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This paper presents a methodology for the physical analysis of defects on p-GaN power HEMTs that have been electrically stressed under DC surge or voltage switching stresses. The methodology includes a backside approach for sample preparation and defect localization. It is crucial to adapt the preparation process according to the position of the defect in the device structure (including metallurgy, dielectric layers, epitaxy, etc.), which depends on the type of stress applied. In our study of the reliability of the transistor under increased electrical stress in lifetime operation mode, failure analysis is used to identify the weakest areas in the design with respect to the type of stress applied. This paper presents a failure analysis consisting of techniques such as electrical characterization, photon emission microscopy and lock-in thermography for defect localization, focused ion beam slice and view, transmission electron microscopy analysis, and frontside conductive atomic force microscopy after immersion in hydrofluoric acid. [ABSTRACT FROM AUTHOR]

The field of energy storage and conversion materials has witnessed transformative advancements owing to the integration of advanced in situ characterization techniques. Among them, numerous real-time characterization techniques, especially in situ transmission electron microscopy (TEM)/scanning TEM (STEM) have tremendously increased the atomic-level understanding of the minute transition states in energy materials during electrochemical processes. Advanced forms of in situ/operando TEM and STEM microscopic techniques also provide incredible insights into material phenomena at the finest scale and aid to monitor phase transformations and degradation mechanisms in lithium-ion batteries. Notably, the solid–electrolyte interface (SEI) is one the most significant factors that associated with the performance of rechargeable batteries. The SEI critically controls the electrochemical reactions occur at the electrode–electrolyte interface. Intricate chemical reactions in energy materials interfaces can be effectively monitored using temperature-sensitive in situ STEM techniques, deciphering the reaction mechanisms prevailing in the degradation pathways of energy materials with nano- to micrometer-scale spatial resolution. Further, the advent of cryogenic (Cryo)-TEM has enhanced these studies by preserving the native state of sensitive materials. Cryo-TEM also allows the observation of metastable phases and reaction intermediates that are otherwise challenging to capture. Along with these sophisticated techniques, Focused ion beam (FIB) induction has also been instrumental in preparing site-specific cross-sectional samples, facilitating the high-resolution analysis of interfaces and layers within energy devices. The holistic integration of these advanced characterization techniques provides a comprehensive understanding of the dynamic changes in energy materials. This review highlights the recent progress in employing state-of-the-art characterization techniques such as in situ TEM, STEM, Cryo-TEM, and FIB for detailed investigation into the structural and chemical dynamics of energy storage and conversion materials. [ABSTRACT FROM AUTHOR]

In recent years, research on hyperdoped semiconductors has accelerated, displaying dopant concentrations far exceeding solubility limits to surpass the limitations of conventionally doped materials. Nitrogen defects in silicon have been extensively investigated for their unique characteristics compared to other pnictogen dopants. However, previous practical investigations have encountered challenges in achieving high nitrogen defect concentrations due to the low solubility and diffusivity of nitrogen in silicon, and the necessary non-equilibrium techniques, such as ion implantation, resulting in crystal damage and amorphisation. In this study, we present a single-step technique called high-pressure gas immersion excimer laser doping (HP-GIELD) to manufacture nitrogen-hyperdoped silicon. Our approach offers ultrafast processing, scalability, high control, and reproducibility. Employing HP-GIELD, we achieved nitrogen concentrations exceeding 6 at% (3.01 × 1021 at/cm3) in intrinsic silicon. Notably, nitrogen concentration remained above the liquid solubility limit to ~1 µm in depth. HP-GIELD's high-pressure environment effectively suppressed physical surface damage and the generation of silicon dangling bonds, while the well-known effects of pulsed laser annealing (PLA) preserved crystallinity. Additionally, we conducted a theoretical analysis of light-matter interactions and thermal effects governing nitrogen diffusion during HP-GIELD, which provided insights into the doping mechanism. Leveraging excimer lasers, our method is well-suited for integration into high-volume semiconductor manufacturing, particularly front-end-of-line processes. [ABSTRACT FROM AUTHOR]

Grain boundary plays a vital role in thermoelectric transports, leading to distinct properties between single crystals and polycrystals. Manipulating the grain boundary to realize good thermoelectric properties in polycrystals similar as those of single crystals is a long-standing task, but it is quite challenging. Herein, we develop a liquid-phase sintering strategy to successfully introduce Mg2Cu nano-sintering-aid into the grain boundaries of Mg3(Bi, Sb)2-based materials. The nano-aid helps to enlarge the average grain size to 23.7 μm and effectively scatter phonons, leading to excellent electrical transports similar as those of single crystals and ultralow lattice thermal conductivity as well as exceptional thermoelectric figure of merit (1.5 at 500 K) and conversion efficiency (7.4% under temperature difference of 207 K). This work provides a simple but effective strategy for the fabrication of high-performance polycrystals for large-scale applications. The authors develop a liquid-phase sintering strategy to effectively enlarge material's grain sizes, thereby achieving single crystal-like electronic transport properties in polycrystalline Mg3(Bi, Sb)2. [ABSTRACT FROM AUTHOR]

Dislocation motion, an important mechanism underlying crystal plasticity, is critical for the hardening, processing and application of a wide range of structural and functional materials. For decades, the movement of dislocations has been widely observed in crystalline solids under mechanical loading. However, the goal of manipulating dislocation motion via a non-mechanical field alone remains elusive. Here we present real-time observations of dislocation motion controlled solely by using an external electric field in single-crystalline zinc sulfide-the dislocations can move back and forth depending on the direction of the electric field. We reveal the non-stoichiometric nature of dislocation cores and determine their charge characteristics. Both negatively and positively charged dislocations are directly resolved, and their glide barriers decrease under an electric field, explaining the experimental observations. This study provides direct evidence of dislocation dynamics controlled by a non-mechanical stimulus and opens up the possibility of modulating dislocation-related properties., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

Carbon (C) is an important isovalent impurity in silicon (Si) that is inadvertently added in the lattice during growth. Germanium (Ge), tin (Sn), and lead (Pb) are isovalent atoms that are added in Si to improve its radiation hardness, which is important for microelectronics in space or radiation environments and near reactors or medical devices. In this work, we have employed density functional theory (DFT) calculations to study the structure and energetics of carbon substitutional-isovalent dopant substitutional CsDs (i.e., CsGes, CsSns and CsPbs) and carbon interstitial-isovalent dopant substitutional CiDs (i.e., CiGes, CiSns and CiPbs) defect pairs in Si. All these defect pairs are predicted to be bound with the larger isovalent atoms, forming stronger pairs with the carbon atoms. It is calculated that the larger the dopant, the more stable the defect pair, whereas the CsDs defects are more bound than the CiDs defects. [ABSTRACT FROM AUTHOR]

Ingots of highly doped silicon Si:P grown by Bridgman directional crystallization with a small (up to 5 at %) fraction of germanium impurity are studied. The main thermoelectric parameters of the material are measured in the temperature range from 50 to 800°C: Seebeck coefficient, electrical conductivity, and thermal conductivity. On the basis of measurement results, the thermoelectric figure of merit determining the efficiency of thermoelectric conversion was calculated. A study of the electrical properties shows that phosphorus from the SiP compound is incorporated into the lattice as a dopant which provides a high concentration of conduction electrons. Chemical analysis of the ingots shows the presence of additional background impurities in them, the concentration and composition of the impurities vary throughout the bulk of the sample. Despite the presence of impurities, the material demonstrates high thermoelectric characteristics, and the efficiency is at the level of the best world results. Further potential for optimization of thermoelectric characteristics owing to the possibility of forming a fine-grained polycrystalline structure is considered. [ABSTRACT FROM AUTHOR]

Defects and impurities play a fundamental role in semiconductors affecting their mechanical, optical, and electronic properties. Nitrogen (N) impurities are almost always present in a silicon (Si) lattice, either unintentionally, due to the growth and processing procedures, or intentionally, as a result of implantation. Nitrogen forms complexes with intrinsic defects (i.e., vacancies and self-interstitials) as well as with other impurities present in the Si lattice such as oxygen and carbon. It is, therefore, necessary to investigate and understand nitrogen-related defects, especially their structures, their energies, and their interaction with intrinsic point defects and impurities. The present review is focused on nitrogen-related defects (for example Ni, Ns, NiNi, NiNs, NsNs); nitrogen–self-interstitial and nitrogen-vacancy-related complexes (for example NsV, (NiNi)Sii, (NsNs)V); nitrogen–oxygen defects (for example NO, NO2, N2O, N2O2); more extended clusters such as VmN2On (m, n = 1, 2); and nitrogen–carbon defects (for example CiN and CiNO). Both experimental and theoretical investigations are considered as they provide complementary information. [ABSTRACT FROM AUTHOR]

This paper focuses on the research and development of high-purity germanium (HPGe) crystals for detector fabrication, specifically targeting applications in rare-event physics searches. The primary objective was to produce large-scale germanium crystals weighing >1 kg with a controlled diameter of ∼10 cm and an impurity range of approximately 10 10 /cm   3 . Ensuring structural integrity and excellent crystalline quality requires a thorough assessment of dislocation density, a critical aspect of the crystal development process. Dislocation density measurements play a crucial role in maximizing the sensitivity of HPGe detectors, and our findings confirmed that the dislocation density fell within acceptable ranges for detector fabrication. Additionally, this paper examines the segregation coefficient of various contaminants during the crystal development process. Comprehensive analysis of impurity segregation is essential for reducing contaminant quantities in the crystal lattice and customizing purification processes. This, in turn, minimizes undesired background noise, enhancing signal-to-noise ratios for rare-event physics searches and overall detector performance. The investigation included the segregation coefficients of three major acceptors and one donor in crystals grown at the University of South Dakota, providing valuable insights for optimizing crystal purity and detector efficiency. [ABSTRACT FROM AUTHOR]

The doped crystals of the Ge1–x–Six〈Ga〉 and Ge1–x–Six〈Sb〉 solid solutions have been prepared by the hybrid method. The Hall measurements have been carried out on the samples at room temperature, from which the distributions of gallium and antimony impurities along the prepared crystals of Ge1–x–Six〈Ga〉 and Ge1–x–Six〈Sb〉, respectively, have been determined experimentally. At the same time, in the Pfann approximation, the one-dimensional problem on the axial distribution of the gallium and antimony impurities in crystals of the Ge–Si solid solutions grown by the hybrid method has been solved. The results obtained demonstrate good agreement between experimental and calculated data. This fact allows us to conclude, that mathematical modeling gives an opportunity to control, over a wide range, the concentration profile of impurities in the Ge–Si crystals grown by this method by changing the starting concentrations of impurities and creating the respective gradient of temperature in the melt in the section of crystal growth by the directional constitutional supercooling of the melt method and the ratio of the replenishment and crystallization rates of the melt in the section of the homogeneous crystal growth. [ABSTRACT FROM AUTHOR]

One of the primary culprits for limiting the efficiency of multi-crystalline/polycrystalline silicon (mc/pc-Si)-based thin-film solar cells is interface and grain boundary (GB) recombination. In this work, a device simulation model for mc/pc-Si thin-film solar cells has been developed by considering multiple numbers of horizontal- and vertical-like GBs with Gaussian distributed energy levels of donor- and acceptor-like traps. Moreover, the Gaussian distribution of bulk and fixed energy level of interface defect density have been considered in this study. The performance parameters of the device, such as JSC, VOC, FF, and efficiency, have been studied by varying the grain size, interface trap density, and GB trap density. Results show that the grain size variation in the X-direction significantly impacts the device's performance compared to the grain size in the Z-direction. Results also show that increasing interface and GB trap density for both the donor- and acceptor-like traps significantly impacts the efficiency. However, the variation of donor-like trap density has more significant impact on the device's performance in contrast to the acceptor-like trap density. Therefore, optimizing these parameters is essential to enhance the performance of the device. Moreover, it is observed that the device's performance significantly depends on the thickness and doping concentration of the absorber layer. For an optimized absorber of thickness 0.5 µm and doping concentration of 1018 cm−3, the maximum efficiency of ~ 9.1% is obtained, which is an enhancement of > 200% from an experimentally reported result. The developed model is also verified with the available experimental results. [ABSTRACT FROM AUTHOR]

We report on the synthesis of tin(IV) nitride with spinel structure, γ-Sn3N4, from the elements at high pressures and temperatures using a laser-heated diamond anvil cell, and on the Rietveld refinement of the product structure. The procedure described here is, in our opinion, the most reliable method of obtaining high-purity nitrides which are thermodynamically stable only at high pressures. Raman spectroscopy and powder X-ray diffraction were used to characterize the synthesis products. Pressure dependences of the Raman-band frequencies of γ-Sn3N4 were measured and used to determine its average mode Grüneisen parameter, 〈γ〉 = 0.95. Using this value, we estimated the thermal-shock resistance of γ-Sn3N4 to be about half that of γ-Si3N4, which, in turn, is moderately surpassed by β-Si3N4, known to be highly thermal-shock resistant. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 1)'. [ABSTRACT FROM AUTHOR]

The evolution of the dislocation density during Czochralski growth is computed by the combination of global thermal calculations and local computation of the stress and dislocation density in the crystal. The global simulation was performed using the open-source software Elmer (version 8.4) and the local simulation with the open-source software MACPLAS (version of 23.1.2023). Interpolation both in space and time was used to transfer the boundary conditions from the global simulations to the local model, which uses a different mesh discretization and a considerably smaller time step. We applied this approach to the Czochralski growth of a high-purity Ge crystal. The heater power change predicted by the global model as well as the final dislocation density distribution in the crystal simulated by the local model are correlated to the experimental results. [ABSTRACT FROM AUTHOR]

Inorganic semiconductors like silicon and germanium are the foundation of modern electronic devices. However, they have certain limitations, such as high production costs, limited flexibility, and heavy weight. Additionally, the depletion of natural resources required for inorganic semiconductor production raises concerns about sustainability. Therefore, the exploration and development of organic semiconductors offer a promising solution to overcome these challenges and pave the way for a new era of electronics. New applications for electronic and optoelectronic devices have been made possible by the recent emergence of organic semiconductors. Numerous innovative results on the performance of charge transport have been discovered with the growth of organic electronics. These discoveries have opened up new possibilities for the development of organic electronic devices, such as organic solar cells, organic light-emitting diodes, and organic field-effect transistors. The use of organic materials in these devices has the potential to revolutionise the electronics industry by providing low-cost, flexible, and lightweight alternatives to traditional inorganic materials. The understanding of charge carrier transport in organic semiconductors is crucial for the development of efficient organic electronic devices. This review offers a thorough overview of the charge carrier transport phenomenon in semiconductors with a focus on the underlying physical mechanisms and how it affects device performance. Additionally, the processes of carrier generation and recombination are given special attention. Furthermore, this review provides valuable insights into the fundamental principles that govern the behaviour of charge carriers in these materials, which can inform the design and optimisation of future devices. [ABSTRACT FROM AUTHOR]

The floating zone (FZ) is one of the important methods for pulling silicon single crystals, but there are still problems of an unstable thermal field and crystallization difficulties. They will directly affect the growth of single crystals, resulting in defects and even fractures, seriously reducing production efficiency. Based on this, the effect of the modified inductor structure on the FZ thermal field is investigated in this paper. Using COMSOL 6.0 simulation software, 2D and 3D FZ models are established. The inductor steps under the 2D model and the inductor slits under the 3D model are compared to analyze the effects of steps and slits on the 8-inch FZ thermal field and melt flow. The distributions of temperature fields and melt flow in the melting zone under the action of the axial magnetic field are calculated by finite element analysis. The results show that the melt under the introduction of steps in the 2D model and the cross-slit structure in the 3D model is the most stable and favorable for crystal growth, which matches the actual production. [ABSTRACT FROM AUTHOR]

Reducing the defects and impurity contents at the edge of multicrystalline silicon (mc-Si) is an effective way for improving the performance of solar cells. In this work, the effect of nucleation coating based on Si powder with different particle size and thickness on crystal quality of ingot edge is investigated. The results show that a large particle nucleation coating is more helpful in generating small and uniform grains at the ingot sidewall, and it also reduces the width of the red zone due to the decrease of the concentration of metal and oxygen impurities. However, too thick nucleation coating would widen the red zone due to atmosphere contamination during melting, as confirmed by iron concentration distribution. The photoluminescence (PL) images demonstrated that small grains generated continuously at the ingot sidewall could significantly improve defect distribution. The solar cell efficiency of the edge wafers grown with large particle nucleation coating is increased by 0.07% compared to that of conventional edge wafers. [ABSTRACT FROM AUTHOR]

Tissue engineering (TE) and nanomedicine require devices with hydrophilic surfaces to better interact with the biological environment. This work presents a study on the wettability of cubic silicon-carbide-based (SiC) surfaces. We developed four cubic silicon-carbide-based epitaxial layers and three nanowire (NW) substrates. Sample morphologies were analyzed, and their wettabilities were quantified before and after a hydrogen plasma treatment to remove impurities due to growth residues and enhance hydrophilicity. Moreover, sample biocompatibility has been assessed with regard to L929 cells. Our results showed that core–shell nanowires (SiO2/SiC NWs), with and without hydrogen plasma treatment, are the most suitable candidate material for biological applications due to their high wettability that is not influenced by specific treatments. Biological tests underlined the non-toxicity of the developed biomaterials with regard to murine fibroblasts, and the proliferation assay highlighted the efficacy of all the surfaces with regard to murine osteoblasts. In conclusion, SiO2/SiC NWs offer a suitable substrate to develop platforms and membranes useful for biomedical applications in tissue engineering due to their peculiar characteristics. [ABSTRACT FROM AUTHOR]

Rapid industrial advancement over the last few decades has led to an alarming increase in pollution levels in the ecosystem. Among the primary pollutants, harmful organic dyes and pharmaceutical drugs are directly released by industries into the water bodies which serves as a major cause of environmental deterioration. This warns of a severe need to find some sustainable strategies to overcome these increasing levels of water pollution and eliminate the pollutants before being exposed to the environment. Photocatalysis is a well-established strategy in the field of pollutant degradation and various metal oxides have been proven to exhibit excellent physicochemical properties which makes them a potential candidate for environmental remediation. Further, with the aim of rapid industrialization of photocatalytic pollutant degradation technology, constant efforts have been made to increase the photocatalytic activity of various metal oxides. One such strategy is the introduction of defects into the lattice of the parent catalyst through doping or vacancy which plays a major role in enhancing the catalytic activity and achieving excellent degradation rates. This review provides a comprehensive analysis of defects and their role in altering the photocatalytic activity of the material. Various defect-rich metal oxides like binary oxides, perovskite oxides, and spinel oxides have been summarized for their application in pollutant degradation. Finally, a summary of existing research, followed by the existing challenges along with the potential countermeasures has been provided to pave a path for the future studies and industrialization of this promising field., (© 2024 American Society for Photobiology.)

Determining bulk moduli is central to high-throughput screening of ultraincompressible materials. However, existing approaches are either too inaccurate or too expensive for general applications, or they are limited to narrow chemistries. Here we define a microscopic quantity to measure the atomic stiffness for each element in the periodic table. Based on this quantity, we derive an analytic formula for bulk modulus prediction. By analyzing numerous crystals from first-principles calculations, this formula shows superior accuracy, efficiency, universality, and interpretability compared to previous empirical/semiempirical formulae and machine learning models. Directed by our formula predictions and verified by first-principles calculations, 47 ultraincompressible crystals rivaling diamond are identified from over one million material candidates, which extends the family of known ultraincompressible crystals. Finally, treasure maps of possible elemental combinations for ultraincompressible crystals are created from our theory. This theory and insights provide guidelines for designing and discovering ultraincompressible crystals of the future. Fast and accurate prediction of bulk moduli for diverse materials is challenging. Here, the authors introduce the concept of atomic stiffness to accelerate bulk modulus prediction and high-throughput screening of ultra-incompressible crystals. [ABSTRACT FROM AUTHOR]

The fundamental properties of dislocations in diamond-structured Si and sphalerite-structured GaAs, InP and CdTe are investigated based on lattice theory of dislocation, hoping to provide some theoretical references in improving the properties of related materials. The influences of the surface effect(SE) and elastic strain energy on the structure and mechanical property of dislocation are discussed systematically. After considering the SE, the core width of dislocation becomes wider due to the elastic interaction between atoms becomes stronger. Compared to glide partial dislocation, the correction of SE to shuffle dislocation is more obvious. Both the SE and the elastic strain energy affect the energy barrier and Peierls stress of dislocation. The influence of SE on energy barrier and Peierls stress mainly results from the misfit energy and elastic strain energy become lower when the core of dislocation becomes wider. While the influence of elastic strain energy on energy barrier and Peierls stress mainly results from the cancellation between misfit energy and elastic strain energy for they possess comparable amplitudes but opposite phases. In addition, it is deduced that for the studied crystals, the shuffle dislocations control the deformation at medium and low temperatures, while glide partial dislocations are responsible for high temperature plasticity. [ABSTRACT FROM AUTHOR]

In this exercise, I submitted an AL 7075 alloy to a two-step heat treatment procedure known as RRA to look at fatigue behaviour. This procedure combines annealing, high-temperature pre-precipitation, artificial ageing (T6), retrogression, and re-aging, among other heat treatments. The samples are heated to 473o first, then quenched in water medium. The samples are heated further to 18 hours, 22 hours, and 26 hours, respectively. After this, the specimens are heated to 230°, 250°, 270°, and 290° for various lengths of time--7 & 14 minutes, respectively--to increase the material's strength. This process is known as retrogression and re-aging. Following this trial discovered that the RRA approach allows us to maximise the material's strength. [ABSTRACT FROM AUTHOR]

Monocrystalline silicon is an important raw material in the semiconductor and photovoltaic industries. In the Czochralski (CZ) method of growing monocrystalline silicon, various factors may cause node loss and lead to the failure of crystal growth. Currently, there is no efficient method to detect the node loss of monocrystalline silicon at industrial sites. Therefore, this paper proposed a monocrystalline silicon node-loss detection method based on multimodal data fusion. The aim was to explore a new data-driven approach for the study of monocrystalline silicon growth. This article first collected the diameter, temperature, and pulling speed signals as well as two-dimensional images of the meniscus. Later, the continuous wavelet transform was used to preprocess the one-dimensional signals. Finally, convolutional neural networks and attention mechanisms were used to analyze and recognize the features of multimodal data. In the article, a convolutional neural network based on an improved channel attention mechanism (ICAM-CNN) for one-dimensional signal fusion as well as a multimodal fusion network (MMFN) for multimodal data fusion was proposed, which could automatically detect node loss in the CZ silicon single-crystal growth process. The experimental results showed that the proposed methods effectively detected node-loss defects in the growth process of monocrystalline silicon with high accuracy, robustness, and real-time performance. The methods could provide effective technical support to improve efficiency and quality control in the CZ silicon single-crystal growth process. [ABSTRACT FROM AUTHOR]

Gallium nitride continues to be a material of intense interest for the ongoing advancement of electronic and optoelectronic devices. While the bulk of today's markets for low-performance devices is still met with silicon and blue/UV LEDs derived from metal–organic chemical vapor deposition gallium nitride grown on foreign substrates such as sapphire and silicon carbide, the best performance values consistently come from devices built on bulk-grown gallium nitride from native seeds. The most prominent and promising of the bulk growth methods is the ammonothermal method of high-pressure solution growth. The state-of-the-art from the last five years in ammonothermal gallium nitride technology is herein reviewed within the general categories of growth technology, characterization and defects as well as device performance. [ABSTRACT FROM AUTHOR]

The character of dislocations at the emission sites observed in p–n diodes on (0001) GaN by emission microscopy under reverse biasing is investigated. The dislocation is a c-type threading dislocation formed by the reaction of c+a and -a dislocations. The c-type threading dislocation is closed-core, screw type, and helical, formed by vacancy desorption with a 0.2 μm cavity approximately 2 μm beneath the surface. The band-edge photoluminescence under multiphoton excitation at the dislocation in the p layer is brighter than that of the surrounding non-defective area. [ABSTRACT FROM AUTHOR]

The dynamics of dislocations introduced through indentation or scratching at room temperature into a few GaN layers that were grown using the HVPE, MOCVD and ELOG methods and had different dislocation densities were studied via the electron-beam-induced current and cathodoluminescence methods. The effects of thermal annealing and electron beam irradiation on dislocation generation and multiplication were investigated. It is shown that the Peierls barrier for dislocation glide in GaN is essentially lower than 1 eV; thus, it is mobile even at room temperature. It is shown that the mobility of a dislocation in the state-of-the-art GaN is not entirely determined by its intrinsic properties. Rather, two mechanisms may work simultaneously: overcoming the Peierls barrier and overcoming localized obstacles. The role of threading dislocations as effective obstacles for basal plane dislocation glide is demonstrated. It is shown that under low-energy electron beam irradiation, the activation energy for the dislocation glide decreases to a few tens of meV. Therefore, under e-beam irradiation, the dislocation movement is mainly controlled by overcoming localized obstacles. [ABSTRACT FROM AUTHOR]

This study investigated the relationship between the Σ3 boundaries, dislocation slip, and plasticity in pure nickel wires after grain boundary (GB) modification. Both quasi in situ tensile tests and simulations were employed. During plastic deformation, twins surrounded by Σ3 boundaries may exhibit a good deformation coordination. With an increase in strain, the slip systems corresponding to the maximum Schmid factor and the actual activated slip systems remain unchanged. Even sub-grains can maintain the dominant slip system of their origin matrix grains. Slip systems with slip planes (111) and (1−1−1) are the most active. Moreover, random boundaries have strong hindering effects on dislocations, and the nearby stress accumulates continuously with an increase in strain. In contrast, Σ3 boundaries demonstrate weak blocking effects and can release the nearby stress due to their unique interfacial structures, which is favorable for improving plasticity. They are more penetrable for dislocations or may react with the piled dislocations. In addition, some Σ3 boundaries can improve their geometrical compatibility factor with an increase in the strain, which enhances the deformation coordination of the grains. The research results provide a better understanding of the plasticizing mechanism for face-centered cubic (fcc) materials after grain boundary modification. [ABSTRACT FROM AUTHOR]

Lattice defect engineering has attracted attention due to its ability to develop thermoelectric materials with low thermal conductivity. For Mg2Si single crystals (SCs), Si vacancy (VSi) defects can be introduced and consequently result in the formation of dislocation cores. These lattice defects confer Mg2Si SCs with a lower thermal conductivity compared to Mg2Si polycrystals. To reveal a mechanism for the stabilisation of VSi in the Mg2Si SCs, we investigated the effects of oxygen (O) on lattice defects by performing electronic structure calculations, secondary ion mass spectrometry, X-ray photoelectron spectroscopy, and photoelectron holography. On the basis of these calculations, we predicted that O stabilised the formation of VSi when it was located at the Si site or at an interstitial site. All experiments confirmed the presence of O inside the Mg2Si SCs. However, O was suggested to be located not at the specific site in the crystal lattice of Mg2Si but at dislocation cores. The interaction between O and the dislocation cores in the Mg2Si SC is expected to immobilise dislocation cores, leading to the stabilisation of VSi formation. [ABSTRACT FROM AUTHOR]

The authors prepared multilayered Si‐based Ge quantum dots (Ge/Si QDs) by using the magnetron sputtering technique and reported the corresponding morphology evolution by atomic force microscope (AFM), scanning electron micrograph (SEM), X‐ray photoelectron spectroscopy (XPS), Raman and X‐ray diffraction (XRD) tests. The increased temperature can improve the Si‐isolated‐layer crystallinity and Ge atom mobility to increase the density, size, and spatial distribution uniformity of top‐layer QDs. The morphology and vertical correlation between the layers of QDs at different temperatures exhibited different phenomena or laws, and had been explained in this paper. The authors' work made it possible to control the quality of multilayer QDs by high‐rate deposition technology and laid a foundation for the industrial production of multilayer QDs in the future. [ABSTRACT FROM AUTHOR]

In this study, nanoindentation tests at three different strain rates within 100 nm indentation depth were conducted on an a-plane ( 11 2 ¯ 0 ) ZnO single crystal to investigate the effect of strain rate on its nano-scale mechanical behavior. The load–indentation-depth curves, pop-in events, hardness and Young's moduli of an a-plane ( 11 2 ¯ 0 ) ZnO single crystal at different strain rates were investigated at the nano-scale level. The results indicated that, with the indentation depth increasing, the load increased gradually at each maximum indentation depth, hma, during the loading process. A distinct pop-in event occurred on each loading curve except that corresponding to the hmax of 10 nm. The applied load at the same indentation depth increased with the increasing strain rate during the nanoindentation of the a-plane ( 11 2 ¯ 0 ) ZnO single crystal. The higher strain rate deferred the pop-in event to a higher load and deeper indentation depth, and made the pop-in extension width larger. The hardness showed reverse indentation size effect (ISE) before the pop-in, and exhibited normal ISE after the pop-in. Both the hardness and the Young's modulus of the a-plane ( 11 2 ¯ 0 ) ZnO single crystal increased with the increasing strain rate, exhibiting the positive strain-rate sensitivity. [ABSTRACT FROM AUTHOR]

The problem of generating a high amount of heat in microelectronic equipment should be minimized properly. Allowing systems to run for long periods of time in high temperatures can reduce the performance and reliability of equipment. The microchannel heat sink is an efficient cooling technology to prevent the generation of very high heat fluxes. In the present study, the effect of the applied heat fluxes and geometric parameters such as rib width on the entire thermal resistance and cooling capacity of the heat sink is examined numerically. Besides, the substrate's material changed from silicon to AlN ceramic. Because of the higher thermal conductivity of AlN, a more unfluctuating temperature distribution in the battom wall and a reduction of about 31% in the entire thermal resistance of the heat sink are reported. Additionally, the entire thermal resistance of heat sinks is greatly dependent on its geometric parameters such as rib width. Reducing the rib width results in a considerable diminish in total thermal resistance and betterment in the cooling capacity of the microchannel heat sink. [ABSTRACT FROM AUTHOR]

Laser-induced periodic surface structure (LIPSS), which has a period smaller than the laser wavelength, is expected to become a potential technique for fine surface processing. We report the microscopic and macroscopic observations of the crystallinity of LIPSSs, where the characteristics such as defects generation and residual strain were analyzed, respectively. The LIPSSs were formed on a Si substrate using two different femtosecond pulses from Ti:Sapphire laser with near-infrared wavelength (0.8 μm) and free-electron laser (FEL) with mid-infrared wavelength (11.4 μm). The photon energies of the former and latter lasers used here are higher and lower than the Si bandgap energies, respectively. These LIPSSs exhibit different crystalline states, where LIPSS induced by Ti:Sapphire laser show residual strain while having a stable crystallinity; in contrast, FEL-LIPSS generates defects without residual strain. This multiple analysis (microscopic and macroscopic observations) provides such previously-unknown structural characteristics with high spatial resolution. To obtain LIPSS with suitable properties and characteristics based on each application it is paramount to identify the laser sources that can achieve such properties. Therefore, identifying the structural information of the LIPSS generated by each specific laser is of great importance. [ABSTRACT FROM AUTHOR]

We manufactured two high performance multi-crystalline silicon ingots and investigated the effects of heat extraction methods on the quality of silicon ingots. The results show that the two heat extraction methods caused different supercooling and solid-liquid interface shape during the process of crystal growth, and further effected the qualities of silicon ingots and the performance of solar cells. Due to the increase of supercooling, the method of overall fast heat extraction (the temperature of TC2 and TC3 decreased by more than 120 °C within 30 min) could obtain smaller grains, more grain boundaries and less dislocations than those of the method of fast heat extraction in the center and slow heat extraction on both sides of the ingot. Meanwhile, a slightly convex solid-liquid interface was obtained, which reduced the growth stress of grains and the formation probability of dislocations. In addition, the resistivity distribution would be more uniform in different regions of silicon ingot, which is beneficial to improving the performance of solar cells. [ABSTRACT FROM AUTHOR]

Si(1-x)Gex is an alloy whose properties strongly depend on the molar fraction, x, of Ge. It is our aim to quantify the effects of x on some elastic parameters such as surface acoustic wave, SAW, velocities (longitudinal, VL, transverse, VT, and Rayleigh, VR,) as well as acoustic impedances, Z. What is the evaluation of Silicon acoustic properties in Si(1-x)Gex binary alloy? From the numerical calculations of the elastic properties which have combined with the most powerful technique of the SAM scanning acoustic microscopy, we have succeeded in quantifying the evaluation of the acoustic properties of Silicon in the SiGe alloy. A general semi-empirical formula was determined for all SAW velocities of the form: V i SiGe = V i Si − 2 V i Si + V i Ge x / 5 + 3 V i Ge x 2 / 8 where the subscript i stands for longitudinal, transverse and Rayleigh modes. Moreover, a new relation for acoustic impedance, Z(x) of Si(1-x)Gex alloys was proposed in terms of known impedance values of Si and Ge, i.e., Z SiGe = Z Ge − Z Ge − Z Si e − 9 x / 2 . The importance of these relations lies in the possibility of deducing and predicting elastic properties of any given composition of SiGe alloys. [ABSTRACT FROM AUTHOR]

Herein, facets and related phenomena are studied for silicon crystals grown in the <100> and <111> directions, using the Zone Melting and Floating Zone techniques. Investigating the central facets of dislocation-free <111> crystals as a baseline allowed for the determination of the local temperature gradients. When comparing these results to dislocated <111> crystals, the presence of dislocations caused a clear reduction in the facet size, correlated with a reduction in the required local supercooling to estimated maximum values of around 0.6 K. Furthermore, for crystals grown on the rough {100} interface, attempts to provoke a morphological instability of the local phase boundary succeeded for crystallization velocities in the range of 10–16 mm/min, in good agreement with theory. Contrary to this observation, crystals grown in the <111> direction remained morphologically stable even at higher crystallization velocities due to the stabilizing effect of the atomically smooth interface. Additionally, crystals grown in the <111> direction with an oxygen skin by the Zone Melting technique reproducibly showed a non-periodic fluctuation of the central facet diameter at a certain translation velocity. [ABSTRACT FROM AUTHOR]

The preparation of high-quality GaAs crystals is the basis for the development of high-frequency microwave electronic devices and light-emitting devices. A molecular dynamics (MD) simulation of the directional solidification of GaAs was conducted. The anisotropic growth process and structural defects have been analyzed by radial distribution function, the largest standard cluster analysis, and visualization analysis. The results indicate that induced crystallization with different crystal orientations leads to different microstructural changes, which in turn cause the anisotropic growth of GaAs crystals. During the [100] crystal-oriented solidification, only sphalerite crystal structures were present in the system, while wurtzite structures were also formed in the [110] and [111] crystal orientation systems, and the [111] crystal orientation system is the more obvious. In addition, due to the dense packing structure of the (111) plane, numerous partial dislocations with a Burgers vector of 1/6< 112 > are formed in the GaAs crystal, and there is also a companion relationship between such dislocations and twins, which significantly reduces the crystallization effect. The study of the microstructure evolution of GaAs on the atomic scale provides a reference for the theory of crystal growth. [ABSTRACT FROM AUTHOR]

The paper presents the results of an investigation of the influence of technological parameters on the microstructure, optical, electrical and nanomechanical properties of zinc oxide coatings prepared using the pulsed reactive magnetron sputtering method. Three sets of ZnOx thin films were deposited in metallic, shallow dielectric and deep dielectric sputtering modes. Structural investigations showed that thin films deposited in the metallic mode were nanocrystalline with mixed hexagonal phases of metallic zinc and zinc oxide with crystallite size of 9.1 and 6.0 nm, respectively. On the contrary, the coatings deposited in both dielectric modes had a nanocrystalline ZnO structure with an average crystallite size smaller than 10 nm. Moreover, coatings deposited in the dielectric modes had an average transmission of 84% in the visible wavelength range, while thin films deposited in the metallic mode were opaque. Measurements of electrical properties revealed that the resistivity of as-deposited thin films was in the range of 10−4 Ωcm to 108 Ωcm. Coatings deposited in the metallic mode had the lowest hardness of 2.2 GPa and the worst scratch resistance among all sputtered coatings, whereas the best mechanical properties were obtained for the film sputtered in the deep dielectric mode. The obtained hardness of 11.5 GPa is one of the highest reported to date in the literature for undoped ZnO. [ABSTRACT FROM AUTHOR]

Nanoindentation studies on bulk and epitaxial semiconductor crystals have been reviewed in general. The common materials of technological interest such as Si, Ge, GaAs, GaN, InP, CdZnTe, HgCdTe etc. have been included. Issues related with the measurement and analysis of load–displacement characteristics have been discussed in detail, including those for cyclic nanoindentation and continuous stiffness measurements. Common mistakes/oversights in the extraction of mechanical properties, particularly for the elastic modulus, have been highlighted. Various features observed in load–displacement curves are discussed in connection with different semiconductor materials. These include pop-in/pop-out events and serrations observed in general, and the open-jaw and hysteresis like features in cyclic nanoindentation. Cathodoluminescence studies on indented surfaces have also been included to highlight the deformation behaviour of some of the crystalline semiconductor materials. [ABSTRACT FROM AUTHOR]

Crystalline silicon (Si) is the key material of the semiconductor industry, with significant applications for electronic and microelectronic devices. The properties of Si are affected by impurities and defects introduced into the material either during growth and/or material processing. Oxygen (O) and carbon (C) are the main impurities incorporated into the crystal lattice during growth via the Czochralski method. Both impurities are electrically neutral, however, implantations/irradiations of Si lead to the formation of a variety of oxygen-related and carbon-related defects which introduce deep levels in the forbidden gap, inducing generally detrimental effects. Therefore, to control Si behavior for certain applications, it is important to have an understanding of the properties and fundamental processes related with the presence of these defects. To improve Si, isovalent doping during growth must be employed. Isovalent doping is an important defect-engineering strategy, particularly for radiation defects in Si. In the present review, we mainly focus on the impact of isovalent doping on the properties and behavior of oxygen-related and carbon-related defects in electron-irradiated Si. Recent experimental results from infrared spectroscopy (IR) measurements coupled with theoretical studies involving density functional theory (DFT) calculations, are discussed. Conclusions are reached regarding the role of isovalent doping (carbon, (C), germanium (Ge), tin (Sn), and lead (Pb)) on the suppression of detrimental effects introduced into Si from technologically harmful radiation clusters induced in the course of material processing. [ABSTRACT FROM AUTHOR]

We used in situ transmission electron microscopy (TEM) to observe the dynamic changes of Si nanowires under electron beam irradiation. We found evidence of structural evolutions under TEM observation due to a combination of electron beam and thermal effects. Two types of heating holders were used: a carbon membrane, and a silicon nitride membrane. Different evolution of Si nanowires on these membranes was observed. Regarding the heating of Si nanowires on a C membrane at 800 °C and above, a serious degradation dependent on the diameter of the Si nanowire was observed under the electron beam, with the formation of Si carbide. When the membrane was changed to Si nitride, a reversible sectioning and welding of the Si nanowire was observed. [ABSTRACT FROM AUTHOR]

Nanoindentations and the Raman spectroscopy measurements were carried out on the (001) surface of undoped and S-doped InP crystal. The samples were indented with the maximum load ranging from 15 mN to 100 mN. The phase transition B3→B1 was not confirmed by spectroscopic experiments, indicating a plastic deformation mechanism governed by dislocations activity. Increasing the maximum indentation load shifts and the longitudinal and transverse optical Raman bands to lower frequencies reveals a reduction in the elastic energy stored in the plastic zone right below the indentation imprint. Mechanical experiments have shown that a shift in Raman bands occurs alongside the indentation size effect. Indeed, the hardness of undoped and S-doped InP crystal decreases as a function of the maximum indentation load. [ABSTRACT FROM AUTHOR]

High‐tech ceramics are typically engineered by controlling point defects and interfaces while one‐dimensional dislocations have found much less attention so far. Nevertheless, their impact on almost any functional property and the sudden ease to fabricate them with novel synthesis methods, such as rapid densification, brings spotlight attention to dislocations as design dimension. Although the typical brittleness of ceramics insinuates the irrelevance of dislocations for mechanical behavior, abundant literature is spread over materials, decades, and disciplines, however, often unconnected. Here, a conceptual framework for dislocation mechanics in ceramics separated into five logical aspects, (1) fundamental mobility, (2) obstacles to motion, (3) limitation by necessity of nucleation, (4) motion complexity, and (5) avoidance of competing mechanisms, brings oversight into the complex behavior. In consequence, quicker identification of the limiting step allows to estimate the potential involved more precisely and to identify open research questions with greater ease. An introduction to dislocations and the functionality involved, a look back over the last six decades, and highlights of open question are dedicated to provide a framework and bridge the gap between the attached research fields. [ABSTRACT FROM AUTHOR]

The epitaxial deposition of a precise number, or even fractions, of monolayers of indium (In)-rich semiconductors onto gallium arsenide (GaAs) substrates enables the creation of quantum dots based on InAs, InGaAs and indium phosphide (InP) for infrared light-emitting and laser diodes and the formation of indium antimonide (InSb)/GaAs strained layer superlattices. Here, a facile method based on energy-dispersive X-ray spectroscopy (EDXS) in a scanning electron microscope (SEM) is presented that allows the indium content of a single semiconductor layer deposited on a gallium arsenide substrate to be measured with relatively high accuracy (±0.7 monolayers). As the procedure works in top-down geometry, where any part of a wafer can be inspected, measuring the In content of the surface layer in one location without destroying it can also be used to map the lateral indium distribution during quantum dot formation and is a method suitable as an in-situ quality control tool for epitaxy. [ABSTRACT FROM AUTHOR]

In this manuscript, a novel dual-step selective epitaxy growth (SEG) of Ge was proposed to significantly decrease the defect density and to create fully strained relaxed Ge on a Si substrate. With the single-step SEG of Ge, the threading defect density (TDD) was successfully decreased from 2.9 × 107 cm−2 in a globally grown Ge layer to 3.2 × 105 cm−2 for a single-step SEG and to 2.84 × 105 cm−2 for the dual-step SEG of the Ge layer. This means that by introducing a single SEG step, the defect density could be reduced by two orders of magnitude, but this reduction could be further decreased by only 11.3% by introducing the second SEG step. The final root mean square (RMS) of the surface roughness was 0.64 nm. The strain has also been modulated along the cross-section of the sample. Tensile strain appears in the first global Ge layer, compressive strain in the single-step Ge layer and fully strain relaxation in the dual-step Ge layer. The material characterization was locally performed at different points by high resolution transmission electron microscopy, while it was globally performed by high resolution X-ray diffraction and photoluminescence. [ABSTRACT FROM AUTHOR]

A technique based on the Bridgman method was used to make single crystals of AgInS2. X-ray diffraction was used to determine the crystal structure (XRD). An energy-dispersive X-ray fluorescence spectrometer was used to determine the crystals' atomic composition (EDXRF). The lattice constant and Wyckoff locations for AgInS2 crystal are determined using Rietveld refinement analysis. Temperatures ranging from 128 to 628 K were used to assess electrical conductivity, Hall effect, and thermoelectric power (TEP). Various physical characteristics for both majority and minority carriers were estimated during these studies, including carrier mobilities, carrier concentration, effective masses of charge carriers, diffusion coefficient, relaxation time, and diffusion length. Furthermore, the activation energy was discovered to be 0.132 eV, and the energy gap width to be 1.86 eV. The thermal power factor, the electronic thermal conductivity, and the figure of merit were calculated for all samples. All crystals were found to be of p-type conductivity. [ABSTRACT FROM AUTHOR]

Outstanding improvement in power conversion efficiency (PCE) over 25% in a very short period and promising research developments to reach the theoretical PCE limit of single junction solar cells, 33%, enables organic–inorganic perovskite solar cells (OIPSCs) to gain much attention in the scientific and industrial community. The simplicity of production of OIPSCs from precursor solution either on rigid or flexible substrates makes them even more attractive for low-cost roll-to-roll production processes. Though OIPSCs show as such higher PCE with simple solution processing methods, there are still unresolved issues, while attempts are made to commercialize these solar cells. Among the major problems is the instability of the photoactive layer of OIPSCs at the interface of the charge transport layers and /or electrodes during prolonged exposure to moisture, heat and radiation. To achieve matched PCE and stability, several techniques such as molecular and interfacial engineering of components in OIPSCs have been applied. Moreover, in recent times, engineering on additives, solvents, surface passivation, and structural tuning have been developed to reduce defects and large grain boundaries from the surface and/or interface of organic–inorganic perovskite films. Under this review, we have shown recently developed additives and passivation strategies, which are strongly focused to enhance PCE and long-term stability simultaneously. [ABSTRACT FROM AUTHOR]