Crystal Orientation Research Articles

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.

Thin film lithium niobate electro-optic modulator with reduced half-wave voltage length product through design

This paper aims at shortening electrode spacing in a thin film lithium niobate (TFLN) electro-optic modulator (EOM) while avoiding an increase in metal absorption loss, thereby reducing the half-wave voltage length product (V π ⋅L). Through numerical simulations, we find that metal absorption loss reaches its peak values when the optical modes of the metal-clad dielectric waveguide and ridged waveguide hybridize. This negative effect can be mitigated by adjusting the electrode width to modify the optical mode of the metal-clad dielectric waveguide. In addition, we raise the vertical position of the electrodes to further mitigate metal absorption loss and reduce the electrode spacing. By calculating the optimal buffer layer thickness for two crystal axis orientations, our findings reveal a 19% reduction in V π ⋅L at conventional crystal axis orientation (θ=±90∘) and a 16% decrease at unconventional crystal axis orientation (θ=54∘). Notably, V π ⋅L at unconventional crystal axis orientation is 5% lower than at conventional crystal axis orientation. These findings demonstrate the effectiveness of geometric configuration optimization toward enhancing the efficiency and performance of the TFLN EOM.

Global Selection Rules and Giant Enhanced Harmonic Generations in LiNbO3 Nonlinear Meta‐Optics

AbstractNonlinear optical metasurfaces provide nanoscale‐level control of harmonic waves, making them highly promising platforms for both fundamental research and applications in nonlinear optics. However, the traditional selection rules theory, which has long served as a guiding principle for nonlinear meta‐optics, is local and neglects the significance of meta‐atomic lattice symmetry. In addition, achieving high‐efficiency harmonic generation along with nonlinear optical Pancharatnam‐Berry (PB) phase control remains challenging. To this end, a novel global selection rule jointly determined by the symmetries of both meta‐atom and lattice is proposed. Nonlinear metasurfaces designed based on this theory enable frequency conversions forbidden by previous local selection rules. A more comprehensive relationship between the nonlinear PB phase and the meta‐atomic rotation angle is revealed. Moreover, an efficient nonlinear PB metasurface platform for second harmonic generations is first demonstrated using LiNbO3 thin films with aligned crystal orientations in a hybrid design. The normalized conversion efficiency reaches approximately two orders of magnitude higher than that of existing nonlinear PB metasurfaces working in the near‐infrared band. These findings not only shed light on the underlying mechanisms of nonlinear light‐matter interactions, but also open up exciting possibilities in terahertz, entangled photon pairs, and high harmonic generations.

Enhanced Impact Resistance, Oxygen Barrier, and Thermal Dimensional Stability of Biaxially Processed Miscible Poly(Lactic Acid)/Poly(Butylene Succinate) Thin Films

This study investigates the crystallization, microstructure, and performance of poly(lactic acid)/poly(butylene succinate) (PLA/PBS) thin films processed through blown film extrusion and biaxial orientation (BO) at various blend ratios. Succinic anhydride (SA) was used to enhance interfacial adhesion in PLA-rich blends, while blends near 50/50 formed co-continuous phases without SA. Biaxial stretching and annealing, adjusted according to the crystallization behavior of PLA and PBS, significantly influenced crystallinity, crystallite size, and molecular orientation. Biaxial stretching induced crystallization and ordered chain alignment, particularly at the cold crystallization temperature (Tcc), leading to a 70–80-fold increase in impact resistance compared to blown films. Annealing further enhanced crystallinity, especially at the Tcc of PLA, resulting in larger crystallite sizes. BO films demonstrated reduced thermal shrinkage due to improved PLA crystalline structure, whereas PLA-rich blown films showed higher shrinkage due to PLA’s lower thermal resistance. The SA-miscibilized phase reduced oxygen transmission in blown films, while BO films exhibited higher permeability due to anisotropic crystal orientation. However, the annealing of BO films, especially at high temperature (Tcc of PLA), further lowered oxygen permeability by promoting the crystallization of both PLA and PBS phases. Overall, the combination of SA compatibilization, biaxial stretching, and annealing resulted in substantial improvements in mechanical strength, dimensional stability, and oxygen barrier properties, highlighting the potential of these films for packaging applications.

Controlling Crystal Orientation in Films of Conjugated Polymers by Tuning the Surface Energy

Controlling Crystal Orientation in Films of Conjugated Polymers by Tuning the Surface Energy

Heteroepitaxy of ε‐Ga2O3 thin film for artificial synaptic device

AbstractEmerging‐wide bandgap semiconductor Ga2O3 shows distinct characteristics for optoelectronic applications and a stable crystal phase of Ga2O3 is highly desired. Herein, we have first reported a metal‐semiconductor‐metal structure photonic synaptic device based on the ε‐Ga2O3 thin film. The ε‐Ga2O3 epilayer is grown on the c‐sapphire with a low temperature nucleation layer, which presents a crystal orientation relationship with the c‐sapphire (ε‐Ga2O3 &lt;010&gt; // c‐sapphire &lt;1–100&gt; and ε‐Ga2O3 &lt;001&gt; // c‐sapphire &lt;0001&gt;). The ε‐Ga2O3 photonic device was stimulated by UV pulses at different pulse widths, pulse intervals, and reading voltages. Under the UV pulse excitation, the photonic device exhibits primary synaptic functions including excitatory postsynaptic current, short term memory, pair pulse facilitation, long term memory, and STM‐to‐LTM conversion. In addition, stronger and repeated stimuli can naturally contribute to the higher learning capability, thus prolonging the memory time.

Study on the uniaxial tensile mechanical behavior of two-dimensional single-crystal aluminum nitride

Abstract To investigate the tensile behavior and mechanical properties of single-crystal aluminum nitride (AlN) at the microscopic level, molecular dynamics simulations were used to study the effects of crystal orientation, strain rate, environmental temperature, and hole defect size on fracture strength, fracture mechanism, and potential energy during uniaxial tensile. The results show that the tensile strength of AlN in the [100] crystal direction is stronger. The anisotropic behavior characteristics of Al-N bonds fracture mechanism, crack growth rate, and cracking degree are significant when stretched along the [100], [010], and [110] crystal directions. Under high temperature condition, the lattice structure undergoes changes, causing grain boundaries to move and slip. This facilitates the breaking of bonds, leading to a decrease in tensile strength and a reduction in stored potential energy. Hole defects cause more lattice damage, reducing the energy required for Al-N bonds breakage and facilitating the propagation of microcracks. Additionally, it was found that the strain rate affects the stress-strain behavior of the model. An increase in strain rate leads to an increase in breaking stress, and the rapid deformation of AlN results in more energy being stored in the lattice in the form of potential energy. Therefore, the tensile strength and potential energy are improved.

Mechanical and high-temperature steam oxidation properties of Cr coatings deposited via high-power impulse magnetron sputtering

Applying protective coatings to Zr alloy cladding surfaces is one of the better methods to design fuel tolerant materials. In this study, the surface of a Zr-4 alloy was coated with Cr using high-power impulse magnetron sputtering. Furthermore, the mechanisms by which bias voltages affect the mechanical characteristics, resistance to high-temperature steam oxidation, and coating structure were elucidated. The coating exhibits a strong (200) weave structure with coarse grains at a bias voltage of -100 V. With increasing bias, the energy of deposited particles increases, grains continue to grow, (200) preferential growth orientation disappears, and the coating exhibits a (110) crystal orientation. The growth structure of the coating first shows a tendency to be dense and then loose. For the Cr coating with a (200) crystal orientation, a dense oxide layer is preferentially formed after oxidation, which can effectively block the internal diffusion of O. With increasing oxidation time, coarse Cr grains can effectively block the external diffusion of Zr. Furthermore, the Cr coating exhibiting a (110) crystal orientation was severely oxidized after oxidation, resulting in the formation of cracks at the film base; this accelerated the outward diffusion of Zr.

Synthesis of Multifunctional Organic Molecules via Michael Addition Reaction to Manage Perovskite Crystallization and Defect

AbstractAdditive engineering plays a pivotal role in achieving high‐quality light‐absorbing layers for high‐performance and stable perovskite solar cells (PSCs). Various functional groups within the additives exert distinct regulatory effects on the perovskite layer. However, few additive molecules can synergistically fulfill the dual functions of regulating crystallization and passivating defects. Here, we custom‐synthesized 2‐ureido‐4‐pyrimidone (UPy) organic small molecules with diverse functional groups as additives to modulate crystallization and defects in perovskite films via the Michael addition reaction. Theoretical and experimental investigations demonstrate that the −OH groups in UPy exhibit significant effects in fixing uncoordinated Pb2+ ions, passivation of lead‐iodide antisite defects, alleviating hysteresis, and reducing non‐radiative recombination. Furthermore, the enhanced C=O and −NH2 motifs interact with the A‐site cation via hydrogen bonding, which relieves residual strain and adjusts crystal orientation. This strategy effectively controls perovskite crystallization and passivates defects, ultimately enhancing the quality of perovskite films. Consequently, the open‐circuit voltage of the UPy‐based p‐i‐n PSCs reaches 1.20 V, and the fill factor surpasses 84 %. The champion device delivers a power conversion efficiency of 25.75 %. Remarkably, the unencapsulated device maintained 96.9 % and 94.5 % of its initial efficiency following 3,360 hours of dark storage and 1,866 hours of 1‐sun illumination, respectively.

Comparison between carrier transport property and crystal quality of TlBr semiconductors

Thallium bromide (TlBr) semiconductor detectors are being developed as promising candidates for high-detection-efficiency, high-energy-resolution, and room-temperature gamma-ray spectrometers. This study presents methods for evaluating TlBr crystal quality and carrier transport characteristics using neutron Bragg-dip imaging and the time-of-flight method for pulsed-laser-induced carriers, respectively. Neutron Bragg-dip imaging effectively determines the crystal orientation distribution, revealing crystal imperfections and grain boundaries. Time-of-flight measurements provide a spatial distribution of carrier mobility. In this study, two samples obtained from both the upstream and downstream region in the crystal ingot were evaluated. Although both samples show similar crystal quality, the upstream sample showed high carrier mobility across all areas, whereas the downstream sample exhibits low mobility in some areas. These findings suggest that, at least within the range of carrier mobility currently obtained, the effect of crystal integrity on carrier mobility is less significant than that of impurities. In conclusion, combining neutron Bragg-dip imaging with carrier mobility measurements offers a comprehensive approach to evaluating and improving TlBr detectors.

Improved Charge‐Transfer Doping in Crystalline Polymer for Efficient and Stable Perovskite Solar Cells

AbstractPerovskite solar cells (PSCs) have significant potential for next‐generation photovoltaic technology applications. However, the instability of hole transport layers (HTLs) becomes the major obstacle to long‐term operational devices, which are affected by the intrinsic thermal instability and loose structure of hole transport materials, as well as the hygroscopicity and migration of dopants. Here, poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) is used as a model crystalline polymer to thoroughly investigate effective p‐type doping strategies and the underlying mechanism. According to Hard–Soft‐Acid–Base theory, the soft base P3HT is more likely to form a stable Lewis acid–base adduct with the reactive soft acid radical, resulting in a strong charge‐transfer interaction, thereby enhancing conductivity and regulating the energy band of the HTL. Meanwhile, the radical cation salt can promote pre‐nucleation to optimize the crystallization orientation of P3HT. The resulting PSCs exhibited the efficiency of 25.16%, which is the highest efficiency reported so far based on doped P3HT. In addition, the resulting devices demonstrated excellent stability, maintaining 96.5%, 96%, and 91% of their initial efficiency after aging under continuous illumination for 2028 h, at 85 °C for 1080 h, and at maximum power point (MPP) tracking under continuous 1 Sun illumination at 85 °C for 528 h, respectively.

Study of the effect of SMAW welding speed on the microstructure and crystal stability of X70 steel using X-ray diffraction

This study investigates the impact of manual electric arc welding (SMAW) speed on the microstructure of X70 steel. Welding was performed at two distinct speeds: S1 = 20 mm/min and S2 = 35 mm/min, at the COSIDER BISKRA workshop in Algeria. X-ray diffraction (XRD) analysis was conducted on the welded zones to examine crystal orientation, size, dislocation density, and structural stability across different welding areas, including the base metal (MB), heat-affected zones (HAZ1 and HAZ2), and weld zones (WZ1 and WZ2). The XRD results revealed that key crystal peaks, such as {110} and {200}, retained their positions at both welding speeds, though variations in {110} peak intensity were noted. The lower welding speed (S1) resulted in a higher heat input, which enhanced crystal stability, increased crystal size, and reduced dislocation density. On the other hand, the higher speed (S2) produced lower heat input, leading to smaller crystal sizes, increased residual stresses, and a greater number of defects due to rapid cooling. These findings underscore the critical influence of welding speed on heat input, cooling rates, and their consequent effects on microstructure. The study highlights the importance of optimizing welding parameters to balance microstructural integrity, mechanical performance, and production efficiency.

Anisotropy of radiation-induced defects in Yb-implanted β-Ga2O3

RE-doped β-Ga2O3 seems attractive for future high-power LEDs operating in high irradiation environments. In this work, we pay special attention to the issue of radiation-induced defect anisotropy in β-Ga2O3, which is crucial for device manufacturing. Using the RBS/c technique, we have carefully studied the structural changes caused by implantation and post-implantation annealing in two of the most commonly used crystallographic orientations of β-Ga2O3, namely the (-201) and (010). The analysis was supported by advanced computer simulations using the McChasy code. Our studies reveal a strong dependence of the structural damage induced by Yb-ion implantation on the crystal orientation, with a significantly higher level of extended defects observed in the (-201) direction than for the (010). In contrast, the concentration and behavior of simple defects seem similar for both oriented crystals, although their evolution suggests the co-existence of two different types of defects in the implanted zone with their different sensitivity to both, radiation and annealing. It has also been found that Yb ions mostly occupy the interstitial positions in β-Ga2O3 crystals that remain unchanged after annealing. The location is independent of the crystal orientations. We believe that these studies noticeably extend the knowledge of the radiation-induced defect structure, because they dispel doubts about the differences in the damage level depending on crystal orientation, and are important for further practical applications.

Nanoscale Wet Etching of Molybdenum Interconnects with Organic Solutions.

Molybdenum (Mo) has emerged as a promising material for advanced semiconductor devices, especially in the design and fabrication of interconnects requiring sub-10nm metal nanostructures. However, current wet etching methods for Mo using aqueous solutions struggle to achieve smooth etching profiles at such scales. To address this problem, we explore wet chemical etching of patterned Mo nanowires (NWs) using an organic solution: ceric ammonium nitrate (CAN) dissolved in acetonitrile (ACN). In this study, we demonstrate two distinct etching pathways by controlling the reaction temperature: i) digital cyclic scheme at room temperature, with a self-limiting Mo recess per cycle of ≈1.6nm, and ii) direct etching at elevated temperature (60°C), with a time-controlled Mo recess of ≈2nm min-1. These methods not only offer a highly controllable nanoscale Mo etching but also ensure smooth and uniform etching profiles independent of the crystal grain orientation of the metal.

Analytical insight into caffeine extraction from typica coffee leaves based on crystallinity enhancement, optical phonon vibration upshift, and morphological evolution.

Caffeine extracted from callus cultures by in vitro technique induced from typica coffee (Coffea arabica L. var. typica) leaves was successfully carried out by a simple Soxhlet method. Analysis of X-ray diffraction patterns showed an increase in crystallinity fraction from leaves (13.56%) to callus (14.46%) and then to caffeine (39.18%). Crystallite size also varied, with average sizes of 18±6, 69±51, and 32.5±17 nm for leaves, callus, and caffeine, respectively. Fourier transmission infrared absorption data confirmed the presence of hydroxyl (OH) groups bound to carbon (C─COH), indicating caffeine content. The high stability of the C─COH is indicated by the broad optical phonon vibrations of the leaves: 247cm-1 to caffeine: 963cm-1. Quantitative analysis of dielectric function and electron loss function intensity peaks of each sample showed that leaves efficiently capture and store light energy while caffeine has less potency. Scanning electron microscopy analysis showed irregular shapes of leaves, oval round shapes for callus, and rectangular crystals for caffeine due to crystal orientation during transformation and had a strong correlation with crystallinity fraction. Finally, the structure-based identification, chemistry, optical-dielectric function, and micro-surface properties have been fully studied, thus unmasking the phenomenon of slow transformation from leaves to caffeine form. PRACTICAL APPLICATION: The result of this study can be applied to uncover new methodologies related to the classification, and biotechnological utilization of callus culture based on structural properties, optical-dielectric function, and micro-surface analysis. Methodologically, the resulting callus culture provides a sustainable and controllable supply of plant material for caffeine extraction, thereby reducing traditional methods involving field-grown plants and avoiding the use of pesticides.

Wrinkled Rhenium Disulfide for Anisotropic Nonvolatile Memory and Multiple Artificial Neuromorphic Synapses.

Two-dimensional materials are emerging as potential solutions for high-density nonvolatile memory and efficient neuromorphic computing. However, integrating multidimensional memory and an ideal linear weight updating synapse in a simple device configuration to achieve versatile biomimetic neuromorphic systems remains challenging. Here, we introduce a wrinkled rhenium disulfide (ReS2) transistor, where the wrinkled structure facilitates the carrier trapping/detrapping at the dielectric interface, thus enabling the fusion of nonvolatile memory and both electronic and optoelectronic synaptic functionalities. As a nonvolatile memory, anisotropic wrinkled ReS2 can yield three distinct sets of data across three crystal orientations under identical programming operations. Each set demonstrates exceptional retention and endurance properties. As a neuromorphic synapse, it realizes the linear and symmetric updates of conductance states up to 9 bits and 8 bits, the ultra-low-energy consumption of 75 fJ and 2.5 pJ under the electrical and optical stimuli, respectively. The artificial neural network (ANN) based on electronic synapses gives a superior recognition accuracy of 92.9% for the original handwritten digits. The anisotropic synaptic responses and multiwavelength sensitivities of optoelectronic synapses enable them to execute advanced memory and recognition functions for complex images that encompass a variety of pattern features or color information. This underscores its substantial potential for integration into efficient biomimetic visual systems.

Atomistic insights into cold welding process of high-entropy alloy nanowires

This research applied molecular dynamics (MD) simulations to investigate the influences of contact pressure, temperature, crystal orientation, and chemical composition on the characteristics of the cold welding joints of CoNiCrFeMn high-entropy alloy (HEA) nanowires. The findings indicate that defect-free cold welded joints can be successfully formed within a contact pressure range of 10 to 10,000 Pa. In addition, changing the contact orientation could cause a significant change in the structure transformation level. The dislocation distribution is continuous when the top and lower blocks are oriented in the same direction. Dislocation lines, on the other hand, stop at the interfacial area and have a discontinuous shape when the weld joints are formed from different orientations. Furthermore, creating from the same orientations leads to a higher ultimate tensile strength (UTS) value than the different orientation cases. In the temperature range of 150 K–350 K, the deformation behaviors of the cold weld joint are stable. Besides, there was no noticeable change in the weld joint when the composition changed. Because of the strong crystal structure of the cold welding joints, the UTS values of the cold-welded joints range from 13.2 to 17.4 GPa, comparable to the bulk samples.

On influence of microstructural anisotropy of additive manufactured structures upon machining dynamics: An example of milling of Ti6Al4V thin-walled parts

Thin-walled structures, as common component specification for aerospace components, easily experience deformation and chatter issues during machining (e.g. milling) operations. With Additively Manufactured (AM) materials being increasingly applied in these areas, it is found that their microstructural anisotropy can lead to varied mechanical properties and machinability in different directions. However, former research on thin-walled parts mainly focused on bulk materials, while the machining performance of these thin-wall structures produced from AM processes remains unclear. In this view, this research aims to reveal the effect of microstructural anisotropy resulting from AM process on the machining (deformation and stability) of thin-walled parts by taking Ti6Al4V as an example. Three kinds of AM Ti6Al4V thin-walled parts were fabricated with different laser scanning strategies, in which the prior columnar β grains were found to grow along the building direction and led to a variation in mechanical properties. Owing to this, the deformation and machining stability varied in the AM thin-walled parts with different β phase crystallization orientations on the same milling directions, which could be attributed to the changes of cutting force and dynamic parameters (e.g., frequency, stiffness (determined by elastic modulus), damping ratio) in different orientations. This investigation could provide a reference for the selection of printing strategies and follow-up machining process of AM thin-walled parts when considering their microstructural anisotropy.

Atomistic understanding on the surface formation mechanism of nanoscale scratches along different crystal orientations of silicon carbide

Single crystal silicon carbide has been widely used in many fields due to its excellent physical and chemical properties. However, these special properties of silicon carbide can lead to surface defects and subsurface damage in precision machining processes. In this research, high-speed scratching experiments and molecular dynamics simulations were used to study the surface formation mechanism of nanoscale scratches along the [1-210] and [1-100] crystal orientations of silicon carbide. For both the simulations and experiments, different scratching crystal orientations result in the formation of different amorphous patterns. The angle between the scratching orientation [1-210] and the amorphous pattern is 60°, while the angle between scratching orientation [1-100] and the amorphous pattern is 30°. The stress concentration during the scratching process along the orientations [1-210] and [1-100] is mainly located at the two edges and one edge of the amorphous patterns, respectively. The amorphous patterns along the < 1-210 > directions on the (0001) plane are caused by dislocations and slips on the {10-10} plane. This study reveals the material deformation mechanism and removal mechanism of silicon carbide along different crystal orientations scratching, providing theoretical guidance for the nanoscale machining of silicon carbide.

Ultrahigh thermal stability and piezoelectricity of lead-free KNN-based texture piezoceramics

The contradiction between high piezoelectricity and uniquely poor temperature stability generated by polymorphic phase boundary is a huge obstacle to high-performance (K, Na)NbO3 -based ceramics entering the application market as Pb-based substitutes. We possess the phase boundary by mimicking Pb(Zr, Ti)O3’s morphotropic phase boundary structure via the synergistic optimization of diffusion phase boundary and crystal orientation in 0.94(Na0.56K0.44)NbO3−0.03Bi0.5Na0.5ZrO3−0.03(Bi0.5K0.5)HfO3 textured ceramics. As a result, a prominent comprehensive performance is obtained, including giant d33 of 550 ± 30 pC/N and ultrahigh temperature stability (d33 change rate less than 1.2% within 25-150 °C), representing a significant breakthrough in lead-free piezoceramics, even surpassing the Pb-based piezoelectric ceramics. Within the same temperature range, the d33 change rate of the commercial Pb(Zr, Ti)O3−5 ceramics is only about 10%, and more importantly, its d33 (~ 350 pC/N) is much lower than that of the (K, Na)NbO3-based ceramics in this work. This study demonstrates a strategy for constructing the phase boundary with MPB feature, settling the problem of temperature instability in (K, Na)NbO3-based ceramics.