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In this paper, we delve into recent advancements in the fabrication of high-performance n-type oxide semiconductor thin-film transistors (TFTs) through crystallization pathways. The last two decades have seen a rapid proliferation of applications employing amorphous oxide semiconductor (AOS) transistors, from display technologies to semiconductor chips. However, with the growing demand for ultra-high-resolution organic light-emitting diodes, flexible electronics, and next-generation electronic devices, interest in oxide semiconductors exhibiting high mobility and exceptional reliability has grown. However, AOS TFTs must balance the competing demands of mobility and stability. Here, we explore various crystallization methods of enhancing the device performance of oxide semiconductors, alongside the intrinsic challenges associated with crystalline oxide semiconductors. Our discussion highlights the potential solutions presented by controlling crystalline quality in terms of grain size and orientation. We propose that advanced manufacturing techniques coupled with a profound understanding of materials science are needed to effectively address these issues. [ABSTRACT FROM AUTHOR]

Harmonic motion is a significant topic in undergraduate lectures for university physics students. A typical example, presented in lectures around the globe, is the motion of a mass at the end of a spring. It should be emphasized that the harmonic motion in the aforementioned case is just an approximation for small displacements. However, the value of this example for teaching purposes is undeniable, if used properly. Its significance is connected to the adoption of an analytical way of thinking by the students that can help them to not only memorize isolated fragments but to really understand the topic in depth. As a result, the students should be able to apply a similar analysis to new and unsolved problems and explore unknown physical systems using basic theoretical tools. To move in the right direction, a new example is presented in this paper: the motion of a rigid sphere on an elastic half space. This phenomenon is extremely complicated. However, in this paper it is shown that for a specific range of values, this motion can be approximated to harmonic motion. This fact will significantly help students to learn how to resolve unknown problems and tasks using their knowledge. In addition, the analysis provided by this paper can be used as an alternative and simpler solution for data processing in nanoindentation experiments. As a result, it can be used as a valuable tool not only for undergraduate physics students but also for young researchers in the fields of nanotechnology and materials science. [ABSTRACT FROM AUTHOR]

Machine learning applications in materials science are often hampered by shortage of experimental data. Integration with external datasets from past experiments is a viable way to solve the problem. But complex calibration is often necessary to use the data obtained under different conditions. In this paper, we present a novel calibration-free strategy to enhance the performance of Bayesian optimization with preference learning. The entire learning process is solely based on pairwise comparison of quantities (i.e., higher or lower) in the same dataset, and experimental design can be done without comparing quantities in different datasets. We demonstrate that Bayesian optimization is significantly enhanced via data integration for organic molecules and inorganic solid-state materials. Our method increases the chance that public datasets are reused and may encourage data sharing in various fields of physics. [ABSTRACT FROM AUTHOR]

With recent developments in direct imaging techniques using x-ray and neutron imaging, there is an increasing need for efficient test setups to study the mechanical and/or transport behavior of porous rocks. Bespoke designs from commercial suppliers are expensive and often difficult to modify. This paper presents a novel design of a portable triaxial cell for imaging deformation (and a suggested adaptation to introduce fluid transport) through rocks/sand/soil under the triaxial states of stress representative of those encountered in the case of groundwater aquifers or subsurface hydrocarbon reservoirs. The design philosophy and the parameters are detailed so that interested researchers can use this experimental setup as a template to design and modify triaxial cells to suit their own experimental requirements. The design has been used in two imaging beamlines: Imaging and Material Science & Engineering (IMAT), ISIS facility, Harwell, Oxfordshire, UK, and BT2 of the National Institute of Standards and Technology Center for Neutron Research, Gaithersburg, MD, USA. The mass attenuation coefficients extracted from the 2D radiograms of the triaxial cell were compared with those reported in the literature. Further suggestions for the adaptation of the triaxial cells for studying the mechanics of deformation and fracture in rocks are included. [ABSTRACT FROM AUTHOR]

Two-dimensional materials with a sheet structure have excellent optical, electrical and mechanical properties, and have attracted much attention in recent years, especially In2Se3 (the N-type semiconductor compound), which has a rapid development in the fields of materials science and optical communication. In this paper, the nonlinear saturation absorption characteristics of In2Se3 are studied. The In2Se3 nanosheet dispersion can be used in ultrafast photonics applications. The nonlinear absorption is measured by power dependent method, and the modulation depth and saturation intensity are 3.8% and 246.6 MW cm−2, respectively. More importantly, In2Se3 is used as a saturable absorber (SA) in a passively mode-locked erbium-doped fiber laser. The proposed mode-locked fiber laser is demenstrated with a center wavelength of 1529.4 nm, a fundamental frequency of 5.9 MHz, a spectral width of 3.96 nm, a pulse width of 1.38 ps, and a signal-to-noise ratio of 55 dB. For the first time, harmonic mode-locking with a high-repetition rate of 431 MHz is achieved when the pump power is 360 mW corresponding to 73rd-order harmonic mode locking. It can be seen that In2Se3 is indeed a new excellent photonic material, which can be used in fiber optic communication, SAs photonics, laser material processing and light modulators. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "High Spin Polarization in All-3d-Metallic Heusler Compounds: The Case of Fe2CrZ and Co2CrZ (Z=Sc, Ti, V)" published in the Journal of Physics D: Applied Physics in 2019. The correction addresses errors in the caption of figure 4 and the first paragraph of subsection 3.3. The errors are related to the representation of the bands and the number of electrons in the minority-spin states. The correction does not affect the final conclusions of the paper. [Extracted from the article]

BiFeO3 has a complex phase diagram as function of both strain and temperature, undergoing a morphotropic phase transformation under large compressive strain. Epitaxial films, grown by pulsed laser deposition, are ideal for the study of the intricate phase coexistence between multiple polymporphs. Three polymorphs have been identified in the literature. They are carefully described in this paper (labelled R′, T′, and S′). As both ferroelectric and magnetic properties are typically strongly linked to structural distortions, the structural, ferroelectric and magnetic transition temperatures are expected to differ between the R′, T′ and S′ polymorphs. In this paper we present a complete strain–temperature phase diagram for each of the polymorphs. [ABSTRACT FROM AUTHOR]

We synthesized a new nanocomposite bearing nitrogen-doped graphene as a carbon additive to the nickel oxide nanoparticles-titanium dioxide nanotubes heterojunction. The main purpose was the comparison of its structural and electronic properties, hence potential applications, with its undoped, reduced graphene oxide (GO) homolog. The beneficial effect of graphene on TiO2 heterojunctions is an accepted fact in the materials science field, mainly in favor of the nitrogen-doped one. Our data show that both graphenes have little influence on the band offset values of the NiO–TiO2 heterojunction. Still, the presence of reduced, undoped GO allows an improved electron transfer process from titania, causing a better charge carriers' separation. This correlates well with their observed photocatalytic activity under visible light exposure, for the degradation of four emerging contaminant pollutants (amoxicillin, acetaminophen, ibuprofen, and β -estradiol). In addition, the band alignment of the NiO–TiO2 heterojunction with graphenes, and the corrected thermodynamic potentials of the organic pollutants explain well the observed photocatalytic behavior. [ABSTRACT FROM AUTHOR]

Recent advances in materials science, device designs and advanced fabrication technologies have enabled the rapid development of transient electronics, which represents a class of devices or systems that their functionalities and constitutions can be partially/completely degraded via chemical reaction or physical disintegration over a stable operation. Therefore, numerous potentials, including zero/reduced waste electronics, bioresorbable electronic implants, hardware security, and others, are expected. In particular, transient electronics with biocompatible and bioresorbable properties could completely eliminate the secondary retrieval surgical procedure after their in-body operation, thus offering significant potentials for biomedical applications. In terms of material strategies for the manufacturing of transient electronics, silicon nanomembranes (SiNMs) are of great interest because of their good physical/chemical properties, modest mechanical flexibility (depending on their dimensions), robust and outstanding device performances, and state-of-the-art manufacturing technologies. As a result, continuous efforts have been made to develop silicon-based transient electronics, mainly focusing on designing manufacturing strategies, fabricating various devices with different functionalities, investigating degradation or failure mechanisms, and exploring their applications. In this review, we will summarize the recent progresses of silicon-based transient electronics, with an emphasis on the manufacturing of SiNMs, devices, as well as their applications. After a brief introduction, strategies and basics for utilizing SiNMs for transient electronics will be discussed. Then, various silicon-based transient electronic devices with different functionalities are described. After that, several examples regarding on the applications, with an emphasis on the biomedical engineering, of silicon-based transient electronics are presented. Finally, summary and perspectives on transient electronics are exhibited. [ABSTRACT FROM AUTHOR]

In this paper, we present the first implementation of the novel localization relationships, formulated in the recently developed mathematical framework called materials knowledge systems (MKS), into a finite element tool to enable hierarchical multiscale materials modeling. More specifically, the MKS framework was successfully integrated with the commercial finite element (FE) package ABAQUS through a user material subroutine. In this new MKS-FE approach, information is consistently exchanged between the microscale and macroscale levels in a fully coupled manner. The viability and computational advantages of the MKS-FE approach are demonstrated through a simple case study involving the elastic deformation of a component made from a composite material. It will be shown that the MKS-FE approach can be used to accurately capture the microscale spatial distributions of the stress or strain fields at each material point in the macroscale FE model with substantial savings in the computational cost. [ABSTRACT FROM AUTHOR]

Materials engineering on the nanoscale by precise control of growth parameters can lead to many unusual and fascinating physical properties. The development of pulsed laser deposition (PLD) 25 years ago has enabled atomistic control of thin films and interfaces and as such it has contributed significantly to advances in fundamental material science. One application area is the research field of spintronics, which requires optimized nanomaterials for the generation and transport of spin-polarized carriers. The mixed-valence manganite La1−xSrxMnO3 (LSMO) is an interesting material for spintronics due to its intrinsic magnetoresistance properties, electric-field tunable metal–insulator transitions, and half-metallic band structure. Studies on LSMO thin-film growth by PLD show that the deposition temperature, oxygen pressure, laser fluence, strain due to substrate–film lattice mismatch and post-deposition annealing conditions significantly influence the magnetic and electrical transport properties of LSMO. For spintronic structures, robust ferromagnetic exchange interactions and metallic conductivity are desirable properties. In this paper, we review the physics of LSMO thin films and the important role that PLD played in advancing the field of LSMO-based spintronics. Some specific application areas including magnetic tunnel junctions, multiferroic tunnel junctions and organic spintronic devices are highlighted, and the advantages, drawbacks and opportunities of PLD-grown LSMO for next-generation spintronic devices are discussed. [ABSTRACT FROM AUTHOR]

Metal plasticity is governed by the motion of dislocations, and predicting the interactions and resulting collective motion of dislocations is a major task in understanding and modeling plastically deforming materials. This task has, despite all the efforts and advances of the last few decades, not yet been fully accomplished. The reason for this is that discrete models which describe the dislocation system with high accuracy are only computationally feasible for small systems, small strains, and high strain rates. Classical continuum models do not suffer from these restrictions but lack sufficiently detailed information about dislocation microstructure. In this paper we present the steps that are needed for averaging systems of discrete dislocations toward a continuous and hence more efficient representation. Our main emphasis lies on investigating the effects of averaging on the description of stress fields and dislocation interactions. We show how the evolution of continuous dislocation fields can then be appropriately described by a dislocation density-based model and validate our results by comparison with discrete dislocation dynamic simulations. [ABSTRACT FROM AUTHOR]

The treatment of atomistic scale interactions via molecular dynamics simulations has recently found favour for multiscale modelling within engineering. The estimation of stress at a continuum point on the atomistic scale requires a pre-defined kernel function. This kernel function derives the stress at a continuum point by averaging the contribution from atoms within a region surrounding the continuum point. This averaging volume, and therefore the associated stress at a continuum point, is highly dependent on the bandwidth and shape of the kernel. In this paper we propose an effective and entirely data-driven strategy for simultaneously computing the optimal shape and bandwidth for the kernel. We thoroughly evaluate our proposed approach on copper using three classical elasticity problems. Our evaluation yields three key findings: firstly, our technique can provide a physically meaningful estimation of kernel bandwidth; secondly, we show that a uniform kernel is preferred, thereby justifying the default selection of this kernel shape in future work; and thirdly, we can reliably estimate both of these attributes in a data-driven manner, obtaining values that lead to an accurate estimation of the stress at a continuum point. [ABSTRACT FROM AUTHOR]

The macroscopic properties of metallic materials depend on the state of the grain microstructure. Recrystallization acts as one of the most important mechanisms in the evolution of the microstructure and hence also of the macroscopic properties. This paper presents a mesoscale model of microstructure evolution due to recrystallization, based on a level set formulation employed in a finite element setting. The use of level sets to represent grains and grain boundaries in polycrystal microstructures is a relatively recent development in computational materials science and the present contribution suggests new methodologies such as interface reconstruction, allowing for example boundary conditions to be prescribed along grain boundary interfaces and distinct localization and representation of grain boundary junctions. Polycrystal plasticity is modeled by considering the evolution of dislocation density in the individual crystals. The influence of grain boundaries on dislocation accumulation is captured in the model, causing the formation of dislocation density gradients within the grains. The model is used in simulations of dynamic recrystallization, taking pure copper as example material. It is shown that the proposed model captures the salient features of dynamic recrystallization during thermomechanical materials processing. [ABSTRACT FROM AUTHOR]

Understanding the applicability and limitations of electronic-structure methods needs careful and efficient comparison with accurate reference data. Knowledge of the quality and errors of electronic-structure calculations is crucial to advanced method development, high-throughput computations and data analyses. In this paper, we present a main-group test set for computational materials science and engineering (MSE), that provides accurate and easily accessible crystal properties for a hierarchy of exchange-correlation approximations, ranging from the well-established mean-field approximations to the state-of-the-art methods of many-body perturbation theory. We consider cohesive energy, lattice constant and bulk modulus of a set of materials that representatives for the first- and second-row elements and their binaries with cubic crystal structures and various bonding characters. A strong effort is made to achieve high numerical accuracy for cohesive properties as calculated using the local-density approximation (LDA), several generalized gradient approximations (GGAs), meta-GGAs and hybrids in all-electron resolution, and the second-order Møller–Plesset perturbation theory (MP2) and the random-phase approximation (RPA) both with frozen-core approximation based on all-electron Hartree–Fock, PBE and/or PBE0 references. This results in over 10 000 calculations, which record a comprehensive convergence test with respect to numerical parameters for a wide range of electronic-structure methods within the numerical atom-centered orbital framework. As an indispensable part of the MSE test set, a web site is established http://mse.fhi-berlin.mpg.de. This not only allows for easy access to all reference data but also provides user-friendly graphical tools for post-processing error analysis. [ABSTRACT FROM AUTHOR]

On a microscopic scale, fresh cement paste is composed of random packing of irregular cement particles, and their initial packing behavior plays an important role in microstructural evolution. The preponderance of previous works has focused on the microstructure model by random packing of three-dimensional spheroidal particles, and little is known about non-spheroidal particles. In this paper, a modified cement particle size distribution function is used to facilitate the particle size distribution of convex polyhedral cement particles. Based on an overlapping detection algorithm, the microstructure model of fresh cement paste is simulated by the random sequential packing of Platonic cement particles of various sizes. Applying stereological tools and the serial sectioning analysis technique, the modeling microstructure composed of polydispersed Platonic cement particles is characterized and compared with that of ellipsoidal cement particles with various aspect ratios. The statistical results are investigated to evaluate the influence of cement particle shape on the microstructure of fresh cement paste. Finally, with the derived experimental and numerical results of microstructural parameters, the reliability of the statistical results is verified. [ABSTRACT FROM AUTHOR]

It has been 30 years since the scanning tunnelling microscope (STM) was invented by G Binnig and H Rohrer. Rapid developments have made STM increasingly powerful as an extremely versatile technique for many disciplines in condensed matter physics, chemistry, biology and other areas. As a state-of-the-art growth method, molecular beam epitaxy (MBE) is a gifted technique for epitaxial growth with atomic-level control. In this paper, by giving several examples, we will show that an STM-MBE combined system is more powerful and unique for studies on low-dimensional and new functional materials. [ABSTRACT FROM AUTHOR]

A key concept in material science is the relationship between the Bravais lattice, the reciprocal lattice and the resulting Brillouin zones (BZ). These zones are often complicated shapes that are hard to construct and visualise without the use of sophisticated software, even by professional scientists. We have used a simple sorting algorithm to construct BZ of any order for a chosen Bravais lattice that is easy to implement in any scientific programming language. The resulting zones can then be visualised using freely available plotting software. This method has pedagogical value for upper-level undergraduate students since, along with other computational methods, it can be used to illustrate how constant-energy surfaces combine with these zones to create van Hove singularities in the density of states. In this paper we apply our algorithm along with the empirical pseudopotential method and the 2D equivalent of the tetrahedron method to show how they can be used in a simple software project to investigate this interaction for a 2D crystal. This project not only enhances students’ fundamental understanding of the principles involved but also improves transferable coding skills. [ABSTRACT FROM AUTHOR]

Leveraging generative Artificial Intelligence (AI), we have transformed a dataset comprising 1000 scientific papers focused on biological materials into a comprehensive ontological knowledge graph. Through an in-depth structural analysis of this graph, we have calculated node degrees, identified communities along with their connectivities, and evaluated clustering coefficients and betweenness centrality of pivotal nodes, uncovering fascinating knowledge architectures. We find that the graph has an inherently scale-free nature, shows a high level of connectedness, and can be used as a rich source for downstream graph reasoning by taking advantage of transitive and isomorphic properties to reveal insights into unprecedented interdisciplinary relationships that can be used to answer queries, identify gaps in knowledge, propose never-before-seen material designs, and predict material behaviors. Using a large language embedding model we compute deep node representations and use combinatorial node similarity ranking to develop a path sampling strategy that allows us to link dissimilar concepts that have previously not been related. One comparison revealed detailed structural parallels between biological materials and Beethoven’s 9th Symphony, highlighting shared patterns of complexity through isomorphic mapping. In another example, the algorithm proposed an innovative hierarchical mycelium-based composite based on integrating path sampling with principles extracted from Kandinsky’s ‘Composition VII’ painting. The resulting material integrates an innovative set of concepts that include a balance of chaos and order, adjustable porosity, mechanical strength, and complex patterned chemical functionalization. We uncover other isomorphisms across science, technology and art, revealing a nuanced ontology of immanence that reveal a context-dependent heterarchical interplay of constituents. Because our method transcends established disciplinary boundaries through diverse data modalities (graphs, images, text, numerical data, etc), graph-based generative AI achieves a far higher degree of novelty, explorative capacity, and technical detail, than conventional approaches and establishes a widely useful framework for innovation by revealing hidden connections.

In 1990, the journal Nanotechnology was the first academic publication dedicated to disseminating the results of research in what was then a new field of scientific endeavour. To celebrate the 20th volume of Nanotechnology, we are publishing a special issue of top research papers covering all aspects of this multidisciplinary science, including biology, electronics and photonics, quantum phenomena, sensing and actuating, patterning and fabrication, material synthesis and the properties of nanomaterials. In the early 1980s, scanning probe microscopes brought the concepts of matter and interactions at the nanoscale into visual reality, and hastened a flurry of activity in the burgeoning new field of nanoscience. Twenty years on and nanotechnology has truly come of age. The ramifications are pervasive throughout daily life in communication, health care and entertainment technology. For example, DVDs have now consigned videotapes to the ark and mobile phones are as prevalent as house keys, and these technologies already look set to be superseded by internet phones and Blu-Ray discs. Nanotechnology has been in the unique position of following the explosive growth of this discipline from its outset. The surge of activity in the field is notable in the number of papers published by the journal each year, which has skyrocketed. The journal is now published weekly, publishing over 1400 articles a year. What is more, the quality of these articles is also constantly improving; the average number of citations to articles within two years of publication, quantified by the ISI impact factor, continues to increase every year. The rate of activity in the field shows no signs of slowing down, as is evident from the wealth of great research published each week. The aim of the 20th volume special issue is to present some of the very best and most recent research in many of the wide-ranging fields covered by the journal, a celebration of the present state of play in nanotechnology and a stimulating glimpse of future directions in the field. [ABSTRACT FROM AUTHOR]

Nb3Sn (TC ≈ 18 K and HSh ≈ 400 mT) is a prospective material to replace Nb (TC ≈ 9 K and Hsh ≈ 200 mT) in SRF accelerator cavities for significant cost reduction and performance enhancement. Because of its material properties, Nb3Sn is best employed as a thin film (coating) inside an already built RF cavity structure. A particular test cavity noted as C3C4 was a 1.5 GHz single-cell Nb cavity, coated with Nb3Sn using Sn vapor diffusion process at Jefferson Lab. Cold measurements of the coated cavity indicated the superconducting transition temperature of about 18 K. Subsequent RF measurements indicated field-dependent surface resistance both at 4.3 and 2.0 K. After initial cold measurements, the cavity RF loss distribution was studied with a thermometry mapping system. Loss regions were identified with thermometry and were cut out for material analysis. The presence of significantly thin patchy regions and other carbon-rich defects is associated with strong local field-dependent surface resistance. This paper summarizes RF and thermometry results correlated with material science findings. [ABSTRACT FROM AUTHOR]

The investigation of superintense laser-driven ion sources and their potential applications offers unique opportunities for multidisciplinary research. Plasma physics can be combined with materials and nuclear science, radiation detection and advanced laser technology, leading to novel research challenges of great fundamental and applicative interest. In this paper we present interesting and comprehensive results on nanostructured low density (near-critical) foam targets for TW and PW-class lasers, obtained in the framework of the European Research Council ENSURE project. Numerical simulations and experimental activities carried out at 100 s TW and PW-class laser facilities have shown that targets consisting of a solid foil coated with a nanostructured low-density (near-critical) foam can lead to an enhancement of the ion acceleration process. This stimulated a thorough numerical investigation of superintense laser-interaction with nanostructured near-critical plasmas. Thanks to a deep understanding of the foam growth process via the pulsed laser deposition technique and to the complementary capabilities of high-power impulse magnetron sputtering, advanced multi-layer targets based on near-critical films with carefully controlled properties (e.g. density gradients over few microns length scales) can now be manufactured, with applications outreaching the field of laser-driven ion acceleration. Additionally, comprehensive numerical and theoretical work has allowed the design of dedicated experiments and a realistic table-top apparatus for laser-driven materials irradiation, ion beam analysis and neutron generation, that exploit a double-layer target to reduce the requirements for the laser system. [ABSTRACT FROM AUTHOR]

The atomic force microscope (AFM) and related scanning probe microscopes have become resourceful tools to study cells, supramolecular assemblies and single biomolecules, because they allow investigations of such structures in native environments. Quantitative information has been gathered about the surface structure of membrane proteins to lateral and vertical resolutions of 0.5 nm and 0.1 nm, respectively, about the forces that keep protein-protein and protein-nucleic acid assemblies together as well as single proteins in their native conformation, and about the nanomechanical properties of cells in health and disease. Such progress has been achieved mainly because of constant development of AFM instrumentation and sample preparation methods. This special issue of Nanotechnology presents papers from leading laboratories in the field of nanobiology, covering a wide range of topics in the form of original and novel scientific contributions. It addresses achievements in instrumentation, sample preparation, automation and in biological applications. These papers document the creativity and persistence of researchers pursuing the goal to unravel the structure and dynamics of cells, supramolecuar structures and single biomolecules at work. Improved cantilever sensors, novel optical probes, and quantitative data on supports for electrochemical experiments open new avenues for characterizing biological nanomachines down to the single molecule. Comparative measurements of healthy and metastatic cells promise new methods for early detection of tumors, and possible assessments of drug efficacy. High-speed AFMs document possibilities to monitor crystal growth and to observe large structures at video rate. A wealth of information on amyloid-type fibers as well as on membrane proteins has been gathered by single molecule force spectroscopy--a technology now being automated for large-scale data collection. With the progress of basic research and a strong industry supporting instrumentation development by improving robustness and reliability and making new instruments available to the community, nanobiology has the potential to develop into a field with great impact on our understanding of the complexity of life, and to provide a major contribution to human health. This special issue of Nanotechnology on nanobiology would not have been possible without the highly professional support from Nina Couzin, Amy Harvey and the Nanotechnology team at IOP Publishing. We are thankful for their most constructive and effective help in pushing the project forward. We are also thankful to all the authors who have contributed with excellent original articles, as well as to the referees who have helped to make this special issue such an insightful document of a rapidly moving field. [ABSTRACT FROM AUTHOR]

Results from molecular dynamics simulations often need to be further processed to understand the physics on a larger scale. This paper considers the definitions of momentum and energy fluxes obtained from a control-volume approach. To assess the validity of these defined quantities, two consistency criteria are proposed. As examples, the embedded atom potential and the Tersoff potential are considered. The consistency is verified using analytical and numerical methods. [ABSTRACT FROM AUTHOR]

The accuracy of molecular dynamics simulation highly depends on the reliability of the empirical potential that it uses. Atomistic simulations of ZnS have attracted a lot of attention in the past few decades due to the technological importance of this material as a semiconductor and the main resource of world zinc production. Although multiple empirical potentials have been suggested for ZnS, there is no comprehensive study that compares the performance of these potentials. In this paper, we have reviewed five of the most used ZnS empirical potentials and have tested their performance in predicting different ZnS properties. Based on the obtained results, we provide recommendations for a proper empirical potential based on the application that the molecular mechanic simulation is aiming for. [ABSTRACT FROM AUTHOR]

Piezoelectric materials have been studied for nearly a century now. Initially employed in sonar technology, piezoelectric materials now have a vast set of applications including energy harvesting, sensing and actuation, and have found their way into our everyday lives. Piezoelectric material properties are being further enhanced to improve their performance and be used in novel applications. This review provides an overview of piezoelectric materials and offers a material science and fabrication perspective on progress towards the development of practical piezoelectric energy harvesters and sensors. Piezoelectric materials have been divided into the three following classes for this review: ceramics, polymers and composites. The prominent materials under each class are examined and compared, with a focus on their linear piezoelectric response in the d33 mode. The three classes of piezoelectric materials are also compared qualitatively for a range of metrics, and the applications that each material class are best suited for is discussed. Novel piezoelectric materials such as ferroelectrets and nanogenerator devices are also reviewed here. It is shown that ceramic piezoelectric materials have strong piezoelectric properties but are stiff and brittle, whereas polymer piezoelectric materials are flexible and lightweight but do not exhibit very good piezoelectric performance. Composite materials are concluded to possess the advantages of both ceramic and polymer materials, with room to tailor-fit properties by modifying the structure and composition. [ABSTRACT FROM AUTHOR]

In semiconductor lasers, quantum well intermixing (QWI) with high selectivity using dielectrics often results in lower quantum efficiency. In this paper, we report on an investigation regarding the effect of thermally induced dielectric stress on the quantum efficiency of quantum well structures in impurity-free vacancy disordering (IFVD) process using photoluminescence and device characterization in conjunction with microscopy. SiO2 and SixO2/SrF2 (versus SrF2) films were employed for the enhancement and suppression of QWI, respectively. Large intermixing selectivity of 75 nm (125 meV), consistent with the theoretical modeling results, with negligible effect on the suppression region characteristics, was obtained. SixO2 layer compensates for the large thermal expansion coefficient mismatch of SrF2 with the semiconductor and mitigates the detrimental effects of SrF2 without sacrificing its QWI benefits. The bilayer dielectric approach dramatically improved the dielectric–semiconductor interface quality. Fabricated high power semiconductor lasers demonstrated high quantum efficiency in the lasing region using the bilayer dielectric film during the intermixing process. Our results reveal that stress engineering in IFVD is essential and the thermal stress can be controlled by engineering the dielectric strain opening new perspectives for QWI of photonic devices. [ABSTRACT FROM AUTHOR]

Chalcogenide phase-change materials (PCMs), such as Ge-Sb-Te alloys, have shown outstanding properties, which has led to their successful use for a long time in optical memories (DVDs) and, recently, in non-volatile resistive memories. The latter, known as PCM memories or phase-change random access memories (PCRAMs), are the most promising candidates among emerging non-volatile memory (NVM) technologies to replace the current FLASH memories at CMOS technology nodes under 28 nm. Chalcogenide PCMs exhibit fast and reversible phase transformations between crystalline and amorphous states with very different transport and optical properties leading to a unique set of features for PCRAMs, such as fast programming, good cyclability, high scalability, multi-level storage capability, and good data retention. Nevertheless, PCM memory technology has to overcome several challenges to definitively invade the NVM market. In this review paper, we examine the main technological challenges that PCM memory technology must face and we illustrate how new memory architecture, innovative deposition methods, and PCM composition optimization can contribute to further improvements of this technology. In particular, we examine how to lower the programming currents and increase data retention. Scaling down PCM memories for large-scale integration means the incorporation of the PCM into more and more confined structures and raises materials science issues in order to understand interface and size effects on crystallization. Other materials science issues are related to the stability and ageing of the amorphous state of PCMs. The stability of the amorphous phase, which determines data retention in memory devices, can be increased by doping the PCM. Ageing of the amorphous phase leads to a large increase of the resistivity with time (resistance drift), which has up to now hindered the development of ultra-high multi-level storage devices. A review of the current understanding of all these issues is provided from a materials science point of view. [ABSTRACT FROM AUTHOR]

While several laboratories can produce 3D models of microstructure from serial sectioning or tomography, the more widespread practice is to attempt to infer 3D shapes from 2D sections of different orientations. We have developed a forward modeling approach that, given a 3D particle shape, produces statistically representative 2D sections whose projections are characterized by 2D moment invariants (MI). Since the sectioning plane is random, each particle will produce a statistical distribution of 2D moments and an ensemble of particles in a microstructure will produce its own characteristic distribution of 2D moments and can be used as a representation of the microstructure. This distribution can be represented as a point in a metric space. We use the Hellinger distance as the measure for this space, which allows us to quantify the similarity of two microstructures. Example applications include: determination of a 3D shape by computing the Hellinger distance between MI density maps derived from random 2D section micrographs and the density map database; automated detection and quantification of rafting in cuboidal microstructures; and quantitative comparison of pairs of microstructures. [ABSTRACT FROM AUTHOR]

This paper describes an electrochemical technique for growing adhesive copper oxide films on copper with attractive colors ranging from gold-brown to pearl with intermediate colors from red violet to gold green. The technique consists of anodically dissolving copper at transpassive potentials in hot sodium hydroxide, and then depositing brilliant color films of Cu2O onto the surface of copper after the anodic potential has been turned off. The color of the copper oxide film depends on the temperature, the anodic potential, the time t1 of polarization, and the time t2, which is the time of immersion after potential has been turned off. (At potentials lower than the transpassive region, that is, in the passive region, the oxide film is a dark gray or dark green matte with a blue powder hydroxide on the surface and it is not attractive.) The brilliant colored films were characterized using glancing angle x-ray diffraction, and the film was found to be primarily Cu2O. Cyclic voltammetry, chronopotentiometry, scanning electron microscopy, and x-ray photoelectron spectroscopy were also used to characterize these films. These techniques show that the different colors were due to differences in porosity and thickness rather than changes in composition. [ABSTRACT FROM AUTHOR]