Crystal Growth Method Research Articles

Linker-Guided Growth of Single-Crystal Covalent Organic Frameworks.

The core features of covalent organic frameworks (COFs) are crystallinity and porosity. However, the synthesis of single-crystal COFs with monomers of diverse reactivity and adjustment of their pore structures remain challenging. Here, we show that linkers that can react with a node to form single-crystal COFs can guide other linkers that form either COFs or amorphous polymers with the node to gain single-crystal COFs with mixed components, which are homogeneous on the unit cell scale with controlled ratios. With the linker-guided crystal growth method, we created nine types of single-crystal COFs with up to nine different components, which are more complex than any known crystal. The structure of the crystal adapted approximately to that of the main component, and its pore volume could be expanded up to 8.8%. Different components lead to complex and diverse pore structures and offer the possibilities to gain positive synergies, as exemplified by a bicomponent COF with 2200 and 733% SO2 uptake capacity of that of the two pure-component counterparts at 298 K and 0.002 bar. The selectivity for separation of SO2/CO2 ranges from 1230 to 4247 for flue gas based on ideal adsorbed solution theory, recording porous crystals. The bicomponent COF also exhibits a 1300% retention time of its pure-component counterparts for SO2 in a dynamic column breakthrough experiment for deep desulfurization.

Intense THz Generation with New Organic NLO Crystal NMBA

AbstractLarge crystal growth and characterization of the optical and terahertz (THz) properties of organic nonlinear optical (NLO) crystal NMBA (4‐Nitro‐4′‐methylbenzylidene aniline) is presented. The reported method of crystal growth consistently produces high‐quality single crystals. The THz generation efficiency and optical properties of NMBA to other THz generation crystals including BNA and MNA are compared. The low THz absorptions that make NMBA an ideal source for THz time‐domain spectroscopy are highlighted.

Structure and electrical properties of Cu, Bi and Mn co-doped K0.5Na0.5NbO3 single crystals grown by the seed-free solid state crystal growth method

Multi-element doped K0.5Na0.5NbO3 single crystals with excellent electrical properties grown by a seed-free solid-state crystal growth (SFSSCG) method.

Development of travelling heater method for growth of detector grade CdZnTe single crystals

Development of travelling heater method for growth of detector grade CdZnTe single crystals

(Invited) Effect of Seed Crystal Orientation on Ammonothermal Growth of GaN

Gallium nitride (GaN) is a wide bandgap semiconductor which has received widespread attention as it has enabled the development of short wavelength (UV, blue) optical emitters and promises a new generation of high efficiency power electronic devices. To enable widespread use of high power, high efficiency devices, the availability of large-area, inexpensive, low-defect-density GaN substrates is necessary.The ammonothermal method is a bulk, single crystal growth method which has demonstrated growth of high structural quality GaN boules greater than 2 inches in diameter. Despite these demonstrations, challenges remain with regards to improving growth rates to reduce cost of boules and understanding the growth behavior of GaN in these environments to further improve upon crystal quality. In particular, the general trend and affect of the GaN seed crystal on growth rates and crystal quality has not been studied in detail.This talk will discuss our current understanding of how the initial seed crystal orientation affects the resulting ammonothermal GaN growth, surface morphology, crystal quality, and impurity incorporation. Seed crystals were sourced from hydride vapor phase epitaxial (HVPE) grown GaN boules that were sliced and polished to atomically smooth crystallographic facets of varying orientations. Three series were created resulting in incrementally changing orientations ranging from +c-plane to m-plane to -c-plane, from +c-plane to a-plane to -c-plane and from m-plane to a-plane.

Simulation of crucible-free growth of monocrystalline silicon fibres for mirror suspension in gravitational-wave detectors

Monocrystalline silicon fibres are a promising candidate to support the test mass needed in gravitational-wave detectors. Stringent requirements on material purity and fibre diameter underscore the imperative for crucible-free crystal growth methods, such as Pedestal and Floating Zone techniques. We developed a multiphysics numerical model that simulates the coupling between electromagnetism, heat transfer, fluid flow and phase boundaries for these techniques within the same mathematical framework, which facilitates direct comparisons of both growth techniques. Model validation was addressed using experimental measurements and other simulation tools, and satisfactory agreement was obtained. Our findings indicate that electromagnetic forces are the primary mechanism responsible for stirring the molten silicon at small crystal diameters. The resulting fluid velocity develops slightly transient behaviour, although this has little impact on the phase boundary shapes. The understanding of the growth process enabled by the model will facilitate future optimization of crystal quality and diameter stability.

Optical and scintillation properties of modified LSO crystals with different ions doping grown by a rapid CZ system

LSO:Ce is a well-known scintillation crystal that is widely used in nuclear medicine, security checks, and high-energy physics. The scintillation properties of LSO can be modified by doping to meet the ever-growing requirements of radiation detection. However, exploring new doping techniques for LSO crystals with self-designed scintillation features remains time-consuming, especially by the Czochralski (CZ) method. In this paper, we established a high-efficiency crystal growth system based on the CZ method for the rapid growth of LSO crystals. The system is regulated by a high-accuracy auto-diameter controller to grow small boules of ϕ 20 mm × 100 mm. By incorporating an arc bottom crucible and optimizing the temperature field, the crystallization fraction of the as-grown crystal can be increased to 95% with the growth period compressed to 48 h. With the aid of the growth system, LSO crystals with Lu3+ partially substituted by optical inertia RE ions (Sc3+, Y3+, La3+, Gd3+), metal cations co-doping (Ca2＋, Li1+, Yb3+), and different luminescent ions doping (Pr3+, Nd3+, Eu3+, Tb3+, Dy3+, Yb3+) are grown. Comparative analysis shows that the Ca co-doped LSO:Ce exhibits the best scintillation performance, taking into account both light output and decay time, among our samples. Moreover, Tb-doped LSO features relatively good scintillation efficiency with various wavelengths of visible light emission.

Crystal Growth and Characterisation of Strontium on Thiourea

Thiourea, being a potential organic Non-linear optical material with high SHG efficiency having application in laser technology and photonic applications are grown as single crystals of Strontium chloride doped thioureaby slow evaporation solution growth technique (SEST), one of the best method for crystal growth at room temperature. It is furtheranalysed by single crystal XRD which infers thatthe Strontium Chloride doped thiourea crystal has monoclinicsystem. The surface morphology was studied by SEM-EDS, that confirms thepresence of Strontium in the doped specimen. FTIR reveals some slight variation in vibrational frequencies and no secondaryvibrational bandsarefoundin the doped specimen indicating the presence of some dopant

Experimental observation of the vertical displacement between heating and levitation regions in an electromagnetic levitation coil

Scientific progress in the relevant fields of science and technology requires the production of crystals with quality beyond the current state of the art. Electro-magnetic levitation (EML) is a prospective method for the growth of high-purity crystals, allowing for avoidance of any contact between the crystal-melt and the crucible. Contactless crystal growth reduces the number of crystal defects commonly abundant in conventional crystal growth methods. The EML method also allows crystal growth of materials with very high melting points. In this article, we report detailed measurements of the EML method. The induction coil used in this study has three turns and one counterturn. We subject different metal material (Al, Cu, Sn, and Ni) samples to the induction coil’s electromagnetic field. For each sample, we measure the induced lift force, Joule heating, and components of magnetic induction as a function of position inside the coil. The results show that the maximum heating in an EML coil is emitted in the area below the levitation zone, a discrepancy not reported earlier. Our findings suggest that this shift should be considered in coil design to avoid instability of the levitated material. We hope this study will serve as a stepping stone for developing EML techniques. The experimental results we provide will be used to evaluate the accuracy of current and future theoretical models of EML coils. This, in turn, will facilitate progress in the application of EML to the growth of larger crystals of higher quality.

Self-sacrifice PbI2 seed layer-assisted crystal growth for improved perovskite thin films for efficient and stable transportation layer-free photodetectors

Recently, the growth of improved perovskite thin films with high crystallinity and low defects has been an important research subject owing to their critical roles in achieving efficient and stable optoelectronic devices. In this work, we introduced a self-sacrifice PbI2 seed layer to prepare improved CH3NH3PbI3 thin films with high crystallinity and reduced defects. It showed that the PbI2 seed layer at the buried interface acted as nuclei and modulated the crystal growth of CH3NH3PbI3, which induced the vertically upward growth of CH3NH3PbI3, resulting in increased sizes of grains and reduced grain boundaries. Further observations verified the suppression of defect and trap states in the obtained CH3NH3PbI3 thin films. On this basis, efficient and stable transportation layer-free Au/CH3NH3PbI3/indium tin oxide photodetectors have been demonstrated, where the responsivity and detectivity are as high as 0.54 A/W and 7.5 × 1012 Jones, respectively, at the bias of 0 V. It is supposed that the self-sacrifice PbI2 seed layer-assisted crystal growth method will find applications in fabricating high-quality and stable perovskite thin film devices in the future.

Construction of highly stable and efficient Zn-based catalyst via Mg modification for propane dehydrogenation

Zn-based catalysts are considered a kind of efficient catalysts for propane dehydrogenation (PDH) because of their low price and non-toxicity. However, Zn-based catalysts still face problems such as the limited diffusion of reaction gas, non-uniform distribution of Zn species, and easy coking. Here, a novel double-layered silicalite-1 (DS-1) support with high specific surface area was synthesized by a crystal growth method, and an alkaline additive modification strategy has been adopted to prepare the Mg-modified Zn-based catalyst (0.1Mg5Zn@DS-1) in order to improve the catalytic activity and stability. The physical characterization results reveal that the Mg modification induces the enhanced electronic interactions between Zn sites and Mg species. Besides, the modified Mg species also reduce the Lewis acidity, allowing easier desorption of propylene and improving the propylene selectivity with anti-coking property. Furthermore, PDH evaluation results demonstrate that the optimal 0.1Mg5Zn@DS-1 catalyst achieves the propylene yield of ∼44 %, propylene selectivity of ∼95 % as well as outstanding stability and regeneration ability. This work provides a novel insight into the design of Zn-based catalysts with high activity and excellent stability.

On the growth and characterization of SmOFe[formula omitted]Co[formula omitted]As single crystals

In this work we report the crystal growth of SmOFe1−xCoxAs single crystals with Co content 0≤x≤0.25 via the solid-state single crystal growth method at ambient pressure. The centrepiece of this method is to trigger the abnormal grain growth process, where only a small amount of grains grows significantly larger than the majority of grains. In its extreme case, this diffusion-controlled process in the solid state may foster large and three-dimensional crystals that grow out of a polycrystalline matrix. Since most parameters known to trigger solid-state single crystal growth are known only empirically, we discuss in detail which are the optimal parameters for the growth of SmOFe1−xCoxAs single crystals and rationalize the mechanisms that may be relevant to activate the diffusion-driven solid-state single crystal growth in the system under study. The plate-like crystals show distinct facets, which is a common feature of crystals grown by this method, with lateral dimensions of up to 4.8mm and a thickness of up to 0.06mm. The single crystals of this series as well as the corresponding polycrystals were characterized and compared regarding their crystal structure, chemical composition, morphology as well as magnetic and superconducting properties. Interestingly, our characterization data suggest a solubility gap for high Co contents. This finding is supported by comparing with previous reports, albeit existence of a solubility gap is not discussed therein. As expected across the series, charge doping suppresses the structural and magnetic transitions until for 5% Co content superconductivity is established. In particular, the splitting and clear differentiation of the structural and subsequent magnetic transition is rarely seen for REOFeAs compounds, but well resolved for the Fe-rich SmOFe1−xCoxAs single crystals and even for the x=0.0125 crystal, but smeared out for the corresponding polycrystalline samples. Hence, the SmOFe1−xCoxAs single crystal presented in this work are of exceptional high quality.

Ultrahigh-performance [001]-oriented porous PZT-5H single crystal grown by the solid state crystal growth method

Porous PZT-5H single crystals are grown by the solid state crystal growth (SSCG) method. The microstructure, phase structure and dielectric/piezoelectric properties are investigated for [001]-oriented porous PZT-5H single crystal. Evolution of phase structure with temperature is researched using in-situ temperature-dependent X-ray diffraction. The effect of pores on performance parameters is simulated using COMSOL Multiphysics® software. Ultrahigh piezoelectric coefficient d33 of up to about 1700 pC/N and effective piezoelectric coefficient d33* of up to about 3700 pm/V at 5 kV/cm are obtained. Moreover, the effective piezoelectric coefficient d33* is stable around 1900 pm/V under 3 kV/cm and 5 kV/cm in the temperature range of 70–160 °C. Importantly, the sample possess an extremely large figure of merit g33*d33 (111 × 10−12 m2/N), which is related to the presence of pores in the single crystal. This work expands the scope of PZT based single crystal and highlights their significant application possibilities in piezoelectric energy harvester, and actuator at high temperature.

High-performance CH3NH3PbBr3 Polycrystalline Wafer Prepared by Hot-pressing Method

Considering the drawbacks of the common methods for CH3NH3PbBr3 single crystal growth, such as the complicated and uncontrollable process, a simple hot-pressing (HP) method was introduced to fabricate CH3NH3PbBr3 polycrystalline wafers. The effect of hot-pressing temperature on the crystalline quality and corresponding optical and electrical properties of the CH3NH3PbBr3 polycrystalline wafers was investigated. The hot-pressing temperature for CH3NH3PbBr3 was optimized at 150°C, and the optimized CH3NH3PbBr3 wafer exhibited a low defect density (1.55×1010 cm−3), long carrier lifetime (1734 ns), and high carrier mobility (51.24 cm2V−1s−1) as a photoconductive detector. Furthermore, the detector showed a highly sensitive weak light response under 525 nm LED illumination with an optical power density of 84 nWcm−2, exhibiting a high responsivity of 63 AW−1, EQE of 1.5×104 %, and detectivity of 2.33×1013 Jones, and a fast response speed with a rise time of 17.7 μs and a fall time of 57.4 μs has been achieved.

Development of continuous solution growth method for growth of large and high-quality perovskite single crystals

Large perovskite single crystals with high quality cannot be obtained by traditional batch-type solution growth techniques, impeding their use in commercial applications. We report on developing a continuous solution growth (CSG) method that enables the growth of large, high-quality perovskite single crystals such as methylammonium lead tribromide (MAPbBr3), as well as triple-cation mixed hybrid. A 40 × 40 × 2 mm3 MAPbBr3 single crystal grown by this method, has a high mobility-lifetime (µτ) product of 3.3 × 10−3 cm2·V−1 and a low trap density of 8.22 ± 0.02 × 108 cm−3. Photoconductors (Au-MAPbBr3-Au) with a low dark current density of 3.9nA·cm−2 at 0.83 V·mm−1 exhibit excellent photons detection of both UV–visible and X-ray photons. For UV–visible photons, the responsivity is about 1.5 A·W−1 and 1.3 A·W−1 to 405 nm and 532 nm photons, respectively; for X-ray sensitivity is up to 2.35 × 105 µC Gyair−1 cm−2 and the lowest detection limit is 15.7 nGyair·s−1. High-contrast X-ray images were obtained with a large (40 mm × 40 mm) pixelated detector with 800 µm × 800 µm pixels. These results demonstrate that the CSG technique can produce high-quality, large perovskite single crystals for commercial applications, including photodetection and ionization radiation detection.

Growth and enhanced electrical properties of PIN-PMN-PT piezoelectric single crystal grown by the solid-state crystal growth method

0.32Pb(In1/2Nb1/2)O3-0.335Pb(Mg1/3Nb2/3)O3-0.345PbTiO3 single crystals were successfully grown by a solid-state crystal growth (SSCG) method through precise control of the key growth parameters. The effects of the sintering temperature and the soaking time on the growth of the PIN-PMN-PT single crystals were investigated. The growth distance is up to 1069 µm for [110]-oriented PIN-PMN-PT single crystal grown at 1150 °C for 50 h. The microstructure, crystal structure and dielectric, ferroelectric and piezoelectric properties were systematically investigated for the SSCG-grown [110]-oriented PIN-PMN-PT single crystals. The [110]-oriented PIN-PMN-PT single crystals exhibit high piezoelectric properties (d33 ∼ 1041pC/N, d33 * ∼ 1024 pm/V), Curie temperature (TC ∼ 250 °C) and ferroelectric properties (EC ∼ 8.4 kV/cm and Pr ∼33 μC/cm2). Further, the [001]-oriented single crystals also possess outstanding piezoelectric properties (d33 ∼ 1004pC/N, d33 * ∼ 1203 pm/V), Curie temperature (TC ∼ 266 °C) and ferroelectric properties (EC ∼ 9.7 kV/cm and Pr ∼36 μC/cm2), which are much superior to those of counterpart ceramics.This work opens the door of growth of PIN-PMN-PT single crystals by SSCG method and the SSCG-grown PIN-PMN-PT single crystals are very promising candidates for high performance electromechanical devices with wide temperature and electric field application.

Synthesis of AlN single crystal by solution growth method using type 430 ferritic stainless steel flux

We propose a new AlN crystal growth method using Fe-based fluxes. AlN single crystals with a thickness of 67–212 µm were epitaxially grown on an AlN bulk substrate by a solution growth method using type 430 ferritic stainless steel flux. The full width at half maximum values of the x-ray rocking curves of (0002) and (10–12) of the synthesized AlN were 137 and 83 arcsec, respectively. The impurity concentrations of carbon were significantly decreased from 3 × 1019 atoms/cm3 in seed crystal to 6 × 1017 atoms/cm3 in synthesized crystal. The features of the method developed in this study are described as follows: (1) steel-based alloys are used as a flux, which are readily available and low-cost; (2) the growth temperature is 1700 °C, which is much lower than that of the sublimation method; (3) no high-pressure vessel is required because growth can be performed under 1 atmospheric pressure conditions; and (4) waste gas detoxification equipment is not required because only N2 gas is used and no toxic or flammable gases are used. Because of the above features (1) through (4), this is an effective crystal growth process from the perspective of ensuring the economics and safety of the facility.

Wafer-Scale Epitaxial Growth of Two-dimensional Organic Semiconductor Single Crystals toward High-Performance Transistors.

The success of state-of-the-art electronics and optoelectronics relies heavily on the capability to fabricate semiconductor single-crystal wafers. However, the conventional epitaxial growth strategy for inorganic wafers is invalid for growing organic semiconductor single crystals due to the lack of lattice-matched epitaxial substrates and intricate nucleation behaviors, severely impeding the advancement of organic single-crystal electronics. Here, an anchored crystal-seed epitaxial growth method for wafer-scale growth of 2D organic semiconductor single crystals is developed for the first time. The crystal seed is firmly anchored on the viscous liquid surface, ensuring the steady epitaxial growth of organic single crystals from the crystal seed. The atomically flat liquid surface effectively eliminates the disturbance from substrate defects and greatly enhances the 2D growth of organic crystals. Using this approach, a wafer-scale few-layer bis(triethylsilythynyl)-anthradithphene (Dif-TES-ADT) single crystal is formed, yielding a breakthrough for organic field-effect transistors with a high reliable mobility up to 8.6 cm2 V-1 s-1 and an ultralow mobility variable coefficient of 8.9%. This work opens a new avenue to fabricate organic single-crystal wafers for high-performance organic electronics.

Enhanced electrical properties by AC poling of relaxor-Pb(Zr,Ti)O3 single crystals manufactured by the solid state crystal growth method

An exceptionally large free dielectric permittivity of 14200, piezoelectric coefficient (d 33) of 4800 pC/N and calculated electromechanical coupling factor k 33 of 95.7% were obtained from Pb(Mg1/3Nb2/3)O3 (PMN) - Pb(Zr,Ti)O3 (PZT) single crystals (SCs) under AC poling (ACP). The PMN −0.3PZT SCs grown by a solid-state crystal growth (SSCG) method with high composition uniformity showed a phase change temperature of 57 °C–72 °C and Curie temperature T c of 140 °C. The measured d 33 of 250 pC/N was obtained after a heat treatment at 250 °C, which is 110 °C higher than the T c of the SC. Microstructural observations revealed that the ACP SC showed a different 109° domain wall layers morphology due to the presence of some pores, which is dissimilar to the Bridgman ACP relaxor-PbTiO3 SCs. These outstanding piezoelectric properties, heat durability, lower acoustic impedance, and better machinability of ACP SSCG SCs are promising for future piezoelectric device applications.

Hexagonal Boron Nitride Seed Layer-Assisted van der Waals Growth of BaSnO3 Perovskite Films.

We have succeeded in obtaining BaSnO3 perovskite thin films with remarkable near-infrared luminescence by van der Waals growth. The films were grown on quartz glass substrates by pulsed laser deposition using hexagonal boron nitride as the seed layer, and their crystallinity was confirmed by X-ray diffraction and cross-sectional transmission electron microscopy. The near-infrared emission of the grown film exhibited a broad emission peak centered at 920 nm. The transparency of the BaSnO3 film (thickness = 1000 nm)/ hexagonal boron nitride /double-sided optically polished quartz glass substrate was approximately 90% at approximately 500 nm with or without the BaSnO3 film. Films showing remarkable near-infrared emission and high transparency obtained by van der Waals-type growth could be used in practical wavelength conversion devices that improve the efficiency of Si single-crystal solar cells. The hexagonal boron nitride seed layer supporting the van der Waals growth is an effective method for high-quality crystal growth of films. It can be used for perovskite-type oxides with many functionalities.