Growth Of Single Crystals Research Articles

Дослідження розподілу кисню по довжині монокристалів кремнію, легованих компонентами з різним типом провідності

The purpose of the article is the study of convective flows and their influence on the growth of single crystals of silicon by the Czochralsky method from a large melt, which contributes to the emergence of non-stationary convection. Therefore, simulation of convection for the growth of silicon single crystals is an important step in the development of conditions for the growth of perfect single crystals. Silicon substrates are used to manufacture more than 90% of semiconductor devices and solar cells. A special role in the development of electronics is played by monocrystalline silicon, which is used for the manufacture of semiconductor devices and integrated microcircuits. The main requirements for the development of technology for the production of silicon substrates is an increase in quality at a decrease in cost. Promising technologies of 10-nm size and 3D-transistor structures significantly increase the requirements for uniformity of distribution of components, including layering in silicon single crystals. For the mathematical modeling of convective flows, melt flows were considered for a cylindrical crucible with a radius of 150 mm at a melt height of up to 40 mm. Such parameters ensure stationary convection in molten silicon. Methods of reducing stratification have been studied and developed for more than 50 years, but have not yet found a definitive solution. This method of single crystal growth is the most controlled and allows to influence the convective flows in the silicon melt below the phase interface with ultrasonic waves in the megahertz range. The effectiveness of using ultrasound in the extraction of semiconductor single crystals depends on the creation of special conditions for introducing them into the melt. 
 Reducing the influence of oxygen on the electrophysical properties of silicon single crystals is an intractable problem of silicon technology. One of the ways to solve this problem is alloying with an isomorphic impurity, for example, tin. The development of a method of doping single crystals of silicon with tin requires determination of its concentration in the liquid and solid phases

Single crystal growth of 1,2,3-Benzotriazole 3,5-dinitrobenzoic acid (BTNBA) by slow evaporation solution technique (SEST) for nonlinear optical (NLO) applications

The organic single crystal of 1,2,3-benzotriazole 3,5-dinitrobenzoic acid was synthesized and grown by slow evaporation solution technique (SEST) for the first time reported in the literature. The lattice parameters of the grown crystal were confirmed by single crystal X-ray diffraction analysis. Using powder X-ray diffraction analysis, miller index and (h k l) planes were identified. The 1H NMR and 13C NMR spectral analysis was used to confirm the chemical environment of various protons and carbons present in a BTNBA structure. The optical quality of the grown crystal was identified by the UV–Visible NIR spectrum analysis. The grown crystal has good optical transmittance in the range of 400 –800 nm. Functional groups of BTNBA crystal were confirmed by Fourier Transform Infrared spectrum analysis. The thermal behaviour of the BTNBA crystal was investigated by thermogravimetric and differential thermal analysis. The photoconductivity analysis was carried out to calculate the photo and dark current values. Intermolecular interactions of BTNBA are executed by the Hirshfeld surface analysis. Vickers microhardness analysis was carried out to identify the mechanical stability of the grown BTNBA crystal. The dielectric constant (ε') and dielectric loss (tan δ) as a function of frequency were measured for the grown crystal. The third-order nonlinear optical properties such as nonlinear refractive index (n2), absorption co-efficient (β) and susceptibility (χ(3)) were studied by Z-scan technique at 632.8 nm using He-Ne laser. The crystal grown by the SEST method shows high mechanical strength, and good third order nonlinear susceptibility with less defects which makes it suitable for photonics and optical limiting.

Nitride Synthesis under High-Pressure, High-Temperature Conditions: Unprecedented In Situ Insight into the Reaction.

High-pressure, high-temperature (HP/HT) syntheses are essential for modern high-performance materials. Phosphorus nitride, nitridophosphate, and more generally nitride syntheses benefit greatly from HP/HT conditions. In this contribution, we present the first systematic in situ investigation of a nitridophosphate HP/HT synthesis using the reaction of zinc nitride Zn3N2 and phosphorus(V) nitride P3N5 to the nitride semiconductor Zn2PN3 as a case study. At a pressure of 8 GPa and temperatures up to 1300 °C, the reaction was monitored by energy-dispersive powder X-ray diffraction (ED-PXRD) in a large-volume press at beamline P61B at DESY. The experiments investigate the general behavior of the starting materials under extreme conditions and give insight into the reaction. During cold compression and subsequent heating, the starting materials remain crystalline above their ambient-pressure decomposition points, until a sufficient minimum temperature is reached and the reaction starts. The reaction proceeds via ion diffusion at grain boundaries with an exponential decay in the reaction rate. Raising the temperature above the minimum required value quickly completes the reaction and initiates single-crystal growth. After cooling and decompression, which did not influence the resulting product, the recovered sample was analyzed by energy-dispersive X-ray (EDX) spectroscopy.

Numerical simulation of temperature gradient effects on gallium nitride crystal growth by sodium-flux method

During the growth of gallium nitride single crystals by sodium-flux method, temperature significantly impacts crystal quality. In this study, the mechanism of the effect of different temperature gradients on crystal growth is analyzed in depth using a combination of numerical simulation and experiment. The experimental results show that epitaxial growth of crystals occurs under positive temperature gradient conditions, while there is dissolution of seed crystals under negative temperature gradient conditions. The temperature, flow, and concentration data of the melted material during crystal growth were calculated using numerical simulation. The simulation findings reveal that the distribution of solution supersaturation varies according to temperature. High supersaturation at the bottom of the melt is favorable for crystal epitaxial growth on the surface of seed crystals under a positive temperature gradient. Meanwhile, low supersaturation at the top of the melt suppresses the hard polycrystalline layer here. Under negative temperature gradient conditions, low supersaturation at the bottom of the melt may lead to remelting of seed crystals, which is consistent with the experimental phenomenon. Furthermore, we propose an optimized heat source profile. This profile manages high supersaturation near seed crystals, aiding continuous growth. Finally, we have applied the curve in an applied way by proposing a multi-stage heating device, based on which the desired arbitrary temperature profile can be modulated. This research has broad applications in a variety of crystal growth experiments using fluid as the mother phase.

Study on growth, mechanical, optical, and topological properties of sodium p-nitrophenolate p-nitrophenol dihydrate single crystal

Study on growth, mechanical, optical, and topological properties of sodium p-nitrophenolate p-nitrophenol dihydrate single crystal

Femtosecond Laser Slicing of Single Crystal AlN Layer Grown by Hydride Vapor Phase Epitaxy on an AlN Substrate Generated by Physical Vapor Transport

Femtosecond Laser Slicing of Single Crystal AlN Layer Grown by Hydride Vapor Phase Epitaxy on an AlN Substrate Generated by Physical Vapor Transport

Effects of Surface Size and Shape of Evaporation Area on SiC Single-Crystal Growth Using the PVT Method

Silicon carbide (SiC) polycrystalline powder. As the raw material for SiC single-crystal growth through the physical vapor transport (PVT) method, its surface size and shape have a great influence on growth of crystal. The surface size and shape of the evaporation area filled with polycrystalline powder were investigated by numerical simulation in this study. Firstly, the temperature distribution and deposition rate distribution for the PVT system were calculated by global numerical simulation, and the optimal ratio of polycrystalline powder surface diameter to seed crystal diameter was determined to be 1.6. Secondly, the surface of the evaporation area filled with polycrystalline powder was covered by a graphite ring and a graphite disc, respectively, to change its surface shape. The results show that adjusting the surface size and shape of the evaporation area filled with polycrystalline powder is an effective method to control the growth rate, growth stability, and growth surface shape of the single crystal. Finally, the result obtained by selecting appropriate covered structures for actual growth indicates that this process can act as a reference for improving the quality of single crystals.

Revealing the influence of aerosol particle state on the high-quality α-Ga2O3 single crystal thin film growth by Mist CVD epitaxy

There is little research on α-Ga2O3 single crystal film because it is a metastable phase of Ga2O3 crystal and difficult for controllable fabrication. In this paper, highly crystallized Ga2O3 thin films of poly-crystalline, α-Ga2O3 and β-Ga2O3 were prepared by modulating the growth temperature from 400 °C to 700 °C by mist-assisted CVD (Mist CVD) method. The results show that films grown at 525 °C owes the best crystalline quality of α-Ga2O3 film. To further improve the crystallinity of α-Ga2O3 thin film, a systematic simulation revealing the distribution changes of aerosol particle size, flow field, and temperature gradient in the reaction chamber were explored. The optimal growth region C with uniform particle size, well-distribute temperature gradient and stable flow field is determined. Meanwhile, the experimental results of α-Ga2O3 thin films grown at different positions in the reaction chamber was proved to consistent with the simulation results. Furthermore, the optimal single crystallized α-Ga2O3 thin films with smooth surface morphology and optical property were obtained. The PL spectrum operated at room temperature show the α-Ga2O3 film with low defect density and high crystalline quality. It shows that the single crystallized α-Ga2O3 is orientated grown on sapphire substrate with epitaxial relationship of α-Ga2O3 (0006)//c-Al2O3 (0006). Although, slight lattice mismatch is observed on the selected area electron diffraction pattern of the interface between sapphire and α-Ga2O3 film, it is ideal for further application in devices. This work reveals the key point for α-Ga2O3 single crystal film growth by mist CVD is to construct a steady and orderly environment through controlling aerosol particle state.

Towards growth of pure AB-stacked bilayer graphene single crystals

Towards growth of pure AB-stacked bilayer graphene single crystals

Effect of adding technologically processed antibodies to interferon-gamma into a parent solution on the structural features of triglycine sulfate crystals grown from this solution

Objectives. Ferroelectric triglycine sulfate (TGS) belongs to a group of crystals whose properties are sensitive even to minor changes in growth conditions. The mechanism of spontaneous polarization in TGS is associated with the adjustment of protons which participate in the formation of hydrogen bonds. Therefore, the state of the parent solution plays an important role in the crystal formation. The study aims to investigate the structural features of TGS crystals grown using aqueous alcoholic solutions of technologically processed antibodies to interferon-gamma, in comparison with those of the crystals grown using the control solutions (technologically processed phosphate-buffered saline and intact aqueous alcoholic solution).Methods. X-ray diffraction assay and Raman spectroscopy.Results. The effect of solutions of the technologically processed antibodies to interferongamma added to a parent solution on the growth of TGS single crystals is established. This effect manifests in the changing in occupancy of the proton sublattice of the crystal grown from the parent solution containing technologically processed antibodies to interferon-gamma, as compared with the crystals grown from the control solutions. In the case of the crystal grown from the solution containing technologically processed antibodies to interferon-gamma, this change in the occupancy of the proton lattice is expressed in an increase in the length of N2–C3 bonds.Conclusions. Adding the technologically processed antibodies in the parent solution before the crystal growth can affect the structure of TGS crystals.

Relationship of single crystal growth and luminescence properties of Cr-doped gadolinium gallium garnet crystals for radiation dose-rate monitoring systems

For the decommissioning of Fukushima Daiichi Nuclear Plants, a novel real-time dose-rate monitor consisting of a scintillator, 100-m long optical fiber and CCD spectrometer has been proposed, and this scintillation material is required to have an emission wavelength of longer than approximately 650 nm. In this paper, as a candidate material for the system, we focused on Ce/Cr co-doped Gd3Ga5O12 (Ce/Cr:GGG) single crystals grown by the micro-pulling down method. Since the light output of this material was expected to depend on the Cr3+ concentration, we investigated the relationship between Cr segregation and luminescence properties in Ce/Cr:GGG crystal. Generally, a single photon counting method is not available to evaluate its light output accurately due to the long decay time, we used a novel technique “emission-intensity two-dimensional- mapping method” (2D-image method) to verify the light intensity at each point of the sample. This method realized estimation of the light intensity within the sample, though segregation of Cr3+ is observed. The results showed that Cr was concentrated in the center part along the radial direction in the grown crystals, while all parts had an emission wavelength of approximately 730 nm excited by X-ray. Using the 2D-image method, emission intensity was found to correspond to the Cr concentration, and its correlation coefficients between emission intensity and Cr concentration were over 0.8. We found that our material is available for the monitoring system when the Cr dense part of the crystal is cut and used.

Substrate Screening for the Epitaxial Growth of a Single-Crystal Graphene Wafer.

Epitaxial growth of a two-dimensional (2D) single crystal necessitates the symmetry group of the substrate being a subgroup of that of the 2D material. As a consequence of the theory of 2D material epitaxy, high-index surfaces, which own very low symmetry, have been successfully used to grow various 2D single crystals, while the rule of selecting the best substrates for 2D single crystal growth is still absent. Here, extensive density functional theory calculations were conducted to investigate the growth of graphene on abundant high-index Cu substrates. Although step edges are commonly regarded as the most active sites for graphene nucleation, our study reveals that, in some cases, graphene nucleation on terraces is superior than that near a step edge. To achieve parallel alignments of graphene islands, it is essential to either suppress terrace nucleation or ensure consistent orientations templated by both the terrace and step edge. In agreement with most experimental observations, we show that Cu substrates for the growth of single-crystalline graphene include vicinal Cu(111) surfaces, vicinal Cu(110) surfaces with Miller indices of (nn1) (n > 3), and vicinal Cu(100) surfaces with Miller indices of (n11) (n > 3).

Oxygen reduction through specific surface area control of AlN powder for AlN single-crystal growth by physical vapor transport

In the physical vapor transport (PVT) growth of AlN, re-oxidation of aluminum nitride (AlN) source powder happening in the process of setting seed crystal into crucible seems to be unavoidable. This process introduces oxygen just before AlN growth and has a significant impact on the crystal quality. In this paper, a high and low-temperature alternative sintering method (HLAS) is proposed based on the idea of specific surface area control to reduce the re-oxidation of AlN source powder. This method introduces cyclic sintering between 1500 °C and 1900 °C to the conventional three-step treatment repeatedly, which utilizes possible phase-transition along with the processes of powder sintering back and forth to increase the particle size and decrease the specific surface area significantly. The scanning electron microscope and Brunauer, Emmett, and Teller results showed that the specific surface area of AlN powder treated with the HLAS method can be reduced to one-third of that with the conventional method. Thus, the secondary ion mass spectrometry confirmed the reduction of oxygen impurity in AlN single-crystals to a good level of 1.5 × 1017 cm−3. It is clear that this HLAS process is an effective way of controlling the specific surface area of AlN source powder, which contributes to the suppression of oxygen influence on PVT-AlN growth.

Room temperature growth of CsPbBr3 single crystal for asymmetric MSM structure photodetector

UV–visible broadband light harvesting ability is critical for photodetectors, and all inorganic perovskite CsPbBr3 is regarded as a promising candidate as the response active material. Herein, a saturated-solution crystallization method is employed to synthesize CsPbBr3 single crystal. Temperature-dependent photoluminescence spectra with one-photon and two-photon excitation are systematically investigated, determining a large exciton binding energy of 39.8 meV. This allows the stable excitonic emission of CsPbBr3 single crystal at room temperature. Subsequently, an asymmetric structure CsPbBr3 photodetector is fabricated by using InGa alloy as the Ohmic electrode and Au as the Schottky electrode. At -8 V, the device exhibits a prominent response to the irradiation from UV to green band with a maximum responsivity of 2.56 A/W, an external quantum efficiency of 580 %, and a detectivity of 1.24 × 1013 Hz1/2 W−1. In addition, the CsPbBr3 photodetector also presents rapid response speeds at both reverse and forward bias voltages and self-powered characteristics owing to the Schottky depletion layer underneath the Au electrode. The demonstration of asymmetric metal-semiconductor-metal (MSM) structure photodetector presents a promising pathway toward next-generation CsPbBr3 optoelectronic devices.

Bismuth chalcogenide topological insulators crystals grown by the optical floating zone technique

In this paper, two procedures for the growth of both binary and ternary single crystals of bismuth chalcogenides by optical floating zone technique are described. Detailed characterization has been carried out on a series of samples, i.e. Bi2SexTe3-x, with x = 0 and 0.9, and Bi2-xSbxSe3, with x = 0 and 0.15, to isolate high quality single crystals, essential for an accurate study of the physical properties of the materials. Systematic compositional and structural analysis on the samples grown by the two different procedures have been compared to infer the optimal growth parameters to obtain the largest possible single crystals. The c-axis lattice parameter of Bi1.85Sb0.15Se3 is reported here for the first time.

Effect of Single Crystal Growth and Solidification Grain Boundaries on Weld Solidification Cracking Behavior of CMSX-4 Superalloy

Single-crystal superalloys have been popularly employed in high-temperature parts of gas turbines, such as blades. However, the welds of such alloys are highly susceptible to solidification cracking, which limits their applicability to high-temperature turbine blades. In this study, the effects of characteristics of weld solidification on solidification cracking susceptibilities (solidification brittle temperature range, BTR) were fundamentally investigated for the CMSX-4 single-crystal superalloy. We applied a transverse-Varestraint test procedure for both the linear and oscillated arc welds by changing the weld solidification characteristics, such as the degree of single crystal growth and formation of solidification grain boundaries. The BTR for the CMSX-4 alloy is 336 K for linear welding condition, whereas the values are 434 K and 342 K for 0.6 and 1.5 Hz oscillated welds. Interestingly, the BTR continuously increases with the weld oscillation frequency. By contrast, almost no changes in the weld mushy-zone temperature range are theoretically calculated for each welding condition via the diffusion-controlled Scheil model. The mechanism underlying the increase in BTR under oscillation welding is clarified based on the relationship between the achievement ratio of the weld single crystal growth and fraction of high-angle (>15<sup>o</sup>) solidification boundaries, which affect severe dendrite coalescence undercooling. The lower fraction of the high-angle weld solidification grain boundaries attributed to the superior achievement ratio of weld single crystal growth, which reduces the dendrite coalescence undercooling and BTR. Consequently, it enhances the solidification crack propagation resistance.

Effect of a traveling magnetic field on cadmium zinc telluride growth by the traveling heater method

The growth of high-quality cadmium zinc telluride (CZT) crystals using the traveling heater method (THM) is strongly influenced by the morphology of growth interface. Here, we investigate the effect of a traveling magnetic field (TMF) on the growth of CZT single crystals by the THM using the multi-physics numerical simulation method. When no magnetic field is applied, the concave morphology of the growth interface caused by the gravity-driven natural convection is confirmed using a multi-component mass transfer model based on the Maxwell-Stefan equations. In contrast, the application of an upward TMF accelerates the flow near the crucible wall and hence the lateral flow along the growth interface, finally leading to a relatively flat growth interface. Conversely, the increase of a downward TMF intensity significantly weakens natural convection in the central melt region; particularly, when the magnetic induction strength is increased to 300 mT at a frequency of 50 Hz, the desired convex-shaped growth interface can be achieved with the appearance of strong vortices at the dissolution interface. Therefore, we conclude that both the upward and downward TMF can improve the growth interface and thereby facilitates the growth of high-quality single crystals.

Effects of gamma-irradiation on the superconducting properties of FeTe0.55Se0.45 single crystals grown by self-flux method

We have investigated the effect of gamma (γ)-irradiation on the structural and superconducting properties of FeTe0.55Se0.45 single crystals grown by the self-flux method. The impact of γ-irradiation on the superconducting transition temperature (TC), critical current density (JC), and vortex pinning mechanism has been systematically studied. The x-ray diffraction study reveals the growth of single crystals along the c-axis. The superconductivity has been confirmed in pristine and γ-irradiated samples through temperature-dependent resistivity (ρ(T)) and magnetization [M(T)] measurements. After irradiation, a slight improvement is observed in the upper critical field Hc2(0) values. The values of thermally activated energy have been calculated and a crossover from a single to collective vortex pinning regime is observed. Additionally, we have analyzed the vortex phase diagrams, revealing a transition from vortex liquid to vortex glass state. Furthermore, the presence of second magnetization peak (SMP) or fishtail effect has been noticed in the M(H) loops, and with increasing temperature, the position of SMP (Hsp) shifts toward lower magnetic field regions. The critical current density has been estimated by Bean's critical state model at different magnetic fields [JC(H)] and temperatures [JC(T)]. The defects through gamma-irradiation lead to a significant threefold increase in JC compared to pristine samples in self-field and at 2 K. The pinning mechanisms have been explained using collective pinning theory and the Dew-Hughes model by analyzing the normalized pinning force density. Our analysis indicates that δl-pinning is dominant and point defects are present in all the samples.

Novel Synthesis of radioluminescent CsI:Tl microcrystals under ambient conditions by antisolvent recrystallization method

Thallium doped Cesium Iodide (CsI:Tl) radioluminescent microcrystals are promising candidate for scintillation applications that include medical imaging, nuclear safety and high energy particle detection applications. This paper introduces, for the very first time, an antisolvent recrystallization method to synthesize microcrystals of CsI:Tl. The antisolvent recrystallization method is useful for synthesizing microcrystals at room temperature under atmospheric pressure and humidity conditions with high product yield approaching ∼90 %. The polycrystalline nature of the CsI:Tl microcrystals is confirmed from the X-ray diffraction analysis, wherein the crystallite size is found to be in the range of 20–25 nm. The scanning electron microscopy revealed the size of microcrystals in the range of 1–13 μm. The doping concentration of thallium (with 0.06, 0.10, 0.20, 0.50 and 1.00 mol%) strongly affects the luminescence yield. At higher concentration of doping, a shift towards long wavelength is observed. The strongest luminescence yield is observed in the sample of 0.2 mol% Thallium doping, which is around 76 % of luminescence compared to single crystal of CsI:Tl. This work provides a low-cost alternative to the growth of radioluminescent microcrystals in comparison with the existing single crystal growth approaches.

Synergistic crystallization regulation and defect passivation for growth of high-quality perovskite single crystals towards ultrasensitive X-ray detection

This report demonstrates a method of synergistic defect passivation and crystallization regulation, which can significantly improve crystal quality and promote X-ray detector performance.