Crystals of Benzamide, the First Polymorphous Molecular Compound, Are Helicoidal
Abstract not provided
Shtukenberg, Alexander G.↗
SEARCH · Engineering Papers
Results for “Crystal Growth”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Data for "High dopant activation in arsenic doped single-crystal CdTe thin films: Insights from MBE growth and rapid thermal processing"
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14 SOLAR ENERGY↗
Template-Assisted Growth of High-Quality α-Phase FAPbI 3 Crystals in Perovskite Solar Cells Using Thiol-Functionalized MoS 2 Nanosheets
Formamidinium lead iodide (FAPI) has gained attention for hybrid perovskite solar cell (PSC) applications due to its enhanced stability and narrow bandgap. However, a significant challenge remains in inducing and stabilizing the elusive perovskite “black phase”—photoactive cubic α-FAPI—as the relatively bulky FA + cations tend to favor the thermodynamically stable nonphotoactive “yellow phase”. Here, in this study, we present a templated growth strategy employing thiol-functionalized MoS 2 nanosheets as templates. By introduction of 3-mercaptopropionic acid (MPA)-functionalized MoS 2 as a growth template, precise control over crystal formation was achieved, favoring the growth of high-quality α-FAPI films. These advanced templated films exhibited substantial improvements in charge transport properties, efficient light absorption, and enhanced charge extraction. As a result, the PSCs achieved a significantly enhanced power conversion efficiency (PCE) compared to the nontemplated control device, increasing from 20.6 to 22.5%. The MoS 2 -incorporated device also demonstrated excellent shelf stability, maintaining 91% of the initial PCE even after 1600 h of storage without device encapsulation.
36 MATERIALS SCIENCE↗
Strain-Induced Growth of Twisted Bilayers during the Coalescence of Monolayer MoS 2 Crystals
Tailoring the grain boundaries (GBs) and twist angles between two-dimensional (2D) crystals are two crucial synthetic challenges to deterministically enable envisioned applications such as moiré excitons, emerging magnetism, or single-photon emission. Here, we reveal how twisted 2D bilayers can be synthesized from the collision and coalescence of two growing monolayer MoS 2 crystals during chemical vapor deposition. The twisted bilayer (TB) moiré angles are found to preserve the misorientation angle (θ) of the colliding crystals. The shapes of the TB regions are rationalized by a kink propagation model that predicts the GB formed by the coalescing crystals. Optical spectroscopy measurements reveal a θ-dependent long-range strain in crystals with stitched grain boundaries and a sharp (θ > 20°) threshold for the appearance of TBs, which relieves this strain. Reactive molecular dynamics simulations explain this strain from the continued growth of the crystals during coalescence due to the insertion of atoms at unsaturated defects along the GB, a process that self-terminates when the defects become saturated. The simulations also reproduce atomic-resolution electron microscopy observations of faceting along the GB, which is shown to arise from the growth-induced long-range strain. These facets align with the axes of the colliding crystals to provide favorable nucleation sites for second-layer growth of a TB with twist angles that preserve the misorientation angle θ. This interplay between strain generation and aligned nucleation provides a synthetic pathway for the growth of TBs with deterministic angles.
2D materials↗
Mechanisms of Skyrmion and Skyrmion Crystal Formation from the Conical Phase
Real-space topological magnetic structures such as skyrmions and merons are promising candidates for information storage and transport. However, the microscopic mechanisms that control their formation and evolution are still unclear. In this work, using in situ Lorentz transmission electron microscopy, we demonstrate that skyrmion crystals (SkXs) can nucleate, grow, and evolve from the conical phase in the same ways that real nanocrystals form from vapors or solutions. More intriguingly, individual skyrmions can also “reproduce” by division in a mitosis-like process that allows them to annihilate SkX lattice imperfections, which is not available to crystals made of mass-conserving particles. Combined string method and micromagnetic calculations show that competition between repulsive and attractive interactions between skyrmions governs particle-like SkX growth, but nonconservative SkX growth appears to be defect mediated. Our results provide insights toward manipulating magnetic topological states by applying established crystal growth theory, adapted to account for the new process of skyrmion mitosis.
36 MATERIALS SCIENCE↗
What Controls Crystal Diversity and Microphysical Variability in Cirrus Clouds?
Abstract Variability of ice microphysical properties like crystal size and density in cirrus clouds is important for climate through its impact on radiative forcing, but challenging to represent in models. For the first time, recent laboratory experiments of particle growth (tied to crystal morphology via deposition density) are combined with a state‐of‐the‐art Lagrangian particle‐based microphysics model in large‐eddy simulations to examine sources of microphysical variability in cirrus. Simulated particle size distributions compare well against balloon‐borne observations. Overall, microphysical variability is dominated by variability in the particles' thermodynamic histories. However, diversity in crystal morphology notably increases spatial variability of mean particle size and density, especially at mid‐levels in the cloud. Little correlation between instantaneous crystal properties and supersaturation occurs even though the modeled particle morphology is directly tied to supersaturation based on laboratory measurements. Thus, the individual thermodynamic paths of each particle, not the instantaneous conditions, control the evolution of particle properties.
54 ENVIRONMENTAL SCIENCES↗
Classification of Cloud Particle Imagery and Thermodynamics (COCPIT): A New Databasing Tool for the Characterization of Cloud Particle Images Captured During DOE Field Campaigns
The Department of Energy for decades has explored the earth system and atmosphere through research and deployment of in-situ and remote sensing platforms during field campaigns. Among these datasets exists a vast supply of cloud particle images that provide visual insight into the complex microphysics in the clouds that span our globe. The millions of images collected over decades of deployments provides a unique opportunity to further our understanding of our atmosphere down to the crystal size. This work over the past 5 years has sought to organize these images into digestible datasets that can then be used by scientists to further our understanding of microphysics. A machine learning model was developed that categorizes over 1.5 million images across 11 weather events with over 90% accuracy according to particle type. The database was then extended to include dimensional characteristics of the particle as well as co-location of environmental properties, such as temperature and water content. Then, to initialize the connection between these data and our understanding of how crystals form and grow, weather research and forecasting simulations were run to generate the growth histories of the classified crystals. This research culminates with 2 databases per event: (1) a database of all classified crystals and their dimensional and environmental properties and (2) simulated growth histories of each crystal. Finally, a user interface was created to allow researchers to explore data statistics.
54 ENVIRONMENTAL SCIENCES↗
Influence of growth temperature of KTiOAsO{sub 4} single crystals on their physicochemical parameters and formation of domain structures
A potassium titanyl arsenate (KTiOAsO{sub 4}, KTA) crystal 50 × 80 × 60 mm in size has been grown by upgraded Czochralski method from flux (TGGS) with a decrease in temperature from 900 to 770 °C during pulling. It is shown that the spectroscopic properties of the parts of KTA crystals grown at 900 and 770 °C are close, whereas the electrical conductivity of the low-temperature (770 °C) KTA part turned out to be an order of magnitude lower than that of the high-temperature part. Visualisation of the domain structure by second-harmonic generation microscopy revealed a more efficient domain intergrowth (throughout the sample) in the low-temperature KTA, which is important for forming a regular domain structure (RDS) in a KTA-based nonlinear optical element. It is established that the quantum efficiency of parametric generation of light in the RDS formed in low-temperature KTA is several times higher than in the case of high-temperature KTA. The results obtained are important for optimising RDS parameters. (paper)
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Development of the Advanced MPE CVD System for Growth of Large Diffraction Grade Single-Crystal Diamonds with the exceptionally low density of defects
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43 PARTICLE ACCELERATORS↗
Remote Epitaxy of III-V Solar Cells via Hydride Vapor Phase Epitaxy
The promise of remote epitaxy, in which epitaxial registry of a film can still be maintained through two-dimensional layers, has emerged from an advanced understanding of the interactions between two dimensional materials and bulk semiconductors. A promising application of this technology is to facilitate substrate reuse in epitaxial III-V systems, which could significantly reduce material cost and improve commercial viability of this high-efficiency photovoltaic technology. In this process the weak van der Waal bonds between the 2D layer and the III-V substrate make separation of epitaxially-grown layers simple and leaves a smooth substrate that can be reused for cost reduction. Here we present a study of growth parameters of GaAs on AlGaAs through a low dimensional carbon interlayer via hydride vapor phase epitaxy (HVPE). We Investigate the effect of various GaAs nucleation conditions such as V/III ratio, temperature and growth rate on film roughness, crystallinity, and degree of epitaxial alignment. We demonstrate growth of single crystal GaAs layer on top of the low dimensional carbon that follow the crystal orientation of the substrate. Surface roughness measured via AFM found that lower V/III ratios result in smoother III-V films grown on the low dimensional carbon, with a lowest RMS of ~60 nm obtained at a V/III ratio of 5. Growth temperatures are optimized at 650 C, as temperatures below 550 C show non-crystalline growth and higher temperature samples display very rough surfaces. Additionally, we investigate HVPE growth on various forms of low-dimensional carbon including transferred graphene, CVD-grown graphene, and MOCVD-growth amorphous carbon and find the latter to be most well suited for III-V growth as this method results in cleaner interface and potential for direct, large-area coverage. We also identify techniques to mitigate surface degradation in carbon layers as a function of both exposure time and growth environment by analyzing surface changes via x-ray reflectivity. We show growth of heteroepitaxial III-V solar cells on carbon interlayers and preliminary cell results, which are currently limited to 4% efficiency under one sun.
AlGaAs↗
Synthesis, Crystal and Electronic Structure of the New Ternary Compound Ca3InAs3
Crystals of a new ternary compound in the Ca-In-As family, Ca3InAs3, have been successfully synthesized via flux growth techniques. This is only the third known compound between the respective elements. As elucidated by single-crystal X-ray diffraction measurements, Ca3InAs3 crystallizes in the orthorhombic space group Pnma (No. 62, Pearson symbol oP28) with unit cell parameters a = 12.296(2) Å, b = 4.2553(7) Å, and c = 13.735(2) Å. The smallest building motifs of the structure are InAs4 tetrahedra, which are connected to one another by shared As corners, forming infinite [InAs2As2/2] chains. The latter propagate along the crystallographic b-axis. The As-In-As bond angles within the InAs4 tetrahedra deviate from the ideal 109.5° value and range from 98.12(2)° to 116.53(2)°, attesting to a small distortion from the regular tetrahedral geometry. Electronic structure calculations indicate the opening of a bandgap, consistent with the expected (Ca2+)3(In3+)(As3–)3 formula breakdown based on conventional oxidation numbers. The calculations also show that the Ca–As interactions are an intermediate between covalent and ionic, while providing evidence of strong covalent features of the In–As interactions. Weak s-p hybridization of In states was observed, supporting the experimentally found deviation of the InAs4 moiety from the ideal tetrahedral symmetry.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Transport properties and thermal behavior of YbMnSb 2 semimetal above room temperature
Single crystals of ytterbium manganese diantimonide, YbMnSb 2 have been grown from a high-temperature reaction of the elements, employing molten Sb as self-flux. This phase crystallizes in the tetragonal centrosymmetric space group P4/nmm (No. 129) and adopts the ZrCuSiAs structure type. Here, the structure consists of Sb-based square nets and PbO-type layers formed by fused [MnSb 4/4 ] tetrahedra. YbMnSb 2 is stable under ambient atmosphere and incongruently melts at a temperature of ca. 1120 K. In the temperature range from 300 K to 450 K, the electrical resistivity of the as-grown single-crystalline material is as low as 3.2 mΩ cm, while its thermopower is as high as 180 μV/K. As such, YbMnSb 2 shows promise for thermoelectric applications in the mid-temperature region, with an estimated power factor of 0.85–0.95 mW/(m K 2 ).
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Binary and Ternary Colloidal Cu–Sn–Te Nanocrystals for Thermoelectric Thin Films
Recent advances in copper chalcogenide-based nanocrystals (NCs), copper sulfide, and copper selenide derived nanostructures, have drawn considerable attention. However, reports of crystal phase and shape engineering of binary or ternary copper telluride NCs remain rare. Here, a colloidal hot-injection approach for producing binary copper/tin telluride, and ternary copper tin telluride NCs with controllable compositions, crystal structures, and morphologies is reported. Here, the crystal phase and growth behavior of these tellurides are systematically studied from both experimental and theoretical perspectives.
30 DIRECT ENERGY CONVERSION↗
In situ X-ray measurements over large Q-space to study the evolution of oxide thin films prepared by RF sputter deposition
Sputter deposition is a versatile and industrially important deposition technique for thin films, with increasing demand for matching the characteristics of thin film materials to specific requirements. Additionally, the actual film properties are largely determined by sputtering parameters such as pressure conditions, temperature and power settings. By means of various X-ray diffraction and scattering techniques, it is shown that the characterization of film formation and growth is feasible in real time at synchrotron sources, thus adding an important dimension to the fundamental understanding of the evolution of thin film microstructure. In particular, grazing incidence small-angle X-ray scattering, grazing incidence X-ray powder diffraction and X-ray reflectometry are used in a complementary manner to study the influence of deposition temperature and substrate choice on the crystallization kinetics and growth of polycrystalline BaTiO 3 films.
36 MATERIALS SCIENCE↗
Magnetic transition behavior in epitaxial Fe 47 Rh 47 Pd 6 films
The properties of Fe–Rh–Pd epitaxial thin films grown on MgO(001) were studied as a function of growth temperature. Films grown above 400°C exhibit a first-order antiferromagnetic to ferromagnetic magnetic phase transition with a transition temperature that decreases as the growth temperature is increased. The chemical order parameter computed from the ratio of intensities of the (001) and (002) diffraction peaks is nearly independent of the growth temperature, while the lattice constants change slightly. A comparison of our structural, magnetic, and electrical transport results with first-principle-based calculations as well as literature results indicates that the transition temperature of Fe–Rh-based alloy films depends sensitively on the lattice parameters and is of electronic origin. The transition temperature and its width can be tuned over a wide range by controlling the crystal structure via growth conditions or postdeposition annealing.
36 MATERIALS SCIENCE↗
Hematite Crystallization from a Two-Line Ferrihydrite Suspension
Rational design and synthesis of materials, determination of environmental conditions at the time of mineral formation, and definition of mechanisms in biomineralizing systems all require an understanding of the effect of multiple factors on modulating crystallization pathways. In this study, we investigate the influence of temperature, oxalate additive, aging time, and addition of seed crystals on hematite (α-Fe 2 O 3 , Hm) crystallization from a two-line ferrihydrite (Fe 2 O 3 ·xH 2 O, Fh) suspension. We also investigate the effect of temperature on the aging of spindle-shaped Hm mesocrystals, which we synthesize through the addition of sodium oxalate. The results show that Hm mesocrystals form in a temperature window of 45 °C-130 °C. Temperatures ≥ 140 °C favor formation of rhombohedral Hm, suggesting classical monomer-by-monomer growth dominates, whereas crystallization by particle attachment (CPA) is dominant between 45 and 90 °C, while the two processes compete in the intermediate temperature range. Aging of mesocrystals in the original solution at 90 °C or 180 °C leads to a slow morphological evolution towards rhombohedral crystals due to Ostwald ripening. Then, by utilizing rhombohedral Hm and rod-shaped goethite as substrates on which to assemble the mesocrystals, we demonstrate formation of complex heterogeneous structures.
36 MATERIALS SCIENCE↗
Water-Surface Drag Coating: A New Route Toward High-Quality Conjugated Small-Molecule Thin Films with Enhanced Charge Transport Properties
Electronic properties of organic semiconductor (OSC) thin films are largely determined by their morphologies and crystallinities. However, solution-processed conjugated small-molecule OSC thin films usually exhibit abundant grain boundaries and impure grain orientations because of complex fluid dynamics during solution coating. Here, a novel methodology, water-surface drag coating, is demonstrated to fabricate high-quality OSC thin films with greatly enhanced charge transport properties. This method utilizes the water surface to alter the evaporation dynamics of solution to enlarge the grain size, and a unique drag-coating process to achieve the unidirectional growth of organic crystals. Furthermore, using 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene (Dif-TES-ADT) as an example, thin films with millimeter-sized single-crystal domains and pure crystallographic orientations are achieved, revealing a significant enhancement (4.7 times) of carrier mobility. More importantly, the resulting film can be directly transferred onto any desired flexible substrates, and flexible transistors based on the Dif-TES-ADT thin films show a mobility as high as 16.1 cm 2 V -1 s -1 , which represents the highest mobility value for the flexible transistors reported thus far. The method is general for the growth of various high-quality OSC thin films, thus opening up opportunities for high-performance organic flexible electronics.
36 MATERIALS SCIENCE↗
Final Technical Report for DE-FG02-86ER45268
This work addresses several key issues for understanding the unusual superconductivity in IBS, already shown to be technologically useful materials. 1a). Are reactive gasses like fluorine, chlorine, or water vapor behaving simply as electron donors to cause the superconductivity (at T conset =21 K) in undoped IBS like BaFe 2 As 2 ? 1b). Does exposure to fluorine increase T c in electron-doped IBS materials that are underdoped, e. g. Ba(Fe 0.96 Co 0.04 ) 2 As 2 ? 1c). Can fluorine as a reactive electron-donor, with its relatively greater ease of introduction into the lattice, be used as a rapid tool to search for superconductivity in new materials under investigation? Method of investigation: Using electron probe microanalysis, x-ray photoemission spectroscopy, and dynamical mean field theory calculations, we found that fluorine substitutes for As in the BaFe 2 As 2 lattice, and should therefore behave as an electron donor. We will F-dope Ba(Fe 0.96 Co 0.04 ) 2 As 2 and several new compounds under investigation for superconductivity upon doping to determine fluorine’s effect. Potential impact: If – like for fluorine - a brief exposure to hydrogen indeed causes superconductivity to a depth of 10 microns, this technique could be useful in creating long lengths of superconducting tape without the chemical aggressiveness of fluorine. Using the F ion, which substitutes for As - away from the Fe planes, in underdoped IBS like Ba(Fe 0.96 Co 0.04 ) 2 As 2 may form optimally doped IBS with less impurity scattering of the superconducting Fe 3d electrons resulting in improved superconducting properties. Another potential impact is the speed of checking for superconductivity in new materials under investigation for superconductivity upon doping. 2. What are the effects of Be substitution into IBS, beginning with FeSe and its derivatives (FeSe 1-x S x and FeSe 1-x Te x ) and BaFe 2-x Co x As 2 ? Method of investigation: We recently succeeded in adding Be to the FeSe lattice and found, surprisingly, a factor of four improvement of the low temperature residual resistivity ratio, consistent with improved electronic ordering. Using single crystal x-ray diffraction and x-ray dispersive spectroscopy, determine the concentration and location of the Be dopant. Using resistivity, determine if there is improvement in the residual resistivity achieved by Be doping in the FeSe derivatives (using AlCl 3 :KCl flux growth) and Co-doped BaFe 2 As 2 (using self-flux single crystal growth). Measuring resistivity under strain, determine the changes of the nematic susceptibility at the structural ordering transition causes by the increase in electronic order caused by Be doping in FeSe. Potential impact: Further understanding of IBS, including FeSe which - under physical pressure - has a T c increase to 40 K and -prepared as a monolayer - has a T c reported to be over 100 K. 3. In collaboration, prepare light atom compounds involving Be and look for high pressure-induced superconductivity.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗