Crystal Orientation Research Articles

Impact of Surface Microstructure and Properties of Aluminum Electrodes on the Plating/Stripping Behavior of Aluminum-Based Batteries Using Imidazolium-Based Electrolyte.

The 99.99% Al used for negative Al electrodes in aluminum-based battery studies is expensive. This is primarily due to the complex challenges associated with fabricating 99.99% Al, particularly the removal of Fe impurities from Al melts. Despite the importance of this issue for the future commercialization of Al-based batteries, it has been largely overlooked. This work accordingly studied the plating/stripping behavior of Al containing 1 wt % iron (Al 1% Fe) as an alternative electrode using conventional ([EMIm]Cl and AlCl3) electrolyte. Simultaneously, the impact of the surface microstructure of Al 1% Fe on the plating/stripping behavior was examined. The results indicate that the difference in the plating/stripping cycling of Al 1% Fe alloys and 99.99% Al is negligible. Thus, Al 1% Fe negative electrodes could serve as an efficient and commercially viable alternative to 99.99% Al for plating/stripping in Al-based batteries. This is an essential finding because facile and commercial fabrication of Al 1% Fe electrodes is absolutely feasible. The results are further discussed in terms of the impact of the Al surface microstructure (i.e., grain size, defect density, grain boundary distribution, crystal orientation, and intermetallic phases) on plating/stripping behavior. Moreover, this study provides insights into how the interphase layer formed on Al electrodes influences plating/stripping behavior.

Linearly Scaling Molecular Dynamic Modeling To Simulate Picosecond Laser Ablation of a Silicon Carbide Crystal.

A molecular dynamics model for picosecond laser ablation of nanoscale silicon carbide crystals was established by linearly scaling the laser focal diameter, and the correlation between the molecular dynamic simulation of the nanoscale and the experimental reproduction of the microscale was achieved. The calculation accuracy of the molecular dynamic model was verified by ablating the surface of silicon carbide wafers with a laser pulse width of 37 ps. On this basis, this paper further investigated the influence of the laser pulse width and fluence on the surface ablation damage and modification width, threshold, and lattice temperature. The results showed that, when the laser pulse width is higher than 10 ps, the silicon carbide damage threshold increases with increasing the pulse width, while the modification threshold is almost unaffected by the pulse width. In addition, the influence of crystal orientation has been studied, and laser irradiation along the [1-100] crystal orientation induces a higher peak temperature, larger damage, and modification width and threshold, followed by irradiation along the [0001] crystal orientation and lowest along the [11-20] crystal orientation. Finally, with the linear scaling value increasing, the spatial distribution of the laser energy field deviates more from the actual situation, resulting in the calculated results being more consistent with the experimental results. Through this paper, it is demonstrated that this linearly scaled molecular dynamics model can be used to study laser ablation results over tens of micrometers.

Inductively Coupled Plasma Reactive Ion Etching of (−201) β‐Ga2O3 Nano‐Fins

This study reports the effect of inductively coupled plasma reactive ion etching using a BCl3/Ar gas mixture on the sidewall taper angle (STA), etch rate, and surface morphology of (−201) β‐Ga2O3 substrates, as well as (−201)‐oriented β‐Ga2O3 films on sapphire, for nano‐fins of ≈200 nm width. Various etch parameters are systematically investigated for the β‐Ga2O3 films on sapphire, revealing that the STA is lower at high plasma density when chemical component increases, and the ion scattering decreases; achieving a STA of 1.5° ± 0.7°, accompanied by an etch rate of 114 nm min−1 and a reduction in surface roughness compared to before etching. Additionally, a strong positive correlation between the STA and the crystal orientation in the β‐Ga2O3 substrates is observed at lower plasma density, while a weak correlation is found between the STA and the crystal orientation at high plasma density. This study provides valuable insights for the fabrication of β‐Ga2O3 devices.

Damage Characteristics and Mechanical Properties of DD6 Single‐Crystal Alloy Based on Crystal Plasticity Theory under Uniaxial Tensile Conditions

Herein, the mechanical behavior and damage characteristics of DD6 nickel‐based single crystal alloy under different crystal orientation conditions are studied based on the theory of crystal plasticity coupled with damage constitutive equations using the crystal plasticity finite‐element method. The results indicate that the crystal plastic finite‐element model coupled with damage constitutive equations can well describe the entire deformation process from elasticity to damage. Under the reference orientation condition, the damage starts from the center position inside the test specimen and extends to the surrounding areas. The stress value in the damaged area decreases gradually from the periphery to the center of the test specimen, and an external stress reduction zone is formed. The crystal exhibits the best elasticity properties in the [0, 1, 1] orientation and the best plasticity properties in the [0, tan22.5°, 1] orientation. As the rotation angle of crystal orientation increases, the damage zones of X‐Z, Z‐Y, and X‐Y sections all exhibit clockwise rotation characteristics.

All-optical manipulation of bandgap dynamics via coherent phonons

The ability to actively and dynamically control electronic states at ultrafast timescales opens up a wide range of potential applications across optoelectronics, quantum computing and sensing, energy conversion and storage, etc. Yet, achieving dynamic electronic manipulation via coherent phonons has posed a considerable challenge. Here, employing time-resolved high-harmonic generation (tr-HHG) spectroscopy, we demonstrate the manipulation of bandgap dynamics in a BaF2 crystal by coherent phonons. The tr-HHG spectrum perturbed by a triply degenerate phonon mode T2g exhibits simultaneously a remarkable two-dimensional (2D) sensitivity, i.e., in both intensity and energy domains. The dynamic compression and enhancement of the harmonics in the intensity domain showed a π/2 phase shift compared to the manifestation of shifts of the harmonics in the energy domain, an astounding example of a physical phenomenon being observed simultaneously in two different perspectives. We employed a quantum model incorporating the electron–phonon coupling to complement our experimental observations, successfully reproducing the results. In addition, we demonstrated complete control over the strength and initial phase of the coherent phonon oscillations by varying the incident electric field polarizations across different crystal orientations. Our findings lay a foundation for engineering the electronic structure through coherent phonons within the terahertz frequency and picosecond to nanosecond time regimes.

Electromagnetic Absorption Mechanism of TPMS‐Based Metastructures: Synergy Between Materials and Structures

Abstract3D metastructure absorbers have gained attention for their lightweight, load‐bearing capabilities, and superior electromagnetic wave absorption. However, the complex interplay between unit cell geometry, material properties, and electromagnetic response is not well understood, hindering the design of high‐performance devices. A multi‐scale model, validated is presented by simulations and experiments, that clarify the relationship between materials, structures, and electromagnetic behavior in 3D metastructures. By systematically investigating strut‐based and sheet‐based structures, volume fraction, unit size, crystal lattice orientation, and density gradient within TPMS‐based unit cells, it is revealed that unit geometry significantly influences electromagnetic field propagation and reflection loss. Specifically, under the same unit size, sheet‐based TPMS metastructures exhibit stronger reflectivity than strut‐based ones, while multilayer structures show the opposite trend. The direct correlation is also further confirmed between geometric symmetry and polarization insensitivity, with orthogonal isotropic superstructures displaying excellent polarization‐insensitive properties. This finding provides a new design principle for achieving robust, angle‐independent absorption in these materials. This work enhances understanding of the structure‐electromagnetic behavior interplay, guiding the design of next‐generation broadband, wide‐angle, and polarization‐insensitive devices.

A universal reverse‐cool annealing strategy makes two‐dimensional Ruddlesden‐popper perovskite solar cells stable and highly efficient with Voc exceeding 1.2 V

AbstractTwo‐dimensional Ruddlesden‐Popper (2D RP) layered metal‐halide perovskites have garnered increasing attention due to their favorable optoelectronic properties and enhanced stability in comparison to their three‐dimensional counterparts. Nevertheless, precise control over the crystal orientation of 2D RP perovskite films remains challenging, primarily due to the intricacies associated with the solvent evaporation process. In this study, we introduce a novel approach known as reverse‐cool annealing (RCA) for the fabrication of 2D RP perovskite films. This method involves a sequential annealing process at high and low temperatures for wet perovskite films. The resulting RCA‐based perovskite films show the smallest root‐mean‐square value of 23.1 nm, indicating a minimal surface roughness and a notably compact and smooth surface morphology. The low defect density in these 2D RP perovskite films with exceptional crystallinity suppresses non‐radiative recombination, leading to a minimal non‐radiative open‐circuit voltage loss of 149 mV. Moreover, the average charge lifetime in these films is extended to 56.3 ns, thanks to their preferential growth along the out‐of‐plane direction. Consequently, the leading 2D RP perovskite solar cell achieves an impressive power conversion efficiency of 17.8% and an open‐circuit voltage of 1.21 V. Additionally, the stability of the 2D RP perovskite solar cell, even without encapsulation, exhibits substantial improvement, retaining 97.4% of its initial efficiency after 1000 hours under a nitrogen environment. The RCA strategy presents a promising avenue for advancing the commercial prospects of 2D RP perovskite solar cells.image

Crystallization dynamics of MAPbI3 perovskite solar cells via solvent engineering methods

Perovskite materials have attracted interest in solar cells due to ease of processing from salts. However, the complex crystal formation of perovskite from solvents is poorly understood. Solvent engineering approach to determine the crystallization dynamics and orientation of MAPbI3 films using grazing incidence wide angle x-ray scattering (GIWAXS) and micro diffraction measurements were studied. The study further probes the effect of moisture, PTAA and PEDOTS: PSS hole transport layers on the stability of MAPbI3 films. Precursor solutions were prepared by dissolving MAI and PbI2 in pure DMF and mixture of DMF: DMSO in 4:1 v/v. Chlorobenzene and Ethyl acetate were used as antisolvent. Films prepared from DMF: DMSO mixture showed no PbI2 signature while those prepared from DMF only, showed PbI2 signature at q= 0.9 A-1. This was attributed to solvent engineering of DMF/DMSO that leads to the formation of MAI/PbI2/DMSO intermediate that delays the crystallization and promotes vertical growth of films. q= 0.9 A-1 signal was associated with high volatility of DMF which led to faster but discrepant nucleation and crystallization rate. Microdiffraction results showed insignificant influence of antisolvent on the perovskite structure. Humidity has a strong influence on the stability of MAPbI3 films. PbI2 intensity in the GIWAXS maps increased with increasing humidity while MAPbI3 intensity decreased. This implied increased degradation of MAPbI3 film with humidity due to recombination of charge carriers. A band gap of 1.57 eV, efficiency of 8.5% and Et of 26 meV were obtained. Films with good crystallization are desirable in solar cells.

Programmable orientation of blue phase soft photonic crystal

Understanding the structure formation and its underlying physical mechanism is a fundamental topic in condensed matter systems, with both academic and practical implications. Soft matter is playing a remarkable role in current era of information explosion, demonstrating enormous potential in integrated functional photonics. As unique soft photonic crystals with cubic symmetries, not only liquid crystalline blue phases (BPs) have circularly polarized selective reflection and ultra-fast electro-optical response, but also their three-dimensional photonic structures increase degrees-of-freedom for multiplexed optical modulation. In the thriving field of soft-matter-based photonics, precise and programmable engineering of BP crystal orientation is of vital importance for planar optical elements, which remains a challenging task due to the complexity of the nucleation process as well as the interaction between the BP building blocks and the boundary conditions. Aiming to gain a comprehensive understanding of how to tailor the orientation of BP crystals for the photonic applications of next generation, here we discuss the solutions for uniformity improvement and orientation control of BP crystals, about which a few of examples in combination with the underlying mechanisms are explained. In addition, the remaining challenges and the efforts that are expected are also reviewed. We expect this work provides a deeper understanding of phase transitions and resulting structures in soft crystals, which may open encouraging perspectives for their applications in photonics, biosensing, interfacial, and chemical engineering.

Natural and Nature-Inspired Biomaterial Additives for Metal Halide Perovskite Optoelectronics.

This comprehensive review meticulously categorizes and discusses the applications of diverse biomaterials, specifically natural and nature-inspired synthetic materials in metal halide perovskite optoelectronics. Applications range from solar cells to light-emitting diodes, photodetectors, and X-ray detectors. Emphasis is placed on the intricate interactions between bio-additives and perovskite crystals, highlighting their influence on the grain size, crystal orientation, grain boundaries, and surface passivation. This review also explores the advantages and disadvantages of each natural or nature-inspired material and their unique properties compared with conventional additives. Special attention is given to the mechanistic and functional viewpoints, showing how these biomaterials enhance device performance. Through additive engineering with ecofriendly biomaterials, defects in metal halide perovskite thin films can be effectively passivated, thus extending the photostability or in some cases mechanical flexibility of devices. This review provides valuable insights for selecting and designing next-generation biomaterial additives, offering new prospects for achieving high-performance perovskite layers and advancing the field of peorvskite- based optoelectronics.

Piezoelectric MEMS microphones based on rib structures and single crystal PZT thin film

In this study, a controllable mass‒frequency tuning method is presented using the etching of rib structures on a single-crystal PZT membrane. The rib structures were optimized to reduce the membrane mass while maintaining the stiffness; therefore, the center frequency could be increased to improve the low-frequency bandwidth of microphones. Additionally, this methodology could reduce the modulus and improve the sensitivity for the same resonant frequency, which typically indicates the maximum acoustic overload point (AOP). The PZT film was chosen because of its greater density; the simulation results showed that PZT could provide a greater frequency tuning (24.9%) compared to that of the AlN film (5.8%), and its large dielectric constant enabled the optimal design to have small electrodes at the maximum stress location while mitigating the sacrificial capacitance effect on electrical gain. An analytical model of rib-structure microphones was established and greatly reduced the computing time. The experimental results of the impedance tests revealed that the center frequencies of the six microphones shifted from 74.6 kHz to 106.3 kHz with rib-structure inner radii ranging from 0 μm to 340 μm; this result was in good agreement with the those of the analytical analysis and finite element modeling. While the center frequency greatly varied, the measured sensitivities at 1 kHz only varied within a small range from 22.3 mV/Pa to 25.7 mV/Pa; thus, the membrane stiffness minimally changed. Moreover, a single-crystal PZT film with a (100) crystal orientation and 0.24-degree full width at half maximum (FWHM) was used to enable differential sensing and a low possibility of undesirable polarization. Paired with a two-stage differential charge amplifier, a differential sensing microphone was experimentally demonstrated to improve the sensitivity from 25.7 mV/Pa to 36.1 mV/Pa and reduce the noise from −68.2 dBV to −82.8 dBV.

Facet dependent ultralow thermal conductivity of zinc oxide coated silver fabric for thermoelectric devices

The conversion efficiency of a thermoelectric power generator depends on the dimensionless figure-of-merit (ZT) of the constituent thermoelectric materials, which is mainly determined by their Seebeck coefficient as well as the electrical and thermal conductivity. ZnO holds promise for thermoelectric applications, yet its use is currently limited by low electrical conductivity and high thermal conductivity. Herein, we demonstrate how thermal conductivity of ZnO can be significantly reduced by intelligently combining it with a cellulose-based Ag fabric using a one-step hydrothermal method, and how different ratios of zinc nitrate hexahydrate (ZNH) to hexamethylenetetramine (HMT) can be used to fine-tune the thermoelectric performance of the resulting composite. We show that as-prepared samples have a composite structure of Ag, Zn and O without any other impurity phases. We propose that the facet dependent crystal growth orientation, from the c-axis in (101) planes to the a-axis in (100) plane, amplify phonon scattering within the material, impeding effective heat transfer and thereby lowering overall thermal conductivity to 0.046 W/mK at room temperature for composites with a 1:1 ZNH to HMT ratio.

Exploiting Friedel pairs to interpret scanning 3DXRD data from complex geological materials

The present study introduces a processing strategy for synchrotron scanning 3D X-ray diffraction (s3DXRD) data, aimed at addressing the challenges posed by large, highly deformed, polyphase materials such as crystalline rocks. Leveraging symmetric Bragg reflections known as Friedel pairs, our method enables diffraction events to be precisely located within the sample volume. This method allows for fitting the phase, crystal structure and unit-cell parameters at the intra-grain scale on a voxel grid. The processing workflow incorporates several new modules, designed to (i) efficiently match Friedel pairs in large s3DXRD datasets containing up to 108 diffraction peaks; (ii) assign phases to each pixel or voxel, resolving potential ambiguities arising from overlap in scattering angles between different crystallographic phases; and (iii) fit the crystal orientation and unit cell locally on a point-by-point basis. We demonstrate the effectiveness of our technique on fractured granite samples, highlighting the ability of the method to characterize complex geological materials and show their internal structure and mineral composition. Additionally, we include the characterization of a metal gasket made of a commercial aluminium alloy, which surrounded the granite sample during experiments. The results show the effectiveness of the technique in recovering information about the internal texture and residual strain of materials that have undergone high levels of plastic deformation.

Phosphorene junctions as a platform for spin-selective quantum dots in next-generation devices

The impact of vacancies on spin-resolved electronic properties of quantum dots (QDs) in phosphorene-based junctions is investigated numerically. Regardless of the crystal orientation, a phosphorene nanoribbon containing a monovacancy is found to exhibit a topological quasi-flatband that emerges within the bandgap. The electronic properties of QDs, including spatial confinement and energy level distribution, can be strongly tuned by controlling the topological structure of the QDs and by applying electric fields. Additionally, these QDs exhibit remarkable spin-selective properties under a ferromagnetic exchange field, enabling the manipulation of QD features. This opens up the potential for novel applications such as quantum computing, magnetic sensing, spin-based light emission.

Investigation of etch rate distribution by micro-hemisphere for the anisotropic wet etching of Ga-face gallium nitride crystal

The Ga-face gallium nitride (GaN) crystal has recently attracted significant research interest in the micro/nano device due to its exceptional properties. Therefore, exploring low-cost and high-efficiency anisotropic wet etching processes for GaN material is essential. This research investigates the measurement of the overall anisotropic etching rates by introducing a novel micrometer-level hemispherical structure. For the first time, we report the full anisotropic etching rate distribution for Ga-face GaN crystal planes based on the etched results of the micro hemisphere and wagon-wheel structure specimen. The etching experiments were carried out in 85 %wt H₃PO₄ etchant at 130°C and 150°C. The etching result of Ga-face GaN crystal orientations displays a hexagonal symmetry pattern. In addition, the overall etch rates measurement enables the identification of the crystal planes with maximum and minimum etch rates at different temperatures, and the experiment also shows the etch rate of primary crystallographic orientations, such as +c-plane, m-plane, and a-plane. Finally, the atomic structures of GaN crystallographic planes are analyzed to explain the anisotropy in the etching process on different crystal zones by the step-flow mechanism. The resulting etch rate database allows the numerical simulation of the etch front and helps understand the etching mechanism of the GaN crystal.

Thermal conductivity of WC: Microstructural design driven by first-principles simulations

The relationships between the microstructure and the thermal conductivity of binderless WC have been quantified, considering crystal orientation, isotopic abundance, porosity, and grain size. A significantly higher conductivity is predicted in the out-of-plane (c-axis) direction vs. the in-plane (a-axis) direction, using first principles simulations. Isotopic enrichment of the tungsten sublattice is predicted to increase conductivity, e.g., by a factor of 4–5 in the absence of boundary scattering. The results suggest that for an isotopically pure single crystal a thermal conductivity exceeding 1000 W m−1 K−1 may be achievable normal to the basal plane. The conductivity of samples with various porosities could be well fit by a minimum surface area (exponential) model, with a porosity exponent of b = 4.4. Experiment and simulation show a strong grain size dependence to conductivity below 1 µm, with a saturation beyond ∼10 µm. The experimental plateau values for κ were ∼45 % lower than those of the simulations due to deviations from perfect stoichiometry. We also find a higher scattering coefficient in the experiments, likely due to effects of grain size distribution and elongation. Our study clarifies the physical origin of disagreeing literature reports as being predominantly due to grain boundary scattering and enables microstructural design for thermally demanding environments.

Efficient photocatalytic activity over α-MnS/ZIF-67 p-n junction: Revealing the synergistic effects of exposed crystal facets and built-in electric field mechanism

In this investigation, we explored two series of composites comprising p-type α-MnS with selectively exposed {001} or {111} facets, coated with n-type ZIF-67 nanoparticles, to enhance the photocatalytic activity on Rhodamine B (RhB) degradation. The influence of the crystal facet orientation and the p-n junction on the photocatalytic efficacy was also well studied. The α-MnS/ZIF-67 composites displayed enhanced separation of charge carriers and superior light absorption capabilities, benefiting for efficient photocatalysis. The composites with cubic α-MnS morphology exhibited a pronouncedly higher photocatalytic activity relative to those with octahedral α-MnS morphology. The composition of α-MnS with ZIF-67 constructed the formation of a p-n junction with build-in electric field, extending the response into the visible region and promoting the mobility of charge carriers, thereby improving the photocatalytic performance. Our findings revealed that superoxide radicals (O2-) were the major reactive species in the photocatalytic degradation process. This study contributes novel insights into the development of high-performance and stable metal-organic framework (MOF)-based photocatalysts through the crystal facet engineering and the construction of p-n junctions.

A method for determining efficiency parameters based on efficiency-quality graph in incremental sheet forming

This study reveals the mechanisms by which efficiency parameters affect surface quality, mechanical properties, and configuration offset in incremental sheet forming (ISF), focusing on surface morphology and microstructural evolution. By constructing an efficiency-quality graph, a method is developed to determine efficiency parameters that balance quality and efficiency synergistically. The results show that increasing Z and decreasing v intensify plowing and adhesion effects at the interface, degrading surface quality and enriching the presence of {001}<100> Cube and {112}<111> Copper textures, while the cross-sectional crystal orientation remains unaffected. Additionally, increasing Z enlarges grain size and reduces high-angle grain boundaries (HAGBs), amplifying micro-stress and defects, which deteriorates mechanical properties and increases configuration offset. Conversely, increasing v has minimal impact on mechanical properties but significantly increases configuration offset due to the rise in HAGBs, micro-stress, and defects. The efficiency-quality graph elucidates the complex synergistic relationship between forming efficiency and comprehensive quality of the formed parts, and the optimal efficiency parameters are identified by considering the priority order of different quality dimensions. Specifically, when prioritizing surface quality and hardness, the optimal parameters are Z=0.1mm and v=5000mm/min; when prioritizing configuration offset, the optimal parameters are Z=0.1mm and v=1000mm/min. Therefore, this study provides a comprehensive method for evaluating efficiency parameters in incremental sheet forming, emphasizing the importance of balancing efficiency with quality.

First principles study of the electronic and mechanical properties of a porous carbon

Carbon is a versatile element in the periodic table, which can form many allotropes with various properties in nature. In this work, the electronic and mechanical properties of a low energy porous carbon, a topological nodal line material, are studied by first principles method. Elastic and dynamical stabilities under hydrostatic pressure are investigated, which reveal that the dynamical instability occurs first. It is a material with negative linear compressibility along the a axis. Tension and compression strains are applied in different crystal orientations to obtain the corresponding stresses. The results indicate that the c axis can endure the smallest strains, the a axis can withstand moderate ones while the b axis can bear the largest ones, however, the resulted stresses have very different behaviors. Shear strains are exerted on different crystal planes to see the corresponding mechanical responses, which uncover that the (100,010] shear pattern has the lowest critical stress than other shear patterns. The crystal structure, dynamical stability, and electron density difference under the critical strains are checked. The reasons for the different mechanical behaviors under pressure and strain are proposed. The effects of pressure and strain on its topological property are also studied.

Optimization of the Raman spectroscopic method for crystal orientation and residual stress of aluminum oxide

Optimization of the Raman spectroscopic method for crystal orientation and residual stress of aluminum oxide