Growth Of Single Crystals Research Articles

Controlling inversion disorder in a stoichiometric spinel magnet

In the study of frustrated quantum magnets, it is essential to be able to control the nature and degree of site disorder during the growth process, as many measurement techniques are incapable of distinguishing between site disorder and frustration-induced spin disorder. Pyrochlore-structured spinel oxides can serve as model systems of geometrically frustrated three-dimensional quantum magnets; however, the nature of the magnetism in one well-studied spinel, ZnFe2O4, remains unclear. Here, we demonstrate simultaneous control of both stoichiometry and inversion disorder in the growth of ZnFe2O4 single crystals, directly yielding a revised understandingof both the collective spin behavior and lattice symmetry. Crystals grown in the stoichiometric limit with minimal site inversion disorder contravene all the previously suggested exotic spin phases in ZnFe2O4. Furthermore, the structure is confirmed on the [Formula: see text] space group with broken inversion symmetry that induces antiferroelectricity. The effective tuning of magnetic behavior by site disorder in the presence of robust antiferroelectricity makes ZnFe2O4 of special interest to multiferroic devices.

Control of the growth quality by optimizing the crucible structure for growth of large-sized SiC single crystal

Silicon carbide (SiC), as the wide bandgap semiconductor, has gradually attracted attention from investigators due to the excellent integrated performance, widely recognized as a revolution in the electronic devices. For these applications, it is crucial to prepare the high-quality SiC crystal ingot by optimizing growth parameters and crucible structures. In this study, the effect of TaC coating and graphite paper on the growth process of SiC ingot were investigated compared to the growth in conventional graphite crucible through modeling and experiment. We demonstrated that the grown crystal using TaC-coated graphite relay ring and graphite paper surrounded the inner wall of powder container shows the superior characteristics in terms of the crystalline perfection and interface shape. In addition, the new crucible structure can provide a low-cost solution to prepare SiC crystal ingot using PVT method.

Physical-Vapor-Transport growth of 4H silicon carbide single crystals by a tiling method

Increasing the diameter and reducing the dislocation density of 4H silicon carbide (4H-SiC) single crystals are the development tendency of 4H-SiC single-crystal substrate to reduce the cost of 4H-SiC based devices. In this work, we use the growth of a 100 mm 4H-SiC single crystal as an example to demonstrate that the tiling approach is attractive to enlarge the diameter of physical-vapor-transport (PVT)-grown 4H-SiC single crystals by a single growth period. By titling four pieces of 4H-SiC seed crystals, a 100 mm 4H-SiC boule without crystal deterioration is obtained by the PVT growth method. The shape of the growth interface is convex and complete after the PVT growth, indicating the tiling gaps between neighboring seed-crystal pieces are healed after the PVT growth of 25-mm thick 4H-SiC. Wafers are obtained after sequential slicing, lapping, and chemical mechanical polishing (CMP). The high-resolution X-ray diffraction (HRXRD) rocking curve measurements of the wafer at the latest growth stage indicate that the 4H-SiC crystal is basically healed, with mesoscopic boundaries being created at the central area of the wafer. Raman spectra indicate that the healing polymorph across the tiling gaps is 4H-SiC. We find that threading edge dislocations (TEDs) dominate the dislocation types in the 4H-SiC substrate wafers at the initial, middle, and latest growth stages. As the PVT growth proceeds, the density of dislocations in 4H-SiC wafers significantly decreases, as a result of the crystalline healing. Our work opens a pathway to enlarge the size of 4H-SiC single crystals in a single PVT growth period, which paves the way for the high-efficiency growth of large-size 4H-SiC single-crystals.

(Invited) Progress in Elucidating the Growth Process for Basic Ammonothermal GaN

Gallium nitride (GaN) is an attractive materials platform for the pursuit of high-power, high-efficiency (opto-)electronic devices. Key to allowing this wide band gap material system to achieve its full potential is the availability of low-cost, large-area, high-crystal-quality native substrates. While important advances have been made to this effect, continued progress and breakthroughs are required to truly meet this objective.The ammonothermal method, which utilizes supercritical ammonia to preferentially dissolve and crystalize GaN on a native seed, offers a true bulk crystal growth process to yield large, inexpensive GaN substrates. To further enhance the growth rate and quality of GaN, much still needs to be learned and gained from an improved understanding of the chemical processes and growth mechanisms occurring in the ammonothermal environment. A key challenge to achieving this, is the difficulty in obtaining in-situ information during growth of GaN due to the use of thick-walled autoclaves containing the corrosive environment at temperatures up to ~ 650 °C and pressures up to ~ 2500 atm.This talk will present the progress made in our understanding of the underpinnings of the basic ammonothermal growth of GaN. Specifically, it will discuss advances made to allow us to understand the thermodynamic foundation of the solvent, for the first time. This is achieved by the creation and application of a new, simple equation of state for supercritical ammonia under ammonothermal conditions. Additionally, by combining this solvent knowledge with in-situ temperature, total system measurements, and GaN single crystal growth, various aspects of the crystal growth process and solute behaviors are elucidated and will be presented. Consequences towards our ability to enhance the growth rate of basic ammonothermal GaN will then be discussed.

Effect of zinc acetate dihydrate on the crystal growth, structural, optical, mechanical, dielectric, and NLO properties of ammonium dihydrogen phosphate single crystals

Effect of zinc acetate dihydrate on the crystal growth, structural, optical, mechanical, dielectric, and NLO properties of ammonium dihydrogen phosphate single crystals

Highly transparent bisthiourea zinc chloride (ZTC) single crystal growth and characterization for optical applications

In this study, ZTC single crystals are grown using slow evaporation solution method. Dimensions of titled crystals are estimated to be 9.9 × 0.7 × 1.0, 8.5 × 0.7 × 1.0 and 10.0 × 0.8 × 1.0 mm3. XRD powder analysis identifies orthorhombic lattice with Pnma non-centrosymmetric space group. UV–Visible linear optical characterization confirms that the ZTC crystal is transparent in range 273–800 nm. The observed optical band gap value is 4.76 eV. Photoluminescence (PL) emission is also studied. In order to identify ZTC’s functional groups, FTIR spectroscopy is used. ZTC possess wide applications due to its non-linear optical properties and can bring into use in laser applications. Being a piezoelectric material, it can be used as a replacement of conventional sources of energy. It can also reduce the environmental damage and thus contribute towards sustainable development.

A systematic investigation on the effect of purity of raw material, crucible and crucible design on the single crystal growth of undoped and Eu doped SrI2

We report a systematic study on the growth of pure and Eu doped SrI2 single crystals by Bridgman technique. The effect of various parameters pertaining to the impurity in raw material as well as in crucibles on the quality of the grown crystal has been experimentally checked and documented. Further we have also studied that nucleation behavior changes with selection of crucibles design. We have established that high purity raw material and OH free high pure fused quartz crucible enables the growth of good quality single crystal of pure SrI2 and lower concentration of Eu doped SrI2 without putting much effort in designing of crucible or furnace. For higher concentration of Eu doped SrI2 single crystal growth, modification in crucible design is required to grow good quality single crystals. We believe that this work will guide young researchers struggling in growth of good quality single crystals of similar alkali halide scintillators.

Influence of glycine and ammonium dihydrogen phosphate on their growth and characterization of l-Alanine single crystal for nonlinear optical applications

A non-linear optical single crystal of l-Alanine has been synthesized using the glycine and l-Alanine doped with various concentration of ammonium dihydrogen phosphate (ADP) (0.25, 0.30, 0.35 & 0.45 M%) through slow evaporation technique at ambient temperature. The characterization of single and powder XRD crystal reveals their crystal structure, lattice parameters and various reflecting planes. Different vibration modes of functional groups in the crystal can be identified by FTIR. The optical transmission property and their corresponding band gap value were determined by UV–Vis study. Thermal stability and melting point were investigated using TG-DTA analysis. Vickers micro hardness study used to find out the mechanical strength and Meyer's index value ‘n’ of the crystal. Dielectric constant and dielectric loss response curves were plotted over the frequency range from 50 Hz to 1 MHz. The existence of nonlinear property produces the SHG efficiency that is 0.75 times higher than KDP through the Kurtz-Perry powder technique.

Solution Growth and Characterization of 4-Carboxyanilinium Tartrate Single Crystal

Solution Growth and Characterization of 4-Carboxyanilinium Tartrate Single Crystal

Single Crystal Growth of 4‐Aminobenzophenone (ABP) by Solution and Seeded Czochralski Pulling Techniques for Second Harmonic Generation Applications

AbstractHighly efficient 4‐aminobenzophenone (ABP) single crystals are grown from melt by employing the seeded Czochralski pulling technique for second harmonic generation (SHG) applications. The as‐grown seed crystals from solution with dominant (100) and (001) facets are utilized to trigger the directional solidification. For successive growth, initial measurements of the furnace temperature distribution, heat flow structure, and solidification temperature of ABP in correlation with differential scanning calorimetry (DSC) analysis are made. The controlled diffusion is ensured by monitoring the interfacial layer between the melt and the growing crystal and is maintained by optimizing the melt temperature and pulling and rotation rates. Color change of the melt due to thermal‐oxidation is prevented by appropriate control of the growth environment. A slow and steady growth rate affirms the good quality of the ABP single crystal. The anisotropic growth behavior of ABP from solution and melt is reported. Internal molecular structure, crystalline purity, molecular vibrational modes, optical transmission, and thermal behavior are studied using single crystal and powder X‐ray diffraction, FTIR, UV–vis–NIR and DSC analyses. The obtained higher SHG efficiency of the grown ABP in comparison with that of the organic and inorganic standards urea and KDP reveals its suitability for SHG applications.

Anisotropic magnetic properties and tunable conductivity in two-dimensional layered NaCrX2 (X=Te,Se,S) single crystals

Monolayer NaCrX2 (X=Te,Se,S) were theoretically proposed to be two-dimensional intrinsic ferromagnetic semiconductors while their physical properties have not been thoroughly investigated in bulk single crystals. We report the single-crystal growth, structural, magnetic and electronic transport properties of NaCr(Te1-xSex)2 (0 6 x 6 1) and NaCrS2. For NaCr(Te1-xSex)2, the strong perpendicular magnetic anisotropy of NaCrTe2 can be gradually tuned to be a nearly isotropic one by Se-doping. Meanwhile, a systematic change in the conductivity with increasing x is observed, displaying a doping-induced metal-insulator-like transition. Under magnetic field larger than 30 koe, both NaCrTe2 and NaCrSe2 can be polarized to a ferromagnetic state. While for NaCrS2, robust antiferromagnetism is observed up to 70 kOe and two field-induced metamagnetic transitions are identified along H||ab. These intriguing properties together with the potential to be exfoliated down to few-layer thickness make NaCrX2 (X=Te,Se,S) promising for exploring spintronic applications.

Single crystal growth and magnetism of Sr3NaIrO6 and Sr3AgIrO6 : Tracking the J=0 ground state of Ir5+

Single crystals of Sr3NaIrO6 and Sr3AgIrO6 have been successfully grown using hydroxides flux. Sr3NaIrO6 and Sr3AgIrO6 crystallize in the K4CdCl6-type structure with the space group R-3c (No.167). Sr3NaIrO6 and Sr3AgIrO6 are electrically insulating with estimated activation gaps of 0.68 eV and 0.80 eV, respectively. Sr3NaIrO6 and Sr3AgIrO6 show paramagnetic behavior down to 2 K.

Technology and thermomechanics in growing tubular silicon single crystals

The problem of growing high-resistance low-dislocation tubular silicon single crystals for non-planar manufacturing technologies of epitaxial p-n junctions and the production of new-generation power semiconductor devices is considered. The possibilities of Stepanov method for growing volumetric profiled crystalline products, the application of which is based on the use of shapers of various designs, are discussed. In particular, the shortcomings of shapers associated with the melt contamination by foreign particles and impurities are discussed. Therefore, the main attention is paid to the use of equipment that implements crystal growth from a melt without a shaper by Czochralski method. The processes of thermal mechanics are preliminary analyzed in relation to the existing and well-established process of growing polycrystalline highly dislocation silicon pipes of large diameter by Czochralski method for epitaxial reactors.It is noted that the growth of tubular low-dislocation small diameter silicon single crystals requires a significant modernization of the standard hot zone, which in this work is implemented for “REDMET-10” Czochralski furnace. By means of computer simulation, thermal mechanical processes are calculated for such a modernized Czochralski furnace. The parameters of grown tubular silicon single crystals are characterized, and their manufacturing suitability for power semiconductor devices using nonplanar technology is assessed.

GADOLINIUM(III) COMPLEX OXIDE COMPOUNDS OF OBTAINED FROM MOLYBDATE-PHOSPHATE MOLTEN SALT

The peculiarities of K2Gd(PO4)(MoO4) single crystal growth from combined phosphate-molybdate melts have been investigated. The formation regions of GdPO4, KGd(MoO4)2 and their cocrystallization fields with the mixed anionic compound potassium – gadolinium have been established. IR spect­roscopy showed that in all compounds molybdenum and phosphorus are in a tetrahedral environment, and the phase composition was confirmed by X-ray powder. Crystallization of the target compound K2Gd(PO4)(MoO4) is observed in the pseudobinary section K2Mo2O7-KPO3 orthiorombic system, space group Ibca, Z = 8, а = 19,694(4) Å, b = 12,260(3) Å, c = 6,961(3) Å. Double phosphate K3Gd(PO4)2 crystallizes in the form of colorless prismatic crystals from the melts with the initial ratio K/P = 1.7–3.3, which practically corresponds to the section K2MoO4 – K4P2O7. Phosphate GdPO4 crystallizes in the form of colorless prismatic crystals up to 0.1 mm in size at the maximum KPO3 content in the melt, which corresponds to K/P ratio = 0.20–0.50 and K/(Mo+P) = 0.25–0.33. Crystal-chemical criteria for the formation of mixed-anion-type layered frameworks, island structures, and three-dimensional frameworks based on mixed phosphate-molybdate systems and rare earth elements are proposed. The key factor in the formation of complex oxide compounds of rare earth elements from combined molybdate-phosphate melts is the ratio of K/Mo in the initial solution - melt: 1) at K/Mo = 0.5–1.1, LnPO4 orthophosphates are formed, which are characterized by a 3D framework on the basis of LnO7/LnO8poly­hedra condensed into a three-dimensional framework; at K/Mo = 1.2–1.5, mixed anionic compounds of the composition K2Ln(PO4)(MoO4) (Ln – Gd- Tb) with a layered structure are formed, where LnО8 forms zigzag chains; 3) at K/Mo = 1.6–3.0, double orthophosphates of the composition K3Ln(PO4)2 with an island structure are formed.

CRYSTAL GROWTH OF ARGYRODITE Ag8GeS6

The mineral Ag8GeS6 is the first compound of a wide class of tetrahedrally close packed phases united by the common name argyrodites. Ternary argyrodites are complex chalcogenides formed on the basis of multi- and single-charged cations. Structural polyhedrons are tetrahedra formed on the basis of a multicharged cation and chalcogens, and the single-charged cations occupy the formed voids. Argyrodites belong to promising solid-state conductors and thermoelectric materials. This work is aimed to develop close to optimal conditions for single crystals growth of Ag8GeS6 by the method of directional crystallization from the melt. The initial Ag8GeS6 alloy was obtained using high purity elementary components by a two-stage single-temperature method. The congruent nature of the melting of Ag8GeS6 (Tmelt = 958°C) and the passage of the structural phase transition Pna21 → F-43m at a temperature of 227 ° C was confirmed by the DTA method. The Ag8GeS6 single crystal was grown from the melt by directional crystallization method. The growth regime of Ag8GeS6 was selected taking into account the nature of the thermal behavior of the compound based on DTA data. The grown single crystal of Ag8GeS6 is ~ 30 mm long and 12 mm in diameter and has a medium degree of cleavage. According to the results of XRD analysis, it was established that the obtained single crystalline sample of Ag8GeS6 is single-phase and crystallizes by low-temperature modification SG Pna21 with following lattice parameters: a = 15.147 Å, b = 7.469 Å, c = 10.584 Å.

CRYSTAL GROWTH OF Ag7PS6 BY DIRECTIONAL CRYSTALLIZATION METHOD

Argyrodites are a class of compounds united by a similar structural motif. Typical for argyrodites is the coexistence of rigid anionic and disordered cationic sublattices. Due to this, argyrodites exhibit a wide range of properties. This work is devoted to the development of the single crystal growth regime of high-quality single-crystalline samples of Ag7PS6, which belongs to the compounds with argyrodite structure. The initial Ag7PS6 alloy is obtained from high purity elementary components by a two-step and one-temperature method. The maximum synthesis temperature was 850°C. The obtained alloy was investigated by DTA and XRD methods. The congruent melting of Ag7PS6 (Tmelt = 801°C) and the structural phase transition P213 → F-43m at a temperature of 271°C was confirmed. The study of the phase composition established the synthesized alloy is single-phase. The growth of Ag7PS6 was carried out by the directional crystallization method from the melt. The growth regime of Ag7PS6 was selected taking into account the nature of the thermal behavior of the compound based on DTA data. As a result, the grown Ag7PS6 single crystal of ~ 40 mm long and 12 mm in diameter was obtained. According to the results of XRD, it has been established that the grown Ag7PS6 single crystal is single-phase and crystallizes in a primitive cubic cell with lattice parameters of 10.3917 Å.

Single-crystal organometallic perovskite optical fibers.

Semiconductors in their optical-fiber forms are desirable. Single-crystal organometallic halide perovskites have attractive optoelectronic properties and therefore are suitable fiber-optic platforms. However, single-crystal organometallic perovskite optical fibers have not been reported before due to the challenge of one-directional single-crystal growth in solution. Here, we report a solution-processed approach to continuously grow single-crystal organometallic perovskite optical fibers with controllable diameters and lengths. For single-crystal MAPbBr3 (MA = CH3NH3+) perovskite optical fiber made using our method, it demonstrates low transmission losses (<0.7 dB/cm), mechanical flexibilities (a bending radius down to 3.5 mm), and mechanical deformation–tunable photoluminescence in organometallic perovskites. Moreover, the light confinement provided by our organometallic perovskite optical fibers leads to three-photon absorption (3PA), in contrast with 2PA in bulk single crystals under the same experimental conditions. The single-crystal organometallic perovskite optical fibers have the potential in future optoelectronic applications.

Non-Negligible Modulation Role of the Solvent in the Asymmetric Growth of α-Resorcinol

It is accepted that the asymmetric growth of α-resorcinol is an intrinsic property and the solvent only plays a secondary role. Therefore, this work combines single-crystal growth experiments and molecular dynamics simulations to quantify the non-negligible modulation role of the solvent in the asymmetric growth of α-resorcinol. According to the experimental results, the growth rate ratio of α-resorcinol in water is the largest, followed by that in ethyl acetate, and ethanol had the least influence. The (01̅1̅) face along the polar −c axis is a hydroxyl-rich surface, and the capability of hydrogen bond formation determines the magnitude of the growth rate. However, the (011) face along the polar +c axis is a hydrogen-rich surface, and the growth rate mainly depends on the molecular structure of the crystalline surface and the steric hindrance between molecules. In general, the molecular arrangement of α-resorcinol along both ends of the polar c-axis makes the solvent exhibit significant modulation differences in the asymmetric growth, which are entirely attributed to the mechanisms of solvent action on the specific crystalline surface. This work will further enrich the asymmetric growth mechanism of α-resorcinol in solution and potentially provide some guidance for the selection of the solvent for other organic polar crystals.

Growth of bilayer MoTe2 single crystals with strong non-linear Hall effect

The reduced symmetry in strong spin-orbit coupling materials such as transition metal ditellurides (TMDTs) gives rise to non-trivial topology, unique spin texture, and large charge-to-spin conversion efficiencies. Bilayer TMDTs are non-centrosymmetric and have unique topological properties compared to monolayer or trilayer, but a controllable way to prepare bilayer MoTe2 crystal has not been achieved to date. Herein, we achieve the layer-by-layer growth of large-area bilayer and trilayer 1T′ MoTe2 single crystals and centimetre-scale films by a two-stage chemical vapor deposition process. The as-grown bilayer MoTe2 shows out-of-plane ferroelectric polarization, whereas the monolayer and trilayer crystals are non-polar. In addition, we observed large in-plane nonlinear Hall (NLH) effect for the bilayer and trilayer Td phase MoTe2 under time reversal-symmetric conditions, while these vanish for thicker layers. For a fixed input current, bilayer Td MoTe2 produces the largest second harmonic output voltage among the thicker crystals tested. Our work therefore highlights the importance of thickness-dependent Berry curvature effects in TMDTs that are underscored by the ability to grow thickness-precise layers.

Effect of crucible location on heat transfer in GaN crystal growth using Na flux method

A global model of heat transfer, considering convection, conduction, radiation as well as mass transfer, is established for GaN single crystal growth system employing the Na flux method. Global simulations are carried out to investigate the effects of crucible locations on the heat and mass transfer during growing. It was found that the crucible location has a significant effect on the heat transfer in the melt. When the crucible moves down, the flow in the upper region of melt is enhanced, while that near the crucible bottom is weaken. This flow structure leads to high supersaturation at the crucible bottom, which is favorable to accelerate crystallization. Therefore, it can be concluded that the crucible location should be lowered properly to achieve a better condition for crystallization. The research provides directions to the design of GaN growing systems.