Layer Lattice Research Articles

Microheater Controlled Crystal Phase Engineering of Nanowires Using In Situ Transmission Electron Microscopy

AbstractCrystal Phase Quantum Dots (CPQDs) offer promising properties for quantum communication. How CPQDs can be formed in Au‐catalyzed GaAs nanowires using different precursor flows and temperatures by in situ environmental transmission electron microscopy (ETEM) experiments is studied. A III‐V gas supply system controls the precursor flow and custom‐built micro electro‐mechanical system (MEMS) chips with monocrystalline Si‐cantilevers are used for temperature control, forming a micrometer‐scale metal–organic vapor phase epitaxy (µMOVPE) system. The preferentially formed crystal phases are mapped at different precursor flows and temperatures to determine optimal growth parameters for either crystal phase. To control the position and length of CPQDs, the time scale for crystal phase change is investigated. The micrometer size of the cantilevers allows temperature shifts of more than 100 °C within 0.1 s at the nanowire growth temperature, which can be much faster than the growth time for a single lattice layer. For controlling the crystal phase, the temperature change is found to be superior to precursor flow, which takes tens of seconds for the crystal phase formation to react. This µMOVPE approach may ultimately provide faster temperature control than bulk MOVPE systems and hence enable engineering sequences of CPQDs with quantum dot lengths and positions defined with atomic precision.

Carrier modulation and effective passivation of tin oxide thin-film transistors by organic surface doping

Doping is a useful technique for metal oxide thin-film transistors (TFTs) to adjust the threshold voltage and charge carrier density. However, a notable drawback is the disruption of the microstructure caused by doping crystalline lattice, leading to a partial decrease in charge carrier mobility. In this work, we suggest a surface doping technique that modifies the carrier concentration and passivates the device surface while preserving the channel layer lattice structure through the use of organic dopant molecules. It is shown that tin oxide (SnO2) TFTs doped in this manner typically exhibit improved electrical characteristics, particularly greater mobility and a noticeably lower threshold voltage, without negatively affecting the devices on/off current ratio. Furthermore, compared to pristine devices, bias stress stability and long-term durability are also enhanced. These findings suggest that surface doping may find use in high-performance oxide semiconductor devices and circuits.

Doping Profile Meter for Semiconductor Structures

ABSTRACT A measuring device designed to gauge the distribution of electrically charged impurities within strongly asymmetric p – n junctions, Schottky barriers, and metal – insulator – semiconductor structures, employs the capacitance – voltage method. This device is controlled by a personal computer through a microcontroller. The coordinates of the concentration profile points are determined through a simultaneous selection of signals proportional to the concentration and its spatial coordinate, achieved by the selective hardware separation of information frequencies from a polyharmonic voltage. This process occurs in a structure installed in the negative-feedback circuit of the operational amplifier. The entire profiling process takes 30 seconds. It boasts a depth resolution of 15 angstroms (equivalent to 3‒4 atomic layers of the crystal lattice) at an impurity concentration of 5 × 1017 cm−3, with a maximum measured concentration of 5 × 1018 cm−3. The dimensions of the measuring device are 180 × 120 × 50 mm. The study presents examples of its practical applications.

Spontaneous symmetry breaking of cooperation between species.

In mutualistic associations, two species cooperate by exchanging goods or services with members of another species for their mutual benefit. At the same time, competition for reproduction primarily continues with members of their own species. In intra-species interactions, the prisoner's dilemma is the leading mathematical metaphor to study the evolution of cooperation. Here we consider inter-species interactions in the spatial prisoner's dilemma, where members of each species reside on one lattice layer. Cooperators provide benefits to neighbouring members of the other species at a cost to themselves. Hence, interactions occur across layers but competition remains within layers. We show that rich and complex dynamics unfold when varying the cost-to-benefit ratio of cooperation, r. Four distinct dynamical domains emerge that are separated by critical phase transitions, each characterized by diverging fluctuations in the frequency of cooperation: (i) for large r cooperation is too costly and defection dominates; (ii) for lower r cooperators survive at equal frequencies in both species; (iii) lowering r further results in an intriguing, spontaneous symmetry breaking of cooperation between species with increasing asymmetry for decreasing r; (iv) finally, for small r, bursts of mutual defection appear that increase in size with decreasing r and eventually drive the populations into absorbing states. Typically, one species is cooperating and the other defecting and hence establish perfect asymmetry. Intriguingly and despite the symmetrical model set-up, natural selection can nevertheless favour the spontaneous emergence of asymmetric evolutionary outcomes where, on average, one species exploits the other in a dynamical equilibrium.

Ammonium Polyuranates: Old Dog, New Structural Tricks.

The crystal structure of ammonium polyuranates xUO3·yNH3·zH2O has been investigated. Powder X-ray diffraction (PXRD) has been employed to define single-phase samples within a series of synthesized compounds, which are further characterized by elemental analysis to ascertain the stoichiometry, revealing compositions of 3UO3·NH3·5H2O and 2UO3·NH3·3H2O. Analysis using extended X-ray absorption fine structure and vibrational spectroscopy has elucidated that both 3UO3·NH3·5H2O and 2UO3·NH3·3H2O possess a local structure similar to the metaschoepite─layered U(VI) oxohydroxide UO3·2H2O, but with H2O and NH4+ groups in the interlayers. The structures of ammonium polyuranates are solved from PXRD data, revealing their relationship to the U(VI) oxohydroxide with the established composition of NH4[(UO2)3O2(OH)3]·3H2O and NH4[(UO2)2O2(OH)]·2H2O for 3UO3·NH3·5H2O and 2UO3·NH3·H2O, respectively. These structures maintain the arrangement of U-O polyhedra as pentagonal bipyramids. However, disparities in lattice parameters, space group, and layer topology from UO3·2H2O emphasize significant structural modifications resulting from the substitution of water by ammonium. Moreover, the anion topology of the NH4[(UO2)2O2(OH)]·2H2O has no analogues among uranium oxohydroxide minerals. Notably, ammonium polyuranates, when compared, have minimal alterations in lattice parameters regardless of the presence of ammonia within the structure. The revealed results contribute valuable insights into the UO3-NH3-H2O system and hold potential applications in the field of nuclear power as ammonium polyuranates form during actinide precipitation in back-end of the nuclear fuel cycle and also serve as precursors in the fabrication of nuclear fuel.

A novel 3D Z-shape design of compression-twist coupling metamaterial

Compression-twist coupling (CTC) metamaterials are the type of mechanical metamaterials which can convert the axial deformation into circumferential deformation. In order to design CTC metamaterials, connecting two lattice layers with chiral oblique rods is an effective method, and the unit cell is a cube with 2D Z-shape structure on the lateral side. In this study, a new 3D spatial Z-shape CTC structure is firstly proposed by rotating the upper layer with different angles in the traditional 3D Z-shape structure. Then, the torsion angles are analyzed with changes of unit cell geometries by theoretical method, finite element simulation and experiments. Finally, by extending the new 3D Z-shape structures, the typical pyramid frustum and oblique-rod-enhanced structures are designed and their mechanical behaviors are studied.

Growth of Size-Tunable Ag2O Polyhedra and Revelation of Their Bulk and Surface Lattices.

By primarily adjusting the reagent amounts, particularly the volume of AgNO3 solution introduced, Ag2O cubes with decreasing sizes from 440 to 79 nm, octahedra from 714 to 106 nm, and rhombic dodecahedra from 644 to 168 nm are synthesized. 733 nm cuboctahedra are also prepared for structural analysis. With in-house X-ray diffraction (XRD) peak calibration, shape-related peak shifts are recognizable. Synchrotron XRD measurements at 100 K reveal the presence of bulk and surface layer lattices. Bulk cell constants also deviate slightly. They show a negative thermal expansion behavior with shrinking cell constants at higher temperatures. The Ag2O crystals exhibit size- and facet-dependent optical properties. Bandgaps red-shift continuously with increasing particle sizes. Optical facet effect is also observable. Moreover, synchrotron XRD peaks of a mixture of Cu2O rhombicuboctahedra and edge- and corner-truncated cubes exposing all three crystal faces can be deconvoluted into three components with the bulk and the [111] microstrain phase as the major component. Interestingly, while the unheated Cu2O sample shows clear diffraction peak asymmetry, annealing the sample to 450 K yields nearly symmetric peaks even when returning the sample to room temperature, meaning even moderately high temperatures can permanently change the crystal lattice.

Microstructure and properties of 316 L lattice/Al composites by additive manufacturing and infiltration with different temperature

Interface between lattice reinforcement and matrix played a key factor on properties of the lattice reinforced aluminum matrix composites. However, the effect of interface composed of intermetallic compounds on the properties of 316 L lattice/Al composites was still unclear. In this study, 316 L lattice reinforced aluminum composite with continuous interface were prepared by combining laser powder bed fusion (LPBF) and vacuum infiltration, and effect of infiltration temperature on interface evolution and properties of the composite was investigated. Results indicated that a continuous dual-phase interfacial layer consisting of hard intermetallic compounds η-Fe2Al5 and θ-FeAl3 was formed between the reinforcement and matrix due to diffusion and reaction of iron and aluminum atoms, and the size of needle-type FeAl3 phase in the interfacial zone increased when infiltration temperature was up from 800 °C to 900 °C. It also confirmed that reinforced by 316 L lattice and hard intermetallic compounds layer, the composite showed excellent mechanical and wear resistant properties, with compressive strength of 657 ± 32 MPa and specific wear rate of 0.20 × 10−3 (mm3/N·m) for the sample prepared at 800 °C, which were over 10 times and one fifth of that of the aluminum matrix individually. This study provides a new strategy for developing 316 L lattice/Al composites with excellent properties.

Static and resonant properties of decorated square kagomé lattice KCu[formula omitted](TeO[formula omitted])(SO[formula omitted])[formula omitted]Cl

The magnetic subsystem of nabokoite, KCu7(TeO4)(SO4)5Cl, is constituted by copper ions forming a buckled square kagomé lattice decorated by quasi-isolated ions. This combination determines peculiar physical properties of this compound evidenced in electron spin resonance (ESR) spectroscopy, dielectric permittivity ɛ, magnetization M and specific heat Cp measurements. At lowering temperature, the magnetic susceptibility χ=M/H passes through a broad hump inherent for low-dimensional magnetic systems at about 150 K and a sharp peak at antiferromagnetic phase transition at TN=3.2 K. The Cp(T,H) curves demonstrate additional peak-like anomaly at Tpeak=5.7 K robust to magnetic field. The latter can be ascribed to low-lying singlet excitations filling the singlet-triplet gap in magnetic excitation spectrum of the square kagomé lattice (Richter et al., 2022). ESR spectroscopy provides indications that antiferromagnetic structure below TN is non-collinear. Separate issue is the observation of antiferroelectric-type behavior in ɛ at low temperatures, which tentatively reduces the symmetry and partially lifts frustration of magnetic interactions of decorating copper ions with buckled square kagomé lattice. These complex thermodynamic and resonant properties signal the presence of two weakly coupled magnetic subsystems in nabokoite, namely a spin-liquid in square kagomé lattice layers and an antiferromagnet represented by decorating ions.

Effect of density grading on the mechanical behaviour of advanced functionally graded lattice structures

Lattice structures have found significant applications in the biomedical field due to their interesting combination of mechanical and biological properties. Among these, functionally graded structures sparked interest because of their potential of varying their mechanical properties throughout the volume, allowing the design of biomedical devices able to match the characteristics of a graded structure like human bone. The aim of this works is the study of the effect of the density grading on the mechanical response and the failure mechanisms of a novel functionally graded lattice structure, namely Triply Arranged Octagonal Rings (TAOR). The mechanical behaviour was compared with the same lattice structures having constant density ratio. Electron Beam Melting technology was used to manufacture titanium alloy specimens with global relative densities from 10% to 30%. Functionally graded structures were obtained by increasing the relative density along the specimen, by individually designing the lattice's layers. Scanning electron and a digital microscopy were used to evaluate the dimensional mismatch between actual and designed structures. Compressive tests were carried out to obtain the mechanical properties and to evaluate the collapse modes of the structures in relation to their average relative density and lattice grading. Open-source Digital Image Correlation algorithm was applied to evaluate the deformation behaviour of the structures and to calculate their elastic moduli. The results showed that uniform density structures provide higher mechanical properties than functionally graded ones. The Digital Image Correlation results showed the possibility of effectively designing the different layers of functionally graded structures selecting desired local mechanical properties to mimic the different characteristics of cortical and cancellous bone.

GdFe-based nanostructured thin films with large perpendicular magnetic anisotropy for spintronic applications

In this study, we investigated the impact of geometric factors on the magnetic anisotropy of Gd-Fe alloy thin films deposited on nanoporous alumina membranes. By synthesizing Gd-Fe alloy nanostructure thin films with different hole diameters (ranging from 45 to 90 nm) and keeping the layer thickness and lattice parameters fixed at 45 nm and 105 nm, respectively, we observed a significant perpendicular magnetic anisotropy (PMA) in samples with hole diameter above 65 nm. The transition from in-plane to out-of-plane magnetization in Gd-Fe alloy nanostructure thin films occurred at a critical antidot hole diameter of 75 nm. The observed variations in coercivity and remanence with the nanohole diameter are attributed to substantial changes in the magnetization mechanisms induced by the nanoholes. This novel induction of PMA in Gd-Fe alloy nanostructure thin films through the manipulation of geometric parameters in the antidot arrays opens new possibilities for tailoring the magnetic behavior of ferromagnetic metals with pronounced PMA.

The pressure-stabilized polymorph of indium triiodide.

A layered rhombohedral polymorph of indium(III) triiodide is synthesized at high pressure and temperature. The unit cell symmetry and approximate dimensions are determined by single crystal X-ray diffraction. Its R3̄ crystal structure, with a = 7.214 Å, and c = 20.47 Å, is refined by the Rietveld method on powder X-ray diffraction data. The crystal structure is based on InI6 octahedra sharing edges to form honeycomb lattice layers, though with considerable stacking defects. Different from ambient pressure InI3, which has a monoclinic molecular structure and a light-yellow color, high pressure InI3 is layered and has an orange color. The band gaps of both the monoclinic and rhombohedral variants of InI3 are estimated from diffuse reflectance measurements.

Silicon lattice layer regulation: A close-to-atomic-scale method for optimizing infrared optical properties

Silicon lattice layer regulation: A close-to-atomic-scale method for optimizing infrared optical properties

Construction of 2D sandwich-like Na2V6O16·3H2O@MXene heterostructure for advanced aqueous zinc ion batteries

Aqueous zinc ion batteries (AZIBs) have attained enormous attention in the last few years. The cathode materials of aqueous zinc ion batteries play a vital effect in their electrochemical and battery properties. In this manuscript, Sandwich-like MXene@Na2V6O16·3H2O (NVO@MXene) heterostructure was successfully prepared by the combination and cooperation of the layer lattice structure of Na2V6O16·3H2O and the high conductivity of MXene. When used as the cathode material for AZIBs, NVO@MXene demonstrates preeminent rate capability and excellent reversible capacity of 175 mAh/g after 3000 cycles at 5 A/g with a retention rate of 88.9 % of initial discharge capacity. The outstanding battery performance can be attributed to the MXene layers with high conductivity for accelerating the ion diffusion rate and reducing the agglomeration of Na2V6O16·3H2O nanowires during the (dis)charge process. Meanwhile, the stable layered structure of Na16V6O6·3H2O with wide interlamellar spacing (d = 7.9 Å) is also favorable for the s fast intercalation/deintercalation of Zn2+. Finally, ex-situ X-ray diffraction and X-ray photoelectron spectroscopy were applied to study and reveal the energy storage mechanism of this novel material for aqueous zinc ion batteries.

Mechanical Performance and Failure Analysis of a 3D-Printed "Continuous Layer-Lattice Layer-Continuous Layer" Sandwich Structure.

Sandwich structures are engineered with continuous layers surrounding the inner lattices, which combines the advantages of the high strength of the continuous layer and the light weight of the lattice layer. They are widely employed in weight-critical energy-absorbing engineering fields such as aerospace, automobile, and robotics. However, the application of sandwich structures made of polymer matrix composites is still limited due to lack of essential performance investigation and adequate reference data. The following innovative works are accomplished in this paper: (i) Continuous long glass fiber (CGF) is employed within the continuous layer of the sandwich structure, with composite short carbon fiber/polyamide (SCF/N) applied within the lattice layer. (ii) Sandwich structures with different cell types and orientations of the lattice infills are designed and prepared by additive manufacturing. (iii) The basic mechanical properties of the sandwich structures, i.e., the bi-directional tension/compression compound performance, failure modes and mechanisms in characteristic directions, are analyzed systematically. (iv) The effects of geometric features on the three-point bending properties of L-shaped sandwich structures are investigated and compared with those of pure SCF/N structures. The results show that the bending resistance per unit weight was up to 54.3% larger than that of pure SCF/N, while the weight could be decreased by 49%, and the bending flexibility before fracture could be increased by 44%. These studies contribute fundamental research data to the application of sandwich structures prepared by fiber reinforced polymer matrix composites.

Graphene nanonetwork embedded with polyaniline nanoparticles as anode of Li-ion battery

A simple and solvent-free approach is proposed to prepare graphene nanonetwork-polyaniline (PANI) nanocomposite with enhanced electrical conductivity and Li-ion storage performance. To this end, acidic graphene oxide (AGO) and PANI are ball-milled followed by low-temperature chemical expansion leading to the formation of chemically expanded graphene (CEG) in the form of mesoporous nanonetworks with the lattice layer spacing of 0.362 nm embedded with PANI nanoparticles. CEG-PANI nanocomposite outperforms CEG, exhibiting a specific reversible capacity of 664 mAh·g−1 at 200 mA·g−1 after 150 cycles, and the discharge capacity of 253 mAh·g−1 after 350 cycles at 2000 mA·g−1. The enhanced electrochemical performance of CEG-PANI can be attributed to its large specific surface area, mesoporous structure and conductive homogeneous graphene nanonetwork doped with of N heteroatoms embedded with polyaniline, providing sufficient active sites for facile Li-ion storage. Nanostructured CEG-PANI is a promising candidate for anode of Li-ion batteries.

Flexural Behavior of Bidirectionally Graded Lattice

This study aims to investigate the flexural behavior of newly designed bidirectionally graded lattice beams with body‐centered cubic unit cells made of stainless steel 316 L. Uniform and unidirectionally graded lattice beams are also studied for comparison. All the lattice beams are fabricated by electron beam melting and tested under quasi‐static bending loads. The experimental results reveal that the flexural stiffness and strength of bidirectional lattice beams are higher than those of both the uniform and unidirectional counterparts. The unidirectional lattice beams display the lowest strength owing to the easier collapse of thinner lattice layers on the impact side with the indenter. Finite element models, developed and validated using the experimental results, are used to evaluate the effects of the density gradient and the loading velocity on the performance of bidirectional lattice beams. The parametric study shows that the flexural stress and the specific energy absorption capacity of bidirectional functionally graded lattice beams increase with increasing loading velocity and can be enhanced by manipulating the layer density gradient.

Influence of diverse timescales on the evolution of cooperation in a double-layer lattice

This paper studies the influence of diverse strategy-updating timescales on the evolution of cooperation, defection, and extortion strategies in a double-layer lattice. Individuals can adjust the frequencies with which they updating their strategies adaptively according to their fitness and interlayer information. On the basis of Fermi dynamics, we find that information sharing between the two lattice layers can effectively promote cooperative behavior in a double-layer lattice. In each lattice layer, cooperation–extortion alliances can be formed to defend against invasion by defection. We find that there exists an optimal value of the extortion factor to promote the evolution of cooperation and that the frequency of cooperation in a double-layer lattice is higher than that in a single-layer one.

B-doping on the electronic structure and photocatalytic properties of g-C3N4/Janus PtSSe heterojunctions: A first-principles study

The effect of B doping on the stability, electronic structure, work function, and optical properties of g-C3N4/Janus PtSSe heterojunctions has been investigated based on the density-functional theory plane-wave ultrasoft pseudopotential approach. It is shown that the binding energy of g-C3N4/PtSSe after B doping is negative and has a low layer spacing and lattice mismatch rate. It is stable at a room temperature of 300 K, proving its structural and thermodynamic stability. B-atom doping of g-C3N4/SPtSe and g-C3N4/SePtS heterojunctions leads to the upward shift of the Fermi energy level resulting in a significant reduction of the band gap and significant orbital hybridization. The impurity band near the Fermi energy level easily transfers electrons from the valence band into the conduction band, which makes electron leaps easier. Different built-in electric fields are formed when the g-C3N4 and Se(S) atomic layers are in contact. The reduction of the bandgap after B doping enables the photogenerated electron-hole pairs between the heterojunction interfaces to be better separated under the action of the built-in electric field, which reduces the composite rate of the electron-hole pairs and greatly improves the carrier migration and photocatalytic performance. The absorption and reflection coefficients of g-C3N4/SPtSe-BNC and g-C3N4/SePtS-BNC are the highest and decrease slowly in the visible region, which indicates that they have the optimal photocatalytic performance, and they can effectively broaden the range of light absorption and promote the utilization of light. The introduction of the B–B bonding effectively improves the photocatalytic activity of the heterojunction.

Two-Dimensional Van Der Waals Thin Film and Device.

In the rapidly evolving field of thin-film electronics, the emergence of large-area flexible and wearable devices has been a significant milestone. Although organic semiconductor thin films, which can be manufactured through solution processing, have been identified, their utility is often undermined by their poor stability and low carrier mobility under ambient conditions. However, inorganic nanomaterials can be solution-processed and demonstrate outstanding intrinsic properties and structural stability. In particular, a series of two-dimensional (2D) nanosheet/nanoparticle materials have been shown to form stable colloids in their respective solvents. However, the integration of these 2D nanomaterials into continuous large-area thin with precise control of layer thickness and lattice orientation still remains a significant challenge. This review paper undertakes a detailed analysis of van der Waals thin films, derived from 2D materials, in the advancement of thin-film electronics and optoelectronic devices. The superior intrinsic properties and structural stability of inorganic nanomaterials are highlighted, which can be solution-processed and underscor the importance of solution-based processing, establishing it as a cornerstone strategy for scalable electronic and optoelectronic applications. A comprehensive exploration of the challenges and opportunities associated with the utilization of 2D materials for the next generation of thin-film electronics and optoelectronic devices is presented.