Growth Of Bulk Single Crystals Research Articles

Growth of water-insoluble rutile GeO2 thin films on (001) TiO2 substrates with graded Ge x Sn1−x O2 buffer layers

Rutile GeO2 (r-GeO2) is an ultrawide bandgap semiconductor with the potential for ambipolar doping and bulk single-crystal growth. In this study, we investigated r-GeO2 thin films grown on (001) TiO2 substrates with graded Ge x Sn1−x O2 buffer layers. GeO2 grown on bare TiO2 substrates via mist chemical vapor deposition exhibited water-soluble amorphous and/or α-quartz phases alongside the rutile phase. In contrast, the insertion of graded Ge x Sn1−x O2 buffer layers on the TiO2 substrate allowed the growth of single-phase water-insoluble r-GeO2 thin films. This study contributes to the development of water-insoluble r-GeO2 thin films for various applications.

A Congruent-Melt Infrared Nonlinear Optical Crystal Na4SrAs2S8.

A quaternary metal thioarsenate infrared (IR) nonlinear optical (NLO) compound Na4SrAs2S8 was successfully prepared by a high-temperature reaction method from stoichiometric agents. It crystallizes in the tetragonal P4n2 with the unit cell parameters a = 10.0393(3) Å, c = 6.9638(3) Å, and Z = 2, with the basic structural groups of isolated AsS4 tetrahedra. Compared with benchmark IR NLO crystal AgGaS2 (AGS), the title compound exhibits balanced optical properties of large band gap (3.05 eV vs. 2.60 eV) and considerable second harmonic generation response (0.95 × AGS). Moreover, the combined powder X-ray diffraction and differential scanning calorimetry analyses demonstrate that Na4SrAs2S8 is a congruent-melting compound with a low melting point of 668 °C, which is benefical for bulk single crystal growth. Experimental and theoretical calculation results indicate that Na4SrAs2S8 is a practically usable IR NLO crystal, also motivating the exploration of thioarsenates as high-performance IR NLO candidates.

AAg2MS4 (A = Na, K, Rb; M = P, As) Nonlinear Optical Series with Unique Cation‐Regulated Highly Anisotropic [AgS4] Hypertetrahedral Layered Framework

AbstractCommercial infrared (IR) nonlinear optical (NLO) materials are mainly from chalcopyrite‐type AMQ2 (A = Ag, Zn, M = Ga, Ge, Q = S, Se, P) crystals such as AgGaS2 (AGS), AgGaSe2 (AGSe), and ZnGeP2 (ZGP), in which the basic NLO‐active groups are MQ4 tetrahedral units. However, the small anisotropic character of them critical for small birefringence hinders the practical applications in the available IR wavelength range. In this study, a novel strategy for modulating birefringence is proposed using a cation regulation‐driven compressed hypertetrahedral layer approach and a family of AAg2MS4 (A = Na, K, Rb; M = P, As) IR NLO crystals are successfully obtained. Remarkably, the title compounds increase the birefringence to 0.12–0.15, about three times larger than that of AGS (0.04), while they can maintain large bandgaps and strong NLO effects. In addition, they exhibit congruent‐melting properties, beneficial for bulk single crystal growth. The work offers a firsthand access for designing and fabricating high‐performance IR NLO materials.

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

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

Chemical Bonding Induces One-Dimensional Physics in Bulk Crystal BiIr4Se8.

One-dimensional (1D) systems persist as some of the most interesting because of the rich physics that emerges from constrained degrees of freedom. A desirable route to harness the properties therein is to grow bulk single crystals of a physically three-dimensional (3D) but electronically 1D compound. Most bulk compounds which approach the electronic 1D limit still field interactions across the other two crystallographic directions and, consequently, deviate from the 1D models. In this paper, we lay out chemical concepts to realize the physics of 1D models in 3D crystals. These are based on both structural and electronic arguments. We present BiIr4Se8, a bulk crystal consisting of linear Bi2+ chains within a scaffolding of IrSe6 octahedra, as a prime example. Through crystal structure analysis, density functional theory calculations, X-ray diffraction, and physical property measurements, we demonstrate the unique 1D electronic configuration in BiIr4Se8. This configuration at ambient temperature is a gapped Su-Schriefer-Heeger system, generated by way of a canonical Peierls distortion involving Bi dimerization that relieves instabilities in a 1D metallic state. At 190 K, an additional 1D charge density wave distortion emerges, which affects the Peierls distortion. The experimental evidence validates our design principles and distinguishes BiIr4Se8 among other quasi-1D bulk compounds. We thus show that it is possible to realize unique electronically 1D materials applying chemical concepts.

Bulk single crystal growth and optoelectronic properties of the quasi-two-dimensional perovskites (CH3NH3)3Bi2X9 (X− = Br− and I−)

Single crystals of MA3Bi2X9 (X = Br, I) with quasi-two-dimensional structures were successfully grown and the relationship between the compositions, dimensionality, and properties were discussed.

Flux Growth and Characterization of Bulk InVO4 Crystals

The flux growth of InVO4 bulk single crystals has been explored for the first time. The reported eutectic composition at a ratio of V2O5:InVO4 = 1:1 could not be used as a self-flux since no sign of melting was observed up to 1100 °C. Crystals of InVO4 of typical size 0.5 × 1 × 7 mm3 were obtained using copper pyrovanadate (Cu2V2O7) as a flux, using Pt crucibles. X-ray powder diffraction confirmed the orthorhombic Cmcm structure. Rests of the flux material were observed on the sample surface, with occasional traces of Pt indicating some level of reaction with the crucible. X-ray absorption spectroscopy showed that oxidation states of indium and vanadium ions are +3 and +5, respectively. The size and high quality of the obtained InVO4 crystals makes them excellent candidates for further study of their physical properties.

The Bridgman method of (BiAs)2 (TeSe)3 bulk single crystal growth by spontaneous nucleation

The Bi0.5As1.5Te2.98Se0.02 single crystal in 11 mm?80 mm size was grown using the Bridgman method. Energy dispersive spectrometry (EDS) analysis was used to determine the chemical composition of the studied samples, as well as for checking and confirming the homogeneity of the samples. Mobility, concentration of charge majority carriers and Hall coefficient of single crystal, were determined using a Hall Effec system based on the Van der Pauw method. Hall Effect was measured at room temperature with four ohmic contacts and at temperature of liquid nitrogen with silver contacts with an applied magnetic field strength of 0.37 T at different current intensities. The expected improvement in the mobility of obtained single crystal doped with this content of arsenic was not obtained.

Fabricating Ba0.5Cs0.5Fe2As2 films on BaFe2As2 substrates and their superconducting properties

Ba0.5Cs0.5Fe2As2 films on BaFe2As2 substrates with T c ∼ 29.8 K have been synthesized by a simple one-step self-flux method. Quasi-single-crystal Ba0.5Cs0.5Fe2As2 films are more favorable in 122-type crystal structure but not in 1144-type. Based on the obtained Ba0.5Cs0.5Fe2As2 films, the temperature and angle-dependent resistivity are measured under a magnetic field up to 9.0 T. The results indicate that the films exhibited high upper critical fields, strong flux pinning potential and low anisotropic factors. By scaling the resistivity within the framework of the anisotropic Ginzburg–Landau (GL) theory, the angle-dependent resistivity of Ba0.5Cs0.5Fe2As2 films under various magnetic fields at a fixed temperature can be scaled to one curve. Both the Werthamer–Helfand–Hohenberg and GL methods give a similar anisotropic factor ∼3.0. Ba0.5Cs0.5Fe2As2, cannot naturally grow bulk single crystals but only form film on the surface of BaFe2As2 crystal under normal pressure. It is reasonable to infer that surface strain should play a key role in the formation of Ba0.5Cs0.5Fe2As2 films. Thus, it is believed that element doping or substitution may be one of the most effective methods to obtain doped-Ba0.5Cs0.5Fe2As2 bulk single crystals.

Ammonia-free epitaxy of single-crystal InN using a plasma-integrated gas-injection module

Group III nitride semiconductors are used for optical, high-frequency electronic, and power devices. In particular, indium nitride (InN) and In-rich indium gallium nitride (InGaN) are attractive materials for a wide range of carbon-neutral and post-5 G (5th generation mobile communication system) applications. However, the growth of high-quality bulk single crystals of both InN and In-rich InGaN cannot be ideally achieved owing to a mismatch between the low evaporation temperature of indium and the high temperature required to provide an adequate supply of reactive nitrogen species via the thermal decomposition of ammonia gas. In this study, we obtained a very-high-quality bulk InN material via epitaxial growth on a GaN template with the lowest dislocation density (∼3 × 109 cm–2) reported to date, and a narrow room-temperature full-width-at-half-maximum (∼0.1 eV) of the photoluminescence peak at 0.687 eV. These were achieved using a newly developed method obtained by combining microstrip-line microwave plasma irradiation with metal organic chemical vapor deposition. In this method, trimethylindium gas and pure nitrogen plasma (for producing a high density of nitrogen atoms) were supplied to a template independently, simultaneously, and continuously. We believe that the proposed procedure can serve as a standard guideline for non-toxic, low-energy-consumption, and low-cost manufacturing of numerous nitride-compound semiconductors.

Advanced inorganic halide ceramic scintillators

Research in ceramic scintillators has steadily progressed alongside the research in bulk single crystal scintillator growth. As interest in faster scintillation material production with lower cost increases, more research on scintillating ceramics is needed. Research targeting optimization of optically transparent ceramics that can rival bulk-grown crystals grown may lower cost, increase yield, increase volume, and improve energy resolution in applications and systems currently using sodium iodide and alike. Ceramic scintillators that are dense (>5 g/cm3), have high effective Z (>60), are bright (>40,000 photons/MeV), and are not sensitive to moisture as well as those that can be handled without protection are desired. Ultra-fast ceramic materials are also of interest. This paper presents an equipment design and technique to produce inorganic halide ceramic scintillators Cs2HfCl6 (CHC) and Tl2HfCl6 (THC). Improvements and optimization of CHC and THC ceramic scintillator fabrication are gauged by monitoring the energy resolution and peak position of 137Cs full energy peak at 662 keV. With a 1-inch diameter CHC ceramic scintillator, energy resolution of 5.4% (FWHM) and light yield of 20,700 ph/MeV are achieved, while with a 16-mm diameter THC ceramic scintillator, energy resolution of 5.1% (FWHM) and light yield of 27,800 ph/MeV are achieved. Decay times of 0.6 microseconds (21%) and 3.0 microseconds (79%) are measured for CHC and 0.3 microseconds (13%) and 1.0 microseconds (87%) for THC. Both ceramic CHC and THC scintillators have similarly good proportionality data when compared to their single crystal counterparts.

RENiO3 Single Crystals (RE = Nd, Sm, Gd, Dy, Y, Ho, Er, Lu) Grown from Molten Salts under 2000 bar of Oxygen Gas Pressure

The electronic properties of transition-metal oxides with highly correlated electrons are of central importance in modern condensed matter physics and chemistry, both for their fundamental scientific interest, and for their potential for advanced electronic applications. The design of materials with tailored properties has been, however, restricted by the limited understanding of their structure-property relationships, which are particularly complex in the proximity of the regime where localized electrons become gradually mobile. RENiO3 perovskites, characterized by the presence of spontaneous metal to insulator transitions, are one of the most widely used model materials for the investigation of this region in theoretical studies. However, crucial experimental information needed to validate theoretical predictions is still lacking due to their challenging high-pressure synthesis, which has prevented to date the growth of sizable bulk single crystals with RE different than La, Pr and Nd. Here we report the first successful growth of single crystals with RE = Nd, Sm, Gd, Dy, Y, Ho, Er and Lu and sizes up to ~75 {\mu}m, grown from molten salts in temperature gradient under 2000 bar oxygen gas pressure. The crystals display regular prismatic shapes with flat facets, and their crystal structures, metal-insulator and antiferromagnetic order transition temperatures are in excellent agreement with previously reported values obtained from polycrystalline samples. The availability of such crystals opens access to measurements that have hitherto been impossible to conduct. This should contribute to a better understanding of the fascinating properties of materials with highly correlated electrons, and guide future efforts to engineer transition metal oxides with tailored functional properties.

Phase Equilibria of the MnTe-Sb2Te3 System and Synthesis of Novel Ternary Layered Compound – MnSb4Te7

By using Differential Thermal Analysis (DTA) and Powder X-ray Diffraction (PXRD) techniques, the phase diagram of the MnTe-Sb2Te3 system has been constructed for the first time in the entire composition range. The system features two ternary layered van der Waals (vdW) compounds. Apart from known MnSb2Te4, novel MnSb4Te7 which a structural analogous of the known MnBi4Te7 was found in the system. Crystal structure parameters of both compounds were determined by Rietveld refinement using the fundamental parameter approach. Both compounds were found to decompose via peritectic reactions and possess significant homogeneity ranges. The title system is also characterized by the existence of the wide solid solution field based on the starting Sb2Te3. The present results would be useful for the bulk single crystal growth of both compounds from the liquid phase via the determination of primary crystallization areas.

“Liquinert” Process for High-Quality Bulk Single Crystal Growth

Bulk crystal growth technologies originate from the Czochralski (CZ) and Vertical Bridgman (VB) methods developed almost one century ago. Both methods were applied to prepare single crystals of many kind of inorganic materials, for example, semiconductors, halides and many oxides. In the VB process, molten raw materials are wetting the crucible wall easily. This phenomenon causes the sticking of grown crystals with crucibles and often leads to the cracking of the crystal and crucible. These issues prohibit us from obtaining high quality single crystals. Therefore, practical application of VB method is limited only on several materials such as CaF₂ and GaAs single crystals. The issue of crucible’s wetting is present in the CZ method as well. For example, the purity of silicon single crystals is degraded from 11N raw material to 5~6N level by the oxygen and carbon contamination caused by the wetting between silicon melt and quartz crucible. These issues are yet to be solved in VB and CZ methods. Many molten materials reach the spherical shape driven by the surface tension when a residual moisture (H₂O) is completely removed from the raw material, the crucible, and atmosphere. We denote this condition as the “Liquinert” state meaning “liquid being in an inert state”, non-wetting and non-reactive with the crucible at high temperature. The author has prepared many high-quality bulk crystals of mainly metallic halides and semiconductors, except oxides, by VB method when applying the “Liquinert” process. This technology is applicable to high quality bulk crystal growth of silicon as well as other inorganic materials of huge industrial interest. In this review, the “Liquinert” process, its background, methodology, examples of applications in fundamental research, and practical development are exposed. In addition, we also discuss the future of this industrial process on bulk silicon crystals for semiconductors and solar cells.

Superconducting and Electromagnetic Properties of YBaCuO Using Effective Melt Growth Process.

The interior seed melting growth (ISMG) method was applied to overcome the shortcomings of the seeded melt growth. According to the results of measuring captured magnetic force at 77 K, the interior side showed a higher captured magnetic force at 2.27 kG the top side at 2.08 kG. The combination of the top seed method and the interior seed method could improve both the magnetic levitation force and the captured magnetic force of both the interior and top sides. When the bulk samples were compared before and after neutron irradiation, the bulk samples after irradiation showed relatively improved material properties when compared to those before irradiation. To measure changes in other material properties by ab/ab + ac sector in YBaCuO bulk single crystal growth, superconducting properties were measured by varying the ab area size area, and when seeding was changed in a vertical direction, higher to measure different property changes in ab/ab + ac sector, it could obtain high magnetic levitation force and captured magnetic force. This result seems to because the ab area with high superconducting properties showed a relatively larger growth.

Bulk Single Crystal Growth of W Co-Doped Ce:Gd₃Ga₃Al₂O₁₂ by Czochralski Method

Effects of the tungsten (W) ions co-doping on the crystal growth, optical and scintillation properties for the Czochralski (Cz) grown Ce:Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> (GGAG) single crystals were investigated. The W 0%, 0.1%, 0.3%, 1%, and 5% co-doped Ce 1%:GGAG single crystals with a diameter of 1 in and length of 60-80 mm were grown by the Cz method. The effective segregation coefficient of the W ions was found as 0.002, 0.001, and 0.005 for W 0.1%, 0.3%, and 1%, Ce:GGAG, respectively. The segregation of W ions in GGAG host, light yield, and scintillation decay of the W co-doped Ce:GGAG were evaluated. The light yield decreased as the concentration of W co-dopant increased and toward the tail of the crystal. Furthermore, the defect role and related charge trapping in the W co-doped crystals were monitored by the thermo-stimulated luminescence.

Chemical vapor transport growth of bulk black phosphorus single crystals

Recent progress in growth of bulk black phosphorus single crystal by CVT method has been briefly reviewed with the emphasis on reaction system, nucleation and growth mechanism as well as advancement in growth of doped BP bulk single crystal.

Growth and characterization of two-dimensional crystals for communication and energy applications

This review article covers the growth and characterization of two-dimensional (2D) crystals of transition metal chalcogenides, h-BN, graphene, etc. The chemical vapor transport method for bulk single crystal growth is discussed in detail. Top-down methods like mechanical and liquid exfoliation and bottom-up methods like chemical vapor deposition and molecular beam epitaxy for mono/few-layer growth are described. The optimal characterization techniques such as optical, atomic force, scanning electron, and Raman spectroscopy for identification of mono/few-layer(s) of the 2D crystals are discussed. In addition, a survey was done for the application of 2D crystals for both creation and deterministic transfer of single-photon sources and photovoltaic systems. Finally, the application of plasmonic nanoantenna was proposed for enhanced solar-to-electrical energy conversion and faster/brighter quantum communication devices.

Bulk single crystal growth and sample surface preparation of catalytic NaAu2

Here in we have grown bulk single crystals of NaAu2 for the first time to enable surface studies on the nature of the (111) bulk surface. This intermetallic compound exhibits surprisingly high catalytic activity for CO oxidation, a benchmark reaction. Theory predicts NaAu2 to be the most thermodynamically stable composition in the Na-Au binary phase diagram and NaAu2 has been seen to preferentially form in experiments containing Na and Au which supports this prediction. The (111) surface was also predicted to be the most stable and is nearly bulk-terminated making single crystal samples prepared with this crystallographic orientation a fitting choice. The crystal quality and surface composition of the metallographically prepared surface was determined by x-ray diffraction methods in addition to optical and electron microscopy.

Growth of Bulk Single Crystals of Materials for All Solid State Lithium Ion Batteries by The TSFZ Method

Growth of Bulk Single Crystals of Materials for All Solid State Lithium Ion Batteries by The TSFZ Method