Showing papers on "Single crystal published in 2020"

Epitaxial Growth of Centimeter-Scale Single-Crystal MoS2 Monolayer on Au(111).

Abstract: Two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) have emerged as attractive platforms in next-generation nanoelectronics and optoelectronics for reducing device sizes down to a 10 nm scale. To achieve this, the controlled synthesis of wafer-scale single-crystal TMDs with high crystallinity has been a continuous pursuit. However, previous efforts to epitaxially grow TMD films on insulating substrates (e.g., mica and sapphire) failed to eliminate the evolution of antiparallel domains and twin boundaries, leading to the formation of polycrystalline films. Herein, we report the epitaxial growth of wafer-scale single-crystal MoS2 monolayers on vicinal Au(111) thin films, as obtained by melting and resolidifying commercial Au foils. The unidirectional alignment and seamless stitching of the MoS2 domains were comprehensively demonstrated using atomic- to centimeter-scale characterization techniques. By utilizing onsite scanning tunneling microscope characterizations combined with first-principles calculations, it was revealed that the nucleation of MoS2 monolayer is dominantly guided by the steps on Au(111), which leads to highly oriented growth of MoS2 along the ⟨110⟩ step edges. This work, thereby, makes a significant step toward the practical applications of MoS2 monolayers and the large-scale integration of 2D electronics.

The Emergence of Organic Single-Crystal Electronics.

Abstract: Organic semiconducting single crystals are perfect for both fundamental and application-oriented research due to the advantages of free grain boundaries, few defects, and minimal traps and impurities, as well as their low-temperature processability, high flexibility, and low cost. Carrier mobilities of greater than 10 cm2 V-1 s-1 in some organic single crystals indicate a promising application in electronic devices. The progress made, including the molecular structures and fabrication technologies of organic single crystals, is introduced and organic single-crystal electronic devices, including field-effect transistors, phototransistors, p-n heterojunctions, and circuits, are summarized. Organic two-dimensional single crystals, cocrystals, and large single crystals, together with some potential applications, are introduced. A state-of-the-art overview of organic single-crystal electronics, with their challenges and prospects, is also provided.

Microstructural Observations of “Single Crystal” Positive Electrode Materials Before and After Long Term Cycling by Cross-section Scanning Electron Microscopy

Abstract: Single crystal LiNi0.5Mn0.3Co0.2O2 (SC532), LiNi0.6Mn0.2Co0.2O2 (SC622) and LiNi0.8Mn0.1Co0.1O2 (SC811) electrodes were retrieved from heavily cycled commercial-grade pouch cells at 4.3 V for cross-section scanning electron microscopy (SEM). SEM images indicated the single crystals showed very little microcracking, thought by many researchers to be one of the main reasons for cell degradation when polycrystalline materials are used. SEM images of electrodes from heavily cycled cells were compared to those from fresh cells which showed little visual difference. Parallel microcracks within very few single crystal particles were observed for both fresh and heavily cycled materials and are thought to be caused during the electrode calendaring process. It is believed by the authors that single crystal materials are highly promising positive electrode materials for high energy density and long cycle life lithium-ion cells.

Sensitive and Stable 2D Perovskite Single-Crystal X-ray Detectors Enabled by a Supramolecular Anchor.

Abstract: Perovskite X-ray detectors have been demonstrated to be sensitive to soft X-rays (<80 keV) for potential medical imaging applications. However, developing X-ray detectors that are stable and sensitive to hard X-rays (80 to 120 keV) for practical medical imaging is highly desired. Here, a sensitive 2D fluorophenethylammonium lead iodide ((F-PEA)2 PbI4 ) perovskite single-crystal hard-X-ray detector from low-cost solution processes is reported. Dipole interaction of organic ions promotes the ordering of benzene rings as well as the supramolecular electrostatic interaction between electron-deficient F atoms with neighbor benzene rings. Supramolecular interactions serve as a supramolecular anchor to stabilize and tune the electronic properties of single crystals. The 2D (F-PEA)2 PbI4 perovskite single crystal exhibits an intrinsic property with record bulk resistivity of 1.36 × 1012 Ω cm, which brings a low device noise for hard X-ray detection. Meanwhile, the ion-migration phenomenon is effectively suppressed, even under the large applied bias of 200 V, by blocking the ion migration paths after anchoring. Consequently, the (F-PEA)2 PbI4 single crystal detector yields a sensitivity of 3402 μC Gy-1 air cm-2 to 120 keVp hard X-rays with lowest detectable X-ray dose rate of 23 nGyair s-1 , outperforming the dominating CsI scintillator of commercial digital radiography systems by acquiring clear X-ray images under much lower dose rate. In addition, the detector shows high operation stability under extremely high-flux X-ray irradiation.

All-Inorganic Lead-Free Heterometallic Cs4MnBi2Cl12 Perovskite Single Crystal with Highly Efficient Orange Emission

Abstract: Summary A luminescent all-inorganic manganese-bismuth heterometallic Cs4MnBi2Cl12 perovskite single crystal has been synthesized with a [BiCl6]3−-[MnCl6]4−-[BiCl6]3− triple-layered two-dimensional structure Benefit from the effective energy transfer from [BiCl6]3− octahedron donor to luminescent [MnCl6]4− acceptor, Cs4MnBi2Cl12 shows a photoluminescence quantum yield (PLQY) of up to 257% (~610 nm), 51-fold higher than the Bi unalloyed CsMnCl3·2H2O counterpart Suggested by the theoretical calculations, Bi and Mn exhibit hybridization in conduction and valence band, which further results in a favorable low activation energy for exciton transfer (~23 meV) By virtue of all-inorganic chemical composition, Cs4MnBi2Cl12 exhibits impressive stability toward moisture, light, and heat Furthermore, Cs4MnBi2Cl12 features strong soft X-ray attenuation and bright radiative luminescence under X-ray excitation, which pave a way for its application in medical flat-panel X-ray digital radiography This work presents a new avenue toward fabrication of function-directed material with tailored photoelectric properties

Highly Efficient Self-Trapped Exciton Emission of a (MA)4Cu2Br6 Single Crystal.

Abstract: Recently, low-dimensional organic-inorganic lead halide perovskites have attracted a great deal of attention due to their outstanding tunable broadband emission, while the toxicity of lead hinders their further application in the photoelectric field. Here, we report a novel lead-free Cu(I)-based organic-inorganic perovskite-related material of a (MA)4Cu2Br6 single crystal with zero-dimensional clusters, which is a unique Cu2Br64- corner-sharing tetrahedron dimer structure consisting of two connected tetrahedra. The single crystal displays a bright broadband green emission with a high photoluminescence with a quantum yield of ≤93%, a large Stokes shift, and a very long (microsecond) photoluminescence (PL) lifetime, resulting from self-trapped exciton emission. The direct band gap characteristic of (MA)4Cu2Br6 was proven by density functional theory calculation, and its band gap was determined by experiments to be ∼3.87 eV. In the temperature range of 98-258 K, the PL intensity increases gradually with an increase in temperature due to the deep trapping out of strong electro-phonon coupling, while the PL decreases when the temperature increases over 258 K due to phonon scattering. It is worth mentioning that this new material has high chemical and light stability, in contrast to the lead perovskite.

Anchoring Interfacial Nickel Cations on Single Crystal LiNi0.8Co0.1Mn0.1O2 Cathode Surface via Controllable Electron Transfer

Abstract: Severe Ni dissolution and the resulted surface impedance rise for single crystal LiNi08Co01Mn01O2 surface during electrochemical cycles is the main challenge greatly hindering its industrial app

Centimeter-Sized Single Crystal of Two-Dimensional Halide Perovskites Incorporating Straight-Chain Symmetric Diammonium Ion for X-Ray Detection

Abstract: Two-dimensional (2D) AA'n-1 Mn X3n+1 type halide perovskites incorporating straight-chain symmetric diammonium cations define a new type of structure, but their optoelectronic properties are largely unexplored. Reported here is the synthesis of a centimeter-sized AA'n-1 Mn X3n+1 type perovskite, BDAPbI4 (BDA=NH3 C4 H8 NH3 ), single crystal and its charge-transport properties under X-ray excitation. The crystal shows a staggered configuration of the [PbI6 ]4- layers, a band gap of 2.37 eV, and a low trap density of 3.1×109 cm-3 . The single-crystal X-ray detector exhibits an excellent sensitivity of 242 μC Gyair-1 cm-2 under the 10 V bias (0.31 V μm-1 ), a detection limit as low as 430 nGyair s-1 , ultrastable response current, a stable baseline with the lowest dark current drift of 6.06×10-9 nA cm-1 s-1 V-1 , and rapid response time of τrise =7.3 ms and τfall =22.5 ms. These crystals are promising candidates for the next generation of optoelectronic devices.

A Flexible Organic Single Crystal with Plastic-Twisting and Elastic-Bending Capabilities and Polarization-Rotation Function

Abstract: Flexible organic single crystals capable of plastic or elastic deformations have a variety of potential applications. Although the integration of plasticity and elasticity in a crystal is theoretically possible and it may cause rich and complex deformations which are highly demanded for potential applications, the integration is hard to realize in practice. Here, we show that through utilizing different modes of external forces for influencing molecular packing in different crystallographic directions, plastic helical twisting and elastic bending can both be achieved for a crystal, and they can even be realized simultaneously. Detailed crystallographic analyses and contrast experiments disclose the mechanisms behind these two kinds of distinct deformations and their mutual compatibility. Based on the plastically twistable nature of the crystal, a new application field of flexible organic single crystals, namely polarization rotators, is successfully opened up.

Optical Waveguiding Organic Single Crystals Exhibiting Physical and Chemical Bending Features

Abstract: Bendable (elastic and plastic) organic single crystals have been widely studied as emerging flexible materials with highly ordered packing structures. However, even though manifold bendable organic crystals have been recently reported, most of them bend in response to only one stimulus. Herein, we report an organic single crystal of (Z)-4-(1-cyano-2-(4-(dimethylamino)phenyl)vinyl)benzonitrile, which bends under external stress (physical process) and also hydrochloric acid atmosphere (chemical process). This observation indicates that a single organic crystal, whose structure has been optimized simultaneously at both the molecular and supramolecular levels, may display multiple crystal-bending modes. Furthermore, the crystals exhibit bright orange-yellow emission and can serve as an active low-loss optical waveguide in both the straight and the bent state, which indicates a potential optical application.

Perovskite CsPbBr3 crystals: growth and applications

Abstract: The CsPbBr3 perovskite material has excellent optoelectronic properties such as large light absorption coefficient, high carrier mobility, long diffusion length, etc., and thus it shows good application prospects in solar cells, photodetectors, high-energy radiation detectors and other fields. Compared with polycrystalline thin films, a single crystal perovskite without grain boundaries has better photoelectric performance, showing photovoltaic potential with higher efficiency and stability. Therefore, the fabrication of CsPbBr3 perovskite single crystals is very important to further explore the potential of single crystal perovskites in various applications. This review systematically summarizes the latest research progress of perovskite CsPbBr3 crystal growth in recent years, and introduces its applications in photodetectors, high-energy radiation detectors, and solar cells. Finally, the challenges and perspectives of perovskite CsPbBr3 crystals are discussed.

Single crystal structure, vibrational spectroscopy, gas sorption and antimicrobial properties of a new inorganic acidic diphosphates material (NH4)2Mg(H2P2O7)2•2H2O

Abstract: We report on the successful synthesis of diammonium magnesium dihydrogendiphosphate (V) dihydrate compound (NH4)2Mg(H2P2O7)2•2H2O using a wet chemical route. Single crystal X-ray diffraction analysis and micro Raman spectroscopy are employed to characterize the compound. We demonstrate, using a multidisciplinary approach, that this compound is ideal for carbon dioxide (CO2) capture in addition to other anthropogenic gasses. We show here -from both an experimental as well as from a density functional theory (DFT) calculations routes- the potential for adopting this compound into domestic air-conditioning units (ACUs). From these experiments, the resistance to bacterial growth is also investigated, which is critical for the adoption of this compound in ACUs. Our compound exhibits a higher methane (CH4) sorptivity as compared to CO2 at 25 °C and 45 °C under pressures up to 50 bars. Furthermore, DFT electronic structure calculations are used to compute the main structural and electronic properties of the compound, taking into consideration the characteristics of the identified pores as a function of the progressive CO2 vs. CH4 loadings. Finally, the antibacterial assay reveals a strong antibacterial activity against the tested Gram-positive and Gram-negative bacteria, with a large zone of inhibition against the tested E. Coli, S. Aureus and K. Pneumonia.

Intrinsically Ultralow Thermal Conductivity in Ruddlesden–Popper 2D Perovskite Cs2PbI2Cl2: Localized Anharmonic Vibrations and Dynamic Octahedral Distortions

Abstract: Fundamental understanding of the correlation between chemical bonding and lattice dynamics in intrinsically low thermal conductive crystalline solids is important to thermoelectrics, thermal barrier coating, and more recently to photovoltaics. Two-dimensional (2D) layered halide perovskites have recently attracted widespread attention in optoelectronics and solar cells. Here, we discover intrinsically ultralow lattice thermal conductivity (κL) in the single crystal of all-inorganic layered Ruddlesden-Popper (RP) perovskite, Cs2PbI2Cl2, synthesized by the Bridgman method. We have measured the anisotropic κL value of the Cs2PbI2Cl2 single crystal and observed an ultralow κL value of ∼0.37-0.28 W/mK in the temperature range of 295-523 K when measured along the crystallographic c-axis. First-principles density functional theory (DFT) analysis of the phonon spectrum uncovers the presence of soft (frequency ∼18-55 cm-1) optical phonon modes that constitute relatively flat bands due to localized vibrations of Cs and I atoms. A further low energy optical mode exists at ∼12 cm-1 that originates from dynamic octahedral rotation around Pb caused by anharmonic vibration of Cl atoms induced by a 3s2 lone pair. We provide experimental evidence for such low energy optical phonon modes with low-temperature heat capacity and temperature-dependent Raman spectroscopic measurements. The strong anharmonic coupling of the low energy optical modes with acoustic modes causes damping of heat carrying acoustic phonons to ultrasoft frequency (maximum ∼37 cm-1). The combined effect of soft elastic layered structure, abundance of low energy optical phonons, and strong acoustic-optical phonon coupling results in an intrinsically ultralow κL value in the all-inorganic layered RP perovskite Cs2PbI2Cl2.

Interface engineering strategies towards Cs2AgBiBr6 single-crystalline photodetectors with good Ohmic contact behaviours

Abstract: Lead-free double perovskite materials have attracted much interest for optoelectronic applications due to their nontoxicity and high stability. In this work, centimetre-sized Cs2AgBiBr6 single crystals were successfully grown using methylammonium bromide (MABr) as the flux by a top-seeded solution growth (TSSG) method. The low-temperature crystal structure of Cs2AgBiBr6 single crystals was determined and refined. To investigate the interface problems between Cs2AgBiBr6 single crystals and electrodes, the optical band gap, X-ray photoelectron spectroscopy (XPS), and ultraviolet photoemission spectroscopy (UPS) measurements were performed on Cs2AgBiBr6 single crystals. More importantly, we investigated the photodetectors based on Cs2AgBiBr6 single crystals with different contact electrodes (Au, Ag, and Al). It is found that a good Ohmic contact with Ag electrodes enables excellent photo-response behaviors. Furthermore, we studied the photodetectors based on Cs2AgBiBr6 single crystals using Ag electrodes under room and low temperature conditions, which underwent phase transition. Cs2AgBiBr6 single crystal photodetectors show clear differences at room and low temperatures, which is caused by the work function changes of Cs2AgBiBr6 single crystals induced by the reversible phase transition. These attractive properties may enable opportunities to apply emerging double perovskite single-crystalline materials for high-performance optoelectronic devices.

Single-Crystal-to-Single-Crystal [2 + 2] Photocycloaddition Reaction in a Photosalient One-Dimensional Coordination Polymer of Pb(II).

Abstract: In a remarkable example, we report a one-dimensional coordination polymer (CP) of Pb(II) showing photosalient (PS) properties triggered by [2 + 2] cycloaddition of olefinic ligands, which is seldom observed in CPs. Macroscopic rod-shaped crystals show various photomechanical effects such as jumping, splitting, rolling, and breaking upon UV illumination. In this rare example, we could determine the solid-state structure of the 100% dimerized product and three intermediate structures, even after the shattering of crystals into small pieces. Detailed mechanistic investigation from the single-crystal data indicates that the strain generated in the unit cell due to anisotropic expansion played a bigger role for the PS effects. Nucleated growth of the photoproduct crystal created different domains inside the single crystal, which multiplied the already developed stress leading to the photomechanical movements. This example falls in the gray area of a clean single-crystal-to-single-crystal (SCSC) transformation and violent PS effect. Such photochemical behavior has never been reported before.

Hysteresis Photomodulation via Single-Crystal-to-Single-Crystal Isomerization of a Photochromic Chain of Dysprosium Single-Molecule Magnets

Abstract: A one-dimensional coordination solid 1c is synthesized by reaction of a bispyridyl dithienylethene (DTE) photochromic unit with the highly anisotropic dysprosium-based single-molecule magnet [Dy(Tppy)F(pyridine)2]PF6. Slow magnetic relaxation characteristics are retained in the chain compound 1c, and photoisomerization of the bridging DTE ligand induces a single-crystal-to-single-crystal transformation that can be monitored using photocrystallography. Notably, the resulting chain compound 1o exhibits faster low-temperature relaxation than that of 1c, which is apparent in magnetic hysteresis data collected for both compounds as high as 4 K. Ab initio calculations suggest that this photomodulation of the magnetic relaxation behavior is due to crystal packing changes rather than changes to the crystal field splitting upon ligand isomerization.

Realizing Tunable White Light Emission in Lead-Free Indium(III) Bromine Hybrid Single Crystals through Antimony(III) Cation Doping

Abstract: Low-dimensional metal halide hybrids (OIMHs) have recently been explored as single-component white-light emitters for use in solid-state lighting. However, it still remains challenging to realize tunable white-light emission in lead-free zero-dimensional (0D) hybrid system. Here, a combination strategy has been proposed through doping Sb3+ enabling and balancing multiple emission centers toward the multiband warm white light. We first synthesized a new lead-free 0D (C8NH12)6InBr9·H2O single crystal, in which isolated [InBr6]3- octahedral units are separated by large organic cations [C8NH12]+. (C8NH12)6InBr9·H2O exhibits dual-band emissions with one intense cyan emission and a weak red emission tail. The low-energy ultrabroadband red emission tail can be greatly enhanced by the Sb3+ doping. Experimental data and first-principles calculations reveal that the original dominant cyan emission is originated from the organic cations [C8NH12]+ and that the broadband red emission is ascribed to self-trapped excitons in [In(Sb)Br6]3-. When the Sb concentration is 0.1%, a single-component warm white-light emission with a photoluminescence quantum efficiency of 23.36%, correlated color temperature of 3347 K, and a color rendering index up to 84 can be achieved. This work represents a significant step toward the realization of single-component white-light emissions in environmental-friendly, high-performance 0D metal halide light-emitting materials.

Air-Stable Bulk Halide Single-Crystal Scintillator Cs3Cu2I5 by Melt Growth: Intrinsic and Tl Doped with High Light Yield.

Abstract: Ternary metal halides with large exciton binding energy have recently gained considerable attention in the optoelectronic field due to their high photoluminescence quantum yield and large Stokes sh...

Antiferromagnetic topological insulator MnBi2Te4: synthesis and magnetic properties

Abstract: Recently, MnBi2Te4 has been discovered as the first intrinsic antiferromagnetic topological insulator (AFM TI), and it will become a promising material to discover exotic topological quantum phenomena. In this work, we have realized the successful synthesis of high-quality MnBi2Te4 single crystals by solid-state reactions. The as-grown MnBi2Te4 single crystal exhibits a van der Waals layered structure, which is composed of septuple Te-Bi-Te-Mn-Te-Bi-Te sequences as determined by X-ray diffraction and high-resolution high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The magnetic order below 25 K as a consequence of A-type antiferromagnetic interaction between Mn layers in the MnBi2Te4 crystal suggests the unique interplay between antiferromagnetism and topological quantum states. Moreover, the transport measurements of MnBi2Te4 single crystals further confirm its magnetic transition. This study on the first AFM TI of MnBi2Te4 will guide the future research on other potential candidates in the MBixTey family (M = Ni, V, Ti, etc.).

Fast-Response, Highly Air-Stable, and Water-Resistant Organic Photodetectors Based on a Single-Crystal Pt Complex

Abstract: Organic semiconductors demonstrate several advantages over conventional inorganic materials for novel electronic and optoelectronic applications, including molecularly tunable properties, flexibility, low-cost, and facile device integration. However, before organic semiconductors can be used for the next-generation devices, such as ultrafast photodetectors (PDs), it is necessary to develop new materials that feature both high mobility and ambient stability. Toward this goal, a highly stable PD based on the organic single crystal [PtBr2 (5,5'-bis(CF3 CH2 OCH2 )-2,2'-bpy)] (or "Pt complex (1o)") is demonstrated as the active semiconductor channel-a material that features a lamellar molecular structure and high-quality, intraligand charge transfer. Benefitting from its unique crystal structure, the Pt-complex (1o) device exhibits a field-effect mobility of ≈0.45 cm2 V-1 s-1 without loss of significant performance under ambient conditions even after 40 days without encapsulation, as well as immersion in distilled water for a period of 24 h. Furthermore, the device features a maximum photoresponsivity of 1 × 103 A W-1 , a detectivity of 1.1 × 1012 cm Hz1/2 W-1 , and a record fast response/recovery time of 80/90 µs, which has never been previously achieved in other organic PDs. These findings strongly support and promote the use of the single-crystal Pt complex (1o) in next-generation organic optoelectronic devices.

CsPbBr3 Single Crystal X-ray Detector with Schottky Barrier for X-ray Imaging Application

Abstract: A high Z CsPbBr3 halide perovskite with large charge carrier diffusion length was used for radiation detection applications. The high sensitivity X-ray detector is expected to be used for imaging a...