Showing papers on "Crystal published in 2019"
TL;DR: Rare-earth doping is identified as a general strategy for introducing local structural heterogeneity in order to enhance the piezoelectricity of relaxor ferroelectric crystals.
Abstract: High-performance piezoelectrics benefit transducers and sensors in a variety of electromechanical applications. The materials with the highest piezoelectric charge coefficients (d33) are relaxor-PbTiO3 crystals, which were discovered two decades ago. We successfully grew Sm-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (Sm-PMN-PT) single crystals with even higher d33 values ranging from 3400 to 4100 picocoulombs per newton, with variation below 20% over the as-grown crystal boule, exhibiting good property uniformity. We characterized the Sm-PMN-PT on the atomic scale with scanning transmission electron microscopy and made first-principles calculations to determine that the giant piezoelectric properties arise from the enhanced local structural heterogeneity introduced by Sm3+ dopants. Rare-earth doping is thus identified as a general strategy for introducing local structural heterogeneity in order to enhance the piezoelectricity of relaxor ferroelectric crystals.
442 citations
TL;DR: It is proposed that hcp-NiFe possesses favorable electronic property to expedite the reaction on the NC surface, resulting higher catalytic activity for OER, and provides a new insight to design more efficient electrocatalysts by considering the crystal phase correlated electronic property.
Abstract: Tuning the crystal phase of metal alloy nanomaterials has been proved a significant way to alter their catalytic properties based on crystal structure and electronic property. Herein, we successfully developed a simple strategy to controllably synthesize a rare crystal structure of hexagonal close-packed (hcp) NiFe nanoparticle (NP) encapsulated in a N-doped carbon (NC) shell (hcp-NiFe@NC). Then, we systemically investigated the oxygen evolution reaction (OER) performance of the samples under alkaline conditions, in which the hcp-NiFe@NC exhibits superior OER activity compared to the conventional face-centered cubic (fcc) NiFe encapsulated in a N-doped carbon shell (fcc-NiFe@NC). At the current densities of 10 and 100 mA cm-2 , the hcp-NiFe@NC with Fe/Ni ratio of ≈5.4 % only needs ultralow overpotentials of 226 mV and 263 mV versus reversible hydrogen electrode in 1.0 m KOH electrolyte, respectively, which were extremely lower than those of fcc-NiFe@NC and most of other reported NiFe-based electrocatalysts. We proposed that hcp-NiFe possesses favorable electronic property to expedite the reaction on the NC surface, resulting higher catalytic activity for OER. This research provides a new insight to design more efficient electrocatalysts by considering the crystal phase correlated electronic property.
235 citations
TL;DR: In this article, a layered manganese oxide that contains a high content of crystal water (∼10 wt%) as an aqueous zinc battery cathode was reported.
Abstract: Aqueous zinc (Zn)-ion batteries are gaining considerable attention as grid-scale energy storage systems due to their advantages in rate performance, cost, and safety. Here, we report a layered manganese oxide that contains a high content of crystal water (∼10 wt%) as an aqueous zinc battery cathode. The interlayer crystal water can effectively screen the electrostatic interactions between Zn2+ ions and the host framework to facilitate Zn2+ diffusion while sustaining the host framework for prolonged cycles. By virtue of these ‘water’ effects, this material exhibits a high reversible capacity of 350 mA h g−1 at 100 mA g−1, along with decent cycling and rate performance, in a two-electrode cell configuration. Density functional theory (DFT) calculations and extended X-ray absorption fine structure (EXAFS) analyses jointly reveal that upon Zn2+ ion intercalation, a stable inner-sphere Zn-complex coordinated with water molecules is formed, followed by the formation of a Zn–Mn dumbbell structure, which gives a clue for the observed electrochemical performance. This work unveils the useful function of crystal water in enhancing the key electrochemical performance of emerging divalent battery electrodes.
228 citations
TL;DR: In this paper, a van der Waals crystal, α-MoO3, is shown to support in-plane hyperbolic polariton guided modes at mid-infrared frequencies without the need for patterning.
Abstract: Hyperbolic media have attracted much attention in the photonics community due to their ability to confine light to arbitrarily small volumes and their potential applications to super-resolution technologies. The two-dimensional counterparts of these media can be achieved with hyperbolic metasurfaces that support in-plane hyperbolic guided modes upon nanopatterning, which, however, poses notable fabrication challenges and limits the achievable confinement. We show that thin flakes of a van der Waals crystal, α-MoO3, can support naturally in-plane hyperbolic polariton guided modes at mid-infrared frequencies without the need for patterning. This is possible because α-MoO3 is a biaxial hyperbolic crystal with three different Reststrahlen bands, each corresponding to a different crystalline axis. These findings can pave the way toward a new paradigm to manipulate and confine light in planar photonic devices.
215 citations
183 citations
TL;DR: In this paper, a reliable sol-gel approach, which combines the formation of ZnO nanocrystals and a solvent driven, shape-controlled, crystal growth process to form well-organized ZnOsO nanostructures at low temperature is presented.
Abstract: A reliable sol–gel approach, which combines the formation of ZnO nanocrystals and a solvent driven, shape-controlled, crystal-growth process to form well-organized ZnO nanostructures at low temperature is presented. The sol of ZnO nanocrystals showed shape-controlled crystal growth with respect to the solvent type, resulting in either nanorods, nanoparticles, or nanoslates. The solvothermal process, along with the solvent polarity facilitate the shape-controlled crystal growth process, augmenting the concept of a selective adhesion of solvents onto crystal facets and controlling the final shape of the nanostructures. The XRD traces and XPS spectra support the concept of selective adhesion of solvents onto crystal facets that leads to yield different ZnO morphologies. The shift in optical absorption maxima from 332 nm in initial precursor solution, to 347 nm for ZnO nanocrystals sol, and finally to 375 nm for ZnO nanorods, evidenced the gradual growth and ripening of nanocrystals to dimensional nanostructures. The engineered optical band gaps of ZnO nanostructures are found to be ranged from 3.10 eV to 3.37 eV with respect to the ZnO nanostructures formed in different solvent systems. The theoretical band gaps computed from the experimental XRD spectral traces lie within the range of the optical band gaps obtained from UV-visible spectra of ZnO nanostructures. The spin-casted thin film of ZnO nanorods prepared in DMF exhibits the electrical conductivity of 1.14 × 10−3 S cm−1, which is nearly one order of magnitude higher than the electrical conductivity of ZnO nanoparticles formed in hydroquinone and ZnO sols. The possibility of engineering the band gap and electrical properties of ZnO at nanoscale utilizing an aqueous-based wet chemical synthesis process presented here is simple, versatile, and environmentally friendly, and thus may applicable for making other types of band-gap engineered metal oxide nanostructures with shape-controlled morphologies and optoelectrical properties.
177 citations
TL;DR: It is demonstrated that transport under steady-state illumination is considerably altered at the structural phase transition in the MA compounds, providing advanced insights into the evolution of the crystal structure with decreasing temperature that are essential to interpret the growing interest in investigating the electronic, optical, and photonic properties of lead-halide perovskite materials.
Abstract: The extraordinary properties of lead-halide perovskite materials have spurred intense research, as they have a realistic perspective to play an important role in future photovoltaic devices. It is known that these materials undergo a number of structural phase transitions as a function of temperature that markedly alter their optical and electronic properties. The precise phase transition temperature and exact crystal structure in each phase, however, are controversially discussed in the literature. The linear thermal expansion of single crystals of APbX3 (A = methylammonium (MA), formamidinium (FA); X = I, Br) below room temperature is measured using a high-resolution capacitive dilatometer to determine the phase transition temperatures. For δ-FAPbI3 , two wide regions of negative thermal expansion below 173 and 54 K, and a cascade of sharp transitions for FAPbBr3 that have not previously been reported are uncovered. Their respective crystal phases are identified via powder X-ray diffraction. Moreover, it is demonstrated that transport under steady-state illumination is considerably altered at the structural phase transition in the MA compounds. The results provide advanced insights into the evolution of the crystal structure with decreasing temperature that are essential to interpret the growing interest in investigating the electronic, optical, and photonic properties of lead-halide perovskite materials.
165 citations
TL;DR: A simulation of the effect of the crystallite size on the shape and width of the X-ray patterns was done using PDF-4 software which confirmed that raw ordered bone crystals produce broad peaks which so far have been erroneously assigned to polycrystalline hydroxyapatite with low crystalline quality.
Abstract: This paper focuses on the study of the effect of the change of the crystal size on the shape and width of the X-ray diffraction patterns for defatted and deproteinized bones as well as incinerated biogenic hydroxyapatite obtained from bovine, porcine, and human bones. Inductively Couple Plasma showed the presence of some ions such as Mg, K, Al, Fe, Zn, and Na for all samples. The nanometric size of the crystals was determined through High Resolution Transmission Electron Microscopy in which ordered crystals were found. The calcination of raw clean bones at 720 °C produced a transition of crystal size from nano to micro due to a coalescence phenomenon, this was accompanied by a decrease of the peak width of the X-ray diffraction patterns due to the decrease of the inelastic scattering contribution from the microcrystals. A simulation of the effect of the crystallite size on the shape and width of the X-ray patterns was done using PDF-4 software which confirmed that raw ordered bone crystals produce broad peaks which so far have been erroneously assigned to polycrystalline hydroxyapatite with low crystalline quality.
152 citations
TL;DR: Analysis of van der Waals crystal VI3 reveals that it exhibits a structural transition from monoclinic C2/ m to rhombohedral R3̅ at Ts ≈ 79 K, similar to CrX3, and is a candidate for two-dimensional FM semiconductors.
Abstract: We report structural properties, physical properties, and the electronic structure of van der Waals (vdW) crystal VI3. Detailed analysis reveals that VI3 exhibits a structural transition from monoc...
145 citations
TL;DR: The cross-linked porous mesh structures growing on the {001} crystal plane strengthen the mixing with conductive carbon, inducing preferable conductivity, as well as increasing the area of ion contact and the number of active sites, enable the hexagonal Ni-MOF to exhibit excellent electrochemical performance as supercapacitor electrode materials.
Abstract: Hexagonal nickel-organic framework (Ni-MOF) [Ni(NO3 )2 ·6H2 O, 1,3,5-benzenetricarboxylic acid, 4-4'-bipyridine] is fabricated through a one-step solvothermal method. The {001} crystal plane is exposed to the largest hexagonal surface, which is an ideal structure for electron transport and ion diffusion. Compared with the surrounding rectangular crystal surface, the ion diffusion length through the {001} crystal plane is the shortest. In addition, the cross-linked porous mesh structures growing on the {001} crystal plane strengthen the mixing with conductive carbon, inducing preferable conductivity, as well as increasing the area of ion contact and the number of active sites. These advantages enable the hexagonal Ni-MOF to exhibit excellent electrochemical performance as supercapacitor electrode materials. In a three-electrode cell, specific capacitance of hexagonal Ni-MOF in the 3.0 m KOH electrolyte is 977.04 F g-1 and remains at the initial value of 92.34% after 5,000 cycles. When the hexagonal Ni-MOF and activated carbon are assembled into aqueous devices, the electrochemical performance remains effective.
132 citations
TL;DR: In this paper, the inner chemical etching reactivity of a crystal can be enhanced at the nanoscale by means of direct laser writing, which allows to produce cm-scale arbitrary three-dimensional nanostructures with 100 nm feature sizes inside large crystals in absence of brittle fracture.
Abstract: Nanostructuring hard optical crystals has so far been exclusively feasible at their surface, as stress induced crack formation and propagation has rendered high precision volume processes ineffective. We show that the inner chemical etching reactivity of a crystal can be enhanced at the nanoscale by more than five orders of magnitude by means of direct laser writing. The process allows to produce cm-scale arbitrary three-dimensional nanostructures with 100 nm feature sizes inside large crystals in absence of brittle fracture. To showcase the unique potential of the technique, we fabricate photonic structures such as sub-wavelength diffraction gratings and nanostructured optical waveguides capable of sustaining sub-wavelength propagating modes inside yttrium aluminum garnet crystals. This technique could enable the transfer of concepts from nanophotonics to the fields of solid state lasers and crystal optics.
TL;DR: In this paper, the authors focused on the glass forming, crystallization, and physical properties of ZnO doped MgO-Al2O3-SiO2-B 2O3 glass-ceramics and revealed a rational mechanism of glass formation, crystal precipitation, and evolution between structure and performance.
Abstract: This study focused on the glass forming, crystallization, and physical properties of ZnO doped MgO-Al2O3-SiO2-B2O3 glass-ceramics. The results show that the glass forming ability enhances first with ZnO increasing from 0 to 0.5 mol%, and then weakens with further addition of ZnO which acted as network modifier. No nucleating agent was used and the crystallization of studied glasses is controlled by a surface crystallization mechanism. The predominant phase in glass-ceramics changed from α-cordierite to spinel/gahnite as ZnO gradually replaced MgO. The phase type did not change; however, the crystallinity and grain size in glass-ceramics increased when the glasses were treated from 1030 °C to 1100 °C. The introduction of ZnO can improve the thermal, mechanical, and dielectric properties of the glass-ceramics. The results reveal a rational mechanism of glass formation, crystal precipitation, and evolution between structure and performance in the xZnO-(20-x)MgO-20Al2O3-57SiO2-3B2O3 (0 ≤ x ≤ 20 mol%) system.
TL;DR: Density functional theory calculations reveal that the FA/MA ratio affects the surface energy of the mixed perovskites, leading to the variation of preferential orientation consequently, and the present work provides a vital step in understanding the intrinsic properties of mixed-cation Perovskite optoelectronics.
Abstract: Crystal orientation has a great impact on the properties of perovskite films and the resultant device performance. Up to now, the exquisite control of crystal orientation (the preferred crystallographic planes and the crystal stacking mode with respect to the particular planes) in mixed-cation perovskites has received limited success, and the underlying mechanism that governs device performance is still not clear. Here, a thermodynamically favored crystal orientation in formamidinium/methylammonium (FA/MA) mixed-cation perovskites is finely tuned by composition engineering. Density functional theory calculations reveal that the FA/MA ratio affects the surface energy of the mixed perovskites, leading to the variation of preferential orientation consequently. The preferable growth along the (001) crystal plane, when lying parallel to the substrates, affects their charge transportation and collection properties. Under the optimized condition, the mixed-cation perovskite (FA1- x MAx PbI2.87 Br0.13 (Cl)) solar cells deliver a champion power conversion efficiency over 21%, with a certified efficiency of 20.50 ± 0.50%. The present work not only provides a vital step in understanding the intrinsic properties of mixed-cation perovskites but also lays the foundation for further investigation and application in perovskite optoelectronics.
TL;DR: Hydrogen bonds containing spacers are used to synthesize highly luminescent perovskites with fully isolated lead-bromide octahedras and shed light on the origin of the emission.
Abstract: As one of next-generation semiconductors, hybrid halide perovskites with tailorable optoelectronic properties are promising for photovoltaics, lighting, and displaying. This tunability lies on variable crystal structures, wherein the spatial arrangement of halide octahedra is essential to determine the assembly behavior and materials properties. Herein, we report to manipulate their assembling behavior and crystal dimensionality by locally collective hydrogen bonding effects. Specifically, a unique urea-amide cation is employed to form corrugated 1D crystals by interacting with bromide atoms in lead octahedra via multiple hydrogen bonds. Further tuning the stoichiometry, cations are bonded with water molecules to create a larger spacer that isolates individual lead bromide octahedra. It leads to zero-dimension (0D) single crystals, which exhibit broadband 'warm' white emission with photoluminescence quantum efficiency 5 times higher than 1D counterpart. This work suggests a feasible strategy to modulate the connectivity of octahedra and consequent crystal dimensionality for the enhancement of their optoelectronic properties.
TL;DR: The room-temperature phosphorescent DBBZL crystals could exhibit reversible bending and irreversible bending based on one crystal, demonstrating the application of flexibility.
Abstract: Recently, the study of flexible (elastically bendable and plastically bendable) organic single crystals has become a hot research field in crystal engineering. In general, crystal elasticity and plasticity are incompatible with each other. Different from the applications of fluorescent crystals, the applications of room-temperature phosphorescence (RTP) materials generally ignore the crystallographic nature of large single crystals. Herein, we creatively combine elasticity and plasticity based on one RTP crystal 4,4′-dibromobenzil DBBZL. The in-depth study of the irreversible transformation between elastic bending and plastic bending provided important insights into the mechanism of both elastically bendable crystals and plastically bendable crystals in crystal engineering. The DBBZL crystal exhibits elastic bending (reversible) under external stress, whereas it shows plastic bending (irreversible) after excessive bending. Notably, the first phosphorescent optical waveguides of large single RTP crystals are realized not only in straight state, but also in elastic bent state and plastic bent state.
TL;DR: In this paper, the synergetic optimization of electronic and thermal transport properties in rhombohedral GeTe doped with transition metal Ti is reported, where the Seebeck coefficient of Ge1-xTixTe is significantly increased and the corresponding thermal conductivity is decreased.
TL;DR: In this paper, Li-ion conductor materials are comprised of a mobile L-ion sublattice hosted in a crystal structural framework of immobile polyanion groups, which facilitates the transport of a large number of Li ions and yields high ionic conductivity.
Abstract: DOI: 10.1002/aenm.201902078 replacement of liquid electrolyte and has the potential to achieve improved safety, higher energy density, and longer cycle life than current commercial lithiumion batteries with liquid electrolytes.[17] Despite significant research efforts, only a few Li SIC materials exhibit an ionic conductivity of >10−3 S cm−1 at room temperature, and some Li SICs suffer from limited stability, poor interfacial compatibility, or high cost in processing and manufacturing.[6,7,18] A strong need exists for fundamental understanding of these SIC materials in order to design and discover new Li SIC materials. A Li-ion conductor material is comprised of a mobile Li-ion sublattice hosted in a crystal structural framework of immobile polyanion groups. The empty space in between these polyanion groups hosts Li ions as Li sites and forms interconnected channels. Li ions migrate among the sites through these channels, contributing to overall ionic transport. Well-known crystal structural frameworks of SICs include NASICON structure of LiM2(PO4)3 (M = Ge, Ti, Sn, Hf, Zr) compositions,[19] garnet structure of LixLa3M2O12 (5 ≤ x ≤ 7, M = Nb, Ta, Sb, Zr, Sn) compositions,[20] and LGPS-type structure of Li10+xM1+xP2−xS12 (0 ≤ x ≤ 1, M = Si, Ge, Sn) compositions.[21] Recent studies have demonstrated that the crystal structural framework determines Li sites, migration pathways, and the energy landscape, and particular crystal structural frameworks are optimal for low energy barrier Li ion migration.[10,22,23] For example, the crystal structural framework with a body-centered cubic (bcc) anion sublattice, such as found in LGPS and Li7P3S11, has been shown to have an energy landscape with the lowest barrier compared to other anion sublattices, such as in facecentered cubic and hexagonal close packed sublattices.[10] However, some SICs with crystal structural frameworks of non-bcc anion sublattices, such as lithium garnet (e.g., LLZO) and lithium NASICON (e.g., LATP), also exhibit high Li+ conductivities as high as ≈10−3 S cm−1 at RT. It remains an open question as to what features of these crystal structure frameworks enable super-ionic conduction. Due to their unique crystal structural frameworks, SIC materials have highly mobile Li-ion sublattices, which are drastically different from those in typical solids (Figure 1). The disordered Li sublattice of SICs facilitates the transport of a large number of Li ions and yields high ionic conductivity. In the disordered Li sublattice, the Li-ion diffusion mechanism is also distinctive As technologically important materials for solid-state batteries, Li superionic conductors are a class of materials exhibiting exceptionally high ionic conductivity at room temperature. These materials have unique crystal structural frameworks hosting a highly conductive Li sublattice. However, it is not understood why certain crystal structures of the super-ionic conductors lead to high conductivity in the Li sublattice. In this study, using topological analysis and ab initio molecular dynamics simulations, the crystal structures of all Li-conducting oxides and sulfides are studied systematically and the key features pertaining to fast-ion conduction are quantified. In particular, a unique feature of enlarged Li sites caused by large local spaces in the crystal structural framework is identified, promoting fast conduction in the Li-ion sublattice. Based on these quantified features, the high-throughput screening identifies many new structures as fast Li-ion conductors, which are further confirmed by ab initio molecular dynamics simulations. This study provides new insights and a systematic quantitative understanding of the crystal structural frameworks of fast ion-conductor materials and motivates future experimental and computational studies on new fast-ion conductors.
TL;DR: In this paper, the spontaneous polarization of barium ferrites partially substituted with In, Al, Ga and Sc ions was found out in solid solutions, partially substituting with In and Al ions that is an evidence of their ferroelectric properties.
TL;DR: In this article, the authors examined earth-abundant, metal-free, graphitic C3N4 with exceptional optical and electronic properties, excellent chemical and thermal stability, an appropriate band gap, and non-toxicity for QLED applications.
TL;DR: The authors show the synthesis of monolayer Sb2O3 molecular crystals on mica substrates by passivator-assisted vapor deposition, which can be extended to the controlled growth of other two-dimensional inorganic molecular crystals and open up opportunities for potential molecular electronic devices.
Abstract: Two-dimensional molecular crystals, consisting of zero-dimensional molecules, are very appealing due to their novel physical properties. However, they are mostly limited to organic molecules. The synthesis of inorganic version of two-dimensional molecular crystals is still a challenge due to the difficulties in controlling the crystal phase and growth plane. Here, we design a passivator-assisted vapor deposition method for the growth of two-dimensional Sb2O3 inorganic molecular crystals as thin as monolayer. The passivator can prevent the heterophase nucleation and suppress the growth of low-energy planes, and enable the molecule-by-molecule lateral growth along high-energy planes. Using Raman spectroscopy and in situ transmission electron microscopy, we show that the insulating α-phase of Sb2O3 flakes can be transformed into semiconducting β-phase under heat and electron-beam irradiation. Our findings can be extended to the controlled growth of other two-dimensional inorganic molecular crystals and open up opportunities for potential molecular electronic devices.
TL;DR: Here, it is discussed how the effects of the elastic and plastic deformation of molecular crystals on the diffraction signature give primary evidence of their degree of crystallinity.
Abstract: The mention of the word "crystal" invokes images of minerals, gems, and rocks, all of which are inevitably solid, hard, and durable entities with well-defined smooth faces and straight edges. With the discovery in the first half of the 20th century that many molecular crystals are soft and can be deformed in a similar way as rubber or plastic, this perception is changing, and both the concept and formal definition of what a crystal is may require reinterpretation. The seemingly naive question posed in the title of this Minireview does not have a simple answer. Here, we discuss how the effects of the elastic and plastic deformation of molecular crystals on the diffraction signature give primary evidence of their degree of crystallinity. In most cases, the definition of a crystal holds for both elastically and plastically deformed crystals and, unless there is significant or complete physical separation of the crystal during the deformation, they can safely be considered (deformed) single crystals with a high concentration of defects.
TL;DR: The direct imaging of the crystal surface of MOF MIL-101 synthesized with different additives is reported, using low-dose high-resolution transmission electron microscopy (HRTEM), and three distinct surface structures are identified, at subunit cell resolution.
Abstract: Metal-organic frameworks (MOFs) are often synthesized using various additives to modulate the crystallization. Here, we report the direct imaging of the crystal surface of MOF MIL-101 synthesized with different additives, using low-dose high-resolution transmission electron microscopy (HRTEM), and identify three distinct surface structures, at subunit cell resolution. We find that the mesoporous cages at the outermost surface of MIL-101 can be opened up by vacuum heating treatment at different temperatures, depending on the MIL-101 samples. We monitor the structural evolution of MIL-101 upon vacuum heating, using in situ X-ray diffraction, and find the results to be in good agreement with HRTEM observations, which leads us to speculate that additives have an influence not only on the surface structure but also on the stability of framework. In addition, we observe solid-solid phase transformation from MIL-101 to MIL-53 taking place in the sample synthesized with hydrofluoric acid.
TL;DR: The first elastically bendable single-component pharmaceutical crystal, celecoxib, was reported in this paper, which exhibited both therapeutic effects and elastic mechanical behavior, and could be used to manufacture functional microdevices with novel medical applications.
Abstract: We report here the first elastically bendable single-component pharmaceutical crystal, celecoxib. Interlocked molecular packing without the slip plane and the presence of an isotropic hydrogen bond network are major structural features responsible for both the exceptional elastic flexibility and high stiffness of the celecoxib crystal as revealed by bending and nanomechanical studies. The molecular model of the exceptional elasticity is rationalized by the inhomogeneous spatial separations of molecules in the bent crystal, which is further confirmed by micro-Raman spectroscopy. The celecoxib crystal, exhibiting both therapeutic effects and elastic mechanical behavior, could be used to manufacture functional microdevices with novel medical applications.
TL;DR: In this article, the gate-tunable giant anisotropic resistance effect of few-layer semiconducting GaTe was shown to be gate-table with van der Waals floating gate.
Abstract: Anisotropy in crystals arises from different lattice periodicity along different crystallographic directions, and is usually more pronounced in two dimensional (2D) materials. Indeed, in the emerging 2D materials, electrical anisotropy has been one of the recent research focuses. However, key understandings of the in-plane anisotropic resistance in low-symmetry 2D materials, as well as demonstrations of model devices taking advantage of it, have proven difficult. Here, we show that, in few-layered semiconducting GaTe, electrical conductivity anisotropy between x and y directions of the 2D crystal can be gate tuned from several fold to over 103. This effect is further demonstrated to yield an anisotropic non-volatile memory behavior in ultra-thin GaTe, when equipped with an architecture of van der Waals floating gate. Our findings of gate-tunable giant anisotropic resistance effect pave the way for potential applications in nanoelectronics such as multifunctional directional memories in the 2D limit. Some atomically thin crystals feature crystallographic anisotropy, but demonstrations of electrical anisotropy are scarce. Here, the authors show that the electrical conductivity of few-layered GaTe along the x and y directions can be widely gate tuned up to 103, and demonstrate anisotropic non-volatile memory behavior.
TL;DR: The reported structural insight will enable to decipher the structure/photophysical property relationship for this class of emitters and open up a myriad of new research opportunities in fluorescence imaging and sensing using noble metal clusters in general.
Abstract: DNA has been used as a scaffold to stabilize small, atomically monodisperse silver nanoclusters, which have attracted attention due to their intriguing photophysical properties. Herein, we describe the X-ray crystal structure of a DNA-encapsulated, near-infrared emitting Ag16 nanocluster (DNA-Ag16 NC). The asymmetric unit of the crystal contains two DNA-Ag16 NCs and the crystal packing between the DNA-Ag16 NCs is promoted by several interactions, such as two silver-mediated base pairs between 3'-terminal adenines, two phosphate-Ca2+ -phosphate interactions, and π-stacking between two neighboring thymines. Each Ag16 NC is confined by two DNA decamers that take on a horse-shoe-like conformation and is almost fully shielded from the solvent environment. This structural insight will aid in the determination of the structure/photophysical property relationship for this class of emitters and opens up new research opportunities in fluorescence imaging and sensing using noble-metal clusters.
TL;DR: A method for growing large (30×30×1 μm3 ) monocrystalline MAPb(Brx I1-x )3 single crystals is presented and the direct visualization of the growth of nanocluster-like I-rich domains throughout the entire crystal revealed that grain boundaries are not required for this transformation.
Abstract: Mixed organolead halide perovskites (MOHPs), CH3 NH3 Pb(Brx I1-x )3 , have been shown to undergo phase segregation into iodide-rich domains under illumination, which presents a major challenge to their development for photovoltaic and light-emitting devices. Recent work suggested that phase-segregated domains are localized at crystal boundaries, driving investigations into the role of edge structure and the growth of larger crystals with reduced surface area. Herein, a method for growing large (30×30×1 μm3 ) monocrystalline MAPb(Brx I1-x )3 single crystals is presented. The direct visualization of the growth of nanocluster-like I-rich domains throughout the entire crystal revealed that grain boundaries are not required for this transformation. Narrowband fluorescence imaging and time-resolved spectroscopy provided new insight into the nature of the phase-segregated domains and the collective impact on the optoelectronic properties.
TL;DR: In this paper, the phase changes of photoelectrochemical (PEC) and solar cell applications were evaluated in detail, at which conditions which phase or phases are present, and the changes of PEC activities were examined comparatively.
TL;DR: It is reported that upon bending, terephthalic acid crystals can undergo a mechanically induced phase transition without delamination and their overall crystal integrity is retained and it is anticipated that similar memory and restorative effects are common for other molecular crystals having metastable polymorphs.
Abstract: Molecular crystals can be bent elastically by expansion or plastically by delamination into slabs that glide along slip planes. Here we report that upon bending, terephthalic acid crystals can undergo a mechanically induced phase transition without delamination and their overall crystal integrity is retained. Such plastically bent crystals act as bimorphs and their phase uniformity can be recovered thermally by taking the crystal over the phase transition temperature. This recovers the original straight shape and the crystal can be bent by a reverse thermal treatment, resulting in shape memory effects akin of those observed with some metal alloys and polymers. We anticipate that similar memory and restorative effects are common for other molecular crystals having metastable polymorphs. The results demonstrate the advantage of using intermolecular interactions to accomplish mechanically adaptive properties with organic solids that bridge the gap between mesophasic and inorganic materials in the materials property space. Molecular crystals can be bent elastically by expansion or contraction on opposite faces, or plastically by delamination into slabs that glide along slip planes. Here the authors report crystals that can be bent plastically while undergoing a mechanically induced phase transition without delamination.