This Special Issue reprint presents articles from researchers working on materials processing via electron beams as well as on their characterization, properties, and applications. The articles ...presented cover various topics, including metal melting and welding, additive manufacturing, electron beam irradiation, electron beam lithography, process modeling, etc.
The present article gives a summary of recent technological and scientific developments in the field of polycrystalline silicon (poly-Si) thin-film solar cells on foreign substrates. Cost-effective ...fabrication methods and cheap substrate materials make poly-Si thin-film solar cells promising candidates for photovoltaics. However, it is still the challenge for research and development to achieve the necessary high electrical material quality known from crystalline Si wafers on glass as a prerequisite to harvest the advantages of thin-film technologies. A wide variety of poly-Si thin-film solar cell approaches has been investigated in the past years, such as thermal solid phase crystallization – the only technology that had already been matured to industrial production so far – the seed layer concept where a large-grained seed layer is epitaxially thickened, direct growth of fine grained material, and liquid phase crystallization methods by laser or electron beam. In the first part of this paper, the status of these four different poly-Si thin-film solar cell concepts is summarized, by comparing the technological fabrication methods, as well as the structural and electrical properties and solar cell performances of the respective materials. In the second part, three promising technologies are described in more detail due to their highly auspicious properties regarding material quality and throughput aspects during fabrication: (1) High-rate electron–beam evaporation of silicon for the low-cost deposition of high-quality material, (2) large-area periodic nano- and micro-structuring of poly-Si by the use of imprinted substrates providing a large absorption enhancement by a factor of six at a wavelength of 900nm, (3) liquid-phase crystallization of silicon thin-film solar cells by electron–beam, yielding an excellent poly-Si material quality reflected by an open-circuit voltage of 582mV which has been achieved only very recently. A successful combination of these three complementary technologies is envisaged to be the basis for a prospective low-cost and highly efficient poly-Si solar cell device.
•Various poly-Si thin-film solar cell technologies are reviewed and compared.•Liquid phase crystallized Si has largest grains and best electrical material quality.•Nanophotonic poly-Si light trapping structures yield large absorption enhancement.•Poly-Si thin-film solar cells with 580mV open circuit voltage are realized.
Additive manufacturing (AM), also known as 3D printing or rapid prototyping, is gaining increasing attention due to its ability to produce parts with added functionality and increased complexities in ...geometrical design, on top of the fact that it is theoretically possible to produce any shape without limitations. However, most of the research on additive manufacturing techniques are focused on the development of materials/process parameters/products design with different additive manufacturing processes such as selective laser melting, electron beam melting, or binder jetting. However, we do not have any guidelines that discuss the selection of the most suitable additive manufacturing process, depending on the material to be processed, the complexity of the parts to be produced, or the design considerations. Considering the very fact that no reports deal with this process selection, the present manuscript aims to discuss the different selection criteria that are to be considered, in order to select the best AM process (binder jetting/selective laser melting/electron beam melting) for fabricating a specific component with a defined set of material properties.
Plasmonic nanostar‐dimers, decoupled from the substrate, have been fabricated by combining electron‐beam lithography and reactive‐ion etching techniques. The 3D architecture, the sharp tips of the ...nanostars and the sub‐10 nm gap size promote the formation of giant electric‐field in highly localized hot‐spots. The single/few molecule detection capability of the 3D nanostar‐dimers has been demonstrated by Surface‐Enhanced Raman Scattering.
Focused electron beam induced deposition (FEBID) is a direct-write method for the fabrication of nanostructures whose lateral resolution rivals that of advanced electron beam lithography but is in ...addition capable of creating complex three-dimensional nano-architectures. Over the last decade several new developments in FEBID and focused electron beam induced processing (FEBIP) have led to a growing number of scientific contributions in solid state physics and materials science based on FEBID-specific materials and particular shapes and arrangements of the employed nanostructures. In this review an attempt is made to give a broad overview of these developments and the resulting contributions in various research fields encompassing mesoscopic physics with nanostructured metals at low temperatures, direct-write of superconductors and nano-granular alloys or intermetallic compounds and their applications, the contributions of FEBID to the field of metamaterials, and the application of FEBID structures for sensing of force or strain, dielectric changes or magnetic stray fields. The very recent development of FEBID towards simulation-assisted growth of complex three-dimensional nano-architectures is also covered. In the review particular emphasis is laid on conceptual clarity in the description of the different developments, which is reflected in the mostly schematic nature of the presented figures, as well as in the recurring final sub-sections for each of the main topics discussing the respective “challenges and perspectives”.
•The first comprehensive review of FEBID for materials science and condensed matter physics is given.•Topics are all-metal structures, superconductors, alloys, metamaterials, sensors and 3D structures.•Focus is on conceptual clarity.•For each topic challenges and perspectives are outlined.
Atomic‐resolution imaging of halide perovskites (HPs) using transmission electron microscopy (TEM) is challenging because of the sensitivity of their structures to the electron beam. In this article, ...recent achievements in this area are reviewed, covering both all‐inorganic and organic–inorganic hybrid HPs, with an emphasis on the specific imaging conditions that have proven to be effective in avoiding electron beam‐induced structural damage. The discussion focusses on the total electron dose that HPs can bear before being damaged and the effects of different imaging modes, accelerating voltages, and temperatures. The crucial role of a direct‐detection electron‐counting camera in reducing the required electron dose is outlined, which is indispensable for imaging extremely sensitive organic–inorganic hybrid perovskites. In addition to reviewing published works, the results of initial attempts to perform atomic‐resolution elemental mapping for an all‐inorganic HP and image a hybrid HP using scanning TEM are introduced. The preparation of a TEM specimen from macroscopic crystals or devices of HPs, which is very important for practical applications but has not yet received attention, is also discussed. This article aims to provide guidance on the acquisition of atomic‐resolution TEM images of HPs and inspire the development of more imaging technologies for sensitive materials.
Electron microscopy characterization of halide perovskite materials at the atomic resolution is difficult due to their extreme sensitivity to electron‐beam irradiation. Imaging conditions that are used to capture intact structures of various halide perovskites are summarized and analyzed, with the aim of providing guidance on this challenging subject.
Due to its emulsifying and thickening properties, konjac glucomannan (KGM) is widely used in the food, medicine, and materials industries. Nevertheless, its high viscosity and significant water ...absorption limit its application range. Therefore, electron beam (e-beam) irradiation pretreatment was carried out to improve the deacetylation efficiency of KGM, and the physicochemical and gel properties of KGM were investigated. The results show that e-beam irradiation and deacetylation decrease the water absorption, solubility, transparency, molecular weight, and viscosity of KGM. Conversely, the moisture content, thermal stability, and water-binding capacity increase. FTIR and X-ray diffraction analysis revealed no significant changes in the chemical and crystalline structure of KGM before and after modification. However, modification weakens the intermolecular interaction of KGM hydrosols, which affects their rheology. Furthermore, deacetylation improves the mechanical properties and water retention capacity of KGM gels. Overall, the e-beam irradiation pretreatment provides a method to increase the efficiency of KGM deacetylation and improve the physical and chemical properties of KGM, thus expanding its potential applications in the food and chemical industries, among others.
•An in-situ strengthened dual-phase AlCoCuFeNi HEA is developed via SEBM.•HEA comprised BCC solid solution matrix with FCC precipitates.•Compressive strength and ductility of the SEBM HEA superior to ...SLM HEA.•Electron beam remelting during SEBM could result in superior properties.
The application scope and market demand for additive-manufactured high-entropy alloys (AM HEAs) have broadened of late. However, a long-standing problem associated with AM HEAs is their limited ductility. In this study, a dual-phase AlCoCuFeNi HEA, consisting of body-centered cubic (BCC) solid solution matrix with uniformly dispersed face-centered cubic (FCC) structured precipitates, was fabricated by selective electron beam melting (SEBM). SEBM involved a preheating process can enable the formation of Cu-rich FCC phases with needle-like and spherical morphologies, as well as nanotwins that in-situ precipitated from the metastable BCC(B2) matrix. The compressive strength and ductility of the SEBM HEA were superior to those of the HEAs processed by selective laser melting (SLM) AM technique. Furthermore, using selective electron beam remelting (SEB-RM) during SEBM could result in a higher relative density, finer microstructure, and enhanced compressive properties. Particularly, the SEB-RM sample exhibited a better compressive strength of 2572 MPa, a yield strength of 870 MPa, and a strain of 18.3%. The improved mechanical properties of SEB-RM samples could be ascribed to the refined grains and the formation of FCC precipitates, mostly along the grain boundaries. This provides new insights into the dual-phase HEAs—fabricated via a combination of the SEBM additive manufacturing process and selective electron beam remelting—that exhibit in-situ strengthening.
Liquid phase (or liquid cell) transmission electron microscopy (TEM) has become a powerful platform for
in situ
investigation of various chemical processes at the nanometer or atomic level. The ...electron beam for imaging can also induce perturbation to the chemical processes. Thus, it has been a concern that the observed phenomena in a liquid cell could deviate from the real-world processes. Strategies have been developed to overcome the electron-beam-induced issues. This article provides an overview of the electron-beam effects, and discusses various strategies in liquid cell TEM study of nucleation, growth, and self-assembly of nanoscale materials, where an electron beam is often used to initiate the reactions, and highly electron-beam-sensitive electrochemical reactions.
Graphical abstract
Electron beam microscopy and related characterization techniques play an important role in revealing the microstructural, morphological, physical, and chemical information of halide perovskites and ...their impact on associated optoelectronic devices. However, electron beam irradiation usually causes damage to these beam‐sensitive materials, negatively impacting their device performance, and complicating this interpretation. In this article, the electron microscopy and spectroscopy techniques are reviewed that are crucial for the understanding of the crystallization and microstructure of halide perovskites. In addition, special attention is paid to assessing and mitigating the electron beam‐induced damage caused by these techniques. Since the halide perovskites are fragile, a protocol involving delicate control of both electron beam dose and dose rate, coupled with careful data analysis, is key to enable the acquisition of reliable structural and compositional information such as atomic‐resolution images, chemical elemental mapping and electron diffraction patterns. Limiting the electron beam dose is critical parameter enabling the characterization of various halide perovskites. Novel methods to unveil the mechanisms of device operation, including charge carrier generation, diffusion, and extraction are presented in scanning electron microscopy studies combined with electron‐beam‐induced current and cathodoluminescence mapping. Future opportunities for electron‐beam‐related characterizations of halide perovskites are also discussed.
Electron‐beam‐related characterization techniques play an important role in revealing microstructural, morphological, physical, and chemical information of halide perovskites. A number of experiments that explored the beam sensitivity of various perovskites are highlighted, including estimates of critical dose, and strategies for mitigating damage. An insight into properly characterizing beam‐sensitive halide perovskites or other soft crystalline materials with electron‐beam‐related techniques is provided.
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