Growth Of Single Crystals Research Articles

Single crystal growth and characterization of the intermetallic cage compounds R3Co4Ge13 (R = Y, Gd-Lu)

Single crystal growth and characterization of the intermetallic cage compounds R3Co4Ge13 (R = Y, Gd-Lu)

Synthesis, growth, and characterization of natural dye-doped hexamethylenetetramine p-nitrophenol monohydrate single crystals for nonlinear optical applications

Synthesis, growth, and characterization of natural dye-doped hexamethylenetetramine p-nitrophenol monohydrate single crystals for nonlinear optical applications

High-concentration diamond nitrogen vacancy color center fabricated by microwave plasma chemical vapor deposition and its properties

Diamond nitrogen vacancy (NV) color centers have good stability at room temperature and long electron spin coherence time, and can be manipulated by lasers and microwaves, thereby becoming the most promising structure in the field of quantum detection. Within a certain range, the higher the concentration of NV color centers, the higher the sensitivity of detecting physical quantities is. Therefore, it is necessary to dope sufficient nitrogen atoms into diamond single crystals to form high-concentration NV color centers. In this study, diamond single crystals with different nitrogen content are prepared by microwave plasma chemical vapor deposition (MPCVD) to construct high-concentration NV color centers. By doping different amounts of nitrogen atoms into the precursor gas, many problems encountered during long-time growth of diamond single crystals under high nitrogen conditions are solved. Diamond single crystals with nitrogen content of about 0.205, 5, 8, 11, 15, 36, and 54 ppm (1ppm –10<sup>–6</sup>) are prepared. As the nitrogen content increases, the width of the step flow on the surface of the diamond single crystal gradually widens, eventually the step flow gradually disappears and the surface becomes smooth. Under the experimental conditions in this study, it is preliminarily determined that the average ratio of the nitrogen content in the precursor gas to the nitrogen atom content introduced into the diamond single crystal lattice is about 11. Fourier transform infrared spectroscopy shows that as the nitrogen content inside the CVD diamond single crystal increases, the density of vacancy defects also increases. Therefore, the color of CVD high nitrogen diamond single crystals ranges from light brown to brownish black. Compared with HPHT diamond single crystal, the CVD high nitrogen diamond single crystal has a weak intensity of absorption peak at 1130 cm<sup>–1</sup> and no absorption peak at 1280 cm<sup>–1</sup>. Three obvious nitrogen-related absorption peaks at 1371, 1353, and 1332 cm<sup>–1</sup> of the CVD diamond single crystal are displayed. Nitrogen atoms mainly exist in the form of aggregated nitrogen and single substitutional N<sup>+</sup> in diamond single crystals, rather than in the form of C-defect. The PL spectrum results show that defects such as vacancies inside the diamond single crystal with nitrogen content of 54 ppm are significantly increased after electron irradiation, leading to a remarkable increase in the concentration of NV color centers. The magnetic detection performance of the NV color center material after irradiation is verified, and the fluorescence intensity is uniformly distributed in the sample surface. The diamond single crystal with nitrogen content of 54 ppm has good microwave spin manipulation, and its longitudinal relaxation time is about 3.37 ms.

On luminescent and scintillation properties of CsMgCl3:Eu2+ crystals

The paper reports results of pure CsMgCl3 and CsMgCl3:xEu2+ (x = 0.5, 1 and 1.5 mol. %, in the charge) single crystals growth and investigations of their functional properties. The crystals were grown by Bridgman method and the entry ratio of Eu2+ into CsMgCl3 was determined as 0.021, i.e. in all the europium-activated samples the concentration of the activator was at the level of admixtures. The photoluminescence spectra of CsMgCl3:Eu2+ show that Eu enters in the crystal both as Eu2+ form (main) and Eu3+ one (trace amounts). The shape of the spectra are dependent on excitation wavelength (λex): at λex=350 nm the shape of the spectra corresponds to those of Eu2+ activated halides (the maxima in 470–490 nm range) and at λex=275 nm the shape of spectra corresponds to those of Eu3+-activated phosphors. X-ray luminescence spectra include two bands with the maxima at 460 nm proper for Eu2+- activated halides and at 545 nm which could be ascribed to the distortions of CsMgCl3 crystal lattice due to entering of the slightly isomorphic Eu2+. The X-ray luminescence decay time is estimated within 0.8–0.9 µs. CsMgCl3:Eu2+ crystals possess the light yield of ca. 150 % vs. BGO (Bi4Ge3O12) and it is impossible to determine the concentration dependence since only traces of the activator are incorporated inside CsMgCl3:Eu2+ crystals. The best energy resolution is 18 %.

CRYSTALS GROWTH OF AND CRYSTAL STRUCTURE OF SOLID SOLUTIONS IN THE Ag8SiS6 HOMOGENEITY REGION

Compounds with an argyrodite structure are a family of complex chalcogenides that demonstrate a wide range of properties: superionics, thermoelectrics, sensors, and photovoltaic materials. For sulfur-containing representatives, the main field of application is solid-state ionics. However, the formation of solid solutions is used to modify and improve the functional parameters of individual argyrodites. When solid solutions are formed by iso- or heterovalent substitution, an additional deformation of the crystal structure occurs, which increases the efficiency of ion transport. For the growth of single crystals, the method of direct crystallization by melt-solution technique was used. Based on the results of DTA, technological conditions for growing single crystals of solid solutions of Ag7.75P0.25Si0.75S6 and Ag7.5P0.5Si0.5S6 were developed. The temperature of the melt zone (Tmelt) was 50 K higher than the melting point of the solid solutions, and the temperature of the annealing zone (Tann) was 2/3 of their crystallization temperature determined by the DTA method. As a result, single crystals of dark gray color with a metallic luster were obtained. The crystal structure of the solid solutions of Ag7.75P0.25Si0.75S6 and Ag7.5P0.5Si0.5S6 was determined by the Rietveld method. Both solid solutions crystallize in a rhombic crystal system, SG Pna21, with lattice parameters: a = 15.06 Å, b = 7.44 Å, c = 10.54 Å (Ag7.75P0.25Si0.75S6) and a = 15.06 Å, b = 7.44 Å, c = 10.54 Å (Ag7.5P0.5Si0.5S6).

Ti3AlC2 single crystal growth via controlling horizontal temperature gradient

ABSTRACTGrowth of single‐crystal MAX phases is crucial for studying their intrinsic physical properties. Although Ti3AlC2 is one of the most popular MAX phases for the study of high‐temperature structural materials as well as a precursor for MXene, the growth of Ti3AlC2 single crystals remains a challenge owing to the limited solubility of graphite in the Ti melt via the self‐flux method. In this study, a horizontal temperature gradient was used to resolve the dissolution of graphite in the melt and its diffusion rate. Ti3AlC2 single crystals with an area of 9 mm2 were successfully produced under horizontal temperature gradients. It was tentatively proposed that the crystallinity of Ti3AlC2 single crystals could be reflected by the intensity ratio of the in‐plane and c‐axial phonon vibration modes in the Raman spectra of the MAX phase.

Breaking the Thermodynamic Equilibrium for Monocrystalline Graphene Fabrication by Ambient Pressure Regulation.

Developing high-quality monocrystalline graphene has been an area of compelling research focus in the field of two-dimensional materials. Overcoming growth cessation presents a significant challenge in advancing the production of monocrystalline graphene. Herein, methods for sustaining a steady and consistent growth driving force are investigated based on the single-crystal growth theory. Comparative analysis revealed that each dynamic regulation method significantly increased the size of graphene compared to samples grown under stable pressure conditions. The grain size of high-quality graphene was significantly increased from ∼400 μm to ∼3 mm. Moreover, experimental measurements and numerical simulations were employed to investigate the impact of ambient pressure on the temperature and flow field. By considering the influence of pressure on the boundary layer and reaction rate constant, the mechanism underlying the dynamic regulation of ambient pressure was elucidated. Ultimately, the crystal growth kinetics theory, initially formulated with considerations of undercooling ΔT and supersaturation Seff, was developed by inducing the individual parameter of ambient pressure P. Due to diameter expansion and mechanical property promotion, a bilayer graphene Fabry-Perot interference (1100 μm) sensor with a stable signal response (52 dB) and superior minimum detection pressure at 20 kHz (87 μPa/Hz1/2) was prepared. This innovative approach to regulating ambient pressure during crystal growth enables monocrystalline graphene to possess superior structure and properties for future technologies and provides insights into the production of other two-dimensional materials.

Growth and characterization of malonic acid-doped KDP single crystal

Growth and characterization of malonic acid-doped KDP single crystal

Conventional and unidirectional growth of yttrium-doped sulphamic acid single crystals for NLO applications

Conventional and unidirectional growth of yttrium-doped sulphamic acid single crystals for NLO applications

Solid-state growth of strontium titanate single crystals during flash sintering

Solid-state growth of strontium titanate single crystals during flash sintering

Engineering Insights into Heater Design for Oxygen Reduction in CZ Silicon Growth

Oxygen impurity is unavoidable during the Czochralski (CZ) growth of single silicon crystals. Currently, there are costly methods to control oxygen levels in the final silicon crystal, such as using magnets or high-quality crucibles. This paper proposes a special heater design to decrease and control oxygen concentration during the CZ process without incurring additional costs. Four distinct heater designs are analyzed for their impact on various parameters. The temperature profiles within the heaters, CZ puller, and silicon melt and crystal are studied. The research shows that heater design significantly influences temperature distributions and melt patterns, affecting oxygen distribution and its transport mechanisms. If more heat is supplied at the upper section of the crucible, oxygen solvation near the melt-free surface increases, and oxygen atoms are more likely to evaporate from the melt surface. Furthermore, shifting the high temperature to the crucible's top side wall strengthens buoyancy-thermocapillary vortices while weakening Taylor-Proudman vortices. This helps transport oxygen to the melt-free surface before it reaches the melt-crystal interface. With the optimal heater design, an oxygen reduction of 6 Ppma (parts per million atoms) was achieved by simply altering the heater design configuration.

Fast single-crystallization of Cu foils Facilitated by graphene growth

The production of large-area single-crystal metal foils such as Cu and Ni has recently gained momentum through thermally annealing of commercially available polycrystalline foils. Surface energy plays a pivotal role for grain growth, but is usually insufficient, particularly for adjacent grains with similar surface orientations, causing prolonged annealing time and reproducibility issues. Our method accelerates Cu foil single-crystallization through graphene growth, where graphene coverage on Cu modulates surface energy, enhancing driving forces and accelerating grain growth. This is a critical breakthrough in overcoming the traditional grain growth limitations. We successfully prepare decimeter-sized single-crystal Cu (111) foils with high efficiency and reproducibility and use it for single-crystal graphene growth. Our method paves the way for the scalable production of large-area single-crystal Cu foils, with potential applications extending to other metals, contributing to the ongoing efforts to overcome the challenges associated with traditional single-crystal production methods.

Single-Crystal Dynamic Covalent Organic Frameworks for Adaptive Guest Alignments.

Dynamic 3D covalent organic frameworks (COFs) have shown a concerted structural transformation upon adaptive guest inclusion. However, the origin of the conformational mobility and the host-guest adaptivity remain conjecture of the pedal motions of revolving imine linkages, often without considering the steric hindrance from the interwoven frameworks. Here, we present atomic-level observation of the rotational and translational dynamics in single-crystal COF-300 upon adaptive guest inclusion of various organic molecules, featuring multiple rotamers of covalent linkages and switchable interframework noncovalent interactions. Specifically, we developed a diffusion gradient transimination protocol to facilitate the growth of COF single crystals, enabling a high-resolution X-ray diffraction structural analysis. We uncovered metastable and low-symmetry intermediate phases from contracted to expanded phases during structural evolution. We identified torsion angles in the terephthalaldehyde diimine motifs that switch from anti-periplanar to syn-periplanar/anticlinal conformations. Moreover, the rotational dynamics of the imine linkage were concurrent with the translational dynamics of tetraphenylmethane units, which tend to form the translational quadruple phenyl embrace. Such conformational mobility allows the frameworks to adapt to various guest molecules, such as alcohols, esters, phenols, and diols, featuring double linear, herringbone, zigzag chains, triple helix, and tubular alignments. Quantitative energy analyses revealed that such dynamic structure transformations are not arbitrary but follow specific pathways that resemble protein folding. The work is paving the way to developing robust, dynamic, and crystalline molecular sponges for studying the condensed structure of liquids without the need for further crystallization.

Growth, characterization, and quantum chemical analyses of para-nitrophenol single crystals for laser safety application by optical limiting utilities

Growth, characterization, and quantum chemical analyses of para-nitrophenol single crystals for laser safety application by optical limiting utilities

Space-Confined Vertical Growth of Large-Size Organic Semiconductor Single Crystals.

Organic semiconductor single crystals (OSSCs) have garnered considerable attention because of their high charge mobility and atomic-scale smooth surface. However, their large-size high-quality preparation remains challenging due to the inevitable defects and limited growth speed brought by traditional epitaxial growth. Here, we demonstrate a space-confined strategy, named out-of-plane microspacing in-air sublimation (OPMAS), for growing vertically millimeter-sized OSSCs in several minutes by revolutionizing the heterogeneous epitaxial growth mode severely depending on substrates into a spontaneous homogeneous growth mode free from substrates. The intrinsic driven force of this transformation is proved to be the change of surface energy, and the maximum size of crystals is thermodynamically dependent on the distance of the microspace. OPMAS has been proven to be suitable for preparing single crystals of various typical organic semiconductors. Numerous characterizations have been conducted to prove the high quality and uniformity of the thus-produced OSSCs. In addition, the photoresponse of the prepared OSSCs is highly dependent on the illumination intensities, making it suitable for high-contrast Morse coding process, demonstrating a stable switch ratio of about 3.3. This work provides a universal platform for preparing large-sized OSSCs, advancing both fundamental (opto)electronic studies and a wide range of practical applications.

Single crystal growth by the Bridgman-Stockbarger technique of CaF2-rich - TmF3 solid solutions: Evidence of mixed valence Tm2+ and Tm3+ cations

Crystal growth and numerical simulation of CaF2-rich-based solid solution with TmF3 have been performed by the Bridgman-Stockbarger technique with initial Tm content 0.1 mol%, 1 mol% and 5 mol%. Centimeter-sized single crystals were obtained. Growth in the vicinity of (110) and (210) crystallographic directions have been identified as the natural crystal habit for the CaF2-rich- TmF3 solid solution with an axial thermal gradient about G=12 K.cm−1 and a pulling rate of v=4 mm.h−1. Optical absorption spectroscopy evidenced the presence of both Tm2+ and Tm3+ cations within the matrix. Their respective effective partition coefficients keff(Tm2+) and keff(Tm3+), close to unity, have been calculated. For low TmF3 initial content, with 0.1 mol.% and 1 mol.%, keff(Tm2+) >1 and keff(Tm3+) >1 whereas keff(Tm2+) <1 and keff(Tm3+) <1 for the attempt with 5 mol% TmF3 initial content. For this latter, a global effective partition coefficient, including both Tm3+ and Tm2+ contents, is logically deduced to be keff([Tm])<1. Chemical analysis carried out by ICP-AES and LIBS confirmed this trend with an effective partition coefficient of the global [Tm] content in the crystal that can be lower than 1. The global estimated partition coefficient of [Tm] in CaF2 matrix is thus ranging in between 0.906 and below 1 for 5 mol.% TmF3 molar fraction. The expected congruent melting point in the CaF2-rich-region of the CaF2-TmF3 phase diagram is evidenced and is higher than 1 mol.% and below 5 mol.% TmF3 molar fraction. Finally, carbon environment and TmF3 synproportionation reaction are pointed out as the main likely causes of Tm3+ cation reduction into Tm2+ during the growth process.

Growths of SiC Single Crystals Using the Physical Vapor Transport Method with Crushed CVD-SiC Blocks Under High Vertical Temperature Gradients.

A recent study reported the rapid growth of SiC single crystals of ~1.5 mm/h using high-purity SiC sources obtained by recycling CVD-SiC blocks used as materials in semiconductor processes. This method has gained attention as a way to improve the productivity of the physical vapor transport (PVT) method, widely used for manufacturing single crystal substrates for power semiconductors. When recycling CVD-SiC blocks by crushing them for use as sources for growing SiC single crystals, the properties and the particle size distribution of the material differ from those of conventional commercial SiC powders, making it necessary to study their effects. Therefore, in this study, SiC single crystals were grown using the PVT method with crushed CVD-SiC blocks of various sizes as the source material, and the growth behavior was analyzed. Simulation results of the temperature distribution in the PVT system confirmed that using large, crushed blocks as the SiC source material generates a greater temperature gradient within the source compared to conventional commercial SiC powder, making it advantageous for rapid growth processes. Additionally, when the large, crushed blocks were vertically aligned, good crystal quality was experimentally achieved at high growth rates, even under non-optimized growth conditions.

Luminescence properties of β-Ga2O3:Bi single crystals growth by the optical floating zone method

β-Ga2O3, an advanced semiconductor optical material, exhibits remarkable luminescence properties through doping. In this study, β-Ga2O3:Bi single crystals were successfully grown using the optical floating zone method, and their luminescence mechanisms were investigated. Our results demonstrate that reducing the sintering temperature to 1000 °C enhances the incorporation of Bi into the crystal matrix. Temperature-dependent spectral analysis reveals the non-radiative transitions in the blue light region, contributing to fast luminescence dynamics. These findings deepen our understanding of the luminescence characteristics of β-Ga2O3 single crystals and provide valuable insights for potential applications in radiation detection.

Growth and Photoelectrochemical Characterization of Epitaxial ZnTe Photocathodes for Carbon Dioxide Reduction

We report on the growth and photoelectrochemical (PEC) characterization of single crystal, epitaxial zinc telluride (ZnTe) thin film photocathodes. ZnTe is a II-VI semiconductor that has promising photocathode characteristics, including its suitable band gap alignments to CO2 reduction potentials, chemical stability, strong p-type character, and is theorized to have surface sites suitable for CO2 reduction. To gain a deeper understanding of the fundamental charge transport of the reactivity mechanism for ZnTe, we utilized molecular beam epitaxy (MBE) to grow single crystal thin film photocathodes. This work focuses largely on the synthesis and characterization of degenerately-doped ZnTe films on three different gallium arsenide (GaAs) substrate orientations: (100), (110), and (111)A. ZnTe thin films with a thickness of 300 nm, grown in the temperature range of 340–360ºC, were doped with nitrogen via an in situ RF plasma source and characterized by RHEED, XRD, AFM, and Hall effect measurements. The epitaxial films exhibited p-type characteristics with doping concentrations of 1018 to 1020 cm-3. Photoelectrochemical stability and catalytic selectivity of the ZnTe photocathodes were investigated in a three-electrode compression cell in a CO2-saturated electrolyte (0.1 M KHCO3). Utilizing degenerately doped (100) ZnTe, we have demonstrated high (60%) selectivity for CO2 reduction to CO in the absence of cocatalysts. Overall, we showed the correlation between the CO2R selectivity and ZnTe orientation and this work can be leveraged for developing catalyst-free tandem ZnTe-based photocathodes for carbon dioxide reduction.

(Invited) In-Situ Observation of SiC Solution Growth: Observation Principle and Effect of Al Addition to Si-Cr Solvent

BackgroundsSolution growth of SiC bulk single crystals has been studied as a potential method for growing high-quality crystals with keeping high growth rate. The use of Si-Cr alloy solvent has led to rapid growth rates, and reduction of dislocations using macrosteps has been reported. On the other hand, when the degree of supersaturation is increased to achieve high-speed growth, the distribution of supersaturation causes step bunching, which leads to solvent and polytype inclusions. Therefore, we have established an in-situ observation method at temperatures above 1300 °C to clarify various phenomena at the growth interface. This observation method is based on the transmission property of SiC against visible light. Bright-field observation using a white LED light enables us to obtain the step distributions at the interface, and internal interference observation using a He-Ne laser (632.8 nm) enables to measure the step height and growth rate. In this study, we evaluated temperature dependence of the optical absorption properties of the major SiC polytypes with the aim of enabling the identification of the polytypes during the in-situ observation method. We also focused on Al, which is known to suppress bunching when added in small amounts to the solvent, and investigated the effect of Al on the SiC solution growth interface by in-situ observation.Polytype identification during in-situ observationThe polytypes that easily occur at 1300-2000 °C are 3C, 4H, and 6H-SiC, each of which has its own band gap. Therefore, if the temperature dependence of the optical absorption property of each polytype is known, it is possible to determine the polytype from the observed image. Based on this, we measured the temperature dependence of the optical absorption properties of each polytype and evaluated the band gap. As a result, the band gap of each polytype decreased linearly with temperature, and was found to be larger in the order of 3C, 6H, and 4H-SiC in any temperature range. By referring to the optical absorption properties, it became possible to capture the distribution of different polytypes by using the difference in transmittance when they have a thickness of ~1 μm or more.Effect of Al addition to Si-Cr solvent on SiC growth interfaceIt is known that the solvent system has a significant effect on the step structure of the growth interface in terms of polytype inclusions and step bunching formation. Especially, addition of a small amount of Al is considered to have advantage in improving crystal quality. Therefore, in-situ observation of the growth interface on an on-axis 4H-SiC(000-1) at 1600 °C was performed using Si-40 mol%Cr and Si-40 mol%Cr-2 mol%Al solvents. Without Al, formation of step bunching was observed during the progress of step flow growth, which was induced by the small off-angle of the seed crystal. Eventually, the terrace expanded and bunching of the surrounding steps progressed, resulting in significant roughening of the interface. In contrast, with Al, the growth interface was covered by aligned steps, and step flow growth continued with steps of 10–20 nm in height. Therefore, it was found that Al prevents the formation of step bunching, leading to the suppression of macrostep formation.ConclusionsWe have established in-situ observation method of SiC solution growth interface for clarifying various phenomena at the growth interface. Polytype identification during the in-situ observation was proposed as a further technique, and the temperature dependence of the optical absorption properties of SiC polytypes were summarized as fundamental data. It was also revealed that the addition of Al to the Si-Cr solvent has an effect to suppress the formation of step bunching at the SiC growth interface.