Crystal Growth Technique Research Articles

Conservative finite volume strategy for investigation of solution crystal growth techniques

The article presents a finite volume method for the numerical study of solution crystal growth. The mathematical model is based on the time-dependent Navier-Stokes equations in the stream function/vorticity form, energy and mass transfer equations in solid and liquid phases, and thermodynamics equilibrium conditions at the phase transition interface. The problem is axisymmetric and studied in a cylindrical body-fitted coordinate system. The equations for temperature and composition in the solid and liquid phases, and interface velocity are solved simultaneously. The approach ensures global conservation of kinetic and thermal energy and conservation of the solute. The proposed strategy allows performing a full-scale numerical simulation of a variety of technological regimes with a reversal in the crystal dissolution and growth. Sample calculations are reported for prototypes of liquid phase diffusion growth process and Bridgman-Stockbarger method.

Enhancing crystal growth using polyelectrolyte solutions and shear flow

The ability to grow properly sized and good quality crystals is one of the cornerstones of single-crystal diffraction, is advantageous in many industrial-scale chemical processes1-3, and is important for obtaining institutional approvals of new drugs for which high-quality crystallographic data are required4-7. Typically, single crystals suitable for such processes and analyses are grown for hours to days during which any mechanical disturbances-believed to be detrimental to the process-are carefully avoided. In particular, stirring and shear flows are known to cause secondary nucleation, which decreases the final size of the crystals (though shear can also increase their quantity8-14). Here we demonstrate that in the presence of polymers (preferably, polyionic liquids), crystals of various types grow in common solvents, at constant temperature, much bigger and much faster when stirred, rather than kept still. This conclusion is based on the study of approximately 20 diverse organic molecules, inorganic salts, metal-organic complexes, and even some proteins. On typical timescales of a few to tens of minutes, these molecules grow into regularly faceted crystals that are always larger (with longest linear dimension about 16 times larger) than those obtained in control experiments of the same duration but without stirring or without polymers. We attribute this enhancement to two synergistic effects. First, under shear, the polymers and their aggregates disentangle, compete for solvent molecules and thus effectively 'salt out' (that is, induce precipitation by decreasing solubility of) the crystallizing species. Second, the local shear rate is dependent on particle size, ultimately promoting the growth of larger crystals (but not via surface-energy effects as in classical Ostwald ripening). This closed-system, constant-temperature crystallization driven by shear could be a valuable addition to the repertoire of crystal growth techniques, enabling accelerated growth of crystals required by the materials and pharmaceutical industries.

Nearly Identical but Not Isotypic: Influence of Lanthanide Contraction on Cs2NaLn(PS4)2 (Ln = La-Nd, Sm, and Gd-Ho).

The effect of lanthanide contraction often results in topological and symmetry changes in compounds with the same compositions as a function of lanthanide cation size. Here we report on the first example of a lanthanide thiophosphate exhibiting a change in the lanthanide cation environment without any topological or symmetry change. A series of new lanthanide thiophosphates with mixed alkali cations were obtained via a flux crystal growth technique using a CsI flux. The obtained compounds Cs2NaLn(PS4)2 (Ln = La-Nd, Sm, and Gd-Ho) were grown as large single crystals (∼0.1-1 mm3) and characterized using single-crystal X-ray diffraction and magnetic susceptibility measurements. As we moved across the series, the structural studies revealed a change in the lanthanide coordination environment depending on the identity of the lanthanide. Although all compounds in the Cs2NaLn(PS4)2 series crystallize in the same space group and have the same Wyckoff atom positions, a slight change in size between Sm3+ and Gd3+ causes a subtle change in coordination number from 9 (for Ln = La-Sm) to 8 (for Ln = Gd-Ho), resulting in two distinct but virtually identical structure types. Ab initio calculations were performed, and the observed experimental trend was corroborated computationally. Magnetic measurements performed on the Cs2NaLn(PS4)2 (Ln = Ce, Pr, Nd, Gd, and Tb) compounds revealed paramagnetic behavior.

Antibody Response against SRBC Immunosuppressed with Hydrocortisone Black Raspberry Extract Based Carbon Supported TiO2 Crystal

As an titanium dioxide (TiO2) with carbon supported materials, particularly in anatase phase, have been extensively investigated and utilized in many technological applications due to its excellent physicochemical properties. This article summarizes the recent progress in growing carbon supported anatase TiO2 crystals from the perspectives of Bridgemen technique. The Bridgmen technique is used to grow this crystal with TiO2 directly dissolved with carbon sources and 10 mL of Black Raspberry, as well as the performance in various applications are largely determined by external surfaces exposed, and thus crystal shape engineering is paramount for this type of materials. Furthermore, the antibody response against SRBC immunosuppressed with Hydrocortisone in Mice Model is explained here. This Crystal growth technique is also highlighted which would open a new field for the growth of single crystals with unique morphology. The objective of this study was to examine the effects of a antibody response against SRBC product containing on the induction of the Mice antibody response to various antigens, both systemically and in the gut. The Mice received subsequently were immunized with sheep red blood cells (SRBC) and bovine serum albumin (BSA) to evaluate antibody responses in serum or with tetanus toxoid (TT) to measure the antibody response in gut contents. Control groups received phosphate-buffered saline. Overall, BSA and SRBC induced a detectable antibody response.

Spin accumulation in photo-induced potential dimples generated in semiconductors

Conventional ways of confining charges in semiconductors employ advanced lithographic and crystal-growth techniques. The construction of micro/nano-scale structures is also essential for manipulating spins. However, existing techniques are not always flexible enough to control spins in appropriate positions and timings. Here we report an alternative mechanism, which enables us to design temporal and reconfigurable low-dimensional potentials. The formation of photo-induced potential dimples is deduced from time and spatially-resolved Kerr rotation measurements performed on a GaAs quantum well. Two-dimensional images of spin distributions reveal that the photo-injected electron spins in a small area illuminated by a pump light survive for a time that is two orders of magnitude longer than typical recombination lifetimes. The Kerr rotation dependence on the pump laser conditions implies that the temporally generated dimple-shaped potential profile induced by remote charges effectively confines the electrons and enhances the spin lifetime determined by fluctuating spin-orbit effective magnetic fields.

Current status and near future plan of neutron protein crystallography at J-PARC.

The IBARAKI Biological Crystal Diffractometer (iBIX) has been available for use at MLF (Material and Life Science Facility) in J-PARC (Japan Proton Accelerator Research Complex) since 2008. The development in state-of-the-art detector systems could enable iBIX to become one of the highest-performance neutron single-crystal diffractometers in the world. Here, together with other various developments, such as data reduction software, crystal growth, and new techniques in measurement coupled analysis, we provided new hydrogen and water structural data of several proteins and macromolecules. Although the proton power at MLF has not yet reached its planned maximum (1MW), a more powerful neutron source will be soon needed for neutron protein crystallography. A future idea is also proposed and discussed in this article.

Solid-state crystal growth of lead-free ferroelectrics

Review article of the solid-state crystal growth (SSCG) technique and the progress of lead-free ferroelectric single crystals for piezoelectric applications.

Existence and static stability of a capillary free surface appearing in a dewetted Bridgman process. Part II.

This paper presents six theoretical results concerning the existence and static stability of a capillary free surface appearing in a dewetted Bridgman crystal growth technique. The results are obtained in an axis-symmetric 2D model for semiconductors for which 𝜃𝜃𝑐𝑐+𝛼𝛼𝑒𝑒>𝜋𝜋 (where:𝜃𝜃𝑐𝑐- wetting angle and 𝛼𝛼𝑒𝑒- growth angle). Numerical results are presented in case of GaSb semiconductor growth. The reported results can help, the practical crystal growers, in better understanding the dependence of the free surface shape and size on the pressure difference across the free surface and the right choice of crystal size, pressure difference and thermal conditions for the growth process.

Processing‐Performance Evolution of Perovskite Solar Cells: From Large Grain Polycrystalline Films to Single Crystals

AbstractSolution‐processable halide perovskites have emerged as strong contenders for next‐generation solar cells owing to their favorable optoelectronic properties. To maintain the efficiency momentum of perovskite solar cells (PSCs), development of advanced processing techniques, particularly for the perovskite layer, is imperative. There is a close correlation between the quality of the perovskite layer and its photophysical properties: Highly crystalline large grains with uniform morphology of the perovskite layer and their interface with charge transporters are crucial for achieving high performance. Significant efforts have been dedicated to achieve perovskite films with large grains reaching the millimeter‐scale for high‐efficiency PSCs. Recent work showcases a transition from large grain polycrystalline to single‐crystalline (SC) PSCs made possible by the facile growth of perovskite single crystals. In this review, the recent progress of the large grain polycrystalline PSCs and grain boundary‐free SC‐PSCs is reported, particularly focusing on the recent approach of depositing large‐grained perovskite layers and single crystal growth technique, that have been adopted for fabrication of efficient PSCs. In addition, prospects of SC‐PSCs and their further development in terms of efficiency, device design, scalability, and stability are discussed.

Vibrational spectroscopic investigation and DFT computation of nonlinear optical crystal L-Glutaminium 4-methylbenzenesulfonate

A nonlinear organic crystal, L-Glutaminium 4-methylbenzenesulfonate was synthesized by slow evaporation crystal growth technique. Theoretical as well as experimental FT-IR, FT-Raman and UV–vis spectra were analyzed and the formation of crystal was confirmed using powder X-ray diffraction study. The existence of intramolecular donor-acceptor interactions through N–H⋯O hydrogen bonds were confirmed with vibrational spectroscopic and natural bond orbital methods. The photoluminescence spectrum was recorded and analyzed. Kurtz and Perry powder technique was employed to detect the second harmonic generation of the grown crystal. Moreover, molecular electrostatic potential and Mullikan charge distribution were studied for identifying the most reactive sites of the compound.

Growth of III-V semiconductor crystals under microgravity

The low-gravity environment aboard the space provides a unique platform for both understanding the crystal-growth-related phenomena that are masked by gravity on the earth and exploring new crystal growth techniques. III-V semiconductor crystal growths were carried out under microgravity and the main results include: device-grade semi-insulating GaAs single crystal with improved stoichiometry was grown under microgravity condition, and low noise field-effect transistors and analog switch integrated circuits were fabricated and the performances were better than their terrestrial counterparts; detached Bridgman growth was realized in two model systems of GaSb and InSb by suppressing the hydrostatic pressure of melt, and largely reduced dislocation densities in the materials were observed; the contributions of buoyancy-driven convection, Marangoni convection and rotation magnetic field forced convection on the microscopic segregation were carefully studied; the vertical gradient freezing method was employed to grow semiconductor alloys and chemically homogeneous GaInSb crystal was obtained. In this review, the main progresses in these aspects are summarized and the future challenges are discussed.

Crystal Growth Technique for Formation of Double Roughness Structures Mimicking Lotus Leaf.

Bio-inspired functional materials have received much attention for their potential to provide sustainable and advanced materials. The lotus effect has proven to be one of the most remarkable biomimetic effects since it was discovered by Barthlott. A superhydrophobic surface with the ability to bounce water droplets is the origin of the self-cleaning mechanism that keeps the surface clean by removing dust using water droplets moving with momentum. We have developed a crystal growth technique (CGT) of photochromic diarylethenes over the past decade, and from this, we fabricated a surface structure that closely resembles the natural lotus leaf's characteristic of controlling the Laplace pressure and clarified the importance of the double roughness structure of the surface. The bouncing ability is also discussed in terms of the characteristic size of the double roughness structure theoretically. Moreover, this work clarifies the exquisiteness of the double roughness structure of the leaf. We also show that the CGT is a versatile technique with the potential to fabricate desired structured surfaces.

Existence and static stability of a capillary free surface appearing in a dewetted Bridgman process. Part I.

This paper presents six theoretical results concerning the existence and static stability of a capillary free surface appearing in a dewetted Bridgman crystal growth technique. The results are obtained in an axis-symmetric 2D model for semiconductors for which 𝜃𝜃𝑐𝑐+𝛼𝛼𝑒𝑒<𝜋𝜋 (where:𝜃𝜃𝑐𝑐- wetting angle and 𝛼𝛼𝑒𝑒- growth angle). Numerical results are presented in case of InSb semiconductor growth. The reported results can help, the practical crystal growers, in better understanding the dependence of the free surface shape and size on the pressure difference across the free surface and prepare the appropriate seed size, and thermal conditions before seeding the growth process.

Dual wettability on diarylethene microcrystalline surface mimicking a termite wing

The termite wing has a specific property of wetting in contact with a water droplet: it adsorbs water mist, whereas larger water droplets are bounced on the surface. This is owing to the survival strategy of termites. Here, we reproduce the termite wing’s dual wettability by a photoinduced crystal growth technique. Upon UV irradiation to a microcrystalline surface of a mixture of two diarylethenes, two types of needle-shaped crystals of distinctly different sizes are observed to grow. The surface shows behavior akin to the termite wing’s dual wettability. The bouncing ability of a water droplet is attributed to the smaller-sized needle crystals, whereas the adhesive property is owing to the larger-sized ones, explaining the microstructures of the termite wing. Considering dissipation energy and adhesion energy, the bouncing ability and dual wettability can be explained theoretically. The surface could potentially be used in water harvesting applications.

A Comparative Study of the Crystal Growth Techniques of Silicon Carbide, Technology Adaption and the Road to Low Cost Silicon Carbide Materials

The growing demand for power electronic device for automotive, photovoltaic, transportation, motor drives creates an enormous demand for widebandgap semiconducting materials such as silicon carbide (SiC) and gallium nitride (GaN). While GaN based devices can be used for low voltages, SiC is the workhorse for voltages >600. Progress in the availability of larger diameter SiC wafers has driven the final cost of device assembly down. In this paper we compare different growth techniques for growing high quality SiC crystals, technology adaption and road to low cost SiC materials. GT Advanced Technologies has been involved in SiC sublimation equipment manufacturing since the year 2000 and the results from our 100 mm and 150 mm SiC crystals show high epi-quality.

Study of vibrational modes in (Ga2S3)x−(Ga2Se3)1-x mixed crystals by Raman and infrared reflection measurements

Raman and infrared (IR) reflection characteristics were investigated in the frequency region of 100–450 cm−1 for (Ga2S3)x − (Ga2Se3)1-x mixed crystals for compositions of x increasing from 0.0 to 1.0 by intervals of 0.25 obtained by Bridgman crystal growth technique. In the Raman spectra of these crystals four dominant peak features were observed while two bands were detected in the IR spectra of interest samples. Kramers-Kronig dispersion relations applied to IR spectra presented the frequencies of transverse optical modes. The compositional dependencies of revealed Raman- and IR-active mode frequencies on (Ga2S3)x − (Ga2Se3)1-x crystals were established. One-mode behavior was displayed from indicated dependencies.

Progress in Single Crystal Growth of Wide Bandgap Semiconductor SiC

The research and commercialization of SiC based power device have been burgeoning over the last decade worldwide, which is bringing about an increasing demand on lost-cost and low-defect SiC wafers. To meet this challenge, we have been continuously making efforts on improving the crystal growth and wafer processing techniques. Now, the mass-production of high quality 4-inch, 6-inch n-type and semi-insulating SiC wafers has been realized. Statistically, the micropipe density is lower than 0.5 cm-2. The resistivity of the wafers is lower than 0.02 Ω·cm and up to 108 Ω·cm for n-type and semi-insulating SiC single crystals, respectively. A state of the art processing technique has been developed to control wafer deformation and thickness within the desired values for subsequent epitaxy. The total defect number of the epitaxial layers grown on the "epi-ready" 4-inch SiC wafer is 63, and the usable area is 97.6%, indicating the high quality of our SiC substrates.

(Invited) Atomic-Scale Investigations of TiO2 surfaces in Ambient and Solution Environments

Earth-abundant metal oxide nanocrystals have attracted a great deal of attention for environmental remediation and photocatalysis. These materials are attractive because they are inexpensive, they are typically very stable under reactive conditions, and their semiconducting nature enables efficient generation of long-lived photocarriers that can initiate chemical reactions. Nevertheless, an atomic-scale understanding of their reactivity in ambient and solution environments has proven elusive for two reasons. First, the complex milieu of reactants in these environments makes the discrimination of surface chemistry from adventitious contamination difficult. Second, the small size of nanocatalysts prohibits face-specific studies with most surface science techniques. In this talk, I will review our work in developing “new eyes” for nanocatalysis that address both issues. Over the past few years, researchers around the world have observed the formation of mysterious molecularly ordered structures on the surface of TiO2 photocatalysts in air and solution. These structures have been attributed to many causes, including a new ordered state of adsorbed H2O — persistent in vacuum at room temperature — in which one H2O molecule adsorbs to every other surface Ti atom. Using a combination of atomic-scale microscopy and spectroscopy, we show that these structures are due to the highly selective adsorption of atmospheric formic and acetic acids that are typically present in parts-per-billion concentrations. These surfaces effectively repel other adsorbates, such as alcohols, present in much higher concentrations. The high affinity of the surface towards carboxylic acids is attributed to their bidentate binding. The self-assembled organic acid monolayers have the unusual property of being both hydrophobic and highly water soluble, which may contribute to the self-cleaning properties of TiO2. Interestingly, these monolayers block the undercoordinated surface cation sites typically implicated in photocatalysis. In related work, we have shown that hydrothermal crystal growth techniques can produce anatase nanocrystals suitable for study at the atomic-scale with STM and other surface science techniques, as shown in the accompanying figure. Despite being synthesized in solution, the nanocrystal surfaces are very clean and passivated by a protecting monolayer. Using these crystals, we have shown that the most commonly used functionalization chemistry for oxide nanocatalysts, a carboxylic acid solution, causes the spontaneous reorganization of the nanocatalyst, leading to a five-fold increase in the number of reactive sites and revealing the atomic-scale origins of catalyst activation. Finally, we have investigated the structure of solution-deposited monolayers on TiO2 and demonstrated a rational approach to tuning intermolecular interactions and enabling long-range ordering. We show that simple electrostatic insights can be used to engineer away unfavorable intermolecular interactions, producing monolayers with exceptional long-range ordering. Quantitative measurements of the intermolecular interaction energies from molecularly resolved STM images are a factor of ~7 larger than those predicted by dispersion-corrected density functional theory (DFT). The discrepancy between experiment and simulation is not currently understood. This finding suggests a new path to the production of highly ordered monolayers and superstructures of large molecules. Figure 1

Synthesis of Nanostructure InxGa1−xN Bulk Alloys and Thin Films for LED Devices

In this study, we investigated an innovative method for the fabrication of nanostructure bulk alloys and thin films of indium gallium nitride (InxGa1−xN) as active, thin films for light-emitting diode (LED) devices using both crystal growth and thermal vacuum evaporation techniques, respectively. These methods resulted in some tangible improvements upon the usual techniques of InxGa1−xN systems. A cheap glass substrate was used for the fabrication of the LED devices instead of sapphire. Indium (In) and Gallium (Ga) metals, and ammonia (NH3) were the precursors for the alloy formation. The alloys were prepared at different growth temperatures with compositions ranging from 0.1 ≤ x ≤ 0.9. InxGa1−xN alloys at 0.1 ≤ x ≤ 0.9 had different crystallinities with respect to X-Ray diffraction (XRD) patterns where the energy bandgap that was measured by photoluminescence (PL) fell in the range between 1.3 and 2.5 eV. The bulk alloys were utilized to deposit the thin films onto the glass substrate using thermal vacuum evaporation (TVE). The XRD thin films that were prepared by TVE showed high crystallinity of cubic and hexagonal structures with high homogeneity. Using TVE, the InxGa1−xN phase separation of 0.1 ≤ x ≤ 0.9 was eliminated and highly detected by XRD and FESEM. Also, the Raman spectroscopy confirmed the structure that was detected by XRD. The FESEM showed a variance in the grain size of both alloys and thin films. The InxGa1−xN LED device with the structure of glass/GaN/n-In0.1Ga0.9N:n/In0.1Ga0.9N/p-In0.1Ga0.9N:Mg was checked by the light emitted by electroluminescence (EL). White light generation is a promising new direction for the fabrication of such devices based on InxGa1−xN LED devices with simple and low-cost techniques.

Thermoelectric Properties of Pure SnSe Single Crystal Prepared by a Vapor Deposition Method

AbstractAs a promising eco‐friendly high‐performance thermoelectric material, SnSe single crystal has attracted much attention during the past several years. In this work, SnSe single crystal is prepared through a novel vapor deposition method in which polycrystalline SnSe is volatilized on a hot side (800–850 °C) and single‐crystalline SnSe spontaneously nucleates on the cold side (500–650 °C) based on the inside wall of a quartz ampoule. This crystal growth technique is beneficial for obtaining high‐purity SnSe crystal as some metal ions, such as Li+, Na+, and K+, in the quartz ampoule will be restricted from diffusing into the material. SnSe single crystal along the a‐axis is measured to experience a Pnma–Cmcm phase transition around 800 K where power factor (PF) exhibits the highest value of 6.2 µW cm−1 K−2 and total thermal conductivity ktot shows the lowest value of 0.48 W m−1 K−1. Accordingly, SnSe single crystal reaches a maximum ZT = 0.98 near phase transition temperature. These results not only provide an effective approach for pure SnSe single crystal fabrication, but also reveal the intrinsic electronic and phononic transport properties of thermoelectric SnSe.