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This study carried out interfacial tension (IFT) testing, sand surface element analysis and scanning electron microscope imaging, rock–oil–emulsification system interaction testing, and microstructure, droplet size distribution, and stability of oil in water (O/W) emulsion to clarify the porous media flooding mechanism of a hydrophilic nano-SiO2 enhanced emulsification system. The results show that by adding a small amount of nano-SiO2 (0.01 wt. %) into an anionic surfactant fatty alcohol polyoxyethylene ether sodium hydroxypropyl sulfonate (AEOSHS) solution (0.5 wt. %), the IFT of oil–water was effectively reduced, the adsorption loss of AEOSHS on the formation sand surface was reduced by more than 70%, and the droplet size of the formed O/W emulsion was reduced by 50%. This greatly improves the effective concentration of AEOSHS and emulsifies the heavy oil ability in the formation away from the injection well. Moreover, the spreading ability of oil on the core surface is greatly reduced, and the width of the diffusion zone is narrowed. Meanwhile, a very clear dividing line of oil can be seen, which shows that the wettability of the core has changed to water wet. The stability of the formed O/W emulsion was further enhanced, and the coalescence and migration process of the droplet is extremely slow. The oil recovery of the AEOSHS + nano-SiO2 system can effectively increase 21.95% of the original oil in place. Both the sand-packed tube experiment and the microscopic visual oil flooding experiment show that the system can not only expand the swept volume but also improve the oil displacement efficiency, which means that the combined system can significantly improve the oil displacement effect. [ABSTRACT FROM AUTHOR]

The mechanical properties characterization of silicon nanowires is generally performed by tensile nanomechanical loading tests with in situ strain quantification. While the strain is characterized by electron beam (e-beam) microscopy techniques, the understanding of the sample-electron interaction is essential to guarantee artifact-free measurements. In this work, we investigated suspended strained silicon nanowires under electron beam exposure in a scanning electron microscope (SEM). The fabricated nanowires had their initial stress profile characterized by Raman spectroscopy and finite element method simulations. Then, the sample was exposed to an e-beam where we observed a gradual electrical charging of the sample, verified by the image drift, and down deflection of the suspended nanowire caused by electrostatic forces. These additional stresses induced the mechanical fracture of the nanowires in the corner region due to accumulated stress. These results ascribe electrostatic mechanical loading concerns that may generate undesirable additional stresses in nanomechanical tests performed in SEM, demonstrating the importance of proper sample preparation to avoid electrostatic charging effects. Here, we propose a simple and effective method for imposing the structures under an impinging electron beam at an equipotential, which mitigates the charging effects acting on the nanowire. [ABSTRACT FROM AUTHOR]

We report in this Letter a kind of asymmetric discharge mode in positive and negative half-cycles of dielectric barrier discharge in ambient air. This phenomenon is characterized by homogeneous and filamentary discharges occurring alternately in the two half-cycles, using two different materials of alumina ceramic and quartz as the dielectric barrier at each side. The discharge current waveforms, discharge images, optical emission spectra, and the averaged electron energy are significantly different for the asymmetric discharges. It is suggested that the seed electrons and secondary electron emission from the different dielectric materials acting as the temporary cathode are responsible for the different discharge modes. [ABSTRACT FROM AUTHOR]

We have successfully deposited a thin film of rare earth oxide on a Si substrate. After morphological characterization via a scanning electron microscope and an atomic force microscope, the electrical properties of the Al/Dy2O3/Si MOS structure were investigated using the current–voltage I(V) and capacitance–voltage C(V) measurements, as well as a study in the dynamic regime (AC) via conductance–frequency σ(f) measurements at different temperatures. Based on the classical Schottky model, we were able to determine some physical parameters, namely, the ideality factor and the potential barrier height. The effect of resistance and interface states on the current–voltage characteristics is observable and results in a deviation from the ideality factor. Then, dielectric data have been acquired by means of impedance spectroscopy over a wide frequency and temperature range. These results show that understanding the temperature dependence of the electrical characteristics of this structure may be of great help in improving the quality of Dy2O3 developed on a Si substrate for the future of device technology. [ABSTRACT FROM AUTHOR]

This paper presents a detailed study on the dimensional accuracy of Ti6Al4V parts manufactured by the wire feed laser directed energy deposition process as compared to the design data before any postprocessing, as the majority of the reported research is focused on the mechanical and microstructural properties of the manufactured parts. Due to the large layer thickness (1.2 mm) and high material deposition rate (15 mm/s), smaller rectangular samples were susceptible to more dimensional inaccuracies. Most of the samples have larger dimensions than the design data, which is favorable for postprocessing. Special consideration should be given to the Z axis as the top layer has the most curves on the periphery of the samples due to shrinkage upon cooling. Depositing the material along the periphery of the present layer at the start of each layer minimized the overflow of the molten alloy when the laser is near the edges of the model in each layer. Upon further inspection using an optical microscope and scanning electron microscope analysis, surfaces voids were observed. Only ∼0.5 mm was required to remove from each side to obtain a minimal crack-free flat surface. The microhardness of the samples ranged from 313.64 to 346.17 HV. [ABSTRACT FROM AUTHOR]

Images and spectra obtained from aberration corrected scanning transmission electron microscopes (STEM) are now used routinely to quantify the morphology, structure, composition, chemistry, bonding, and optical/electronic properties of nanostructures, interfaces, and defects in many materials/biological systems. However, obtaining quantitative and reproducible atomic resolution observations from some experiments is actually harder with these ground-breaking instrumental capabilities, as the increase in beam current from using the correctors brings with it the potential for electron beam modification of the specimen during image acquisition. This beam effect is even more acute for in situ STEM observations, where the desired outcome being investigated is a result of a series of complicated transients, all of which can be modified in unknown ways by the electron beam. The aim in developing and applying new methods in STEM is, therefore, to focus on more efficient use of the dose that is supplied to the sample and to extract the most information from each image (or set of images). For STEM (and for that matter, all electron/ion/photon scanning systems), one way to achieve this is by sub-sampling the image and using Inpainting algorithms to reconstruct it. By separating final image quality from overall dose in this way and manipulating the dose distribution to be best for the stability of the sample, images can be acquired both faster and with less beam effects. In this paper, the methodology behind sub-sampling and Inpainting is described, and the potential for Inpainting to be applied to novel real time dynamic experiments will be discussed. [ABSTRACT FROM AUTHOR]

Natural antioxidants are available in various biomass substances which can be used for improving human health and fuel oxidation stability. This research is aimed at using a natural antioxidant powder obtained from Albizia lebbeck leaves powder to improve the oxidation stability of an optimal Jatropha methyl ester (JME)-diesel blend. Initially, Albizia lebbeck leaves are characterized by x-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy, and energy dispersive spectroscopy for their oxidant behavior. The optimal JME diesel blend (JME20) has a mixture of 20% JME and 80% diesel. The antioxidant at different concentrations, viz., 500, 1000, 1500, and 2000 ppm, is doped in JME20, and the blends are designated as AL1, AL2, AL3, and AL4, respectively. The test engine is converted to run on the low heat rejection (LHR) mode by coating the piston with a mixture of two different ceramic materials, i.e., yttria-stabilized zirconia and cerium oxide (CeO2), with a thickness of 0.3 mm of the topcoat and 0.15 mm of the bond coat of material NiAl. The emissions, performance, and combustion of the test engine run on antioxidant-doped JME20 fuels in conventional engine operation and LHR mode are evaluated, analyzed, and presented in this paper. Results indicate that, among the four antioxidant-doped JME20 fuels, JME20AL4 gives better performance and lower exhaust emissions. The engine's cylinder pressure and heat release rate are decreased by about 4.7% and 6.4%, respectively, at full load, for JME20 AL4. The delay period and combustion duration of the fuel are improved by about 26.8% and 10.8%, respectively, at maximum load. The NO, HC, and CO emissions are reduced by about 17.3%, 19.3%, and 44.2%, respectively, for JME20 AL4, at maximum load. [ABSTRACT FROM AUTHOR]

Oxide layer is easily formed on the surface of some metal droplets, which affects the dynamic behavior of droplet impact. In this paper, experiments were conducted for the impacting process of a molten aluminum droplet on a Teflon substrate. The thickness of surface oxide layer of aluminum droplets was controlled by varying oxygen concentrations in the gas atmosphere. The effects of oxygen concentration and Weber number on droplet spread, rebound, and splash behavior were investigated. The results show that the oxygen concentration in the environment directly affects the droplet impact behavior. The differences in the droplet retraction process at different oxygen concentrations are more significant than the spread process. Strong retraction causes droplet rebound (We = 17.11) and splash (We = 102.3) in hypoxic environments, whereas only weak retraction in air. The viscous dissipation of the droplet impact in different oxygen concentration environment is estimated by counting the droplet bounce height, and the dissipation increases with the increase in the oxygen concentration. The thickness of the oxide layer measured by scanning electron microscope became thinner as the oxygen concentration decreases and, accordingly, the aluminum droplet collisions show different dynamic behavior. The experimental results are analyzed and explained regarding the reduction in surface tension, the increase in viscous forces, and the shear-thinning properties which increase the viscous dissipation during retraction. Ryan model was used to predict the droplet maximum spreading factor ξ max with the Weber number to the power of 0.5, better than the energy conservation-based Pasandideh-Fard model. [ABSTRACT FROM AUTHOR]

We have investigated the grain-boundary scattering effect on the thermal transport behavior of uranium dioxide ( UO 2). The polycrystalline samples having different grain-sizes (0.125, 1.8, and 7.2 μ m) have been prepared by a spark plasma sintering technique and characterized by x-ray powder diffraction, scanning electron microscope, and Raman spectroscopy. The thermal transport properties (the thermal conductivity and thermoelectric power) have been measured in the temperature range of 2–300 K, and the results were analyzed in terms of various physical parameters contributing to thermal conductivity in these materials in relation to grain-size. We show that thermal conductivity decreases systematically with lowering grain-size in the temperatures below 30 K, where the boundary scattering dominates the thermal transport. At higher temperatures, more scattering processes are involved in the heat transport in these materials, making the analysis difficult. We determined the grain-boundary Kapitza resistance that would result in the observed increase in thermal conductivity with grain-size and compared the value with Kapitza resistances calculated for UO 2 using molecular dynamics from the literature. [ABSTRACT FROM AUTHOR]

The influence of postgrowth thermal annealing on GaSbBi Schottky barrier diodes has been investigated. The effects of the annealing temperature and time on the material quality and electrical characteristics of the diodes have been studied. The I-V characteristics indicated a better ideality factor and less leakage current at the reverse bias, as the annealing temperature increased up to 500 °C for a duration of 30 min. X-ray diffraction and scanning transmission electron microscope measurements were performed to verify that the bismuth composition was unaffected during the annealing process. Energy dispersive x-ray analysis indicated that Sb clustering occurs at high annealing temperatures, resulting in a concomitant degradation in the electrical performance. The optimum electrical characteristics of the diode were obtained with an annealing temperature of 500 °C for 30 min, resulting in an ideality factor of 1.3 being achieved. [ABSTRACT FROM AUTHOR]

We show that secondary electrons in a scanning electron microscope can provide important information about spatial dopant distribution in p-i-n GaN structures, with the highest contrast observed for a primary electron beam accelerating voltage in the range of 1 to 2 kV. The current through the specimen is used to determine the total backscattered and secondary electron yield. We establish a correlation between the secondary electron emission intensity and the doping characteristics of the material. The secondary electron emission intensity was found to be highest for p-type GaN, intermediate for n-type GaN, and lowest for undoped GaN. Specimen currents are found to have a strong correlation with the Mg concentration in p-GaN films. The contrast associated with dopants is shown to depend on experimental parameters such as primary electron beam voltage, total electron beam exposure, and specimen surface history. This technique can serve as a powerful tool for the development and characterization of thin films for GaN power electronics. [ABSTRACT FROM AUTHOR]

Low temperature Carbon Nano-tubes (CNTs) growth technology is developed in this work with the insert of Al (Aluminum) between Ni (Nickel) and Ti (Titanium) as the reactant. The optimized Al thicknesses are also investigated. CNTs growth at the low temperature below 400 °C is the key factor for the back end of line compatible process integration. In this work, we grow the CNTs by thermal chemical vapor deposition process at 350 and 400 °C. The low ratio of peak ID/IG in Raman spectra and scanning electron microscope images proves the CNTs material quality. On the other hand, the high thermal conductivity (k) value of ∼50 W m − 1 K − 1 is also demonstrated. Both high material quality and k value on our low temperature grown CNTs show promising opportunities for the integration of semiconductor three dimensional packages and power-via related applications. [ABSTRACT FROM AUTHOR]

Owing to the parasitic vibration effect of the cooling medium and pipes of X-ray optics, the vibration decoupling cooling method based on eutectic gallium–indium (EGaIn) alloy has become very crucial for fourth generation synchrotron radiation advanced light sources. However, there is an issue that the corrosion of the EGaIn alloy to the heat sink metal [e.g., copper (Cu) plate] results in the solidification and the failure of eliminating the parasitic vibration effect. To deal with the problem, a novel anti-corrosion coating based on tungsten (W) is presented in this paper. It possesses better corrosion resistance performance compared with the traditional coating of nickel (Ni). The experimental investigation was carried out, in which the EGaIn alloy was exposed to several typical metal materials in conditions of various time durations and various temperatures, which were considered as controls. Furthermore, the corrosion effects are analyzed and evaluated in two aspects of micromorphology and the chemical composition by using an optical microscope and a scanning electron microscope as well as x-ray diffraction. The results show that non obvious corrosion occurred for W, 0.33 mm and 48 µm thick transition micro-area, respectively, for Cu and Ni. In addition, new substances CuGa2 and Ni3Ga7 occurred, respectively, for Cu and Ni for 36 hours at 250 °C. The EGaIn alloy will freeze after corroding 18 µm substrate for Ni or 30 µm for Cu. Furthermore, the W coating that was prepared by magnetron sputtering has been implemented for feasibility validation. [ABSTRACT FROM AUTHOR]

Surface texture has aroused widespread interest due to its role in controlling friction, reducing wear, and improving lubrication performance. As one of the most promising green processing technologies, Laser Powder Bed Fusion (LPBF) can manufacture complex structures, effectively reducing manufacturing constraints and significantly increasing structural design freedom. In this study, the powder bed model was established by numerical simulation, and the influence of different energy inputs on the morphology and characteristics of the molten pool was investigated. Based on this, the optimal forming process parameters of CuSn10 were selected. In addition, LPBF is used to process different textures (square texture, circular texture, hemispheric texture, and triangle texture) on the surface of CuSn10. The surface texture's structural accuracy, surface morphology, and wettability were studied using a profiler, scanning electron microscope, and contact angle measuring instrument, respectively. The research results show that the accuracy of the square texture structure is the closest to the original design model among all the samples and the hemispheric texture surface does not have severe powder adhesion; as a result, it has the lowest average surface roughness of 5.58 µm. However, the triangle texture has the worst formation quality. It was revealed that the stepping effect mechanism of irregularly formed surfaces is the most important reason to cause this phenomenon. In addition, the maximum contact angle of the square texture is 85.59°, which is 15.76% higher than that of the triangle texture. [ABSTRACT FROM AUTHOR]

The photocurrent from a semiconductor photocathode with a negative-electron affinity surface can be arbitrarily controlled by the excitation laser power. Applying this characteristic to a scanning electron microscope allows the probe current to be arbitrarily controlled at any location on the sample. A photocathode with a fast time response is required to control the probe current at high speed. This study used an InGaN photocathode for pulsed electron beam generation and investigated its time response. A pulsed electron beam with 3.8 ns pulse width and 8.1 × 103 A cm−2 current density was observed, and the rise and fall times of the photocurrent were found to be 1.7 and 2.0 ns, respectively. The results show that despite the bottleneck of the time response of the laser power, the InGaN photocathode generates an electron beam that can control the probe current on a pixel-by-pixel for a 270 MHz scan speed. [ABSTRACT FROM AUTHOR]

Pulsed electron beams from a photocathode using an InGaN semiconductor have brought selectively scanning technology to scanning electron microscopes, where the electron beam irradiation intensity and area can be arbitrarily selected within the field of view in SEM images. The p-type InGaN semiconductor crystals grown in the metalorganic chemical vapor deposition equipment were used as the photocathode material for the electron beam source after the surface was activated to a negative electron affinity state in the electron gun under ultrahigh vacuum. The InGaN semiconductor photocathode produced a pulsed electron beam with a rise and fall time of 3 ns, consistent with the time structure of the irradiated pulsed laser used for the optical excitation of electrons. The InGaN photocathode-based electron gun achieved a total beam operation time of 1300 h at 15 μA beam current with a downtime rate of 4% and a current stability of 0.033% after 23 cycles of surface activation and continuous beam operation. The InGaN photocathode-based electron gun has been installed in the conventional scanning electron microscope by replacing the original field emission gun. SEM imaging was performed by selective electron beaming, in which the scanning signal of the SEM system was synchronized with the laser for photocathode excitation to irradiate arbitrary regions in the SEM image at arbitrary intensity. The accuracy of the selection of regions in the SEM image by the selective electron beam was pixel by pixel at the TV scan speed (80 ns/pix, 25 frame/s) of the SEM. [ABSTRACT FROM AUTHOR]

Quantitatively accurate, physics-based, computational modeling of etching and lithography processes is essential for modern semiconductor manufacturing. This paper presents lithography and etch models for a trilayer process in a back end of the line manufacturing vehicle. These models are calibrated and verified against top-down scanning electron microscope (SEM) and cross-sectional SEM measurements. Calibration errors are within 2 nm, while the maximum verification error is less than 3 nm. A fluorocarbon plasma etch of the spin-on-glass (SOG) layer accounts for most of the etch bias present in the process. The tapered profile in the SOG etch step is generated due to the polymerization process by fluorocarbon radicals generated in the plasma. The model predicts a strong correlation between the etch bias in the SOG etch step and the neutral-to-ion flux ratio in the plasma. The second etch step of the flow, which etches the spin-on-carbon (SOC) layer using an H2/N2 plasma, results in a negative etch bias (increase in CDs) for all measured features. The ratio of hydrogen to nitrogen radical fluxes effectively controls the etch bias in this step, with the model predicting an increase in the etch bias from negative to positive values as the H-to-N ratio decreases. The model also indicates an aspect ratio dependent etch rate in the SOG and SOC etch steps, as seen in the etch front evolution in a three-dimensional test feature. The third and final step of the process, SiO2-etch, generates an insignificant etch bias in all the test structures. Finally, the accuracy of the etch simulations is shown to be dependent on the accuracy of the incoming photoresist shapes. Models that consider only the top-down SEM measurement as input and do not account for an accurate photoresist profile, suffered significant errors in the post-etch CD predictions. [ABSTRACT FROM AUTHOR]

High-quality flexible membranes have promoted a myriad of applications in soft electronics or spintronic devices. Nevertheless, magnetic membranes that can withstand strong folding and rolling distortions have rarely been reported. Here, we found that the few to tens of nanometer thick LaMnO3 membranes with single-crystalline qualities exhibit superflexibility, demonstrated by self-folding and rolling into few-micron and sub-micron features. The combined scanning transmission electron microscope and selected area electron diffraction experiments simultaneously confirm the 180° folded single crystalline structure and the associated bending curvature and strain as large as 2 μm−1 and 4%. Furthermore, the scanning electron microscope revealed that as the membrane thickness decreases from 40 to 20 nm and 8 nm, the 180° folding is replaced by self-rolling into few-micron size tubes. Magnetization measurements revealed a large saturation (remnant) magnetization enhancement of 21% (34%) achieved in a macroscopically forced bending state under a similar bending strain of 4.9%. This work demonstrates the superflexibility of manganite oxide membranes which promise superior potential in flexible magnetic device applications. [ABSTRACT FROM AUTHOR]

To test the effect of pre-curing time on the impact resistance of reactive powder concrete (RPC), RPC specimens were cured in a steam curing box at a temperature of 70 °C for 72 h with pre-curing times of 18, 24, and 30 h. At 28 days, the low-speed impact test was carried out on RPC specimens with a Ceast9350 drop weight impact system at an impact rate of 5 m/s and impact energy of 140 J. The variation curves of the impact force and displacement of RPC specimens with impact times were obtained. The results show that the impact resistance of RPC specimens improved with the increased pre-curing time, implying that appropriate pre-curing time (30 h in this case) can improve RPC mechanical properties. At the same time, combined with x-ray diffraction, scanning electron microscope imaging of hydration products, and the energy dispersion spectroscopy test, the influence mechanism of pre-curing time on the impact resistance of RPC is analyzed from the microstructure standpoint. The results show that appropriate pre-curing time can make the hydration of cement form finer particles and make the hardened paste form a protective structure to reduce the damage of steam curing in the strength development process. Through multiscale homogenization calculation via the Mori–Tanaka scheme, it can be seen that RPC's stiffness increases with the prolonged pre-curing time. Optimizing pre-curing time is conducive to improving the mechanical properties of RPC specimens. [ABSTRACT FROM AUTHOR]

The electron beam induced current (EBIC) mode of a scanning electron microscope (SEM) is a widely used technique for the quantitative assessment of minority carrier diffusion length and surface recombination. Point source (one-dimensional) and extended source (two-dimensional) analytical models are two widely used approaches to assess this information in geometry where the electron beam (e-beam) is parallel to the p-n junction. In this article, a two-dimensional (2D) analytical model is evaluated and compared with 2D finite element numerical simulations, where the electron beam-solid interaction is modeled using a Monte Carlo simulation coupled with a drift-diffusion solver. The simulations are computed for both low and high level injection conditions. The effect of an e-beam injection level on the shape of EBIC profiles is analyzed to evaluate limitations of the analytical models. [ABSTRACT FROM AUTHOR]

Taking advantage of electron diffraction based measurements, in a scanning electron microscope, can deliver non-destructive and quantitative information on extended defects in semiconductor thin films. In this work, we have studied a (11-22) semi-polar GaN thin film overgrown on regularly arrayed GaN micro-rod array templates grown by metal organic vapour phase epitaxy. We were able to optimise the diffraction conditions to image and quantify basal plane stacking faults (BSFs) and threading dislocations (TDs) using electron channelling contrast imaging (ECCI). Clusters of BSFs and TDs were observed with the same periodicity as the underlying micro-rod array template. The average BSF and TD densities were estimated to be ≈4 × 104 cm−1 and ≈5 × 108 cm−2, respectively. The contrast seen for BSFs in ECCI is similar to that observed for plan-view transmission electron microscopy images, with the only difference being the former acquiring the backscattered electrons and the latter collecting the transmitted electrons. Our present work shows the capability of ECCI for quantifying extended defects in semi-polar nitrides and represents a real step forward for optimising the growth conditions in these materials. [ABSTRACT FROM AUTHOR]

Interdiffusion in gold/titanium films with titanium evaporated on silicon at different oblique angles (0°, 30°, 50°, and 70°) and gold evaporated under normal incidence is investigated using a scanning electron microscope and in-situ sheet resistance measurements for the optimization of the films' effective gettering ability during and after a low-temperature thermal activation. Films have a tilted columnar structure and a porosity increasing with the deposition angle in agreement with calculated values. The oxygen effective gettering ability, characterized by energy-dispersive X-ray spectroscopy, increases with the deposition angle. It is shown that the gold/titanium film with titanium deposited with an oblique angle of 50° is an optimized condition to obtain the largest sorption capacity after 1 h thermal activation at temperatures lower or equal to 300 °C. This film has a low initial residual stress that becomes highly tensile if thermal activation is performed above 300 °C. [ABSTRACT FROM AUTHOR]

Interdiffusion in gold/titanium films with titanium evaporated on silicon at different oblique angles (0°, 30°, 50°, and 70°) and gold evaporated under normal incidence is investigated using a scanning electron microscope and in-situ sheet resistance measurements for the optimization of the films' effective gettering ability during and after a low-temperature thermal activation. Films have a tilted columnar structure and a porosity increasing with the deposition angle in agreement with calculated values. The oxygen effective gettering ability, characterized by energy-dispersive X-ray spectroscopy, increases with the deposition angle. It is shown that the gold/titanium film with titanium deposited with an oblique angle of 50° is an optimized condition to obtain the largest sorption capacity after 1 h thermal activation at temperatures lower or equal to 300 °C. This film has a low initial residual stress that becomes highly tensile if thermal activation is performed above 300 °C. [ABSTRACT FROM AUTHOR]

The spatial distribution of electron-hole pair generation in β-Ga2O3 as a function of scanning electron microscope (SEM) beam energy has been calculated by a Monte Carlo method. This spatial distribution is then used to obtain the diffusion length of charge carriers in high-quality epitaxial Ga2O3 films from the dependence of the electron beam induced current (EBIC) collection efficiency on the accelerating voltage of a SEM. The experimental results show, contrary to earlier theory, that holes are mobile in β-Ga2O3 and to a large extent determine the diffusion length of charge carriers. Diffusion lengths in the range 350–400 nm are determined for the as-grown Ga2O3, while processes like exposing the samples to proton irradiation essentially halve this value, showing the role of point defects in controlling minority carrier transport. The pitfalls related to using other popular EBIC-based methods assuming a point-like excitation function are demonstrated. Since the point defect type and the concentration in currently available Ga2O3 are dependent on the growth method and the doping concentration, accurate methods of diffusion length determination are critical to obtain quantitative comparisons of material quality. [ABSTRACT FROM AUTHOR]

We report the development of a fully automatic large-volume 3D electron backscatter diffraction (EBSD) system (ELAVO 3D), consisting of a scanning electron microscope (ZEISS crossbeam XB 1540) with a dedicated sample holder, an adapted polishing automaton (Saphir X-change, QATM), a collaborative robotic arm (Universal Robots UR5), and several in-house built devices. The whole system is orchestrated by an in-house designed software, which is also able to track the process and report errors. Except for the case of error, the system runs without any user interference. For the measurement of removal thickness, the samples are featured with markers put on the perpendicular lateral surface, cut by plasma focused ion beam (PFIB) milling. The individual effects of both 1 μm diamond suspension and oxide polishing suspension polishing were studied in detail. Coherent twin grain boundaries (GBs) were used as an internal standard to check the removal rates measured by the side markers. The two methods for Z-spacing measurements disagreed by about 10%, and the inaccurate calibration of the PFIB system was found to be the most probable reason for this discrepancy. The angular accuracy of the system was determined to be ∼2.5°, which can be significantly improved with more accurate Z-spacing measurements. When reconstructed grain boundary meshes are sufficiently smoothed, an angular resolution of ±4° is achieved. In a 3D EBSD dataset of a size of 587 × 476 × 72 μm3, we focused on the investigation of coincidence site lattice ∑9 GBs. While bearing predominantly a pure tilt character, ∑9 GBs can be categorized into three groups based on correlative 3D morphologies and crystallography. [ABSTRACT FROM AUTHOR]

A new type of composite layer material system, Al4Ni/Al2CrCuFeNi2Ti high-entropy alloy, was designed. The Al4Ni transition layer was prepared on the surface of an AZ91D magnesium alloy by laser cladding, which solves the problem of excessive melting point difference between the magnesium alloy and the high-entropy alloy. The Al4Ni/Al2CrCuFeNi2Ti high-entropy alloy composite layer with good surface formation was successfully prepared on the AZ91D magnesium matrix. Optical microscope, scanning electron microscope, and x-ray diffraction were used to characterize the microstructure and properties of the composite layer. It showed that the high-entropy alloy layer was mainly composed of simple BCC and FCC solid solution phases. The Al2CrCuFeNi2Ti high-entropy alloy layer, the Al4Ni layer, and the AZ91D magnesium matrix have excellent metallurgical bonds. The hardness of the high-entropy alloy layer was about 12 times that of the AZ91D magnesium alloy. The corrosion resistance of the high-entropy alloy layer in 3.5 wt. % NaCl was also improved. [ABSTRACT FROM AUTHOR]

The unique degradability and excellent biocompatibility make silk fibroin an attractive material for flexible transient memristors. Materials functionalization from the mesoscopic reconstruction view is a promising route to expand functions and create new types of electronic devices. Here, the transformation of the abrupt-to-progressive switching behavior in fibroin-based memristors is achieved via annealing to adjust the mesoscopic structure. Through electrical test and scanning electron microscope analysis, we study the electrochemical dynamics of metal nanoparticles in switching medium with different mesoscopic structures and directly reveal the microscopic origin of the abrupt-to-progressive transformation in fibroin-based transient memristors. The device exhibits abrupt resistive switching behaviors when the mobility and redox rate are high and displays progressive resistive switching behaviors under the low mobility and low redox rate condition. These findings reveal the microscopic origins of abrupt-to-progressive conversion and provide general guidance for designing high-performance memory devices and artificial synapses. [ABSTRACT FROM AUTHOR]

The electronic spins of rare-earth materials are attractive candidates for spin qubits and quantum memories. To access individual spins, tuning of the g-factor is desirable. Here, we report on local strain-dependent g-factors of the 5D0–7F2 transitions of Eu3+ centers in GaN:Eu thin films. We have found a clear correlation between the effective g-factor and the emission energy shift induced by the local strain. The combination of micro-photoluminescence and scanning electron microscope/electron backscattering diffraction measurements has revealed that the compressive strain of 0.2%–0.4%, relative to a surrounding reference point, induces an energy shift of about 3 meV. The strain decreases the g-factor of the emission at 1.991 eV from 2.5 to 1.5, while the strain increases the g-factor of the emission at 1.994 eV from 1.1 to 1.7. The result suggests that the g-factor can be tuned by the local strain. On the basis of the strain-induced energy shift and the g-factor, we have identified the optical sites. The 5D0–7F2 transitions observed in this study consist of three optical sites with C3v symmetry and one site with C1h symmetry. [ABSTRACT FROM AUTHOR]

To improve the photocatalytic activity of titanium oxide, nanometer titanium oxide powder was mixed with a phosphoric acid solution to form an electrolyte for preparing TiO2/Al2O3 coating on the surface of an aluminum alloy. Hydrothermal technology has been used to adjust the crystalline structure of nanometer titanium oxide. Scanning electron microscope was used to observe the micromorphology of anodic coating before and after treatment using hydrothermal technology. Results indicated that the photocatalyst had a porous structure. Energy dispersive spectrometry, x-ray diffraction, and x-ray photoelectron spectroscopy were used to confirm that titanium oxide was dispersed in the coating. The photocatalyst was used to degrade the methyl orange solution, and its absorbance before and after treatment by catalyst was tested by UV–vis spectroscopy. The results indicated that methyl orange could be degraded when the doping amount of titanium oxide is 8 g/l for 100 min. [ABSTRACT FROM AUTHOR]

Integrated interferometry installed on top of dry etch equipment was developed for the in-process measurement of critical dimension (CD) in vertical NAND flash memory dry etch forming word-line steps, also known as word-line processes. The etching process sequentially consists of mask trimming and mold etching (multilayered structure of Si3N4 and SiO2). In-process real-time CD measurements can be made in a trimming step that etches the photoresist (PR) to form a vertical mask shape. The measurement principle is based on the analysis of the interference fringe signal of light reflection to a single point in the center of the wafer. To check the measurement accuracy of the interferometer, the CD measured with interferometry was compared with an in-line SEM (scanning electron microscope). The correlation coefficient between the interferometric measurements measured during the mask trimming step and the in-line SEM measured after the completed process was 86%. On the other hand, when the mask trimming and the mold etching steps including Si3N4 over etching were added, the total measurement results showed that the correlation coefficient was 95%. This is because the CD value was derived based on the phenomenon that the PR thickness change measured by interferometry in the trimming step was a linear relationship with the change in the lateral PR amount, so the lateral PR amount was weakly etched in the mold etching step after the trimming step, which eventually affected the final formed CD. This metrology method can be simply applied to dry etching equipment in real production lines. [ABSTRACT FROM AUTHOR]

The electrostatic discharge (ESD) from polymer insulators is one of the environment-related anomalies on spacecraft. Theoretically, to mitigate the ESD effects, we could modulate the secondary electron yield (SEY, σ) close to 1 in the entire energy range, suppressing surface charges. However, no single polymer insulator has been reported to achieve this seesaw-type modulation of SEY. Here, we exploringly designed and prepared MgO particles doped polytetrafluoroethylene (PTFE) composite coating to achieve this goal, which exhibits not only the reduced SEY characteristic of the microstructured PTFE coating at low energy but also the enhanced SEY characteristic of the double-layer structure of PTFE and MgO at high energy. The simulation and experiment results demonstrate that MgO particles doped PTFE coating achieves this seesaw-type modulation of SEY. The optimal MgO concentration is 20%, where the maximum SEY (σmax) changes from 2.0 to 1.1; the SEY at 10 keV (σ10k) changes from 0.6 to 0.8, and the higher energy of the SEY equal to 1 (Ep2) increases from 4.5 to 6.5 keV. The discharge test of the microstrip antennas with PTFE-MgO composite coating in a scanning electron microscope verifies the role of the seesaw-type SEY modulation in surface charge suppression. This study supplies an essential reference for suppressing surface charges on vacuum electronics based on modulation of secondary electron emission characteristics. [ABSTRACT FROM AUTHOR]

TiSiCN composite coatings with different N contents based on Cr buffer layer were prepared by plasma-enhanced magnetron sputtering. The surface and cross-sectional morphology, composition, and structure of the coatings were evaluated by scanning electron microscope with energy dispersive spectroscopy, atomic force microscope, x-ray photoelectron spectroscopy, x-ray diffraction, and Raman spectroscopy. The hardness, elastic modulus, and tribological performance were investigated. The results showed that with the addition of N content, the proportion of sp3-hybrized C bonds and amorphous Si3N4 in TiSiCN coatings gradually decreased, while the proportion of graphite phase and CNx gradually increased. The decrease in the sp3—C bonding ratio leads to the decrease of coating hardness, and the composite coating with N content of 7.3% has the highest hardness at 13.2 GPa. The friction experiments exhibited the self-lubrication feature of the internal graphite phase, and the strengthening of moderate amounts of the hard phase can significantly reduce the wear rate. The TiSiCN composite coating with N content of 13.2% had the lowest wear rate. [ABSTRACT FROM AUTHOR]

Highly resistive undoped p-type gallium oxide samples were subjected to cumulative proton irradiation with energies ranging from 25 to 70 keV and doses in the 1.6 × 1014–3.6 × 1014 cm−2 range. Proton irradiation resulted in up to a factor of 2 reduction of minority electron diffusion length in the samples for temperatures between ∼ 300 and 400 K. Electron injection into the samples under test using a scanning electron microscope beam leads to pronounced elongation of diffusion length beyond the pre-irradiation values, thus demonstrating stable (days after injection) recovery of adverse radiation impact on minority carrier transport. The activation energy of 91 meV estimated from the temperature dependent diffusion length vs electron injection duration experiments is likely related to the local potential barrier height for native defects associated with the phenomenon of interest. [ABSTRACT FROM AUTHOR]

Highly resistive undoped p-type gallium oxide samples were subjected to cumulative proton irradiation with energies ranging from 25 to 70 keV and doses in the 1.6 × 1014–3.6 × 1014 cm−2 range. Proton irradiation resulted in up to a factor of 2 reduction of minority electron diffusion length in the samples for temperatures between ∼ 300 and 400 K. Electron injection into the samples under test using a scanning electron microscope beam leads to pronounced elongation of diffusion length beyond the pre-irradiation values, thus demonstrating stable (days after injection) recovery of adverse radiation impact on minority carrier transport. The activation energy of 91 meV estimated from the temperature dependent diffusion length vs electron injection duration experiments is likely related to the local potential barrier height for native defects associated with the phenomenon of interest. [ABSTRACT FROM AUTHOR]

Ultrafast scanning electron microscopy images carrier dynamics and carrier induced surface voltages using a laser pump electron probe scheme, potentially surpassing all-optical techniques in probe resolution and surface sensitivity. Current implementations have left a four order of magnitude gap between optical pump and electron probe resolution, which particularly hampers spatial resolution in the investigation of carrier induced local surface photovoltages. Here, we present a system capable of focusing the laser using an inverted optical microscope built into an ultrafast scanning electron microscopy setup to enable high numerical aperture pulsed optical excitation in conjunction with ultrafast electron beam probing. We demonstrate an order of magnitude improvement in optical pump resolution, bringing this to sub-micrometer length scales. We further show that temporal laser pump resolution can be maintained inside the scanning electron microscope by pre-compensating dispersion induced by the components required to bring the beam into the vacuum chamber and to a tight focus. We illustrate our approach using molybdenum disulfide, a two-dimensional transition metal dichalcogenide, where we measure ultrafast carrier relaxation rates and induced negative surface potentials between different flakes selected with the scanning electron microscope as well as on defined positions within a single flake. [ABSTRACT FROM AUTHOR]

Cu/SiO2 hybrid bonding has been developed for the application of heterogeneous bond interfaces in 3D integrated circuits in which thermal stability and bonding behavior are important. Thus, nano-twinned Cu (NT-Cu) is selected as the bonding material, and the thermal stability of NT-Cu and the bonding behavior of the interface between NT-Cu are investigated using a scanning electron microscope, electron backscatter diffraction, and focused ion beam. In addition to the microstructure analysis, nano-indentation and nano-scratch are employed to characterize the mechanical properties of the matrix and the interface between NT-Cu. As the bonding temperature increases from 200 to 300 °C for NT-Cu, the average grain sizes increase from 0.64 to 0.87 µm, and the rate of grain coarsening increases from 0.14 to 0.25 µm/h1/2. In addition, the fraction of voids at the bonding interface for NT-Cu interconnects decreases from 0.814% to 0.005%, and the penetration depth increases from 228 to 745 nm with an increase in the temperature from 200 to 300 °C. The hardness of the bonding interface obtained by nano-scratch and nano-indentation array testing is ∼1.8 GPa. [ABSTRACT FROM AUTHOR]

Good specimen quality is a key factor in achieving successful scanning transmission electron microscope analysis. Thin and damage-free specimens are prerequisites for obtaining atomic-resolution imaging. Topological insulator single crystals and thin films in the chalcogenide family such as Sb2Te3 are sensitive to electron and ion beams. It is, therefore, challenging to prepare a lamella suitable for high-resolution imaging from these topological insulator materials using standard focused ion-beam instruments. We have developed a modified method to fabricate thin focused ion-beam (FIB) lamellae with minimal ion-beam damage and artifacts. The technique described in the current study enables the reliable preparation of high-quality transmission electron microscope (TEM) specimens necessary for studying ultra-thin surface regions. We have successfully demonstrated that the careful selection of FIB milling parameters at each stage minimizes the damage layer without the need for post-treatment. [ABSTRACT FROM AUTHOR]

Electron beam induced current (EBIC) measurements provide a powerful tool for characterizing semiconductor based materials and devices. By measuring the current generated by the electron beam of a scanning electron microscope (SEM), EBIC allows us to extract the minority carrier diffusion length (L) and the surface recombination velocity to diffusivity ratio (S/D) of a material. When combined with information on minority carrier lifetime (τ), for instance from time-resolved photoluminescence measurements, the minority carrier mobility of the material can be extracted. However, the EBIC technique relies heavily on the accurate modeling of the carrier generation and collection process. Traditionally, this was achieved using a combination of empirical analytical expressions (and later Monte Carlo simulations) for carrier generation and analytical diffusion/ recombination expressions for carrier collection. This approach introduces significant uncertainties into the extracted material parameters. Here, we present a numerical approach to EBIC modeling which improves the spatial resolution of our model, while also retaining information regarding the relative EBIC signal as a function of incident beam energies and currents. We apply this technique to investigate the temperature dependent minority carrier mobility of InAs/InAsSb and InGaAs/ InAsSb strained layer superlattice infrared detectors and compare our results to the values obtained using external quantum efficiency measurements of the same samples. Our approach not only allows for an improvement in the uncertainty of the extracted material parameters, but also offers insight into the material and device behavior as a function of nonequilibrium carrier concentration. The technique presented here offers potentially improved characterization of not only infrared detectors, but a range of semiconductor-based devices. [ABSTRACT FROM AUTHOR]

To produce a realistic tokamak-like plasma environment in linear plasma device, a transient source is needed to deliver heat and particle fluxes similar to those seen in an edge localized mode (ELM). ELMs in future large tokamaks will deliver heat fluxes of ~1GW/m2 to the divertor plasma facing components at a few Hz. An electrothermal plasma source can deliver heat fluxes of this magnitude. These sources operate in an ablative arc regime which is driven by a DC capacitive discharge. An electrothermal source was configured with two pulse lengths and tested under a solenoidal magnetic field to determine the resulting impact on liner ablation, plasma parameters, and delivered heat flux. The arc travels through and ablates a boron nitride liner and strikes a tungsten plate. The tungsten target plate is analyzed for surface damage using a scanning electron microscope. [ABSTRACT FROM AUTHOR]

The evolution of material strength within several dense particle suspensions impacted by a projectile is investigated and shown to be strongly dependent on the particle material in suspension. For stronger particles, such as silicon carbide, the shear strength of the fluid is shown to increase with the ballistic impact strength. For weaker particles, such as silica, the shear strength of the suspension is found to be independent of impact strength in this dynamic range of tests. A soft-capture technique is employed to collect ejecta samples of a silica-based shear thickening fluid, following a ballistic impact and penetration event. Ejecta samples that were collected from impacts at three different velocities are observed and compared to the benchmark particles using a Scanning Electron Microscope. The images show evidence of fractured and deformed silica particles recovered among the nominally 1 µm diameter monodisperse spheres. There is also evidence of particle fragments that appear to be the result of interparticle grinding. The trends observed in the shear strength estimates are interpreted with regards to the particle damage seen in the ejecta recovery experiments to develop a concept of the impact response of these fluids. The results suggest that particle slip through deformation is likely the dominant factor in limiting the transient impact strength of these fluids. Particularly, particle strength is important in the formation and collapse of dynamically jammed particle contact networks in the penetration process. [ABSTRACT FROM AUTHOR]

Investigation of the effect of crystal defects on nonpolar a-GaN films grown by metalorganic chemical vapor deposition on r-sapphire substrates is presented. Samples were grown at different temperatures and the same V/III ratio. High-temperature nucleation in combination with low-temperature GaN buffer layer growth was used to achieve a smooth morphology and "mirror" surface. The macrostructures of the defects were investigated using a scanning electron microscope. Defect concentration via dislocation type correlation was analyzed by diffractometry investigation. Structural quality was investigated via x-ray diffraction. The correlation between the densities of mixed threading dislocations and V-defects was determined. It was detected that the origin of V-defects on the a-plane and c-plane was the same despite having completely different geometries and structures. We also investigated the dependence of V-defect density on a-GaN film growth temperature at a constant hydrogen flow through a triethylgallium source, and we also investigated how the V/III ratio influenced the V-defect structure. Optimum growth parameters for defect concentration reduction were determined. [ABSTRACT FROM AUTHOR]

In this paper, the effects of three modifiers, such as PEG, ATBC, and DOP, on the modification of PBAT/PLA-based fully degradable brush monofilaments were studied. The microstructure and the mechanical properties of the PBAT/PLA brush wire before and after modification were characterized by Fourier-transform infrared spectroscopy, scanning electron microscope, and universal material testing machine. The effect of modifiers on bending recovery was discussed in detail and was analyzed combined with the results of differential scanning calorimetry and low-field nuclear magnetic resonance spectroscopy. The results showed that with an increase in the content of modifiers, the tensile strength and the impact strength of the PBAT/PLA brush wire would decrease, and the bending recovery rate would increase. The effect of PEG and ATBC on bending recovery is weaker than that of DOP, and the bending recovery rate of the PBAT/PLA brush wire modified by DOP is close to 80%. With an increase in the content of modifiers, the melting enthalpy and transverse relaxation time T2 of PBAT/PLA would increase. This research has guiding significance for the preparation of fully degradable brush wires. [ABSTRACT FROM AUTHOR]

Conventional machining of metallic glass is a challenge due to its amorphous nature and inherent brittleness. This work investigates the non-conventional machining of Zr-based metallic glass, Vitreloy-1, using laser processing with a Yb-fiber laser and an electro-jet milling (EJM) process. Grooves were fabricated using these techniques in Vitreloy disks of 1.5 mm thickness to study the machining behavior. The grooves formed with the laser were smooth, although there was observation of dross at the groove edges, which was selectively removed through the EJM process. On the other hand, the EJM process was found to produce dross-free grooves; however, it caused leaching of zirconium from the groove zone, which was understood from the elemental maps obtained using the scanning electron microscope. A comparison of the laser grooving and EJM grooving process was also carried out using Vickers micro-indentation. Indentations made close to the groove edge in laser grooved samples developed shear bands but the same were absent in the EJM grooved samples. Since shear banding tendency is an indicator of the inherent toughness of the metallic glass, the laser grooving technique is found more suitable for nonconventional machining of metallic glass. [ABSTRACT FROM AUTHOR]

The thermal conductivity of individual nanomaterials can vary from sample to sample due to the difference in geometries and internal structures, and thus, concurrent structure observation and thermal conductivity measurement at the nanoscale are highly desired but challenging. Here, we have developed an experimental method that allows concurrently the in situ thermal conductivity measurement and the real-time internal structure observation of a single one-dimensional (1D) material using scanning transmission electron microscopy (STEM) in a scanning electron microscope. In this method, the two ends of the 1D nanomaterial are bonded on a tungsten probe and a suspended platinum nanofilm, respectively. The platinum nanofilm serves simultaneously as a heater and a resistance thermometer, ensuring highly sensitive thermal measurements. The platinum nanofilm is fabricated on the edge of the silicon wafer so that the electron beam can transmit through the 1D material and be detected by the STEM detector, which caters for real-time observation of the inner nanostructure. Using this method, we in situ measured the thermal conductivities of two cup-stacked carbon nanotubes and concurrently observed the internal hollow structures. We found that the sample with more structural disorders had a lower thermal conductivity. Our measurement method can pave the way to the sample-by-sample elucidation of the structure–property relationship for 1D materials. [ABSTRACT FROM AUTHOR]

Multi-tip scanning tunneling microscopy (STM) is a powerful method to perform charge transport measurements at the nanoscale. With four STM tips positioned on the surface of a sample, four-point resistance measurements can be performed in dedicated geometric configurations. Here, we present an alternative to the most often used scanning electron microscope imaging to infer the corresponding tip positions. After the initial coarse positioning is monitored by an optical microscope, STM scanning itself is used to determine the inter-tip distances. A large STM overview scan serves as a reference map. Recognition of the same topographic features in the reference map and in small scale images with the individual tips allows us to identify the tip positions with an accuracy of about 20 nm for a typical tip spacing of ∼ 1 μ m. In order to correct for effects such as the non-linearity of the deflection, creep, and hysteresis of the piezoelectric elements of the STM, a careful calibration has to be performed. [ABSTRACT FROM AUTHOR]

Organic–inorganic perovskite solar cells (PSCs) have been emerging as one of the most promising photovoltaic technologies. Surface morphology is considered as a key-parameter in energy alignment and plays a dominant role in specifying the device performance. The large grains and low roughness enhance the transport of charge carriers from perovskite layers to the transport layers, and this reflects on the delivered power conversion efficiency (PCE). Therefore, in this study, we investigated the influence of the fabrication parameters on the grain size and the morphology of perovskite layers, thereby the PCE of PSCs. These parameters included the anti-solvent nature (chlorobenzene or toluene), annealing temperature, and annealing ramp rate (slow or flash annealing). The scanning electron microscope confirmed that flash annealing results in a better morphology than slow annealing whether by employing an anti-solvent dripping or not. Furthermore, the dripping of chlorobenzene as an anti-solvent produced better morphology and large grains compared with toluene. Therefore, combining chlorobenzene with flash annealing induced the formation of large grains, full cover, and a uniform perovskite layer, which reflects on the performance of the fabricated PSCs. Finally, employing the aforementioned optimum preparation parameters to fabricate carbon-based PSCs resulted in decent PCE, current density short circuit (Jsc), open circuit voltage (Voc), and fill factor (FF) of 7%, 11.3 mA/cm2, 0.74 V, and 34%, respectively. [ABSTRACT FROM AUTHOR]

Secondary-electron yield (SEY) and surface charging of various insulating materials under irradiation of primary electrons (PEs) with energy of lower than 100 eV were investigated. Irradiation energy of the PEs with SEY of 1 (E1) for SiO2 and Si3N4 was about 20 eV and that for the resist using in extreme ultraviolet (EUV) lithography was about 40 eV. Additionally, it was found that E1 corresponds to the lower limit for obtaining scanning electron microscope images of the EUV resist pattern. The surface potential of the pattered EUV resist modulated by PE irradiation was estimated by using a retarding-field energy filter. It was found that the surface potential varies with the width and pitch of the EUV resist pattern. The variation of surface potential depends on the width and pitch due to the fact that the secondary electrons emitted from the space of the resist pattern are absorbed in the sidewalls of the resist pattern as it becomes denser. [ABSTRACT FROM AUTHOR]

Thin films of silver were deposited on nonalkali glass substrates at substrate temperatures ranging from room temperature (28 °C) to 150, 200, 300, 400, and 500 °C at discharge pressures of 0.40, 1.20, and 2.00 Pa using direct current magnetron sputtering. On the basis of the measured cross-sectional and surface morphologies, crystallographic structures, and film properties, I discuss the dependence of the film structure and properties on the substrate temperature. The x-ray diffraction measurements showed that the <111> orientation was preferred for all deposition conditions. Scanning electron microscope observations revealed a microstructure of convex-shaped fine grains for a substrate at room temperature, while laterally growing, mound-shaped grains with flat-topped surfaces appeared at substrate temperatures of 400 and 500 °C. Atomic force microscopy also showed an increase in the lateral size and height of the mound-shaped structures with increasing substrate temperature. The lateral grain size evaluated from the areal particle density obtained from atomic force microscopy increased significantly with increasing substrate temperature, reaching 600–800 nm at a substrate temperature of 500 °C. The film stress also changed from compressive to tensile with increasing substrate temperature. The relative density, defined as the ratio of the deposited amount-of-substance to the physical-thickness, decreased significantly with increasing substrate temperature and, at a substrate temperature of 500 °C, was approximately 0.6 times as large as that obtained for thin films deposited at room temperature. The high surface diffusivity of the Ag adatoms induces the growth of laterally growing, mound-shaped grains. Besides, the energy accumulated in the thin films during sputter deposition induces the void formation to increase the efficiency of energy release in the form of heat. [ABSTRACT FROM AUTHOR]

Forming polymeric core–sheath nanofibers is gaining prominence owing to their numerous potential applications, most notably in functional scenarios such as antiviral filtration, which is attracting significant attention due to the current COVID pandemic. This study has successfully designed and constructed a novel pressurized gyration vessel to fabricate core–sheath polymer nanofibers. Several water-soluble and water-insoluble polymer combinations are investigated. Both polyethylene oxide and polyvinyl alcohol were used as the core while both poly(lactic acid) (PLA) and poly(caprolactone) (PCL) were used as the sheath; PLA and PCL were used as core and sheath, in different instances; respectively. The fluid behavior of the core–sheath within the vessel was studied with and without applied pressure using computational fluid dynamics to simulate the core–sheath flow within the chamber. A high-speed camera was used to observe the behavior of jetted solutions at core–sheath openings, and the best scenario was achieved using 6000 rpm spinning speed with 0.2 MPa (twice atmospheric) applied pressure. The surface morphology of core–sheath fibers was studied using a scanning electron microscope, and focused ion beam milling assisted scanning electron microscopy was used to investigate the cross-sectional features of the produced fibers. Laser confocal scanning microscopy was also used to verify the core–sheath structure of the fibers, which were further characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry. Thus, using a variety of polymer combinations, we show, both theoretically and experimentally, how core–sheath fibers evolve in a vessel that can serve as a scalable manufacturing pressurized gyration production process. [ABSTRACT FROM AUTHOR]

To obtain the relation between spark discharges and the topography of electrode surfaces, some models, such as a micro-initial model of cone and spherical head cylinder, generated from the scanning of a scanning electron microscope are introduced. Based on the principles of energy conservation and thermal equilibrium, the second-order non-homogeneous differential equation is established. The relationships between the temperature of the cathode surface and the distance from the top of micro-protrusions, the cone angle, and the radius of the ball head are derived from a set of second-order non-homogeneous differential equations. When introduced electron emission theory, the main emission type at the initial stage of the discharge is electron field emission. As the discharge progresses, the Joule heat generated by the emission current will cause thermionic emission. During this progress, the emission current density gradually increases. When the temperature of the cathode surface reaches the melting point of the cathode metal, the current density will increase sharply. Observed from the discharge, the temperature of the cathode surface is inversely proportional to the cone angle and the radius of the ball head maintains a gradually decreasing slope. It is proportional to micro-protrusions maintaining a gradually increasing slope. When the cone angle is less than 12° and the radius of the ball head is less than 0.04 µm, the temperature of the cathode surface changes more dramatically. Through this study, a further understanding of factors that affect the density of cathode current emission can be obtained, which is of great significance to improve the capacity of cathode emission. [ABSTRACT FROM AUTHOR]