Monocrystalline Structures Research Articles

Hierarchical ultra-thin porous Co3O4 nanosheets derived from mixed phase α- and β-Co(OH)2 for high sensitivity and ppb-level acetone sensing

Addressing the energy loss of carriers during transmission and achieving high sensitivity detection of target gases facilitates the synthesis of trace-level acetone sensors, which is of great significance in the fields of air quality early warning, health monitoring, and industrial safety monitoring. Here, we propose a strategy where, under hydrothermal conditions, the content of mixed-phase α- and β-Co(OH)2 is regulated by varying the protonation level of 2-methylimidazole in different solutions, leading to the formation of porous monocrystalline Co3O4 microflower structure. The microflower is assembled from ultrathin nanosheets, and the 3D-interconnected macroporous and mesoporous structure provides high surface area and gas diffusion channels. The monocrystalline and two-dimensional structures favor high carrier mobility, enhancing the signal-to-noise ratio. Furthermore, the thickness of the Co3O4 nanosheets is less than twice the Debye length, making their electrical properties completely dependent on surface. DFT calculations also indicate that the few layers Co3O4 model is conducive to acetone adsorption. The Co3O4 sensor exhibits exceptional gas sensing performance towards acetone, with favourable sensitivity (16.83 to 10 ppm), selectivity, and stability, as well as an ultra-low practical detection limit of 10 ppb. Rich point defects and line defects play a significant role in improving the surface activity of the sensitive material as well. This research offers a pathway for designing sensors with exceptional gas sensitivity by employing a straightforward method to control the morphology of sensitive materials, combined with defect engineering to enhance sensing activity.

A new method for improving the solar photovoltaic unit efficiency through neem oil as coolant medium for high power applications—an experimental investigation

The utilization of electric energy is rising in the technological world. Solar PV (photovoltaic) cells convert sunlight into electricity, and sunlight radiation also has heat, reducing the panel's efficiency. The heat should control the limited value or otherwise reduce the panel's performance so that heat is moved to the cooling medium, thus maintaining the heat within the functioning limit. The proposed method is explained by the probability of cooling the monocrystalline and polycrystalline structures used as neem oil through an integrated oil container fitted into the unit's backside—the neem oil acts as phase-changing material (PCM). The solar PV rear side neem oil absorbs the heat of the solar PV panel. The neem oil is not filled in the backside tank completely for the reason that the oil needed some breathing gap. The breathing gap of PCM is to enhance the heat-withstand efficiency. The backside neem oil is replaced every 30 min. As an outcome, the front side of solar PV heat is reduced. Neem oil has not polluted the environment and is thus also used to exchange noxious mineral oils. The neem oil moved from the depository tank to the backside of the unit and together into an additional depositor tank, thus being able to be reused. The proposed method is investigated, and functioning comparison occurs in different PV types, such as monocrystalline and polycrystalline modules, with various kinds of edible oil. Thus, the critical outcomes of the monocrystalline and polycrystalline PV panels are to decrease the panel temperature by 2.29% and 4.34%, respectively, and enhance the efficiency of the PV panels by 15.0% and 17.8%, respectively.

Ab initio investigation of structural, elastic, and thermodynamic characteristics of tetragonal XAgO compounds (X = Li, Na, K, Rb)

The present research utilizes ab initio computations to examine the thermodynamic, structural, and elastic characteristics of XAgO ternary oxides, where X signifies Li, Na, K, and Rb.The GGA-PBE and GGA-WC functionals were used to calculate the ground-state lattice parameters and atomic position coordinates of the title materials. The calculated results were in good agreement with both experimental measurements and theoretical predictions. This suggests that the GGA-PBE and GGA-WC functionals are accurate for describing the structural properties of the material under study.This study offers computational predictions for the elastic properties of monocrystalline structures and polycrystalline aggregates of XAgO compounds. These predictions encompass various key parameters, including single-crystal elastic constants, Young’s modulus, bulk modulus, Lame coefficients, Poisson’s ratio, shear modulus, and Debye temperature. Additionally, the quasi-harmonic Debye approximation is utilized to explore the temperature-dependent behavior of bulk modulus, Debye temperature, volume thermal expansion coefficient, and isobaric and isochoric heat capacities over an extensive temperature range, while maintaining constant pressures. The results obtained from this model are found to be highly successful in accurately predicting the behavior of these properties.

The implementation of thermal and UV nanoimprint lithography for selective area epitaxy

Semiconductor nanowires (NWs) in horizontal configuration could provide a path for scalable NW-based devices. Bottom–up large-scale manufacturing of these nanostructures by selective area epitaxy (SAE) relies on precise nanopatterning of various shapes on the growth masks. Electron beam lithography offers an extraordinary accuracy suited for the purpose. However, this technique is not economically viable for large production as it has a low throughput and requires high investment and operational costs. Nanoimprint lithography (NIL) has the potential to reduce fabrication time and costs significantly while requiring less sophisticated equipment. In this work, we utilize both thermal and UV NIL for patterning substrates for SAE, elucidating the advantages and disadvantages of each lithography technique. We demonstrate the epitaxial growth of Ge and GaAs NWs on these substrates, where we observe high-quality mono-crystalline structures. Even though both processes can produce small uniform structures suitable for SAE, our results show that UV NIL proves to be superior and enables reliable and efficient patterning of sub-100 nm mask features at the wafer scale.

Solar Energy Production in India and Commonly Used Technologies—An Overview

This review uses a more holistic approach to provide comprehensive information and up-to-date knowledge on solar energy development in India and scientific and technological advancement. This review describes the types of solar photovoltaic (PV) systems, existing solar technologies, and the structure of PV systems. Substantial emphasis has been given to understanding the potential impacts of COVID-19 on the solar energy installed capacity. In addition, we evaluated the prospects of solar energy and the revival of growth in solar energy installation post-COVID-19. Further, we described the challenges caused by transitions and cloud enhancement on smaller and larger PV systems on the solar power amended grid-system. While the review is focused on evaluating the solar energy growth in India, we used a broader approach to compare the existing solar technologies available across the world. The need for recycling waste from solar energy systems has been emphasized. Improved PV cell efficiencies and trends in cost reductions have been provided to understand the overall growth of solar-based energy production. Further, to understand the existing technologies used in PV cell production, we have reviewed monocrystalline and polycrystalline cell structures and their limitations. In terms of solar energy production and the application of various solar technologies, we have used the latest available literature to cover stand-alone PV and on-grid PV systems. More than 5000 trillion kWh/year solar energy incidents over India are estimated, with most parts receiving 4–7 kWh/m2. Currently, energy consumption in India is about 1.13 trillion kWh/year, and production is about 1.38 trillion kWh/year, which indicates production capacities are slightly higher than actual demand. Out of a total of 100 GW of installed renewable energy capacity, the existing solar capacity in India is about 40 GW. Over the past ten years, the solar energy production capacity has increased by over 24,000%. By 2030, the total renewable energy capacity is expected to be 450 GW, and solar energy is likely to play a crucial role (over 60%). In the wake of the increased emphasis on solar energy and the substantial impacts of COVID-19 on solar energy installations, this review provides the most updated and comprehensive information on the current solar energy systems, available technologies, growth potential, prospect of solar energy, and need for growth in the solar waste recycling industry. We expect the analysis and evaluation of technologies provided here will add to the existing literature to benefit stakeholders, scientists, and policymakers.

Ultrafast synthesis of HKUST-1 nanoparticles by solvothermal method: Properties and possible applications

Although an astounding variety of Metal-Organic Frameworks (MOFs) has been synthesized so far, the search for fast and efficient methods that yield greener and superior crystalline structures is yet an ongoing challenge. For the first time, the Hong Kong University of Science and Technology (HKUST-1) MOF has been synthesized by an efficient non-conventional solvothermal method through a Monowave 50 (Anton Paar) reactor. The synthesis has been carried out at 5, 10, 15, and 30 min instead of staggering times of 10 to 24 h. Its crystalline structure, crystallite size, morphology, particle size, specific surface, and optical properties have been characterized. The presumed presence of monocrystalline structures along with a roughly band gap energy at 3.5 eV makes them compelling nanostructures for a variety of applications.

Fluoride‐mediately oriented assembly of zirconia nanoparticles: 3D monocrystalline architectures and dye degradation

AbstractNano subunits self‐assembly provides a powerful approach for creating unique architectures of relevance for applications. While the use of organic surfactants to direct the assembly of nanoparticles is most popular, it remains a challenge to manipulate the order‐assembly of a large number of nanoparticles along desirable facets. Here, we describe a fluoride‐mediately solvothermal approach for building 3D monocrystalline ZrO2 architectures through oriented attach of ZrO2 nanoparticles in three dimensions, the preferential adsorption of fluoride on specific crystallographic planes may be critical to promoting the oriented aggregation of ZrO2 nanoparticles along rigid directions. After calcination, the dense monocrystalline architectures are transformed into porous monocrystalline structures with inherited morphology, uniform and well‐dispersed open pores. The sample before calcination exhibits a better performance in photocatalytic degradation of conge red in aqueous solution, while the sample after calcination shows a better adsorption effect in dark, the mechanism is discussed in detail.

Fracture characteristics and heat treatment of laser powder bed fusion additively manufactured GRCop-84 copper

Laser Powder Bed Fusion (LPBF) of Glenn Research Copper 84 (GRCop-84), a Cr2Nb (8 at. % Cr, 4 at. % Nb) precipitation hardened alloy, produces a fully dense high conductivity alloy with a yield strength of 500 MPa and ultimate tensile strength (UTS) of 740 MPa, superior to other competing copper alloys, and 20% elongation at fracture for material stressed perpendicular to the build direction. The high thermal stability of the Cr2Nb precipitate in the copper matrix reduces coarsening and maintains a 300 MPa yield, 520 MPa UTS and 26% elongation after a 900 °C, 5-h heat treatment, while a 3 h 450 °C heat treatment increases yield to 810 MPa, UTS to 970 MPa with 9% elongation at fracture, for samples stressed perpendicular to the build direction. Tensile strength anisotropy based on print direction was attributed to internal stress and columnar grain formation. Void nucleation during tensile fracture was initiated by brittle fracture of precipitate particles within the copper matrix. Fracture cusps contain matching precipitate fragment geometry on opposing sides located near the cusp center in at least 80% of fracture cusps. An optimal precipitate size of 100 nm is predicted for maximum tensile strength from precipitates on fracture surfaces, while tensile testing with varying heat treatments shows maximum strength with 100 nm and smaller precipitates. Cr2Nb precipitates are shown to transition between polycrystalline and monocrystalline structures at high temperature.

Enhanced Isopropanol Sensing Performance of the CdS Nanoparticle Decorated ZnO Porous Nanosheets-Based Gas Sensors

In present work, the CdS nanoparticle decorated ZnO porous nanosheets (CdS NP/ZnO PNs) were successfully synthesized through a facile wet-chemistry method. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive spectrum. The results proved the porous and monocrystalline structures of the ZnO nanosheets. A huge number of tiny CdS nanoparticles evenly cover the surface of the ZnO porous nanosheets, and the average size of the CdS nanoparticles is about 5 nm. The CdS NP/ZnO PNs exhibit excellent sensing activity and selectivity towards isopropanol. The linear response range is 1-100 ppm under the optimized operation temperature of 320 °C, and the detection limit is 1 ppm. The sensing performance of the CdS NP/ZnO PNs towards isopropanol is dramatically higher than that of other VOC gases, indicating the high selectivity to isopropanol. The CdS NP/ZnO PNs based sensor even can distinguish isopropanol from the complex mixed gases. Besides, the responses of the as-prepared sample to isopropanol seldom changed within 15 days. It is believed that the CdS NP/ZnO PNs have great application potential in isopropanol detection.

Selection of the Material for the Sensitive Elements of SAW-based Accelerometers

Introduction. At the present, sensors based on surface acoustic waves (SAW) is a rapidly developing direction and a promising replacement for classical sensors, especially in those areas where long-term performance of latter is questionable. The principle of operation of SAW sensors is based on acoustic vibrations, therefore, the choice of piezoelectric material of а console, considering external influences on a future device and its operating conditions, is the most important task. Currently, many monocrystalline structures and their sections have been synthesized and created for the devices using SAW. The main materials used for the manufacture of substrates are crystals of quartz (SiO2), lithium niobate (LiNbO3), lithium tantalate (LiTaO3) and film aluminum nitride (AlN). Also, new crystal structures: langasite (La3Ga5SiO14), langatate (La3Ga5.5Ta0.5O14), langanite and others were produced. The problem of using such materials for the manufacture of consoles is the lack of systematized data on important characteristics for the propagation of surfactants, for example, the elasticity tensor of the 4th rank. One of the key problems for the further development of SAW-based sensors is the one-way fastening of rectangular and triangular sensitive elements (SE) in sensor housing. In order to overcome the above drawback an MMA surfactant thing based on a membrane SE for a more uniform distribution of a load over the surface of the SE was proposed.Aim. To show the advantages of using AlN as the SE material of a ring wave resonator on SAW.Materials and methods. The theoretical part of the research was carried out using the finite element method. Mathematical processing was implemented in AutoCAD 2019 and in COMSOL Multiphysics 5.4.Results. The use of AlN, which acts as the SE material for measuring an acceleration based on SAW was proposed. The proposed solution was compared with existing prototypes based on the use of SiO2 / LiNbO3 membranes, which were characterized by strong anisotropic properties. A 3D model of the SE of a ring wave resonator on surface waves was created. Using computer simulations and COMSOL Multiphysics software, it was shown that the thing was capable to withstand exposures in excess of 10 000 g, and an isotropic AlN sensor overcomed the limitations of both the low sensitivity of SiO2 and the low temperature stability of LiNbO3. AlN demonstrated almost double resistance to irreversible mechanical deformations as compared to SiO2, which, in turn, allows an additional 1.5-fold increase in sensitivity compared to quartz – based sensors.Conclusion. Based on the data obtained by the modeling, it can be concluded that the use of AIN as SE material is promising, especially for measuring high acceleration values, but with restrictions on temperature sensitivity of the material.

Hyperuniform Monocrystalline Structures by Spinodal Solid-State Dewetting.

Materials featuring anomalous suppression of density fluctuations over large length scales are emerging systems known as disordered hyperuniform. The underlying hidden order renders them appealing for several applications, such as light management and topologically protected electronic states. These applications require scalable fabrication, which is hard to achieve with available top-down approaches. Theoretically, it is known that spinodal decomposition can lead to disordered hyperuniform architectures. Spontaneous formation of stable patterns could thus be a viable path for the bottom-up fabrication of these materials. Here, we show that monocrystalline semiconductor-based structures, in particular Si_{1-x}Ge_{x} layers deposited on silicon-on-insulator substrates, can undergo spinodal solid-state dewetting featuring correlated disorder with an effective hyperuniform character. Nano- to micrometric sized structures targeting specific morphologies and hyperuniform character can be obtained, proving the generality of the approach and paving the way for technological applications of disordered hyperuniform metamaterials. Phase-field simulations explain the underlying nonlinear dynamics and the physical origin of the emerging patterns.

Hydrogenation and Gettering Compatiblep-Type Contacts for Multicrystalline Silicon Cells, Free of Light, and Elevated Temperature Induced Degradation

Results for a room temperature contacting method applied to the p -type rear surface of monocrystalline and multicrystalline solar cell structures are presented. Monocrystalline silicon devices with the rear contacts prepared using the point contacting by localized dielectric breakdown method are reported with an efficiency of 19.2%. The devices show improved measurements of key performance metrics of ρc of 1.6 ± 0.8 mΩcm2 and J 0 c of 2100 ± 650 fAcm−2. This contacting approach is also demonstrated for multicrystalline silicon cells, with no evidence of parasitic breakdown at grain boundary sites. The multicrystalline device implementation highlights a key advantage of this contacting method, namely a relatively free choice of annealing temperature. This flexibility allows process optimization such that the activation of light-and-elevated-temperature-induced degradation is prevented in hydrogenated multicrystalline silicon, while still maximizing the benefits to bulk lifetime.

Multipath energy transfer and NIR luminescent properties of dual-lanthanide complexes

Near infrared (NIR)-emitting lanthanide ions, especially Sm3+, Nd3+, Yb3+, and Er3+, show special advantages in non-damage and deep-reaching biological imaging and telecommunication field. But most lanthanide ions have low luminescent efficiency in the NIR region, as a result of insufficient protection of the metal centers against non-radiative deactivation processes and/or inefficient inter- or intramolecular energy transfer. In recent years, organic ligands have been used as antennas to sensitize lanthanide ions to improve their luminescent efficiency. Because the chemical properties of lanthanide ions are very similar, mixed lanthanide complexes can be formed. At the same time, lanthanide ions have many energy levels, the energy transfer is easy to occur between different lanthanide ions. Thus, we can make use of these multi-path energy transfers to obtain efficient dual/multi-lanthanide multi-component NIR luminescent materials, which can be used for the ideal multi-channel near-infrared luminescence anti-counterfeiting bar code application. Herein, A series of NIR luminescent mono- or dual-lanthanide complexes were synthesized by TVPNTB ligand with lanthanide chloride salts. The monocrystalline structures of these rare earth complexes were obtained by X-ray single crystal diffraction. These lanthanide complexes are all hetero-isomorphic structures, crystallized in the monoclinic system and belong to P 21/ c space group. The phase purity was also proved by powder X-ray diffraction (PXRD). For the series of one component lanthanide complexes, the ligand TVPNTB can transfer energy to the excited state energy level of Sm3+, Nd3+, Er3+, Yb3+, Pr3+, Dy3+, and Ho3+, and produce NIR luminescence of the order of microsecond lifetime. Among them, the NIR luminescence studies of several lanthanide complexes such as Pr3+, Dy3+, Er3+, and Ho3+ are rarely reported. The results showed that the TVPNTB ligand has good near-infrared photosensitization effects on Sm3+, Nd3+, Yb3+, and Er3+. Moreover, by comparing the energy level difference of these ions, it is found that the energy level difference of Sm3+ from 4G2/5 to 6F5/2 is close to the energy level difference of Yb3+ from 2F5/2 to 2F7/2 in the ground state, and the energy level difference of Nd3+ from 4F3/2 to 4I11/2, which may lead to the cross relaxation energy transfer between rare earth ions and enhance the luminescence of Yb3+ and Nd3+. So we prepared a series of dual-lanthanide complexes, such as TVPNTB-Sm x Nd1 −x Cl3, TVPNTB-Sm x Yb1 −x Cl3 and TVPNTB-Sm x Er1 −x Cl3. Energy transfer from the antenna ligand can sensitize both NIR luminescence of the two lanthanide ions, which might serve as NIR polychromatic anti-counterfeiting luminescent barcode materials. We also investigated the energy transfer properties between the dual lanthanide ions, and confirmed that crossing relax energy transfer from Sm3+ to Nd3+, or from Sm3+ to Yb3+ were realized. The largest energy transfer efficiency ( η ) reaches 39% and 36%, leading to 4 or 2 times longer of the decay lifetimes of Nd3+ and Yb3+, respectively. Through the study of NIR luminescence performance of dual-lanthanide complexes with different proportions, it is clear that in addition to the antenna energy transfer from ligand to lanthanide ions, there is also a cross-relaxation energy transfer process from Sm3+ to Nd3+ and Sm3+ to Yb3+, thus achieving the effective energy transfer between dual-lanthanide complexes, thus further improving the NIR luminescence life of Nb3+ and Yb3+. The multi-path energy transfer strategy summarized in this study not only provides a basis for the preparation of novel high-performance NIR luminescent rare earth complexes, but also provides a reference for the design and synthesis of other multifunctional composite optical materials.

Directional Crystallization of 316L Stainless Steel Specimens by Direct Laser Deposition

Advantages of direct laser deposition of metal providing the directional crystallization of 316L stainless steel specimens are shown. It is found that direct laser deposition of metal offers exciting possibilities for obtaining monocrystalline structures by directional crystallization of the deposited metal. The metal structure of the obtained specimens is represented by dendritic crystals oriented toward the thermal center. The cross-section view of the structure, formed by the crystal axes of the first order, is of the form of honeycombs. The thickness of the applied layer (200 µm) in the central part of the specimen does not prevent the development of the dendrite structure and it contributes to the formation of the monocrystalline structures (having no pores and cracks). It was stated that the growth orientation of dendritic crystals is driven by the thermal center determined by the position of the laser spot. A technique of manufacturing stainless steel products by direct laser deposition using the developed algorithm which allowed connecting the movement of the robotic center and specimen, laser switching, and feeding of the gas-powder mixture was presented. The possibilities of estimating the inclination angle of dendritic crystals in the metal relative to the symmetry axis of the specimen using a metallographic software package for analysis of digital images of the microstructures, as well as the quality control of the items obtained by the X-ray tomographic quality control, determination of the parameters of the laser spot on the substrate surface using high-speed photography, and estimation of the phase composition of the deposited metal using X-ray diffraction analysis, are shown. In such a case, the roughness of the specimens determined by the size of the powder particles may be removed by mechanical treatment.

Particulates in the ascending gas caused by the 2013 Ya'an earthquake: A new matter released by earthquake

Earthquakes can be destructive, killing many people and causing great financial loss. Costs from earthquakes are increasing rapidly, and thus seismic research is an important tool for reducing loss. Traditional studies of earthquakes have mainly been based on geophysics (seismic waves, geomagnetism, and geoelectricity), hydrogeology, and geogas. However, earthquakes can also release numerous particulates, which can be carried by ascending gas to reach the surface. These particulates provide us with abundant and direct information about earthquake activity and can serve as a new medium for studying earthquakes. In this study, we first find, using a transmission electron microscope (TEM), that ascending gas in the soil of the 2013 Ya'an earthquake region carries many particulates. These particulates are usually 20–600 nm and are composed of amorphous crystal, monocrystalline, and polycrystalline structures. In addition, these particulates contain O, Na, Mg, Al, Si, P, S, Cl, K, Ca, Cr, Fe, Zn, Ba, Hg, Ti, Mn, Ni, Cu, Cd, Sn, Sb, Cs, Pt, and Pb. Compared to the background areas (Yuhe and Hongzi Village and the Fengguanshan inactive fault), particulates carried by ascending gas in the Ya'an earthquake region have many abnormal elements (element associations), including Ti, Mn, Ni, Cd, Sn, Sb, Pt, and Pb. This finding confirms our hypothesis that earthquakes can release particulates carried by ascending gas that reach the surface. In addition, the elements occurring in these particulates indicate that earthquakes can trigger element activation and migration in the form of particulates. As particulates carried by ascending gas in the earthquake region are significantly different from those in the background areas, they can be used to predict earthquakes. The particulates in our study are significantly different from particulates carried by ascending gas from ruptures caused by the Wenchuan earthquake; therefore, we first propose that particulates in ascending gas from earthquake regions may exhibit a close relationship with the magnitudes and hypocentre depths of earthquakes and can be used to predict earthquakes with larger magnitudes and deeper hypocentre depths.

Exchange-biased hybrid γ-Fe2O3/NiO core-shell nanostructures: three-step synthesis, microstructure, and magnetic properties.

A two-step solvothermal method combining a calcination process was conducted to synthesize γ-Fe2O3/NiO core-shell nanostructures with controlled microstructure. The formation mechanism of this binary system has been discussed, and the influence of microstructures on magnetic properties has been analyzed in detail. Microstructural characterizations reveal that the NiO shells consisted of many irregular nanosheets with disordered orientations and monocrystalline structures, packed on the surface of the γ-Fe2O3 microspheres. Both the grain size and NiO content of nanostructures increase with the increasing calcination temperature from 300 °C to 400 °C, accompanied by an enhancement of the compactness of NiO shells. Magnetic studies indicate that their magnetic properties are determined by four factors: the size effect, NiO phase content, interface microstructure, i.e. contact mode, area, roughness and compactness, and FM-AFM (where FM and AFM denote the ferromagnetic γ-Fe2O3 and the antiferromagnetic NiO components, respectively) coupling effect. At 5 K, the γ-Fe2O3/NiO core-shell nanostructures display certain exchange bias (HE = 60 Oe) and enhanced coercivity (HC = 213 Oe).

Advanced high pressure turbine blade repair technologies

Components in aircraft engines and gas turbines are exposed to extreme conditions in order to increase performance and efficiency of the overall engine, hence there is an increasing need for cost-effective and time-efficient repair strategies. Presented here are two novel approaches to the repair of Nickel-based components. The hybrid brazing process involves the application of a repair coating, a nickel-based filler material, a NiCoCrAlY and an aluminium layer, by thermal spraying followed by a heat treatment and combined brazing-aluminizing process. This significantly shortens the conventional repair brazing process and yields superior results. Single-crystal additive repair by laser cladding is applied for the repair of small or large defects in single-crystal turbine blades by enabling monocrystalline solidification of the cladded material by use of a temperature gradient, thereby allowing for the regeneration of these expensive components. The novel approach that combines layer-wise addition of material and laser melting enables the formation of highly monocrystalline structures.

Electron microscopy by specimen design: application to strain measurements

A bewildering number of techniques have been developed for transmission electron microscopy (TEM), involving the use of ever more complex combinations of lens configurations, apertures and detector geometries. In parallel, the developments in the field of ion beam instruments have modernized sample preparation and enabled the preparation of various types of materials. However, the desired final specimen geometry is always almost the same: a thin foil of uniform thickness. Here we will show that judicious design of specimen geometry can make all the difference and that experiments can be carried out on the most basic electron microscope and in the usual imaging modes. We propose two sample preparation methods that allow the formation of controlled moiré patterns for general monocrystalline structures in cross-section and at specific sites. We developed moiré image treatment algorithms using an absolute correction of projection lens distortions of a TEM that allows strain measurements and mapping with a nanometer resolution and 10−4 precision. Imaging and diffraction techniques in other fields may in turn benefit from this technique in perspective.

Effects of polymer surface energy on morphology and properties of silver nanowire fabricated via nanoimprint and E-beam evaporation

In this paper, we demonstrate that use of different nanoimprint resins as a polymer pattern has a significant effect on the morphology of silver (Ag) nanowires deposited via an E-beam evaporator. RM-311 and Ormo-stamp resins are chosen as a polymer pattern to form a line with dimensions of width (100nm)×space (100nm)×height (120nm) by using nanoimprint lithography (NIL). Their contact angles are then measured to evaluate their surface energies. In order to compare the properties of the Ag nanowires deposited on the various polymer patterns with different surface energies, hydrophobic surface treatment of the polymer pattern surface is implemented using self-assembled monolayers. In addition, gold and aluminum nanowires are fabricated for comparison with the Ag nanowires, with the differences in the nanowire morphologies being determined by the different atomic properties. The monocrystalline and polycrystalline structures of the various Ag nanowire formations are observed using transmission electron microscopy. In addition, the melting temperatures and optical properties of four kinds of Ag nanowire morphologies deposited on various polymer patterns are evaluated using a hot plate and an ultraviolet-visible (UV–vis) spectrometer, respectively. The results indicate that the morphology of the Ag nanowire determines the melting temperature and the transmission. We believe that these findings will greatly aid the development of NIL, along with physical evaporation and chemical deposition techniques, and will be widely employed in optics, biology, and surface wettability applications.

Synthesis and Characterization of Monocrystalline GaPSi3 and (GaP)y(Si)5–2y Phases with Diamond-like Structures via Epitaxy-Driven Reactions of Molecular Hydrides

Hybrid (III–V)–(IV) alloys described using the general formula (GaP)y(Si)5–2y have been synthesized as epitaxial layers on Si(100) using specially designed chemical vapor deposition methods. Reactions of [D2GaN(CH3)2]2 with P(SiH3)3 between 525 and 540 °C gave GaPSi3 (y = 1) with a fixed Si content of 60%, while analogous reactions of [H2GaN(CH3)2]2 at >590 °C produced Si-rich derivatives with tunable Si contents in the range of 75–95% (y < 1). In both cases, diffraction studies and optical characterizations demonstrate single-phase, monocrystalline structures with an average diamond cubic lattice akin to Si. Raman scattering supports the presence of a tetrahedral structure containing isolated Ga–P pairs randomly embedded within the parent Si matrix. This outcome is consistent with theoretical simulations of a crystal growth mechanism involving interlinking GaPSi3 tetrahedra in a manner that precludes the formation of energetically unfavorable Ga–Ga bonds. Ellipsometry measurements of the dielectric funct...