Growth Of Large Single Crystals Research Articles

Low-energy spin excitations in the optimally doped CaFe0.88Co0.12AsF superconductor studied with inelastic neutron scattering

There are few inelastic neutron scattering (INS) reports on the superconducting single crystals of the FeAs-1111 system, even though it was first discovered in 2008, due to the extreme difficulty in large single-crystal growth. In this paper, we have studied the low-energy spin excitations in optimally electron-doped ${\mathrm{CaFe}}_{0.88}{\mathrm{Co}}_{0.12}\mathrm{AsF}$ single crystals with ${T}_{\mathrm{c}}=21$ K by INS. The resonance energy of the superconducting spin resonant mode with ${E}_{\mathrm{r}}=12$ meV amounts to $6.6{k}_{\mathrm{B}}{T}_{\mathrm{c}}$, which constitutes a large ${E}_{\mathrm{r}}/{k}_{\mathrm{B}}{T}_{\mathrm{c}}$ ratio among iron-based superconductors. The large ratio implies a strong coupling between conduction electrons and magnetic excitations in ${\mathrm{CaFe}}_{0.88}{\mathrm{Co}}_{0.12}\mathrm{AsF}$. The resonance possesses a magnonlike upward dispersion along the transverse direction due to the anisotropy of the spin-spin correlation length within the $ab$ plane in the normal state, which points to a spin fluctuation mediated sign-reversed $s\ifmmode\pm\else\textpm\fi{}$ wave pairing in ${\mathrm{CaFe}}_{0.88}{\mathrm{Co}}_{0.12}\mathrm{AsF}$.

A novel two-step route to unidirectional growth of multilayer MoS2 nanoribbons

Alkali-assisted chemical vapour deposition (CVD) of transition metal dichalcogenides (TMDs) has been shown to promote the growth of large single crystals of TMD monolayers. The morphology control of TMDs is a key parameter for the scalable synthesis of versatile layered materials. This work demonstrates that the alkali-assisted synthesis provides a route toward fabricating highly crystalline MoS2 nanoribbons. Our proposed method involves a vapour-liquid–solid phase reaction between MoOx(2 < x < 3) precursors grown by Pulsed Laser Deposition (PLD) and metal alkali halide (i.e., NaF). The growth process evolves via the emergence of the Na–Mo–O liquid phase, which mediates the formation of MoS2 multilayer nanoribbons in a sulfur-rich environment. Moreover, the as-grown MoS2 nanoribbons are surrounded by mono- and multilayer triangles of MoS2 and exhibit a preferential alignment defined by both MoS2 crystal symmetry and the underlying Al2O3 substrate. In addition, we observe a significant built-in strain in the as-grown MoS2 nanostructures, which increase in magnitude from the multilayer nanoribbons to the triangular monolayers, and which can be effectively released upon transfer onto another substrate. The growth method developed here can enable flexibility in designing nanoelectronic devices based on TMDs with tunable dimensions.

A Low-Temperature Structural Transition in Canfieldite, Ag8SnS6, Single Crystals

Canfieldite, Ag8SnS6, is a semiconducting mineral notable for its high ionic conductivity, photosensitivity, and low thermal conductivity. We report the solution growth of large single crystals of Ag8SnS6 of mass up to 1 g from a ternary Ag-Sn-S melt. On cooling from high temperature, Ag8SnS6 undergoes a known cubic (F4̅3m) to orthorhombic (Pna21) phase transition at ≈460 K. By studying the magnetization and thermal expansion between 5-300 K, we discover a second structural transition at ≈120 K. Single crystal X-ray diffraction reveals the low-temperature phase adopts a different orthorhombic structure with space group Pmn21 (a = 7.662 9(5) Å, b = 7.539 6(5) Å, c = 10.630 0(5) Å, Z = 2 at 90 K) that is isostructural to the room-temperature forms of the related Se-based compounds Ag8SnSe6 and Ag8GeSe6. The 120 K transition is first-order and has a large thermal hysteresis. On the basis of the magnetization and thermal expansion data, the room-temperature polymorph can be kinetically arrested into a metastable state by rapidly cooling to temperatures below 40 K. We last compare the room- and low-temperature forms of Ag8SnS6 with its argyrodite analogues, Ag8TQ6 (T = Si, Ge, Sn; Q = S, Se), and identify a trend relating the preferred structures to the unit cell volume, suggesting smaller phase volume favors the Pna21 arrangement. We support this picture by showing that the transition to the Pmn21 phase is avoided in Ge alloyed Ag8Sn1-xGexS6 samples as well as in pure Ag8GeS6.

Frank-van der Merwe growth in bilayer graphene

Frank-van der Merwe growth in bilayer graphene

Synthesis and physical properties of single-crystalline InTe: towards high thermoelectric performance

The growth of large single crystals of InTe enables the first detailed study of its basic thermoelectric properties.

Metal-Free Halide Perovskite Single Crystals with Very Long Charge Lifetimes for Efficient X-ray Imaging.

Metal-free halide perovskites, as a specific category of the perovskite family, have recently emerged as novel semiconductors for organic ferroelectrics and promise the wide chemical diversity of the ABX3 perovskite structure with mechanical flexibility, light weight, and eco-friendly processing. However, after the initial discovery 17 years ago, there has been no experimental information about their charge transport properties and only one brief mention of their optoelectronic properties. Here, growth of large single crystals of metal-free halide perovskite DABCO-NH4 Br3 (DABCO = N-N'-diazabicyclo[2.2.2]octonium) is reported together with characterization of their instrinsic optical and electronic properties and demonstration, of metal-free halide perovskite optoelectronics. The results reveal that the crystals have an unusually large semigap of ≈16 eV and a specific band nature with the valence band maximum and the conduction band minimum mainly dominated by the halide and DABCO2+ , respectively. The unusually large semigap rationalizes extremely long lifetimes approaching the millisecond regime, leading to very high charge diffusion lengths (tens of μm). The crystals also exhibit high X-ray attenuation as well as being lightweight. All these properties translate to high-performance X-ray imaging with sensitivity up to 173 μC Gyair -1 cm-2 . This makes metal-free perovskites novel candidates for the next generation of optoelectronics.

Application of NMR Crystallography to Highly Disordered Templated Materials: Extensive Local Structural Disorder in the Gallophosphate GaPO-34A.

We present an NMR crystallographic investigation of two as-made forms of the recently characterized gallophosphate GaPO-34A, which has an unusual framework composition with a Ga:P ratio of 7:6 and contains both hydroxide and fluoride anions and either 1-methylimidazolium or pyridinium as the structure-directing agent. We combine previously reported X-ray crystallographic data with solid-state NMR spectroscopy and periodic density functional theory (DFT) calculations to show that the structure contains at least three distinct types of disorder (occupational, compositional, and dynamic). The occupational disorder arises from the presence of six anion sites per unit cell, but a total occupancy of five of these, leading to full occupancy of four sites and partial occupancy of the fifth and sixth (which are related by symmetry). The mixture of OH and F present leads to compositional disorder on the occupied anion sites, although the occupancy of some sites by F is calculated to be energetically unfavorable and signals relating to F on these sites are not observed by NMR spectroscopy, confirming that the compositional disorder is not random. Finally, a combination of high-field 71Ga NMR spectroscopy and variable-temperature 13C and 31P NMR experiments shows that the structure directing agents are dynamic on the microsecond time scale, which can be supported by averaging the 31P chemical shifts calculated with the SDA in different orientations. This demonstrates the value of an NMR crystallographic approach, particularly in the case of highly disordered crystalline materials, where the growth of large single crystals for conventional structure determination may not be possible owing to the extent of disorder present.

Large single-crystal growth of tetragonal garnet-type Li7La3Zr2O12 by melting method

A tetragonal Li7La3Zr2O12 single-crystalline rod was grown by the floating zone method for the first time. The single-crystalline rod was 8 mm in diameter and 50 mm in length. Tetragonal Li7La3Zr2O12 crystallized in the tetragonal crystal system, space group I41acd, with lattice parameters of a = 13.1200(7) Å and c = 12.6753(7) Å. The crystal structure of tetragonal Li7La3Zr2O12 was refined to conventional values of R = 3.74% and wR = 3.85% for single-crystal X-ray diffraction data. The crystal structure was the same as that previously reported. The total lithium-ion conductivity in tetragonal Li7La3Zr2O12 was estimated to be 2.58 × 10−5 S cm−1 at 298 K from the results of alternating current (AC) impedance measurements. The lithium-ion conductivity was higher than the value reported for a normally sintered body, and it agreed well with the value of the high-density sintered body produced by the hot-press method.

Ultrafast growth of large single crystals of monolayer WS2 and WSe2.

Monolayer transition metal dichalcogenides (TMDs) have attracted considerable attention as atomically thin semiconductors for the ultimate transistor scaling. For practical applications in integrated electronics, large monolayer single crystals are essential for ensuring consistent electronic properties and high device yield. The TMDs available today are generally obtained by mechanical exfoliation or chemical vapor deposition (CVD) growth, but are often of mixed layer thickness, limited single crystal domain size or have very slow growth rate. Scalable and rapid growth of large single crystals of monolayer TMDs requires maximization of lateral growth rate while completely suppressing the vertical growth, which represents a fundamental synthetic challenge and has motivated considerable efforts. Herein we report a modified CVD approach with controllable reverse flow for rapid growth of large domain single crystals of monolayer TMDs. With the use of reverse flow to precisely control the chemical vapor supply in the thermal CVD process, we can effectively prevent undesired nucleation before reaching optimum growth temperature and enable rapid nucleation and growth of monolayer TMD single crystals at a high temperature that is difficult to attain with use of a typical thermal CVD process. We show that monolayer single crystals of 450 μm lateral size can be prepared in 10 s, with the highest lateral growth rate up to 45 μm/s. Electronic characterization shows that the resulting monolayer WSe2 material exhibits excellent electronic properties with carrier mobility up to 90 cm2 V−1 s−1, comparable to that of the best exfoliated monolayers. Our study provides a robust pathway for rapid growth of high-quality TMD single crystals.

Properties and growth of large single crystals of one-dimensional organic lead iodine perovskite

Here, we demonstrate for the first time the growth of 2 mm × 4 mm × 8 mm sized single crystal one dimensional organic lead iodine perovskite – DMAPbI3 ((CH3)2NH2PbI3).

Ba2Si3P6: 1D Nonlinear Optical Material with Thermal Barrier Chains.

A novel barium silicon phosphide was synthesized and characterized. Ba2Si3P6 crystallizes in the noncentrosymmetric space group Pna21 (No. 33) and exhibits a unique bonding connectivity in the Si-P polyanion not found in other compounds. The crystal structure is composed of SiP4 tetrahedra connected into one-dimensional double-tetrahedra chains through corner sharing, edge sharing, and covalent P-P bonds. Chains are surrounded by Ba cations to achieve an electron balance. The novel compound exhibits semiconducting properties with a calculated bandgap of 1.6 eV and experimental optical bandgap of 1.88 eV. The complex pseudo-one-dimensional structure manifests itself in the transport and optical properties of Ba2Si3P6, demonstrating ultralow thermal conductivity (0.56 W m-1 K-1 at 300 K), promising second harmonic generation signal (0.9 × AgGaS2), as well as high laser damage threshold (1.6 × AgGaS2, 48.5 MW/cm2) when compared to the benchmark material AgGaS2. Differential scanning calorimetry reveals that Ba2Si3P6 melts congruently at 1373 K, suggesting that large single crystal growth may be possible.

Single-Crystal Growth of Metallic Rare-Earth Tetraborides by the Floating-Zone Technique

The rare-earth tetraborides are exceptional in that the rare-earth ions are topologically equivalent to the frustrated Shastry-Sutherland lattice. In this paper, we report the growth of large single crystals of RB 4 (where R = Nd, Gd → Tm, and Y) by the floating-zone method, using a high-power xenon arc-lamp furnace. The crystal boules have been characterized and tested for their quality using X-ray diffraction techniques and temperature- and field-dependent magnetization and AC resistivity measurements.

Synthesis of NaxMoO3 crystals through high pressure solid-state reaction

ABSTRACTWe report growth of high-purity single crystals of the sodium molybdenum bronzes NaxMoO3 through high pressure solid-state reaction routes. Our results demonstrate that the crystallite sizes of NaxMoO3 can rapidly grow to ∼25 μm under a moderate pressure of 4.0 GPa in just 10 min. This discovery provides a starting point for the growth of large single crystals of alkali metal molybdenum bronzes under high pressure.

From Initial Hit to Crystal Optimization with Microseeding of Human Carbonic Anhydrase IX—A Case Study for Neutron Protein Crystallography

Human carbonic anhydrase IX (CA IX) is a multi-domain membrane protein that is therefore difficult to express or crystalize. To prepare crystals that are suitable for neutron studies, we are using only the catalytic domain of CA IX with six surface mutations, named surface variant (SV). The crystallization of CA IX SV, and also partly deuterated CA IX SV, was enabled by the use of microseed matrix screening (MMS). Only three drops with crystals were obtained after initial sparse matrix screening, and these were used as seeds in subsequent crystallization trials. Application of MMS, commercial screens, and refinement resulted in consistent crystallization and diffraction-quality crystals. The crystallization protocols and strategies that resulted in consistent crystallization are presented. These results demonstrate not only the use of MMS in the growth of large single crystals for neutron studies with defined conditions, but also that MMS enabled re-screening to find new conditions and consistent crystallization success.

Growth of Large Single Crystals of Copper Iodide by a Temperature Difference Method Using Feed Crystal Under Ambient Pressure

A large single crystal of CuI was fabricated by the temperature difference method using NH4I aqueous solution. To explore the efficient crystal growth condition, we calculate the phase diagram of c...

Crystallization of Methylammonium Lead Halide Perovskites by Optical Trapping.

Single crystals of organolead halide perovskites attract much attention to electrooptical and photovoltaic applications. They are usually prepared in precursor solutions incubated at controlled temperatures or under optimized vapor atmosphere conditions, and thus, multiple perovskite crystals are nucleated all over the solution. Multiple nucleation of crystals prevents efficient use of precursors in the preferential growth of large single crystals. An innovative approach is presented for spatiotemporally controlled, selective nucleation and growth of single crystals of lead halide perovskites by optical trapping with a focused laser beam. Upon such trapping in unsaturated precursor solutions, nucleation of MAPbX3 (MA=CH3 NH3 + ; X=Cl- , Br- , or I- ) is induced at the focal spot through increase in the concentration of perovskite precursors in the focal volume. The rate at which the nucleated crystal grows depends upon whether the perovskite absorbs the trapping laser or not. These findings suggest that optical trapping would be useful to prepare various perovskite single crystals and modify their optical and electronic properties; thereby, offering new methods for engineering of perovskite crystals.

Crystallization of Methylammonium Lead Halide Perovskites by Optical Trapping

AbstractSingle crystals of organolead halide perovskites attract much attention to electrooptical and photovoltaic applications. They are usually prepared in precursor solutions incubated at controlled temperatures or under optimized vapor atmosphere conditions, and thus, multiple perovskite crystals are nucleated all over the solution. Multiple nucleation of crystals prevents efficient use of precursors in the preferential growth of large single crystals. An innovative approach is presented for spatiotemporally controlled, selective nucleation and growth of single crystals of lead halide perovskites by optical trapping with a focused laser beam. Upon such trapping in unsaturated precursor solutions, nucleation of MAPbX3 (MA=CH3NH3+; X=Cl−, Br−, or I−) is induced at the focal spot through increase in the concentration of perovskite precursors in the focal volume. The rate at which the nucleated crystal grows depends upon whether the perovskite absorbs the trapping laser or not. These findings suggest that optical trapping would be useful to prepare various perovskite single crystals and modify their optical and electronic properties; thereby, offering new methods for engineering of perovskite crystals.

Zn3P2S8: A Promising Infrared Nonlinear-Optical Material with Excellent Overall Properties

The thiophosphate Zn3P2S8 is reported for its potential application in infrared (IR) nonlinear optics. This nondeliquescent compound features a cubic closet packing of the (PS4)3- groups, with Zn2+ filling in three-quarters of the tetrahedral interspaces. The optical band gap of Zn3P2S8 is characterized as 3.12 eV, which is very beneficial to improving the laser damage threshold. Besides, Zn3P2S8 demonstrates good phase matchability (PM)with a strong second-harmonic-generation (SHG) response that is about 2.6 times that of AgGaS2, achieving a valuable balance among good phase matchability, strong SHG response, and large optical band gap. The origin of these attractive optical properties is investigated in detail via theoretical calculations. Moreover, the differential scanning calorimetry curve indicates a congruent-melting thermal behavior of Zn3P2S8, which is conducive to large single-crystal growth. The excellent comprehensive performance of Zn3P2S8 makes it a practically usable IR nonlinear-optical candidate.

Deep-ultraviolet nonlinear optical materials: Development trend and innovative exploration

With the rapid development of all-solid-state laser technology in the field of optical communication, optical processing and optical storage, deep-ultraviolet (deep-UV, wavelengths below 200 nm) nonlinear optical (NLO) materials have become a hot topic at home and abroad. Coherent radiation in the deep-UV is possible with excimer lasers, e.g., F2 excimer at 157 nm. However, solid-state lasers in these wavelength ranges are often preferred owing to handling ease, narrow bandwidth, tunability, high energy density, and high peak power density. An excellent manner to generate coherent deep-UV light is through solid-state lasers using cascaded frequency conversion with NLO materials. Deep-UV NLO crystals, which can double the frequency of incident light to the deep-UV region, are essential for all-solid-state laser. The prerequisites for deep-UV NLO crystals are crystallographically noncentrosymmetric (NCS), wide optical transparency window, large second harmonic generation (SHG) response, phase- matching capability, and easy growth of large (centimeter size) high quality single crystals. For years, there has been a “200 nm wall”, that is, no material is available for deep-UV SHG. Over the past decades, great efforts have been made on chemical design and synthesis of deep-UV NLO materials. Currently, only KBe2BO3F2 (KBBF) crystal is capable for generating deep-UV light through direct sixth harmonic generation of the Nd:YAG laser. The infinite ∞[Be2BO3F2]− single layers in KBBF provide a relatively large SHG coefficient ( d 11=0.47 pm/V) and a sufficient birefringence (Δ n =0.07@1064 nm). However, the KBBF crystals have insurmountable intrinsic defects, such as the high toxicity of the beryllium oxide, and the serious layer growth habit, which greatly restrict its commercialization and application process. Therefore, researchers are actively exploring the next generation of deep-UV NLO materials. In this review, we will first briefly discuss the history of deep-UV NLO crystals. The main factors that restrict the development of deep-UV NLO crystals were highlighted, emphasizing one of the greatest challenges after the material is synthesized is its large single-crystal growth. In the second section, we will focus on progress and trend of deep-UV NLO materials in recent ten years and divide them into different categories according to different material systems and structural features. Five groups of materials are given—beryllium borates, beryllium-free borates, carbonate-fluorides, phosphates and fluorooxoborates. The absorption edge, powder SHG efficiency and birefringence of these materials are summarized in detail. In this section, the development of fluorooxoborates is discussed and the important achievements are reviewed systematically. In addition, the major contradictions among bandgap, NLO coefficient and birefringence were discussed and the methods of theoretical structure prediction algorithms for solving these problems were proposed in order to provide reference for discovering new deep-UV NLO materials.

The Next‐Generation of Nonlinear Optical Materials: Rb3Ba3Li2Al4B6O20F—Synthesis, Characterization, and Crystal Growth

AbstractNonlinear optical (NLO) materials are of intense academic and technological interest attributable to their ability to generate coherent radiation over a range of different wavelengths. The requirements for a viable NLO material are rather strict, and their discovery has mainly been serendipitous. This study reports synthesis, characterization, and, most importantly, growth of large single crystals of a technologically viable NLO material—Rb3Ba3Li2Al4B6O20F. Through the judicious selection of cations, Rb3Ba3Li2Al4B6O20F exhibits a 3D structure that facilitates the growth of large single crystals along the optical axis direction. Measurements on these crystals indicate that Rb3Ba3Li2Al4B6O20F exhibits a moderate birefringence of 0.057 at 1064 nm enabling Type I phase‐matching down to 243 nm. Theoretical calculations indicate the symmetry adapted mode displacement (SAMD) parameter scales with the second‐harmonic generation intensity.