Growth Of Single Crystals Research Articles

Simulation of thermoelastic coupling in silicon single crystal growth based on alternate two-stage physics-informed neural network

This paper proposes a alternate physics-informed neural network (PINN) with a two-stage training strategy to solve the thermoelastic coupling in the growth of Czochralski silicon single crystal. Particularly, neural networks with a two-stage training strategy are established for solving partial differential equations in the thermoelastic coupling model. At present, PINN still faces challenges in solving coupling models. Especially for the imbalance between and within equations in the coupling model. To solve this problem, this paper splits the model into two independent systems with their coupling term exchanged in the alternating iteration. Then, the imbalance inside a single solution of the coupling model is solved by the proposed two-stage training strategy, and the imbalance between solutions is avoided by alternative iterations. Experimental results show that the proposed alternate two-stage PINN (ATPINN) can accurately simulate the temperature and displacement in the thermoelastic coupling model. Compared with the finite element results, the error of temperature prediction and displacement prediction is acceptable. The numerical results demonstrate the feasibility and performance of the ATPINN. Furthermore, ATPINN can be extended to any type of coupling model, especially for coupling models with large differences in the magnitudes of the loss functions. The codes developed in this manuscript are publicy available at https://github.com/callmedrcom/ATPINN.

Single crystal growth and electronic structure of Rh-doped Sr3Ir2O7

Ruddlesden-Popper iridate Sr3Ir2O7 is a spin–orbit coupled Mott insulator. Hole doped Sr3Ir2O7 provides an ideal platform to study the exotic quantum phenomena that occur near the metal–insulator transition (MIT) region. Rh substitution of Ir is an effective method to induce hole doping into Sr3Ir2O7. However, the highest doping level reported in Sr3(Ir1−x Rh x )2O7 single crystals was only around 3%, which is far from the MIT region. In this paper, we report the successful growth of single crystals of Sr3(Ir1−x Rh x )2O7 with a doping level of ~ 9%. The samples have been fully characterized, demonstrating the high quality of the single crystals. Transport measurements have been carried out, confirming the tendency of MIT in these samples. The electronic structure has also been examined by angle-resolved photoemission spectroscopy (ARPES) measurements. Our results establish a platform to investigate the heavily hole doped Sr3Ir2O7 compound, which also provide new insights into the MIT with hole doping in this material system.

SINGLE CRYSTALS GROWTH OF Ag7+x(P1-xGex)S6 (x = 0.1; 0.25; 0.33) SOLID SOLUTIONS

Ternary silver argyrodites exhibit a wide range of properties and are classified as promising solid-state conductors, thermoelectrics, photovoltaic and nonlinear optical materials. This is ensured by the peculiarity of the crystal structure of argyrodites, which combines a rigid anionic and a disordered cationic sublattice. This work is devoted to the development of a technological regime for growing high-quality single-crystalline samples of Ag7+x(P1-xGex)S6 (x = 0.1; 0.25; 0.33) solid solutions by the method of directed crystallization from the melt. Polycrystalline alloys of Ag7+x(P1-xGex)S6 (x = 0.1; 0.25; 0.33) solid solution were obtained from previously synthesized ternary Ag7PS6 and Ag8GeS6. The synthesis was carried out by a single-stage and single-temperature method at a maximum temperature of 1010°C. The phase composition of the synthesized alloys was determined by the XRD method. Phase analysis of the obtained polycrystalline alloys did not reveal reflections of impurity phases. The results of thermal studies of Ag7+x(P1-xGex)S6 alloys were used to develop a technological regime for single crystals growth. Ag7+x(P1-xGex)S6 single crystal was grown from the melt by the directional crystallization method. As a result of the research, high-quality single crystals of Ag7+x(P1-xGex)S6 solid solutions (x = 0.1; 0.25; 0.33) were obtained. According to the results of X-ray diffraction, it was established that the solid solution of the composition Ag7.1(P0.9Ge0.1)S6 crystallizes in the primitive cubic cell of SG P213, and the solid solutions Ag7.25(P0.75Ge0.25)S6 and Ag7.33(P0.67Ge0.33)S6 crystallizes in a metastable at room temperature high-temperature modification with SG F-43m.
 Keywords: argyrodites; single crystals; directional crystallization; phase analysis.

Crystallization of Copper Films on Sapphire Substrate for Large-Area Single-Crystal Graphene Growth.

Chemical vapor deposition synthesis of graphene on polycrystalline copper substrates from methane is a promising technique for industrial production and application. However, the quality of grown graphene can be improved by using single-crystal copper (111). In this paper, we propose to synthesize graphene on epitaxial single-crystal Cu film deposited and recrystallized on a basal-plane sapphire substrate. The effect of film thickness, temperature, and time of annealing on the size of copper grains and their orientation is demonstrated. Under optimized conditions, the copper grains with the (111) orientation and a record size of several millimeters are obtained, and the single-crystal graphene is grown over their entire area. The high quality of synthesized graphene has been confirmed by Raman spectroscopy, scanning electron microscopy, and the sheet resistance measurements by the four point probe method.

A modified CVD method for the synthesis of monolayer MoS2 and photoelectric improvement by HfO2 passivation

Molybdenum disulfide (MoS2) is an emerging class of new materials with a wide range of potential practical applications. However, the uncontrollability of monolayer MoS2 synthesized by traditional chemical vapor deposition method and the low responsivity of MoS2 photodetectors limit its further development in the field of photoelectric detection. To achieve controlled growth of monolayer MoS2 and construct MoS2 photodetectors with a high responsivity, we propose a novel single crystal growth strategy of high-quality MoS2 by controlling the Mo to S vapor ratio near the substrate, and deposit a layer of hafnium oxide (HfO2) on the surface of MoS2 to enhance the performance of the pristine metal-semiconductor-metal structure photodetector. At a reverse bias of 8 V, the HfO2 passivated MoS2 photodetector features an extremely high responsivity of a response time of around 0.5 s, and a detectivity of Meanwhile, we deeply investigate the effect of the HfO2 layer on the performance of the fabricated MoS2 photodetector and propose a physical mechanism to interpret the obtained experiment results. These results might facilitate a better understanding on the performance modulation of the MoS2 photodetectors and accelerate the development of MoS2-based optoelectronic devices.

Transition metal (dis)order in single crystal multicomponent rare earth perovskites

The utilization of configurational entropy in materials design has accelerated the tailoring of oxides for a variety of technological applications. So called “high entropy” oxides (HEO) have more recently been investigated for their use in magnetocaloric refrigeration due to tunability of the spin glass phase. To advance our understanding of these magnetic interactions, we have grown single crystals ( 5 mm diameter, 3 cm length) of the multicomponent perovskite SmCo1/4Cr1/4Fe1/4Mn1/4O3 using the laser diode floating zone technique. This material deviates from its parent SmMO3 (MCo, Cr, Fe, Mn) magnetic behaviors by having two broad transitions with a large bifurcation in the zero-field cooled vs field cooled measurements. Measurements of magnetization as a function of field show spin canting of the transition metal ions, with exchange bias emerging as a function of temperature. Heat capacity measurements are utilized alongside the non-magnetic rare earth analog LaCo1/4Cr1/4Fe1/4Mn1/4O3 to understand the low temperature superexchange interactions. Such comparison supports the two magnetic sublattices operating at different energy scales. Overall single crystal growth of such HEO should be utilized due to the ease of growth using the floating zone technique and insight it gives into the magnetic characterization.

Observation of Asymmetric Oxidation Catalysis with B20 Chiral Crystals**

AbstractThe study of heterogeneous reactions for enantiomeric processes based on inorganic crystals has been resurgent in recent years. However, the question remains how homochirality develops in nature and chemical reactions. Here, the successful growth of B20 group PdGa single crystals with different chiral lattices enabled us to achieve enantioselective recognition of 3,4‐dihydroxyphenylalanine (DOPA) based on a new mechanism, namely orbital angular momentum (OAM) polarization. The orbital textures of PdGa crystals indicate large OAM polarization near the Fermi level and carrying opposite signs. A positive or negative magnetization in the [111] direction is expected depending on the chiral lattice of PdGa crystals. Due to this, the adsorption energies of PdGa crystals and DOPA molecules differ depending on how well the O‐2p orbital of DOPA pairs with the Pd‐4d orbital of PdGa. The results provide one possible explanation for how chirality arises in nature by providing an enantioselective route with pure inorganic crystals.

Observation of Asymmetric Oxidation Catalysis with B20 Chiral Crystals.

The study of heterogeneous reactions for enantiomeric processes based on inorganic crystals has been resurgent in recent years. However, the question remains how homochirality develops in nature and chemical reactions. Here, the successful growth of B20 group PdGa single crystals with different chiral lattices enabled us to achieve enantioselective recognition of 3,4-dihydroxyphenylalanine (DOPA) based on a new mechanism, namely orbital angular momentum (OAM) polarization. The orbital textures of PdGa crystals indicate large OAM polarization near the Fermi level and carrying opposite signs. A positive or negative magnetization in the [111] direction is expected depending on the chiral lattice of PdGa crystals. Due to this, the adsorption energies of PdGa crystals and DOPA molecules differ depending on how well the O-2p orbital of DOPA pairs with the Pd-4d orbital of PdGa. The results provide one possible explanation for how chirality arises in nature by providing an enantioselective route with pure inorganic crystals.

Highly Sensitive X‐Ray Detector Made of Large Lead‐Free Perovskite Cs3Bi2I9 Single Crystals with Anisotropic Response

AbstractDirect X‐ray detectors require high‐quality and large‐size materials to reduce radiation hazards. As an all‐inorganic lead‐free perovskite, Cs3Bi2I9 has good prospects for research and applications in the field of X‐ray detection. A refined evaporation method is proposed for the growth of Cs3Bi2I9 single crystals (SCs), and a high‐quality SC with a size of 18 × 20.5 × 3 mm3 is obtained. Due to the anisotropy of Cs3Bi2I9 SCs, two different device structures, vertical and coplanar, are designed. The coplanar device has a higher sensitivity of 59 464.4 µC Gyair−1 cm−2, while the vertical device performs better on the limit of detection (LoD), with an LodD as low as 1.27 nGyair s−1.

Comparison of (K0.5Na0.5)NbO3 Single Crystals Grown by Seed-Free and Seeded Solid-State Single Crystal Growth.

(K0.5Na0.5)NbO3-based piezoelectric ceramics are of interest as a lead-free replacement for Pb(Zr,Ti)O3. In recent years, single crystals of (K0.5Na0.5)NbO3 with improved properties have been grown by the seed-free solid-state crystal growth method, in which the base composition is doped with a specific amount of donor dopant, inducing a few grains to grow abnormally large and form single crystals. Our laboratory experienced difficulty obtaining repeatable single crystal growth using this method. To try and overcome this problem, single crystals of 0.985(K0.5Na0.5)NbO3-0.015Ba1.05Nb0.77O3 and 0.985(K0.5Na0.5)NbO3-0.015Ba(Cu0.13Nb0.66)O3 were grown both by seed-free solid-state crystal growth and by seeded solid-state crystal growth using [001] and [110]-oriented KTaO3 seed crystals. X-ray diffraction was carried out on the bulk samples to confirm that single-crystal growth had taken place. Scanning electron microscopy was used to study sample microstructure. Chemical analysis was carried out using electron-probe microanalysis. The single crystal growth behaviour is explained using the mixed control mechanism of grain growth. Single crystals of (K0.5Na0.5)NbO3 could be grown by both seed-free and seeded solid-state crystal growth. Use of Ba(Cu0.13Nb0.66)O3 allowed a significant reduction in porosity in the single crystals. For both compositions, single crystal growth on [001]-oriented KTaO3 seed crystals was more extensive than previously reported in the literature. Large (~8 mm) and relatively dense (<8% porosity) single crystals of 0.985(K0.5Na0.5)NbO3-0.015Ba(Cu0.13Nb0.66)O3 can be grown using a [001]-oriented KTaO3 seed crystal. However, the problem of repeatable single crystal growth remains.

Step‐By‐Step Tips to Grow X‐Ray Quality Single Crystals of Metal Macrocyclic Complexes

AbstractMetal macrocyclic complexes, which are formed through a self‐assembly process due to the presence of several coordinating sites in the metal and ligand source, represent an interesting class of complexes due to their intriguing structures and functionalities. Although spectral characterization of metal macrocyclic complexes is reported, elucidation of their exact structure at the molecular level remains challenging. Single‐crystal X‐ray diffraction (SCXRD) is a non‐destructive analytical technique that can provide detailed information about the internal lattice of crystalline structure. However, it requires the growth of single crystals of suitable sizes and quality. This study provides an overview of methods that are most useful for developing single crystals of metal macrocyclic complexes, particularly when the macrocycle of interest is present in extremely low quantities (a few milligrams). The reproducibility of previous methods reporting the crystal growth of different metal macrocycles is also investigated. A review highlighting and summarizing the most common tips to grow single crystals for metal macrocyclic complexes can help in understanding and optimizing the growth of crystals suitable for SCXRD.

Single-Crystal Growth of a Cubic Laves-Phase Ferromagnet HoAl2 by a Laser Floating-Zone Method

The successful growth of single crystals of a cubic Laves-phase material HoAl2 with the space group Fd-3m is reported in this study. The crystals were grown by a floating-zone method with five laser diodes as a heat source. Al-rich feed rods were prepared as compensation for heavy evaporation during the growth. The nominal ratio for the feed rods was optimized as Ho:Al = 1:2.5. Single crystals of HoAl2 with a length of 50 mm were first grown in this technique. Obtaining the large-sized crystal by the floating-zone method enabled us to systematically explore the physical properties using the same batch crystal. The crystal possessed a second-ordered ferromagnetic transition at 29 K and a first-ordered spin-reorientation transition at 20 K. The bulk physical properties, such as specific heat, magnetic susceptibility, isothermal magnetization, and thermal expansion measurements, were measured. Additionally, a magnetocaloric effect was evaluated by the magnetic entropy change. We demonstrate that anisotropic physical properties along the principal axes ([100], [110], and [111]) emerged below the magnetically ordered states, in contrast to the isotropic behavior in the paramagnetic state.

Microfluidic‐Assisted Growth of Perovskite Single Crystals for Photodetectors

AbstractThe organometal halide perovskites (OMHP) are promising candidates for fast, sensitive, and large area photodetectors. In the last decade, several techniques have been developed with complementary advantages. Film devices are thin and can be scaled to large area, but have a large number of grain‐boundaries related defects. Single bulk crystals instead have higher purity, but are thicker and can not be easily produced on large areas. In this work, a microfluidics‐assisted technique to realize a controlled growth of OMHP single crystals, in the form of microwires, directly on a conductive patterned substrates, is presented. This technique enables the realization of vertical devices with a pixelated sensor layer. The resulting devices present gain, a responsivity up to 200 AW−1and a fast rise time down to 35 µs. This is the first demonstration of a OMHP vertical device realized on a patterned substrate using microfluidics‐assisted techniques.

Vapor Deposition Growth of SiC Crystal on 4H-SiC Substrate by Molecular Dynamics Simulation

Due to the lack of appropriate experimental methods for imaging the evolution of the microstructure of materials at the growth conditions, our understanding of the physical behavior of crystal growth and defect formation during the vapor deposition growth of SiC crystals is still rather limited. In the present work, the vapor deposition growth of SiC crystal on a 4H-SiC substrate has been investigated by the molecular dynamics (MD) computer simulation method. Three different lattice planes of 4H-SiC ((0001), (112-0) and (1-100)) were selected as the surface of the substrate, and three different temperatures for substrate (2200 K, 2300 K and 2400 K) were used in growth simulations. The characteristics of the formation of different polytypes of SiC and dislocations in the grown crystals were examined. The results show that the SiC crystals were grown by a subsurface nucleation and growth mode in the vapor deposition process. For substrates with (0001) plane as the surface, the 3C-SiC single crystal was obtained in the deposited thin film. For substrates with (112-0) or (1-100) plane as the surface, the 4H-SiC single crystal was obtained instead. The temperature of the substrate was found to have a significant effect on the dislocation density generated in the grown crystals. The mechanism for the formation of Frank partial dislocations during the growth of SiC crystals has been analyzed, for which the importance of the diffusivity of atoms on the surface layer in growth has been highlighted, and it gives a good explanation of the temperature effect on dislocation formation in the grown crystals. These results can be helpful for experimental vapor deposition growth of SiC single crystals and epitaxial layers of high quality.

BaMn2P2 : Highest magnetic ordering temperature 122-pnictide compound

We report the growth of high-quality single crystals of ${\mathrm{ThCr}}_{2}{\mathrm{Si}}_{2}$-type tetragonal ${\mathrm{BaMn}}_{2}{\mathrm{P}}_{2}$ and investigation of its structural, electrical transport, thermal, and magnetic properties. Our results of basal plane electrical resistivity and heat capacity measurements show that the compound has an insulating ground state with a small band gap. Anisotropic susceptibility ${\ensuremath{\chi}}_{ab,c}(T)$ data infer a collinear local-moment N\'eel-type antiferromagnetic (AFM) ground state below the ordering temperature ${T}_{\mathrm{N}}=795(15)\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, which is highest among all the ${\mathrm{ThCr}}_{2}{\mathrm{Si}}_{2}$- and ${\mathrm{CaAl}}_{2}{\mathrm{Si}}_{2}$-type 122-pnictide compounds reported so far suggesting that the strength of magnetic exchange interactions is strongest in this material. The magnetic transition temperatures of ${\mathrm{BaMn}}_{2}P{n}_{2}$ ($Pn=\mathrm{P}$, As, Sb, Bi) compounds exhibit a monotonic decrease with the increase of tetragonal unit cell parameters $a$ and $c$, suggesting a strong dependence of the strength of the decisive magnetic exchange interactions on the separation between the localized spins residing on the Mn ions. The observed monotonic increase of both ${\ensuremath{\chi}}_{ab}$ and ${\ensuremath{\chi}}_{c}$ for $T&gt;{T}_{\mathrm{N}}$ suggests that short-range dynamic quasi-two-dimensional AFM correlations persist above the ${T}_{\mathrm{N}}$ up to the highest temperature of the measurements. The large ${T}_{\mathrm{N}}$ of ${\mathrm{BaMn}}_{2}{\mathrm{P}}_{2}$ demands for systematic hole-doping studies on this material as similar investigations on related ${\mathrm{BaMn}}_{2}{\mathrm{As}}_{2}$ with ${T}_{\mathrm{N}}=618\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ have led to the discovery of an outstanding ground state where AFM of localized Mn spins and itinerant half-metallic ferromagnetism with ${T}_{\mathrm{c}}\ensuremath{\approx}100\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ originating from the doped holes coexist together.

Growth of (100) β-Ga2O3 single crystal by controlling the capillary behaviors in EFG system

In this study, a numerical simulation of edge-defined film-fed growth (EFG) was performed to determine the appropriate capillary conditions for Ga2O3 melt. Meniscus and capillary rise were significantly influenced by the design of the die in the EFG system. The ratio of the seed crystal and die width was >0.73 for a die width of 4.4 mm. Narrower slit width resulted in higher capillary rise with longer process time compared with wider slit width. Under conditions consistent with the simulation results, highly crystalline (100) β-Ga2O3 single crystals were successfully achieved.

Facile production of CsPbBr3 perovskite single-crystals in a hydrobromic solution

In this study, synthesis of CsPbBr3 perovskite single-crystals in a hydrobromic solution was investigated. Single-crystal growth experiments were conducted at the solution-nucleation border at a constant temperature or controlled cooling conditions. Working at the solution-nucleation border poses some practical difficulties such as fast precipitation. Often researchers opt to oversaturate the solution and use the supernatant after filtration. However, for conditions where the A to B ratio in the precursor solution for the formation of ABX3 is not 1, oversaturation is a waste of resources. In this work, precursor solutions were prepared for a particular working temperature and either held at a constant temperature or were gradually cooled to a predetermined temperature. The constant temperature method resulted in large and clear crystals as it reached saturation more slowly. Crystals prepared at high temperatures appeared to be more transparent with clear facets. Crystals prepared at low temperatures appeared to be opaque with multiple nuclei growth on a single-crystal. Seeding of the saturated solution resulted in larger single-crystals. The procedure adapted in this work made possible the production of clear CsPbBr3 perovskite single-crystals in a hydrobromic acid solution with sizes of up to 5 mm in only 10 days.

Growth of single-crystals and microstructures using benzothiadiazole derivatives for efficient optical waveguide and nonlinearity

Organic nanomaterials have been extensively studied for the applications of the electronic and photonic fields. The bottom-up fabrication through self-assembly provides a powerful strategy to construct the nanostructures. In this work, we synthesized a conjugated molecule, namely, 4-(1-phenyl-1H-1,2,3-triazol-4-yl)benzo[c][1,2,5]thiadiazole (BT-SC), based on benzothiadiazole and benzene moieties bridged by a triazole. Then, a simple solvent-vapor annealing technique was presented to drive the self-assembly of BT-SC into highly uniform microrods or microfibers. The morphology of the self-assembly could be controlled by simply changing the solution concentration. The compound also could be assembled into aligned nanowires by wetting into hard templates of anodic aluminum oxide (AAO). The fabricated microrods showed strong emitter and excellent optical waveguide behaviors excited with a UV laser. Moreover, the microrods displayed nonlinear optical responses of two-photon excited fluorescence and could therefore become building blocks for actual photonic devices.

Growth Process and Optical Properties of Cs2ZrCl6 Doped with Ce3+ and Li+ Crystals

Cs2ZrCl6 (CZC) has very promising scintillation properties in the application of gamma-ray spectroscopy. So far, undoped crystals of this composition have been studied, but the growth of the large-scale doped single crystals has not been reported so far. In this paper, a process improvement strategy is reported. Large-scale Cs2ZrCl6:Ce,Li (CZC:Ce,Li) single crystals with excellent energy resolution are obtained by appropriately adjusting the temperature gradient and growth rate. CZC:Ce,Li single crystals doped with 0.5, 1.5, and 3.0 mol % Ce3+ were grown by the Bridgman method. After the phase purity of the sample was determined by X-ray diffraction analysis, the crystal defects were determined by the energy-dispersive X-ray spectroscopy, and the crystal growth process was improved on this basis. The transmission spectrum confirmed the improvement of crystal quality. The energy resolution of CZC:Ce,Li crystals grown by the improved process is 4.3%, which confirmed that the improved process is conducive to the growth of bulk doped CZC single crystals, and hence, our results provide a basis for the growth of large-scale doped CZC single crystals.

Apigenin Cocrystals: From Computational Prescreening to Physicochemical Property Characterization

Apigenin (4′,5,7-trihydroxyflavone, APG) has many potential therapeutic benefits; however, its poor aqueous solubility has limited its clinical applications. In this work, a large scale cocrystal screening has been conducted, aiming to discover potential APG cocrystals for enhancement of its solubility and dissolution rate. In order to reduce the number of the experimental screening tests, three computational prescreening tools, i.e., molecular complementarity (MC), hydrogen bond propensity (HBP), and hydrogen bond energy (HBE), were used to provide an initial selection of 47 coformer candidates, leading to the discovery of seven APG cocrystals. Among them, six APG cocrystal structures have been determined by successful growth of single crystals, i.e., apigenin–carbamazepine hydrate 1:1:1 cocrystal, apigenin–1,2-di(pyridin-4-yl)ethane hydrate 1:1:1 cocrystal, apigenin–valerolactam 1:2 cocrystal, apigenin-(dl) proline 1:2 cocrystal, apigenin-(d) proline/(l) proline 1:1 cocrystal. All of the APG cocrystals showed improved dissolution performances with the potential to be formulated into drug products.