Search

This paper describes how moiré plasmonic nanoparticle lattices can exhibit lasing action over a broad wavelength and wavevector range. Moiré nanolithography is combined with the PEEL (Photolithography, Etching, Electron‐beam deposition, and Lift‐off) process to fabricate in‐plane incommensurate lattices with optical properties beyond the restricted geometries of Bravais lattices. Because of increased rotational symmetry, moiré lattices support a larger number of transverse electric and transverse magnetic modes relative to their periodic base lattices. It is found that multidirectional lasing characteristics can be predicted by the symmetry of the moiré reciprocal lattice. Incommensurate moiré plasmonic lattices combine advantages of the dense band structures observed in aperiodic lattices with that of predicted modes in Bravais lattices for light‐based technologies in coherent light sources and multiplexed data transfer. [ABSTRACT FROM AUTHOR]

2D materials have received a lot of interest over the past decade. Especially van der Waals (vdW) 2D materials, such as transition metal dichalcogenides (TMDCs), and their heterostructures exhibit semiconducting properties that make them highly suitable for novel device applications. Controllable mixing and matching of the 2D materials with different properties and precise control of the in‐plane twist angle in these heterostructures are essential to achieve superior properties and need to be established through large‐scale device fabrication. To gain fundamental insight into the potential control of these twist angles, 2D heterostructures of tungsten disulfide (WS2) and graphene (Gr) grown by bottom‐up synthesis via metal‐organic chemical vapor deposition (MOCVD) are investigated using a scanning transmission electron microscope (STEM). Specifically, the combination of conventional high‐resolution imaging with scanning nanobeam diffraction (SNBD) using advanced 4D STEM techniques is used to analyze moiré structures. The latter technique is used to reveal the epitaxial alignment within the WS2/Gr heterostructure, showing a direct influence of the underlying Gr layers on the moiré structure in the subsequent WS2 layers. In particular, the importance of grain boundaries (GBs) within the underlying WS2 and Gr layers on the structure of moiré patterns with rotation angles below 2° is discussed. [ABSTRACT FROM AUTHOR]

"On‐Cell Plus", is designed by setting the same size of active area (AA) of the touch sensor and display, and then uses random mesh pattern to prevent moiré issues. Accordingly, the touch sensor and display cell can be designed and produced independently and demonstrate better touch sensitivity. [ABSTRACT FROM AUTHOR]

In the domain of Naked‐eye 3D display technology, the periodic interference between lenticular lens and screen subpixels frequently results in the generation of moiré patterns, which significantly impair image quality. This study proposes a strategy to reduce moir é artifacts by adjusting the tilt angle of the lenticular lens. Relying on the human eye sensitivity function, we have conducted a thorough analysis of the moiré patterns caused by the interference between the lenticular lens and the screen at various tilt angles. After extensive research, it has been discovered that the analytical method which applies spectral sensitivity weighting subsequent to the consideration of the human eye sensitivity function aligns more closely with the actual perception of moiré patterns by the human eye. This approach enables a more precise determination of the optimal tilt angles for lenticular lenses and screens, thereby substantially minimizing the moiré effect. The implications of this finding are significant for the realization of high‐quality, high‐definition naked‐eye 3D image displays, and may positively contribute to advancements within this technical field. [ABSTRACT FROM AUTHOR]

Moire is quite a well‐known phenomenon that can be found in display panels when multiple layouts are overlapped with different pitches. To verify Moire, we applied a step‐wise simulation based on ray‐tracing methodology. First, the CSF contour map was calculated as a function of key design parameters such as the angle and pitch of the metal wire. Then, the sensitivity of Moire image was verified under process variation and viewing angle dependency. A slight change of process variation and viewing angle results in an abrupt change of Moire. CSF value can be increased up to 15 times even a small angle variation such as 0.1 degree [ABSTRACT FROM AUTHOR]

Abstract 2D materials have received a lot of interest over the past decade. Especially van der Waals (vdW) 2D materials, such as transition metal dichalcogenides (TMDCs), and their heterostructures exhibit semiconducting properties that make them highly suitable for novel device applications. Controllable mixing and matching of the 2D materials with different properties and precise control of the in‐plane twist angle in these heterostructures are essential to achieve superior properties and need to be established through large‐scale device fabrication. To gain fundamental insight into the potential control of these twist angles, 2D heterostructures of tungsten disulfide (WS2) and graphene (Gr) grown by bottom‐up synthesis via metal‐organic chemical vapor deposition (MOCVD) are investigated using a scanning transmission electron microscope (STEM). Specifically, the combination of conventional high‐resolution imaging with scanning nanobeam diffraction (SNBD) using advanced 4D STEM techniques is used to analyze moiré structures. The latter technique is used to reveal the epitaxial alignment within the WS2/Gr heterostructure, showing a direct influence of the underlying Gr layers on the moiré structure in the subsequent WS2 layers. In particular, the importance of grain boundaries (GBs) within the underlying WS2 and Gr layers on the structure of moiré patterns with rotation angles below 2° is discussed.

This study takes water patterns and cloud patterns as examples to explore the evolution and contemporary performance of traditional Chinese patterns. Firstly, the background and importance of traditional Chinese patterns in the field of cultural pedagogy are introduced. Subsequently, the purpose and significance of the research are expounded, in order to deeply understand and excavate the development and contemporary expression of traditional Chinese patterns. According to the purpose of the study, the two main research methods of this study were analysis of literature and field research. Through the study of the evolution process of water pattern and cloud pattern, the changes and evolution laws of water pattern and cloud pattern in different historical periods and regions are found. The results show that the water pattern and the cloud pattern have the same material matrix, different modeling structure, and different dyeing materials, which are graphics evolved from traditional patterns, representing the meaning of heart, chest, belly and auspiciousness, respectively. Therefore, traditional patterns can provide inspiration for modern design, extend the role and use of traditional patterns, and provide reference and reference for archaeological pattern research. [ABSTRACT FROM AUTHOR]

This is an update of a previous review (Naumis et al 2017 Rep. Prog. Phys. 80 096501). Experimental and theoretical advances for straining graphene and other metallic, insulating, ferroelectric, ferroelastic, ferromagnetic and multiferroic 2D materials were considered. We surveyed (i) methods to induce valley and sublattice polarisation (P) in graphene, (ii) time-dependent strain and its impact on graphene's electronic properties, (iii) the role of local and global strain on superconductivity and other highly correlated and/or topological phases of graphene, (iv) inducing polarisation P on hexagonal boron nitride monolayers via strain, (v) modifying the optoelectronic properties of transition metal dichalcogenide monolayers through strain, (vi) ferroic 2D materials with intrinsic elastic (σ), electric (P) and magnetic (M) polarisation under strain, as well as incipient 2D multiferroics and (vii) moiré bilayers exhibiting flat electronic bands and exotic quantum phase diagrams, and other bilayer or few-layer systems exhibiting ferroic orders tunable by rotations and shear strain. The update features the experimental realisations of a tunable two-dimensional Quantum Spin Hall effect in germanene, of elemental 2D ferroelectric bismuth, and 2D multiferroic NiI2. The document was structured for a discussion of effects taking place in monolayers first, followed by discussions concerning bilayers and few-layers, and it represents an up-to-date overview of exciting and newest developments on the fast-paced field of 2D materials. [ABSTRACT FROM AUTHOR]

Moiré patterns result from setting a 2D material such as graphene on another 2D material with a small twist angle or from the lattice mismatch of 2D heterostructures. We present a continuum model for the elastic energy of these bilayer moiré structures that includes an intralayer elastic energy and an interlayer misfit energy that is minimized at two stackings (disregistries). We show by theory and computation that the displacement field that minimizes the global elastic energy subject to a global boundary constraint gives large alternating regions of one of the two energy-minimizing stackings separated by domain walls. We derive a model for the domain wall structure from the continuum bilayer energy and give a rigorous asymptotic estimate for the structure. We also give an improved estimate for the L 2 -norm of the gradient on the moiré unit cell for twisted bilayers that scales at most inversely linearly with the twist angle, a result which is consistent with the formation of one-dimensional domain walls with a fixed width around triangular domains at very small twist angles. [ABSTRACT FROM AUTHOR]

The moiré effect arises from the superposition of periodic structures with differences in periods or angles. Although the moiré effect can be exploited as an intriguing tool to fabricate complex metastructures, reduction of the moiré effect can be an important issue in display technology that uses many optical films with periodic patterns. Because of the superposition, dark and bright regions can be seen by the naked eye, which is a reason for the degradation of the visual quality. In this work, the lateral deformation of shape edges of prism films is harnessed to reduce the moiré effect. After the preparation of a microprism array with hydrogel materials, the hydrogel microprism array is swelled via penetration of water molecules into the hydrogel networks. Due to the compressive stress applied by volume expansion with confinement, only the sharp edges laterally buckle randomly. The swollen hydrogel prism array is replicated by photopolymerization, and prism arrays with laterally buckled edges are obtained. The randomized edges help reduce the moiré effect of the optical film when the prism array is overlapped with other periodic devices, such as other prism arrays or display devices consisting of microscale pixels, without a significant decrease in the optical performance. [ABSTRACT FROM AUTHOR]

We report the existence of moiré patterns and magic angle physics in all families of chiral collapsed carbon nanotubes. A detailed study of the electronic structure of all types of chiral nanotubes, previously collapsed via molecular dynamics, has been performed. We find that each family possesses a unique geometry and moiré disposition, as well as a characteristic number of flat bands. Remarkably, all kinds of nanotubes behave the same with respect to magic angle tuning, showing a monotonic behavior that gives rise to magic angles in full agreement with those of twisted bilayer graphene. Therefore, magic angle behavior is universally found in chiral collapsed nanotubes with a small chiral angle, giving rise to moiré patterns. Our approach comprises first-principles and semi-empirical calculations of the band structure, density of states and spatial distribution of the localized states signaled by flat bands. [Display omitted] [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) twisted moiré materials, a new class of van der Waals (vdW) layered heterostructures with different twist angles between neighboring layers, have attracted tremendous attention due to their rich emerging properties. In this review, we systematically summarize the recent progress of 2D twisted moiré materials. Firstly, we introduce several representative fabrication methods and the fascinating topographies of the twisted moiré materials. Specifically, we discuss various remarkable physical properties related to twisted angles, including flat bands, unconventional superconductivity, ferromagnetism, and ferroelectricity. We also analyze the potential applications in various twisted moiré systems. Finally, the challenges and future perspectives of the twisted moiré materials are discussed. This work would spur edge-cutting ideas and related achievements in the scientific and technological frontiers of 2D twisted moiré materials. [ABSTRACT FROM AUTHOR]

The cult of Moirai/ Moerae, their iconography, and the popular faith concerning the goddesses of destiny in the Greek colonies on the western shore of the Pontus Euxinus make the subject of the present study. Our research is based on the study of epigraphic, literary, and archeaological (votive bas-reliefs) documents. The cult of the Moirai is certainly certificated in Naulochos (the modern Obzor, in Bulgaria) and at Istros where two dedications to the goddesses of destiny were found out. A votive aedicula in the temple of Aphrodite at Istros proves the relations between the Moirai and the cult of Aphrodite. The association of the Moirai with Aphrodite is confirmed by the two reliefs discovered at Panticapaion and Tyras, which present a similar composition with the one on the votive relief at Istros. The funeral epitaphs found out along the western shore of the Pontus Euxinus underline the Greeks'popular creeds related to the goddesses of destiny. [ABSTRACT FROM AUTHOR]

When graphene is placed on a crystalline surface, the periodic structures within the layers superimpose and moiré superlattices form. Small lattice rotations between the two materials in contact strongly modify the moiré lattice parameter, upon which many electronic, vibrational, and chemical properties depend. While precise adjustment of the relative orientation in the degree- and sub-degree-range can be achieved via careful deterministic transfer of graphene, we report on the spontaneous reorientation of graphene on a metallic substrate, Ir(111). We find that selecting a substrate temperature between 1530 and 1000 K during the growth of graphene leads to distinct relative rotational angles of 0°, ± 0.6°, ±1.1°, and ±1.7°. When modeling the moiré superlattices as two-dimensional coincidence networks, we can ascribe the observed rotations to favorable low-strain graphene structures. The dissimilar thermal expansion of the substrate and graphene is regarded as an effective compressive biaxial pressure that is more easily accommodated in graphene by small rotations rather than by compression.

As today’s printing volume worldwide decreases, and most traditional printing engines are expensive non-digital devices (offset), the demand for a low-cost digital replacement is rapidly increasing. A main disadvantage of digital presses is the low-resolution capabilities, introducing a compromise in the print quality (PQ). A key factor of print quality is the halftoning algorithm. A very common halftoning method is amplitude modulation (AM) halftone screening, in which dots are placed on a repetitive lattice, varying in size as a function of the grey level. The main AM screen design PQ challenge for low-resolution devices is the quantization frequencies, a disturbing pattern that usually emerges when a screen is approximated to a rational angle due to low resolution. Fourier-based analysis is a classical rule-based method to filter out screens that suffer from visually disturbing quantization patterns. This work presents a new approach that tackles this challenge by incorporating machine learning with the classic Fourier-based approach. Particularly, we show that a binary decision tree classifier with a Fourier-based feature vector has an accuracy of 95% in identifying quantization-free screens compared to the classic rule-based method, which has an accuracy of 66%. We conclude by demonstrating the use of the screen classifier to design a quantization-free screen set. This is done by first applying the screen classifier to the entire screen pool, that is, the set of all possible screens for a given print engine, followed by a rosette zero-moiré offset-like screen design.

We have developed a technique for observing fine wiring patterns using moiré patterns generated by interference between wiring patterns and reference patterns in endpoint detection (EPD) of the CMP. With this technique, wiring pattern images of patterned wafers can be evaluated with a simple and low magnification optical system to observe large moiré patterns. In this process, the large moiré pattern is calculated from the device wiring and other reference pattern layouts. As a result, EPD signals can be detected. [ABSTRACT FROM AUTHOR]

Evaluation of single emitter‐based display technologies like OLED and μLED at modern display resolutions requires high‐resolution measurements. The typically used oversampling often negatively affect cycle times and ILMD complexity. In this contribution, we present, explain, and validate an alternative to performing high‐resolution measurements despite the Moiré phenomenon. [ABSTRACT FROM AUTHOR]

We investigate the existence of higher order topological localized modes in moiré lattices of bilayer elastic plates. Each plate has a hexagonal array of discrete resonators and one of the plates is rotated at an angle (21. 7 8 ∘ ) which results in a periodic moiré lattice with the smallest area. The two plates are then coupled by inter-layer springs at discrete locations where the top and bottom plate resonators coincide. Dispersion analysis using the plane wave expansion method reveals that a bandgap opens on adding the inter-layer springs. The corresponding topological index, namely fractional corner mode, for bands below the bandgap predicts the presence of corner localized modes in a finite structure. Numerical simulations of frequency response show localization at all corners, consistent with the theoretical predictions. The considered continuous elastic bilayered moiré structures opens opportunities for novel wave phenomena, with potential applications in tunable energy localization and vibration isolation. • The dynamics of a bilayer elastic Moire lattice with the smallest unit cell is studied. • Higher order topological localized modes are predicted at all corners from dispersion analysis. • Numerical simulations with plane wave expansion method confirm theoretical predictions. [ABSTRACT FROM AUTHOR]

Interference effects in finite sections of one-dimensional moiré crystals are investigated using a Landauer-Büttiker formalism within the tight-binding approximation. We explain interlayer transport in double-wall carbon nanotubes and design a predictive model. Wave function interference is visible at the mesoscale: in the strong coupling regime, as a periodic modulation of quantum conductance and emergent localized states; in the localized-insulating regime, as a suppression of interlayer transport, and oscillations of the density of states. These results could be exploited to design quantum electronic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Radiofrequency (RF) has been widely used as a noninvasive technique for skin tightening and rejuvenation. Moiré is a type of interference pattern corresponding to the shape of the face. We aimed to objectively evaluate the effect of RF on facial skin laxity using moiré. Ten subjects participated and were treated with a monopolar RF on the face. Clinical photographs and moiré images were obtained at the baseline and after treatment. The periorbital angle from the upper third of the face, zygomatic length ratio (L1/L2), angle from the middle third, perioral perpendicular length, and angle from the lower third were analyzed. After one session of RF treatment, the mean zygomatic length ratio (L1/L2) from the middle third of the face significantly increased in the 4th week (by 49.68%, P =.047). The L1/L2 ratio increased to nearly one, which were not significant after 8 weeks. The mean perioral perpendicular length decreased to 282.25 ± 84.069 pixels (px) after 4 weeks, and to 281.38 ± 76.03 px after 24 weeks; these differences were statistically significant. The parameters of zygomatic length ratio and perioral perpendicular length extracted from illuminated moiré images can be useful for objectively assessing various facial tightening treatments in clinical settings. [ABSTRACT FROM AUTHOR]

The use of artificial intelligence (AI) as a tool supporting the diagnosis and treatment of spinal diseases is eagerly anticipated. In the field of diagnostic imaging, the possible application of AI includes diagnostic support for diseases requiring highly specialized expertise, such as trauma in children, scoliosis, symptomatic diseases, and spinal cord tumors. Moiré topography, which describes the 3-dimensional surface of the trunk with band patterns, has been used to screen students for scoliosis, but the interpretation of the band patterns can be ambiguous. Thus, we created a scoliosis screening system that estimates spinal alignment, the Cobb angle, and vertebral rotation from moiré images. In our system, a convolutional neural network (CNN) estimates the positions of 12 thoracic and 5 lumbar vertebrae, 17 spinous processes, and the vertebral rotation angle of each vertebra. We used this information to estimate the Cobb angle. The mean absolute error (MAE) of the estimated vertebral positions was 3.6 pixels (~5.4 mm) per person. T1 and L5 had smaller MAEs than the other levels. The MAE per person between the Cobb angle measured by doctors and the estimated Cobb angle was 3.42°. The MAE was 4.38° in normal spines, 3.13° in spines with a slight deformity, and 2.74° in spines with a mild to severe deformity. The MAE of the angle of vertebral rotation was 2.9°±1.4°, and was smaller when the deformity was milder. The proposed method of estimating the Cobb angle and AVR from moiré images using a CNN is expected to enhance the accuracy of scoliosis screening.

Epitaxial heterostructures with topological insulators enable novel quantum phases and practical device applications. Their topological electronic states are sensitive to the microscopic parameters, including structural inversion asymmetry (SIA), which is an inherent feature of many real heterostructures. Controlling SIA is challenging, because it requires the ability to tune the displacement field across the topological film. Here, using nanopatterned gates, we demonstrate a tunable displacement field in a heterostructure of the two-dimensional topological insulator cadmium arsenide. Transport studies in magnetic fields reveal an extreme sensitivity of the band inversion to SIA. We show that a relatively small displacement field (∼50 mV/nm) converts the crossing of the two zeroth Landau levels in magnetic field to an avoided crossing, signaling a change to trivial band order. This work demonstrates a universal methodology for tuning electronic states in topological thin films.

In this paper, a precise and effective computational method for moire patterns' simulation and prediction of liquid crystal display (LCD) metal mesh touch panel based on the transmittance calculation of LCD's sub‐pixel is proposed. Firstly, we analyze the actual physical model and build our simulation model. Secondly, we explain the form reason of moire phenomenon and establish the transmittance calculation formula. Finally, we demonstrate the accuracy and validation of our simulation approach by practical experiment. The experimental results show that the simulation matching rate is about 88.2%, and the simulated graphs are extremely similar to the actual moire pattern. We can evaluate the moire degree with our new method; this research is significant to touch panel's production. [ABSTRACT FROM AUTHOR]

Moiré superlattices in two-dimensional van der Waals heterostructures provide an efficient way to engineer electron band properties. The recent discovery of exotic quantum phases and their interplay in twisted bilayer graphene (tBLG) has made this moiré system one of the most renowned condensed matter platforms. So far studies of tBLG have been mostly focused on the lowest two flat moiré bands at the first magic angle θm1 ~ 1.1°, leaving highorder moiré bands and magic angles largely unexplored. Here we report an observation of multiple well-isolated flat moiré bands in tBLG close to the second magic angle θm2 ~ 0.5°, which cannot be explained without considering electron-election interactions. With high magnetic field magnetotransport measurements we further reveal an energetically unbound Hofstadter butterfly spectrum in which continuously extended quantized Landau level gaps cross all trivial band gaps. The connected Hofstadter butterfly strongly evidences the topologically nontrivial textures of the multiple moiré bands. Overall, our work provides a perspective for understanding the quantum phases in tBLG and the fractal Hofstadter spectra of multiple topological bands. [ABSTRACT FROM AUTHOR]

We present strong experimental evidence for the moiré origin of superlattices on graphite by imaging a live transition from one superlattice to another with concurrent and direct measurement of the orientation angle before and after rotation using scanning tunneling microscopy (STM). This has been possible due to a fortuitous observation of a superlattice on a nanometer-sized graphene flake wherein we have induced a further rotation of the flake utilizing the capillary forces at play at a solid–liquid interface using STM tip motion. We propose a more “realistic” tip–surface meniscus relevant to STM at solid–liquid interfaces and show that the capillary force is sufficient to account for the total expenditure of energy involved in the process.

The valence band maxima of most group VI transition metal dichalcogenide thin films remain at the 􀀀 point all of the way from bulk to bilayer. In this paper, we develop a continuum theory of the moire' minibands that are formed in the valence bands of 􀀀-valley homobilayers by a small relative twist. Our effective theory is benchmarked against large-scale ab initio electronic structure calculations that account for lattice relaxation. As a consequence of an emergent D6 symmetry, we find that low-energy 􀀀-valley moire' holes differ qualitatively from their K-valley counterparts addressed previously; in energetic order, the first three bands realize 1) a single-orbital model on a honeycomb lattice, 2) a two-orbital model on a honeycomb lattice, and 3) a single-orbital model on a kagome lattice. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Liquid Crystal & Displays is the property of Chinese Journal of Liquid Crystal & Displays and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Liquid Crystal & Displays is the property of Chinese Journal of Liquid Crystal & Displays and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We have investigated the Moiré interference in pinhole based fingerprint on display technology. The origin of the phenomenon is identified as the interference between discrete OLED pixels and the object outline. A countermeasure is given to overcome its impact on the identification of miniature fingerprint features. [ABSTRACT FROM AUTHOR]

Interference between overlapping periodic patterns gives rise to important phenomena, such as Moiré fringes, appearing when the patterns have different periods or orientations. Here we present a novel phenomenon, applicable to both the classical and quantum regimes, where two one-dimensional localized periodic patterns with the same period interfere to create fringes with anomalous periodicity. We analyze the effect theoretically and demonstrate it with atomic matter waves. When a central parameter of the system is scanned continuously, we observe a discontinuous but piecewise-rigid periodicity of the resulting fringes. We show that this is a universal phenomenon that emerges from a superposition of two spatially shifted localized periodic patterns of any source or nature when they interfere with a global phase difference. The rigidity of the spectrum becomes even more robust for a coherent superposition of non-overlapping wavepackets, although the conventional interferometric visibility drops to zero. The effect is expected to appear in space and time, as well as in the momentum distribution of quantum particles.

We have investigated the Moiré interference in pinhole based fingerprint on display technology. The origin of the phenomenon is identified as the interference between discrete OLED pixels and the object outline. A countermeasure is given to overcome its impact on the identification of miniature fingerprint features. [ABSTRACT FROM AUTHOR]

Digital halftoning is an essential part of the process for printing color, continuous-tone content. Traditionally, the highest quality has been achieved with analog, offset lithographic presses, using color screen sets that yield periodic, clustered-dot halftone patterns. Increasingly, these systems are being supplanted by digital presses that are based on either electrophotographic or inkjet marking processes. Due to the inherent instability of the electrophotographic marking process, periodic, clustered-dot halftone patterns are also widely used with such presses. However, digital presses have much lower resolution than their analog counterparts. Simply mimicking the traditional screen designs used with commercial, offset presses will result in halftone patterns that are more susceptible to moire due to the interaction between the periodic patterns used to render the different color channels. This causes instability in the printed colors. The moire can be reduced by increasing the frequency of the halftone patterns. But this may make the print appear grainier than its analog counterpart. In this paper, we introduce a principled design procedure that allows one to design color screen sets that generate periodic, clustered-dot halftone patterns that improve color stability without increasing graininess. We present experimental results to support the benefits of our new color screen set design framework. [ABSTRACT FROM AUTHOR]

Residual deformation evaluation of underfill (UF) materials in flip chips is crucial to improve the reliability of electronic packages. In this study, we propose to evaluate the residual thermal strain distributions using an inverse method based on the sampling moiré technique. Even if a grid pattern is fabricated on the specimen at room temperature, the residual strain distributions at an arbitrary temperature relative to the specimen formation temperature can be successfully calculated. The residual strain distributions relative to the free contraction state at an arbitrary temperature can also be measured when the coefficient of thermal expansion is available. A thermal chamber for flip chips was designed under a laser scanning microscope. Using the proposed method, the normal, shear and principal internal strain distributions and deformation characteristics of two kinds of UFs in flip chips were investigated relative to 150 °C. The strains of the UF with low glass transition temperature (UF-A) concentrate near the die material, especially at the die corner, while the strain concentration of the underfill with high glass transition temperature (UF-B) mainly occurs at the die corner and the buffer layer. The maximum principal strain of UF-A is greater than that of UF-B around the die corner. The residual maximum principal strain distributions relative to the free contraction state at 25 °C were compared with the simulation results by the finite element method. The residual strain distribution trends from experiments are consistent with those from simulations. [ABSTRACT FROM AUTHOR]

We introduce a general framework to study moiré structures of two-dimensional Van der Waals magnets using continuum field theory. The formalism eliminates quasi periodicity and allows a full understanding of magnetic structures and their excitations. In particular, we analyze in detail twisted bi layers of N ́eelantiferromagnets on the honeycomb lattice. A rich phase diagram with noncollinear twisted phases is obtained, and spin waves are further calculated. Direct extensions to zigzag anti-ferromagnets and ferromagnets are also presented. We anticipate the results and formalism demonstrated to lead to abroad range of applications to both fundamental research and experiments. [ABSTRACT FROM AUTHOR]

Noncommensurate 2D interfaces hold great promise toward low friction and nanoelectromechanical applications. For identical constituents, the crystals interlock at specific rotational configurations leading to high barriers for slide. In contrast, nonidentical constituents comprising different lattice parameters should enable robust superlubricity for all rotational configurations. This is however not the case for gold–graphite interfaces, as both theory and experiments show scaling behavior of the sliding force as a function of the interface contact area. By simulating the sliding force for gold–graphite interfaces, this work shows that the origin for high force barriers at special angular configurations is a result of commensurability between the moiré structure and the contact geometry. Consequently, this paper suggests new geometries that can potentially overcome such commensurability effects to enable robust superlubricity. [ABSTRACT FROM AUTHOR]

The role of moiré graphene superstructures in favoring confined adsorption of different metal atoms is an intriguing problem not yet completely solved. Graphene (G) grown on Ni(100) forms a striped moiré pattern of valleys, where G approaches the nickel substrate and interacts with it rather strongly, and ridges, where G stays far away from the substrate and acts almost free-standing. Combining density functional theory (DFT) calculations and scanning-tunneling microscopy (STM) measurements, we show that this peculiar moiré constitutes a regular nanostructured template on a 2D support, confining in 1D trails single metal atoms and few atoms clusters. DFT calculations show that the confinement is selective and highly dependent on the atomic species, with some species preferring to adsorb on ridges and the other showing preference for valleys. Co and Au adsorbates, for instance, have opposite behavior, as predicted by DFT and observed by STM. The origin of such disparate behavior is traced back to the electrostatic interaction between the charged adsorbate and the nickel surface. Moreover, the selectivity is not restricted to the adsorption process only, but persists as adsorbate starts its diffusion, resulting in unidirectional mass transport on a continuous 2D support. These findings hold great promise for exploiting tailored nanostructured templates in a wide range of potential applications involving mass transport along element-specific routes. [Display omitted] [ABSTRACT FROM AUTHOR]

Twisted double bilayer graphene (tDBG) has emerged as a rich platform for studying strongly correlated and topological states, as its flat bands can be continuously tuned by both a perpendicular displacement field and a twist angle. Here, we construct a phase diagram representing the correlated and topological states as a function of these parameters, based on measurements of over a dozen tDBG devices encompassing two distinct stacking configurations. We find a hierarchy of symmetry-broken states that emerge sequentially as the twist angle approaches an apparent optimal value of θ ≈ 1.34°. Nearby this angle, we discover a symmetry-broken Chern insulator (SBCI) state associated with a band filling of 7/2 as well as an incipient SBCI state associated with 11/3 filling. We further observe an anomalous Hall effect at zero field in all samples supporting SBCI states, indicating spontaneous time-reversal symmetry breaking and possible moiré unit cell enlargement at zero magnetic field.

This is an update of a previous review (Naumis et al 2017 Rep. Prog. Phys. 80 096501). Experimental and theoretical advances for straining graphene and other metallic, insulating, ferroelectric, ferroelastic, ferromagnetic and multiferroic 2D materials were considered. We surveyed (i) methods to induce valley and sublattice polarisation ( P ) in graphene, (ii) time-dependent strain and its impact on graphene's electronic properties, (iii) the role of local and global strain on superconductivity and other highly correlated and/or topological phases of graphene, (iv) inducing polarisation P on hexagonal boron nitride monolayers via strain, (v) modifying the optoelectronic properties of transition metal dichalcogenide monolayers through strain, (vi) ferroic 2D materials with intrinsic elastic ( σ ), electric ( P ) polarisation under strain, as well as incipient 2D multiferroics and (vii) moiré bilayers exhibiting flat electronic bands and exotic quantum phase diagrams, and other bilayer or few-layer systems exhibiting ferroic orders tunable by rotations and shear strain. The update features the experimental realisations of a tunable two-dimensional Quantum Spin Hall effect in germanene, of elemental 2D ferroelectric bismuth, and 2D multiferroic NiI M ) polarisation under strain, as well as incipient 2D multiferroics and (vii) moiré bilayers exhibiting flat electronic bands and exotic quantum phase diagrams, and other bilayer or few-layer systems exhibiting ferroic orders tunable by rotations and shear strain. The update features the experimental realisations of a tunable two-dimensional Quantum Spin Hall effect in germanene, of elemental 2D ferroelectric bismuth, and 2D multiferroic NiI 2 . The document was structured for a discussion of effects taking place in monolayers first, followed by discussions concerning bilayers and few-layers, and it represents an up-to-date overview of exciting and newest developments on the fast-paced field of 2D materials., (Creative Commons Attribution license.)

Two-dimensional Mott materials have recently been reported in the dichalcogenide family with high potential for Mottronic applications. Nevertheless, their widespread use as a single or few layers is hampered by their limited device integration resulting from their growth on graphene, a metallic substrate. Here, we report on the fabrication of 1T-TaSe 2 monolayers grown by molecular beam epitaxy on semiconducting gallium phosphide substrates. At the nanoscale, the charge density wave reconstruction and a moiré pattern resulting from the monolayer interaction with the substrate are observed by scanning tunneling microscopy. The fully open gap unveiled by tunneling spectroscopy, which can be further manipulated by the proximity of a metal tip, is confirmed by transport measurements from micrometric to millimetric scales, demonstrating a robust Mott insulating phase at up to 400 K.

Synthetic materials and heterostructures obtained by the controlled stacking of exfoliated monolayers are emerging as attractive functional materials owing to their highly tunable properties. We present a detailed scanning tunneling microscopy and spectroscopy study of single layer MoS 2 -on-gold heterostructures as a function of the twist angle. We find that their electronic properties are determined by the hybridization of the constituent layers and are modulated at the moiré period. The hybridization depends on the layer alignment, and the modulation amplitude vanishes with increasing twist angle. We explain our observations in terms of a hybridization between the nearest sulfur and gold atoms, which becomes spatially more homogeneous and weaker as the moiré periodicity decreases with increasing twist angle, unveiling the possibility of tunable hybridization of electronic states via twist angle engineering.