaches the maximum of approximately 340 cm2⋅V−1⋅s−1 with carrier concentrations n e ∼ 2 × 1018 cm−3 at 100 K. No magnetic phase transitions are observed from the susceptibility χ(T) and specific heat C p(T) measurements of RhP2. Our results not only provide effective potential as a material platform for studying exotic physical properties and electron band structures but also motivate further exploration of their potential photovoltaic and optoelectronic applications.

Thermal Field Simulation and Optimization of PbF2 Single Crystal Growth by the Bridgman Method

PbF2 single crystals are usually grown in the temperature gradient region by the Bridgman–Stockbarger method. Temperature distribution during the growth process is particularly important for the preparation of high-quality crystals. In this study, the temperature field during the growth of the PbF2 single crystals was simulated based on the finite element method. The temperature distribution and temperature gradient changes in the crucible were investigated at different growth stages, including the seeding, shouldering, and iso-diameters stages. The calculated results show that as the crucible position continues downward during the growth process, the axial temperature gradient increases and then decreases from the bottom to the top of the crucible, with almost flat isotherms near the solid–liquid interface where the axial temperature gradient is larger. At the shoulder below the crucible, the solid–liquid interface was improved by adjusting the tilt angle. Furthermore, based on a novel design of the heat-insulating baffle, the concave solid–liquid interface in the iso-diameter stage can be effectively adjusted to realize a lower radial temperature gradient. This study provides theoretical guidance for the optimization of the growth of high-quality PbF2 crystals by the Bridgman method.

PbBeB2O5: A High-Performance Ultraviolet Nonlinear-Optical Crystal with Functional [BeB2O8]8- Group.

High-performance nonlinear-optical (NLO) crystals need to simultaneously meet multiple basic and conflicting performance requirements. Here, by using a partial chemical substitution strategy, the first noncentrosymmetric (NCS) PbBeB2O5 crystal with a BeB2O8 group was synthesized, exhibiting a two-dimensional [BeB2O5]∞ layer constructed by interconnecting BeB2O8 groups and bridged PbO4 with an active lone pair. The crystal shows a promising UV NLO functional feature, including a strong SHG effect of 3.5 × KDP (KH2PO4), large birefringence realizing phase matchability in the whole transparency region from 246 to 2500 nm, a short UV absorption edge of 246 nm, and single-crystal easy growth. Remarkably, theoretical studies reveal that the BeB2O8 group has high nonlinear activity, which could stimulate the discovery of a series of excellent NLO beryllium borates.

Tools and Tricks for Single Crystal Growth

Tools and Tricks for Single Crystal Growth

Novel compounds in the Sc-rich part of the systems Sc-{Co,Pd,Pt}-Ga: Structure and bonding

The present paper comprises a detailed structural analysis of two novel compounds in the Sc-Co-Ga system: τ3-Sc50Co13Ga3 (space group Fm-3; ε-Mg26-xAg7+x type), and τ4-Sc6Co1.73+x+yGa1-x (space group Immm; x=0.43; y=0.14; Ho6Co2Ga derivative type). Although alloys in the isothermal section are oxygen-free, the alloy of τ3, prepared for single crystal growth via partial melting in an alumina crucible, contained a minor amount of oxygen and can be considered as oxygen-stabilized Sc50Co13Ga3O1.1 (WDX-data). A search for homologous compounds in the systems Sc-{Pd,Pt}-Ga prompted the existence of two compounds Sc54{Pd,Pt,Ga}17, which from X-ray single crystal analyses proved both to be isotypic with the Hf54Os17-type structure (space group Immm). Whereas Sc54(Pd0.652Ga0.348)17 has a very limited homogeneity region at 850°C, Sc54(Pt1-xGax)17 exhibits at 850°C a large homogeneity region (0<x<0.28) extending from Ga-rich Sc76Pt17.2Ga6.8≡Sc54(Pt0.72Ga0.28)17 to novel binary Sc54Pt17. Interestingly, against the usual trend of solution hardening, hardness, Young's modulus and fracture toughness all decrease with increasing Ga-content: this effect is less pronounced for Sc54(Pd1-xGax)17 than for Sc54(Pt1-xGax)17 and is in line with DFT calculations indicating a weakening of bonding with increasing Ga content, thereby overcompensating the solution hardening effect. DFT modeling showed a common bonding feature for all the studied compounds – a strong electron localization inside the Sc6 octahedra, stacking of which leads to the formation of Mackay icosahedra in Sc54(Pd1-xGax)17, Sc54(Pt1-xGax)17, and Sc50Co13Ga3. The band structure of Sc6Co2.25Ga0.625 and Sc50Co13Ga3 indicates their metallic behavior, while Sc54(Pd1-xGax)17 and Sc54(Pt1-xGax)17 show distinct semimetal features. All investigated compounds in this work show similar trends in Bader charge distribution with a positively charged Sc-sublattice and a negatively charged sublattice formed by transition metals (Co, Pd, Pt) and Ga.

Comment on “Growth and characterization of unidirectional benzil single crystal for photonic applications”

Comment on “Growth and characterization of unidirectional benzil single crystal for photonic applications”

Influence of pH on growth, structural, thermal, linear and nonlinear optical properties of L-asparagine monohydrate single crystal

This report presents investigation on influence of pH on growth, structural, thermal, linear and nonlinear optical properties of L-asparagine monohydrate (LAM) single crystal for the first time. Single crystals of LAM were grown at different pH by solution growth method by allowing slow evaporation of solvent. Crystal grown at pH 6.4 grows slowly as compare to other crystals grown at other pH values. The slight variation in lattice parameters of grown crystals has been confirmed by powder X-ray diffraction study. FT-IR study confirms the presence of functional groups of LAM in all grown crystals. Influence of pH on optical quality of crystals has been discussed. The crystal grown at pH 5.4 has maximum optical transparency and shows 2 and 20 % more transmission than crystals grown at pH 4.4 and 6.4, respectively. Other optical parameters like cutoff wavelength (λmax), band gap (Eg), linear refractive index (n), reflectance, extinction coefficient (k), electrical susceptibility (χ), optical conductivity(σop), electrical conductivity (σel) and Urbach energy (Eu) of all crystals have been evaluated from transmission data. The LAM crystal grown at pH 6.4 show high values of third order nonlinear optical parameters, as compare to other grown crystals, that attest its suitability for applications like higher harmonic generation, optical switching, optical limiting and other photonic applications over other grown crystals. Thermal stability of the grown crystals has been attested by TG-DTA study.

Hot-zone design and optimization of resistive heater for SiC single crystal growth

Hot-zone design and optimization of resistive heater for SiC single crystal growth

LBM modeling of three-dimensional mixed convection in CZ crystal growth on curvilinear coordinates system

A three-dimensional (3D) thermal lattice Boltzmann model of crystal growth is presented to study the magneto-hydrodynamics (MHD) mixed convection in the melt of Czochralski silicon single crystal growth in this paper. In order to solve the problem of lattice Boltzmann method’s difficulty in solving the flow of 3D cylindrical cavity, the 3D physical model of crystal growth is transformed from the Cartesian coordinate system to the Curvilinear coordinate system. And the irregular grids in the Cartesian coordinate system are transformed into regular grids in the Curvilinear coordinate system to facilitate the establishment of the Lattice Boltzmann model. Under the above operations, two coupled distribution functions are established to solve the governing equations. Two D3Q19 models are adopted to solve the melt velocity and temperature. And the 3D lattice Boltzmann modeling of crystal growth with cylinder boundary is realized by interpolation in Curvilinear coordinate system. The comparison with the experiment and other references proves that the proposed model and boundary treatment scheme is correct and it proposes a new way for studying the 3D crystal growth or other similar 3D cylindrical cavity simulations. Furthermore, the unstable melt flow for two cases are also simulated in this paper and the critical Reynolds number are also obtained. Results show that the introduction of the transverse magnetic field enhances the stability of the crystal growth system and increases the adjustable range of crystal rotation parameter. The obtained conclusion has an important reference for adjusting the process parameters during the CZ crystal growth.

Verification of the Inverse Scale Effect Hypothesis on Viscosity and Diffusion by Azo-Amino Acid Schiff Base Copper Complexes

Microdroplets generated in microfluidic devices are attracting attention as a new chemical reaction field and are expected to improve reactivity. One of the effects of microscaling is that the ratio of the force that acts on the diffusion and movement of substances to gravity is different from that of ordinary solvents. Recently, we proposed a hypothesis for determining reaction acceleration through micro-miniaturization: If a reaction is inhibited by setting the volume and viscosity of the solution to conditions that are unfavorable to the reaction on a normal scale, that reaction can be promoted in microfluidics. Therefore, for the purpose of this verification, (1) we used an amino acid Schiff base copper(II) complex with an azobenzene group to demonstrate the polarization-induced orientation in a polymer film (the redirection that is mechanically maintained in a soft matter matrix). Numerical data on optical anisotropy parameters were reported. (2) When the reaction is confirmed to be promoted in laminar flow in a microfluidic device and its azo derivative, a copper(II) complex is used to increase the solvent viscosity or diffusion during synthesis on a normally large scale. We will obtain and discuss data on the investigation of changing the solvent volume as a region. The range of experimental conditions for volume and viscosity did not lead to an improvement in synthetic yield, nor did (3) the comparison of solvents and viscosity for single-crystal growth of amino acid Schiff base copper(II) complexes having azobenzene groups. A solvent whose viscosity was measured was used, but microcrystals were obtained using the diffusion method.

Studies on the synthesis, growth, and characterization of 2-cyanopyridinium salicylate single crystals for nonlinear optical applications

By employing methanol as the solvent in slow solvent evaporation method, a new nonlinear optical organic single crystal of 2-cyanopyridinium salicylate (2-CPSC) was grown. The lattice parameters of the 2-CPSC crystals were found out to be a = 7.7764(9) Å, b = 12.3938(17) Å, c = 12.3685(18) Å, and β = 94.44º using single crystal X-ray diffraction (SCXRD) analysis. The confirmation of crystalline nature was done by powder XRD analysis. The 2-CPSC crystal's chemical composition and functional groups were confirmed by Fourier transform infrared (FTIR) spectral analysis. The optical study was done by ultraviolet-visible-near infrared (UV–Vis-NIR) spectral analysis showing a cutoff wavelength of 338 nm. Studies on the grown 2-CPSC crystal's dielectric and Vicker's microhardness were also conducted. The linear dependence of photocurrent with the applied electric field was revealed for the grown crystals. The 2-CPSC crystal's third-order nonlinearity was investigated by the single-beam Z-scan technique using a continuous He-Ne laser. The open aperture Z-scan reveals the two-photo absorption mechanism and the closed aperture Z-scan study reveals the positive nonlinearity of the 2-CPSC crystals with third order susceptibility value of χ3=2.6763×10−6(esu). The density functional theory (DFT) method of B3LYP level with the 6–31++G(d,p) basis set was used for different quantum chemical calculations like geometry optimization, natural bond orbital (NBO) analysis, mulliken atomic charge, and molecular electrostatic potential (MEP). The higher nonlinearity of the 2-CPSC can be a potential alternative for commercially available potassium dihydrogen phosphate (KDP) and candidate for its application in nonlinear optical devices like optical limiting and optical switching.

Progress on the growth of two-dimensional single crystals on insulating substrates

Progress on the growth of two-dimensional single crystals on insulating substrates

Investigation on the growth, characterization, spectroscopic studies and computational analysis of nonlinear optical β-alanine tartrate single crystal

Investigation on the growth, characterization, spectroscopic studies and computational analysis of nonlinear optical β-alanine tartrate single crystal

Simulation of thermal-fluid coupling in silicon single crystal growth based on gradient normalized physics-informed neural network

The thermal-fluid coupling phenomenon of silicon melt is significant in the growth process of silicon single crystals. Complex convection affects the temperature and concentration distribution of the silicon melt. Therefore, establishing and solving the thermal-fluid coupling model of silicon melts is crucial to optimizing the crystal growth process and improving crystal quality. Traditional numerical simulation methods have limitations in regard to optimization, control, and real-time monitoring. Physics-Informed Neural Network (PINN) does not require model discretization, after training, it can make predictions quickly, showing potential for industrial applications. However, when solving practical industrial coupling models, PINN often struggles to converge due to large parameter values and significant gaps between solution variables. Moreover, solving the thermal-fluid coupling model with PINN can be treated as a multitask problem, where the gradients of different equations interfere with each other, leading to gradient confusion, slow convergence, or even divergence. Therefore, this paper proposes a gradient normalized PINN (GNPINN) for solving the thermal-fluid coupling model of silicon melt. GNPINN balances the contribution of each task, ensuring a more equitable training speed between different tasks to stabilize the training process of the coupling model. This paper considers the thermal-fluid coupling model of silicon melt under different rotation conditions. GNPINN can accurately and comprehensively capture the complex temperature, velocity, and pressure distribution of silicon melt compared with other methods. Additionally, the experimental results uncover the flow and heat transfer properties of silicon melt, validating the effectiveness and industrial applicability of GNPINN.

Synthesis and growth of organic 2-ethylimidazolium hydrogen diglycolate single crystal for nonlinear optical applications

A single crystal of 2-Ethylimidazolium hydrogen diglycolate (DAEI) has been grown by slow evaporation solution (SEST) technique at 35 °C. The DAEI crystal belongs to a monoclinic crystal system with a P21/c space group. The Hirshfeld surface analysis determined the grown crystal has the highest intermolecular contribution for O..H interaction. The phase purity and various planes (hkl) of the DAEI crystal system were determined by powder X-ray diffraction analysis (PXRD). The functional groups and their different vibrations of DAEI crystal were identified by Fourier transform infrared analysis. The band gap energy value of the DAEI crystal is found to be 5.32 eV. Photoluminescence measurement reveals that the DAEI crystal has green emission. The material shows major weight losses of around 82.45 % in the temperature between 140 °C and 300 °C. The dielectric analyses were carried out for different frequencies (1Hz–1MHz) and different temperatures. The third-order nonlinear optical properties such as refractive index (n2), absorption coefficient (β) and susceptibility (χ(3)) were determined using the Z-scan technique using a He–Ne laser (λ = 632.8 nm).

Rational design of a Tb3Al4GaO12 magneto-optical crystal for Faraday isolators

Novel magneto-optical crystals are highly demanded to meet the rapid development of high-power laser machinery. The Tb3Al5O12 crystal has been demonstrated to be an excellent magneto-optical crystal, however, only small-sized single crystals can be produced so far due to its incongruent melting behavior. Herein, a Tb3Al4GaO12 crystal with Ga3+ substitution through the TGG structural modulation was designed to improve the bulk single crystal growth. It has been successfully grown by the Czochralski method for the first time. The crystal exhibits superior transmittance of over 80 % and enhanced Verdet constant (∼1.2–1.3 times that of TGG crystal), suggesting a promising application for high-power lasers.

2 in. Bulk β-Ga2O3 Single Crystals Grown by EFG Method with High Wafer-Scale Quality.

2 in. bulk β-Ga2O3 single crystals are successfully grown by the edge-defined film-fed growth method with a homemade furnace system. By considering the significance of wafer quality in future mass manufacture, a nine-point characterization method is developed to evaluate the full-scale quality of the processed 2 in. (100)-orientated β-Ga2O3 single-crystal wafers. Crystalline and structural characteristics were evaluated using X-ray diffraction and Raman spectroscopy, revealing decent crystalline quality with a mean full width at half-maximum value of 60.8 arcsec and homogeneous bonding structures. The statistical root-mean-square surface roughness, determined from nine scanning areas, was found to be only 0.196 nm, indicating superior surface quality. Linear optical properties and defect levels were further investigated using UV-visible spectrophotometry and photoluminescence spectroscopy. The high wafer-scale quality of the processed β-Ga2O3 wafers meets the requirements for homoepitaxial growth substrates in electronic and photonic devices with vertical configurations.