Large-size Single Crystals Research Articles

Carrier Diffusion and Recombination Anisotropy in the MAPbI3 Single Crystal.

MAPbI3, one of the archetypical metal halide perovskites, is an exciting semiconductor for a variety of optoelectronic applications. The photoexcited charge-carrier diffusion and recombination are important metrics in optoelectronic devices. Defects in grain interiors and boundaries of MAPbI3 films cause significant nonradiative recombination energy losses. Besides defect impact, carrier diffusion and recombination anisotropy introduced by structural and electronic discrepancies related to the crystal orientation are vital topics. Here, large-sized MAPbI3 single crystals (SCs) were grown, with the (110), (112), (100), and (001) crystal planes simultaneously exposed through the adjusting ratios of PbI2 to methylammonium iodide (MAI). Such MAPbI3 SCs exhibit a weak n-type semiconductor character, and the Fermi levels of these planes were slightly different, causing a homophylic p-n junction at crystal ledges. Utilizing MAPbI3 SCs, the photoexcited carrier diffusion and recombination within the crystal planes and around the crystal ledges were investigated through time-resolved fluorescence microscope. It is revealed that both the (110) and (001) planes were facilitated to be exposed with more MAI in the growth solutions, and the photoluminescence (PL) of these planes manifesting a red-shift, longer carrier lifetime, and diffusion length compared with the (100) and (112) planes. A longer carrier diffusion length promoted photorecycling. However, excessive MAI-assisted grown MAPbI3 SCs could increase the radiative recombination. In addition, it revealed that the carrier excited within the (001) and (112) planes was inclined to diffuse toward each other and was favorable to be extracted out of the grain boundaries or crystal ledges.

Large‐Size Monolayer MoSe2 Single Crystals: Ultrafast Growth of Large‐Area Uniform, Millimeter‐Size MoSe2 Single Crystals on Low‐Cost Soda‐Lime Glass (Adv. Mater. Interfaces 12/2021)

Soda-lime glass presents a smooth “liquid-phase” surface at high temperature (≈900 °C), which is helpful for the fast growth of large-size monolaye MoSe2 single crystals. The unique “beam-bridge” assisted metal-precursor feeding strategy contributes to sufficient, homogeneous release of Mo-based precursor, thereby leading to the ultrafast growth (≈50 μm s−1) of monolayer MoSe2 single crystals of millimeter-size, as presented in article number 2100415 by Xiaolong Zou, Fenghua Chen, Yanfeng Zhang, and co-workers.

Growth, crystal structure, thermal, spectral studies and density functional theory computational analysis of an organic nonlinear optical crystal: 2‐{3‐[2‐(4‐dimethylaminophenyl)vinyl]‐5,5‐dimethylcyclohex‐2‐enylidene}‐malonitrile

AbstractWe report on synthesis, growth and characterization of an organic nonlinear optical (NLO) crystal 2‐{3‐[2‐(4‐dimethylaminophenylvinyl]‐5,5‐dimethylcyclohex‐2‐enylidene}‐malonitrile (DAT2). The functional groups are identified by 1H‐NMR. Large size single crystal of DAT2 of size 1.2 × 0.5 × 0.2 cm3 is grown for the first time using solution growth technique. The physicochemical properties of DAT2 crystal such as crystal structure, melting point, optical reflectance and photoluminescence are studied experimentally. Density functional theory (DFT) analysis is employed to study the band structure, optical and electronic properties of DAT2. The theoretical bandgap was compared with the experimental one. LDA approximation has been used to compare the GGA results.

The relationship between slip behavior and dislocation arrangement for large-size Mo-3Nb single crystal at room temperature

The slip behavior and mechanism of large-size Mo-3Nb single crystal have been investigated and disclosed comprehensively at room temperature by quasi-static compression with various strains. With the increase of deformation, the slip traces change from shallow non-uniform slip lines to dense and uniform slip bands. Different slip traces in the same deformation condition were observed, suggesting that the slip traces in the single crystal are controlled by different types and arrangement mechanisms of mobile dislocation. To clarify the relationship between slip behavior and dislocation arrangement, TEM and AFM analyses were performed. Significant discrepancy between the mobility of screw segments and edge segments caused by double cross-slip multiplication mechanism is the reason why different slip features were witnessed. During the whole slip deformation process, screw dislocations play a dominant role and they are inclined to form wall-substructures by interaction and entanglement. With the development of dislocation accumulation, the entangled dislocation walls evolve into dislocation cells with higher stability.

Growth and characterization of Dy1-xYxMnO3 single crystals by optical floating zone technique: A combined X-ray diffraction and DC magnetization study

Large size single crystals of DyMnO3, YMnO3 and their solid solutions, Dy1-xYxMnO3, have been grown by the optical floating zone technique. It is shown that pristine DyMnO3 crystals grown in air atmosphere correspond to the orthorhombic phase in the Pnma space group symmetry while growth in the argon atmosphere leads to the hexagonal phase in the P63cm space group symmetry. The crystals grown in air atmosphere for the composition range 0.10 ≤ x ≤ 0.50 show coexistence of orthorhombic and hexagonal phases with increasing hexagonal phase fraction until at x ~ 0.60, the orthorhombic phase completely transforms to the hexagonal phase even in the air atmosphere. On the other hand, all the crystals grown in argon atmosphere correspond to the hexagonal phase only. Our Rietveld refinements using X-ray powder diffraction data on powders obtained after crushing the crystals further confirm the hexagonal structure in the P63cm space group symmetry for all crystals grown in argon atmosphere. The unit cell volume and the lattice parameters obtained by Rietveld refinement are shown to decrease with increasing Y3+ substitution at the Dy3+ site in DyMnO3. DC magnetisation measurements on h-Dy1-xYxMnO3 single crystals reveal that Y3+ substitution marginally increases the antiferromagnetic ordering temperature (TN) from 67 K for h-DyMnO3 to 72 K for h-YMnO3. However, the first spin reorientation (SR) transition temperature (TSR1) of Mn3+ decreases with increasing Y3+ substitutions as per TSR1 ~ k(x-xc)0.3, where k is a proportionality constant and xc is the critical composition for which this transition temperature goes to 0 K. The remaining two magnetic transition temperatures related to Dy3+ reordering (TDy3+)/spin-glass transition (TSG) and second spin reorientation transition (TSR2) show very weak dependence on Y3+ substitution before going to 0 K around x = xc ~ 0.90 composition. A magnetic phase diagram of h-Dy1-xYxMnO3 showing stability field regions in respect of different magnetic phases is also presented.

Microstructure, fracture toughness and high-temperature tensile property of large size Ti–46Al–5Nb-0.18C-0.3Si alloy with oriented lamella by electromagnetic confinement directional solidification

In this paper, the microstructure, fracture toughness, and high-temperature tensile property of the directionally solidified Ti–46Al–5Nb-0.18C-0.3Si alloy are investigated. The lamellar orientation of the alloy is parallel to the growth direction under the action of the seed. Due to the convex shape of the solid-liquid interface, the core grain growth preferentially, and a large-size single crystal is formed in the steady-state region. The results show that the fracture toughness of the alloy increases with the increase of the orientation angle, and the fracture behavior changes from interlamellar to translamellar. The alloy with well-aligned lamellar microstructure possesses the excellent high-temperature tensile properties, and the ultimate tensile strength (UTS) and elongation of the alloys are 636.7 ± 24.2 MPa and 23.9 ± 5.75% at 800 °C, 630.5 ± 38.45 MPa and 20.1 ± 3.6% at 850 °C, 606.9 ± 21.3 MPa and 22.6 ± 0.1% at 900 °C, respectively. Additionally, the toughening mechanism and strengthening mechanism are discussed and concluded.

Eliminate of colour center and growth of large-size Tb3Ga5O12 crystals

A series of large-size TGG single crystals with Φ76 mm * L100 mm were grown successfully by Czochralski (Cz) method. The formation mechanism of colour center was discussed and the results show the colour center of TGG crystals is strongly related with composition of atmosphere and raw material. The large-size TGG crystals with only light-yellow colour center can be obtained by increasing the content of Ga2O3 in the melt. In order to improve the optical properties of crystal, the suitable annealing conditions for TGG crystals were also studied for the first time. The results show the common colour center of TGG crystals can be eliminated by selecting suitable annealing conditions. And the as-grown TGG crystals have good transmittance of 80% and extinction ratio over 35 dB after annealing, which means that it can well meet the current requirements for the application of magneto-optical devices.

Demonstration of Energy-Resolved γ-Ray Detection at Room Temperature by the CsPbCl3 Perovskite Semiconductor.

The detection of γ-rays at room temperature with high-energy resolution using semiconductors is one of the most challenging applications. The presence of even the smallest amount of defects is sufficient to kill the signal generated from γ-rays which makes the availability of semiconductors detectors a rarity. Lead halide perovskite semiconductors exhibit unusually high defect tolerance leading to outstanding and unique optoelectronic properties and are poised to strongly impact applications in photoelectric conversion/detection. Here we demonstrate for the first time that large size single crystals of the all-inorganic perovskite CsPbCl3 semiconductor can function as a high-performance detector for γ-ray nuclear radiation at room temperature. CsPbCl3 is a wide-gap semiconductor with a bandgap of 3.03 eV and possesses a high effective atomic number of 69.8. We identified the two distinct phase transitions in CsPbCl3, from cubic (Pm-3m) to tetragonal (P4/mbm) at 325 K and finally to orthorhombic (Pbnm) at 316 K. Despite crystal twinning induced by phase transitions, CsPbCl3 crystals in detector grade can be obtained with high electrical resistivity of ∼1.7 × 109 Ω·cm. The crystals were grown from the melt with volume over several cubic centimeters and have a low thermal conductivity of 0.6 W m-1 K-1. The mobilities for electron and hole carriers were determined to ∼30 cm2/(V s). Using photoemission yield spectroscopy in air (PYSA), we determined the valence band maximum at 5.66 ± 0.05 eV. Under γ-ray exposure, our Schottky-type planar CsPbCl3 detector achieved an excellent energy resolution (∼16% at 122 keV) accompanied by a high figure-of-merit hole mobility-lifetime product (3.2 × 10-4 cm2/V) and a long hole lifetime (16 μs). The results demonstrate considerable defect tolerance of CsPbCl3 and suggest its strong potential for γ-radiation and X-ray detection at room temperature and above.

Luminescence properties of large-size Li2MoO4 single crystal grown by Czochralski method

Large-size Li2MoO4 single crystal was successfully grown by Czochralski method using the polycrystalline Li2MoO4 bulks synthesized via the conventional solid-state reaction. The phase identification, thermal behavior and optical transmission spectra of Li2MoO4 single crystal were studied systematically. The band gap of Li2MoO4 was estimated from the transmission spectra according to Tauc and Menth’s law. The luminescence spectra and decay characteristics under 355 nm laser excitation were investigated in detail. Li2MoO4 single crystal had a wide luminescence peak around 540 nm as a result of intrinsic luminescence emission of tetrahedral MoO42-. The maximal luminescence intensity increased with the ambient temperature cooling down. Meanwhile, the luminescence decay times decreased monotonically with the temperature increasing from 42 K to 298 K.

Synthesis and Controllable Growth Dynamics of Third Order Nonlinear Optical Material of 2-Amino-4-Methylpyridinium 2-Chloro 4-Nitro Benzoate Electro-Mechanical Investigation and Device Fabrication

An organic nonlinear optical material 2-Amino-4-methylpyridinium 2-chloro 4-nitro benzoate (AMPCNB) was synthesized and large size single crystals were grown by slow evaporation solution growth method. Single crystal X-ray diffraction study showed that the title compound belongs to monoclinic crystal system with P21/n space group. A powder XRD study was performed to ascertain its phase. The UV–VIS-NIR study was performed to investigate the transparency window and lower cutoff wavelength of the compound, no absorption has been observed between 318 and 1100 nm. The third harmonic efficiency of the title compound has been studied using the Z-scan technique using continuous-wave Nd:YAG laser to confirm its saturable absorption and self-defocusing effect. The photo conducting and charge transport properties are analyzed using photoconductivity and dielectric measurements. Theoretical calculation of molecular polarizability, which is helpful in device fabrication, was carried out from Penn gap, Clausius-Mosotti equations and the obtained results were compared. Mechanical properties of the grown crystal were investigated by Vicker’s microhardness study.

Research Status and Prospect on Polishing Technology of Large Size Single Crystal Diamond Substrate

Research Status and Prospect on Polishing Technology of Large Size Single Crystal Diamond Substrate

Potassium L-ascorbate monohydrate: a new metal–organic nonlinear optical crystal

Large size single crystals of potassium L-ascorbate monohydrate (KLAM), (KC6H7O6.H2O) are grown using solution growth technique by lowering the temperature at the rate of 0.24 {\deg}C/h, where water was used as solvent. The structure of KLAM was solved by single crystal XRD. KLAM crystallizes in non-centrosymmetric, monoclinic, P21 space group with lattice parameters a = 7.030(5) {\AA}, b = 8.811(5) {\AA}, c = 7.638(5) {\AA} and \b{eta} = 114.891(5){\deg}. The crystal grows with bulky morphology in all three directions having (100), (-100), (-110), (0-1-1), (0-11), (001) and (00-1) prominent faces. TGA and DSC measurements show that KLAM is stable up to 80 {\deg}C. The crystal shows good optical transparency with a lower cut off as low as 297 nm. Second harmonic conversion efficiency measured on powder sample is 3.5 times that of potassium dihydrogen phosphate (KDP). Phase matching (PM) is observed on a plate of the KLAM. Noncollinear phase matching rings are also observed near the PM directions which help to identify the locus of PM directions. Presence of noncollinear SHG rings up to third order suggests large birefringence and nonlinear optical coefficients. Laser damage threshold value of the crystal is found to be 3.07 GW/cm2, at 1064 nm in 100 direction.

Numerical Analysis of Difficulties of Growing Large-Size Bulk β-Ga2O3 Single Crystals with the Czochralski Method

The difficulties in growing large-size bulk β-Ga2O3 single crystals with the Czochralski method were numerically analyzed. The flow and temperature fields for crystals that were four and six inches in diameter were studied. When the crystal diameter is large and the crucible space becomes small, the flow field near the crystal edge becomes poorly controlled, which results in an unreasonable temperature field, which makes the interface velocity very sensitive to the phase boundary shape. The effect of seed rotation with increasing crystal diameter was also studied. With the increase in crystal diameter, the effect of seed rotation causes more uneven temperature distribution. The difficulty of growing large-size bulk β-Ga2O3 single crystals with the Czochralski method is caused by spiral growth. By using dynamic mesh technology to update the crystal growth interface, the calculation results show that the solid–liquid interface of the four-inch crystal is slightly convex and the center is slightly concave. With the increase of crystal growth time, the symmetry of cylindrical crystal will be broken, which will lead to spiral growth. The numerical results of the six-inch crystal show that the whole solid–liquid interface is concave and unstable, which is not conducive to crystal growth.

Recent Advances in Growth of Large-Sized 2D Single Crystals on Cu Substrates.

Large-scale and high-quality 2D materials have been an emerging and promising choice for use in modern chemistry and physics owing to their fascinating property profile. The past few years have witnessed inspiringly progressing development in controlled fabrication of large-sized and single-crystal 2D materials. Among those production methods, chemical vapor deposition (CVD) has drawn the most attention because of its fine control over size and quality of 2D materials by modulating the growth conditions. Meanwhile, Cu has been widely accepted as the most popular catalyst due to its significant merit in growing monolayer 2D materials in the CVD process. Herein, very recent advances in preparing large-sized 2D single crystals on Cu substrates by CVD are presented. First, the unique features of Cu will be given in terms of ultralow precursor solubility and feasible surface engineering. Then, scaled growth of graphene and hexagonal boron nitride (h-BN) crystals on Cu substrates is demonstrated, wherein different kinds of Cu surfaces have been employed. Furthermore, the growth mechanism for the growth of 2D single crystals is exhibited, offering a guideline to elucidate the in-depth growth dynamics and kinetics. Finally, relevant issues for industrial-scale mass production of 2D single crystals are discussed and a promising future is expected.

Anisotropic Performance of High-Quality MAPbBr3 Single-Crystal Wafers.

It has been proved that bulk single crystals of a halide perovskite behave much better than its polycrystalline counterparts in multiple application scenarios. Thus, the growth of large-sized and high-quality single crystals is significant to guarantee their ultimate device performances. Here, based on our recently invented settled temperature and controlled antisolvent diffusion system, improvements achieved in this work include the following: (1) We modified the growth system to optimize the control over both mass and heat transport to alleviate defect formation. State-of-the-art-quality MAPbBr3 crystals were grown, and from the bulk crystals, differently oriented crystalline wafers were fabricated with the full width at half-maximum of X-ray rocking curves of 40-86 arcsec. (2) The optical band gaps revealed no anisotropy on differently oriented wafers, whereas the refractive index and extinction coefficient exhibited obvious anisotropy. (3) Angle-resolved polarized Raman spectra demonstrate distinct in-plane anisotropy on (100) and (110) wafers but not on the (111) wafer. The equilibrium MA+ orientations are deduced to adopt the <111> direction with the antiparallel MA+ orientation between adjacent domains. (4) Radiation detectors fabricated on differently oriented wafers proved photoresponse anisotropy to both visible and X-ray radiation, following a general order of (100) > (110) > (111). Because anisotropy is an inevitable issue for various applications employing crystalline materials, this study, based on the clarification of the debatable intrinsic dipole configuration in the pseudocubic crystal lattice, will provide quantitative information on physicochemical property anisotropy and subsequently facilitate optimization of device performance referring to crystal orientations of halide perovskite crystals.

The Crystal Stock Phenomenon in the Process of the Plate Shape for Type Ib Large Synthetic Diamond Single Crystals

The crystal stock defect was formed in growing for a long time (22 h) of plate type Ib large diamond single crystals from the NiMnCo−C system at high pressure and high temperature (HPHT). The existence of crystal stock defect has great influence on the synthesis of high quality and large size diamond single crystal. In this paper, the effects of crystal growth rate and catalyst components on diamond crystal stock defects are studied. Firstly, the results show that the growth rate of diamond crystals is closely related to the generating of diamond crystal stock. This defect can be eliminated as the growth rate of diamond crystal synthesized with NiMnCo catalyst is reduced to less than 3 mg/h. Secondly, the composition of the catalyst also affects the formation of the crystal stock. High viscous FeNi catalyst is used to grow high quality large single crystals of diamonds at a growth rate of 3.18 mg/h for a long time (22 h). Thirdly, the effect of catalyst composition on diamond crystal stock was analyzed by testing the micro-morphology and nitrogen content of diamond. It can be shown from the results by scanning electron microscopy (SEM) that the surface of crystals synthesized with low-viscosity catalyst is rough, while it synthesized with high-viscosity catalyst is smooth. It was found from the test results of micro Fourier-transform infrared spectroscopy (FTIR) that the content of nitrogen in the crystals synthesized with FeNi catalyst was much lower than that in the crystals synthesized with NiMnCo. FeNi catalyst can effectively avoid the crystal stock, and is more suitable for the growth of large-size and high-quality diamond single crystal. Changing the composition of the catalyst is an effective way to avoid the crystal stock phenomenon.

Process optimization of large-sized cubic boron nitride single crystal synthesis with Li3N as catalyst

Cubic boron nitride (cBN) was synthesized using cubic press with lithium nitride as the catalyst and hexagon boron nitride as the source material under high temperature and high pressure in this study. The high quality big-sized cBN single crystal can be synthesized with the optimized synthesis process. Comparing two different pressurization process, two different power process and three different heating times, the influence for the quality of cBN single crystal were studied. The results show that the process of gradually elevated pressure, the constant power and 15 minutes heating time are conducive to big-sized cBN crystals synthesis under high temperature and high pressure. Using the optimized synthesis process, the single block output reaches up to more than 120ct, the proportion of cBN crystal bigger than 50 mesh reaches to more than 16%, the static pressure strength of 60/70 mesh single crystal reaches to 30 N. Meanwhile, the cBN single crystals have fewer surface defects. The final result is high quality large-sized cBN single crystal was obtained.

Three-Dimensional Covalent Organic Frameworks: From Topology Design to Applications.

ConspectusCovalent organic frameworks (COFs) represent a novel type of crystalline porous polymers with potential applications in many areas. Considering their covalent connectivity in different dimensions, COFs are classified as two-dimensional (2D) layered structures or three-dimensional (3D) networks. In particular, 3D COFs have gained increasing attention recently because of their remarkably large surface areas (>5000 m2/g), hierarchical nanopores and numerous open sites. However, it has been proven to be a major challenge to construct 3D COFs, as the main driving force for their synthesis comes from the formation of covalent bonds. In addition, there are several stones on the roads blocking the development of 3D COFs. First, the successful topology design strategies of 3D COFs have been limited to [4 + 2] or [4 + 3] condensation reactions of the tetrahedral molecules with linear or triangular building blocks in the first decade, which led to only three available topologies (ctn, bor, and dia) and strongly restricted the incorporation of some important functional units. Next, as it is very challenging to obtain large-size single crystals of 3D COFs and the same building blocks may yield many possible structures that are quite difficult to identify from simulations, their structure determination has been considered a major issue. Last, the building blocks utilized to synthesize 3D COFs are very limited, which further affects their functionalization and applications. Therefore, since it was first announced in 2007, research studies regarding 3D COFs have been underexplored for many years, and very few examples have been reported.To confront these obstacles in 3D COFs, we started contributing to this field in 2016. Considering that many interesting quadrilateral molecules (e.g., pyrene and porphyrin) cannot be easily derivatized into linear or triangular motifs, we developed a novel topology design strategy to construct 3D COFs via [4 + 4] condensation reactions of tetrahedral and quadrilateral building blocks. After many trials, we found that this is a general synthetic strategy to build 3D COFs with the new pts topology. In addition, we explored the structure determination of polycrystalline 3D COFs prepared by our developed strategy via a 3D electron diffraction technique. Moreover, we expanded the toolbox of molecular building blocks for creating 3D COFs and successfully demonstrated the functionalization of 3D COFs with characteristic properties and applications. In this Account, we summarize our above ongoing research contributions, including (i) a novel topology design strategy for the synthesis of 3D COFs; (ii) attempts to determine the crystal structure of polycrystalline 3D COFs with atomic resolution; and (iii) the diversification of building blocks and applications of functionalized 3D COFs. Overall, our studies not only offer a new paradigm of expansion in the topology design strategy and building block families of 3D COFs, but also provide an idea of future opportunities for relevant researchers in this field.

Lead-Free, Water-Stable A3 Bi2 I9 Perovskites: Crystal Growth and Blue-Emitting Quantum Dots [A=CH3 NH3 + , Cs+ , and (Rb0.05 Cs2.95 )+

Despite the great success in the increase in the power conversion efficiency of lead halide perovskite solar cells, the toxicity of lead and the unstable nature of the materials are still major concerns for their wider implementation at the industrial level. Herein, large-size single crystals (SCs) are developed in HI solution by using a temperature lowering method and nanocrystals (NCs) of A3 Bi2 I9 perovskites [where A=CH3 NH3 + (MA)+ , Cs+ , and (Rb0.05 Cs2.95 )+ ] are formed in ethanol (EtOH) and toluene (TOL). The stability of A3 Bi2 I9 perovskite is investigated by immersing the SCs for 24 h and pellets for 12 h in water. Moreover, the A3 Bi2 I9 perovskite NCs displays a promising photoluminescence quantum yield of 17.63 % and a long lifetime of 8.20 ns.

Development of Halide Perovskite Single Crystal for Radiation Detection Applications.

Preface: Recently, low-cost perovskite single crystals have attracted intensive attention due to their excellent optoelectronic properties and improved stability when compared to polycrystalline films for various applications, such as solar cells (Kojima et al., 2009; Lee et al., 2012; Tsai et al., 2016; Sahli et al., 2018), lasers (Gu et al., 2016; Veldhuis et al., 2016), radiation detection (Kim et al., 2017), and so on. The unique optoelectronic properties and low-cost growing processes for large-sized single crystals also make them greatly suitable for radiation detection. In this review, we summarize various synthesis methods of perovskite single crystals and introduced the high radiation detection performance of the perovskite single crystal. The advantages and limitations of halide perovskite single crystals as radiation detector candidates will be discussed in detail, and corresponding future development trends can be expected by overcoming current obstacles (Leijtens et al., 2018; Boyd et al., 2019), such as ion migration (Eames et al., 2015), stability, etc.