Secondary Electron Microscopy Research Articles

Photoresponse in sequentially stacked antimony selenide thin films

Antimony selenide (Sb2Se3), a binary semiconducting compound has widespread research attention due to its excellent optoelectronic properties in the visible region and usefulness in applications such as solar cells, photosensors and photoelectrodes. The presented study explores the thickness dependent photoresponse in Sb2Se3 thin films, prepared by reactive selenization of antimony films having thickness values of ∼938 nm and ∼1879 nm when stacked second time. Growth orientation along [001] direction was achieved through carefully optimized selenization conditions to enable favourable charge transport in anisotropic Sb2Se3. Predominant Sb2Se3 formation was inferred from x-ray diffraction, Raman spectroscopy, secondary electron microscopy and energy-dispersive X-ray analyses. High optical absorption coefficient values of about 1 × 105 cm−1 and 5.7 × 104 cm−1 were observed for ∼938 nm and ∼1879 nm thick Sb2Se3 thin films. Further, the optoelectronic properties were elucidated through current–voltage and transient photoresponse measurements under dark and illumination conditions. The measurements were done under zero and different bias voltages. Sb2Se3 films having∼ 938 nm thickness exhibited self-driven photoresponse with a responsivity of 4.3×10−8 A W−1 and detectivity of 3.5 × 106 jones respectively, under AM 1.5 G illumination conditions.

Mapping elemental solutes at sub-picogram levels during aqueous corrosion of Al alloys using diffusive gradients in thin films (DGT) with LA-ICP-MS

A novel approach using diffusive gradients in thin films (DGT) with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for two-dimensional mapping of elemental solute release at sub-picogram levels during aqueous corrosion of Al alloys is presented. Evaluation of different DGT gels with mixed micro-sized binding phases (polyacrylamide-Chelex-Metsorb, polyurethane (PU)-Chelex-Metsorb, PU-Chelex-Zr(OH)4) demonstrated the superior performance of PU gels due to their tear-proof handling, low shrinkage, and compliance with green chemistry. DGT devices containing PU-Chelex-Zr(OH)4 gels, which have not been characterized for Al sampling before, showed quantitative uptake of Al, Zn, and Cu solutes over time (t = 4–48 h) with higher Al capacity (ΓDGT = 6.25 µg cm−2) than different gels. Application of PU-Chelex-Zr(OH)4 gels on a high-strength Al-Cu alloy (Al2219) exposed to NaCl (w = 1.5%, pH = 4.5, T = 21 °C) for 15 min in a novel piston-type configuration revealed reproducible patterns of Al and Zn co-solubilization with a spatial expansion ranging between 50 and 1000 µm. This observation, together with complementary solid-state data from secondary electron microscopy with energy-dispersive X-ray spectroscopy, showed the presence of localized pitting corrosion at the material surface. Detection limits for total solute masses of Al, Zn, and Cu were ≤0.72 pg, ≤8.38 pg, and ≤0.12 pg, respectively, for an area of 0.01 mm2, demonstrating the method’s unique capability to localize and quantify corrosion processes at ultra-trace levels and high resolution. Our study advances the assessment of Al alloy degradation in aqueous environments, supporting the design of corrosion-resistant materials for fostering technological safety and sustainability.Graphical

A Petrological and Microstructural Study of Ten Brachinites: A Cumulate Texture?

AbstractBrachinites are igneous, ultramafic and unbrecciated primitive achondrites mainly composed of olivine and pyroxene, with a partial melt residue or cumulate origin that is still debated. This study presents a petrological and microstructural study of 10 brachinite meteorites to identify igneous and deformation processes responsible for their formation. Detailed microstructural analyses were performed using secondary electron microscopy, electron probe microanalysis, and electron backscatter diffraction. The olivine‐spinel and two‐pyroxene closure temperatures of these brachinites ranged from 814 ± 27 to 909 ± 20°C. Olivine [001] axes coincide with the elongation of olivine grains and the crystallographic preferred orientations (CPO) of clinopyroxene [001] axes, which led us to infer lineation as olivine [001] axes parallel to X for all samples. Olivine CPO displays a strong or medium concentration of [001] axes parallel to X and [010] axes parallel to Z pointing to a B‐type fabric. Limited internal deformation of olivine grains and slip systems identified from low‐angle boundary misorientation analyses are inconsistent with the CPO and grain misorientation distributions are close to those found in untextured rocks. Olivine B‐type fabrics may therefore result not from plastic deformation but rather from rigid crystal rotation or preferential crystal growth during compaction. Olivine subgrain boundary misorientation axes imply limited activation of [001](100) and [100](001) slip systems, which could be due to primary plastic deformation during or after crystal settling. These new results reveal that brachinites developed a cumulate texture and accommodated only weak plastic deformation during early differentiation processes in the parent body.

Influence of Additional Strut Elements in 3D Re-Entrant Auxetic Unit Cells on the Damage and Energy Absorption Properties

Abstract Background Geometric parameter optimization, novel design, and mechanism modeling of auxetic materials have been widely studied. However, manipulating the topology of the 3d printed auxetic unit cells and its influence on the damage have yet to be explored. Objective This study aims to characterize the energy absorption properties and damage mechanisms of the modified auxetic unit cells. Methods In the current study, bending-dominated re-entrant auxetic unit cells (Cell0), torsion-dominated auxetic unit cells with cross elements (CellX), buckling-dominated auxetic unit cells with vertical elements (CellB), and bending-dominated auxetic unit cells with panels (CellW) have been fabricated by FDM (Fused deposition modeling). Uniaxial compression testing of the PLA (Polylactic acid) unit cells has been carried out, and a camera has observed their deformation behavior. SR- µCT (Synchrotron radiation microtomography) and an SEM (Secondary electron microscope) accomplished further damage analysis of the struts. Results Adding additional struts hinders the lateral shrinking of the re-entrant auxetics, and re-entrant auxetic unit cells with cross elements have shown higher energy absorption capacity and efficiency than others. The struts’ damage has been governed by building direction, printed material, and strut dimensions. Intra-layer and interlayer fracture of the layers and rupture in the circumferential direction of the PLA struts have been observed in the SR- µCT slices. Conclusions By additional struts, it is possible to fabricate complex auxetic structures with enhanced energy absorption properties, but their inherent characteristics dominate the damage of the struts in the auxetic unit cells. Graphical Abstract

High-Resolution Characterization of Enamel Remineralization Using Time-of-Flight Secondary Ion Mass Spectrometry and Electron Microscopy

Introduction: The aim of this in vitro study was to assess the suitability of high-resolution time-of-flight secondary ion mass spectrometry (ToF-SIMS) for visualizing cross-sectional changes in human enamel microstructure and chemical composition during treatment and remineralization cycling of artificially generated caries lesions underneath an artificial plaque. Methods: Treatments consisted of exposure to twice daily toothpaste/water slurries prepared from 0, 1,100, and 5,000 μg/g fluoride (F) NaF/silica toothpastes. In addition, treatments with slurries prepared from 1,100 μg/g F SnF2/silica toothpastes were done using 44Ca in the remineralization solution to allow for differentiation of newly formed mineral and exploration of incorporated metal dopants using ToF-SIMS. Complementary microhardness, scanning electron microscopy, and high-resolution transmission electron microscopy (HR-TEM) investigations were performed on enamel cross sections. Results: HR-TEM was used for the first time to determine the change in crystallinity during remineralization revealing distinct microstructural zones within one lesion. Chemical mapping using ToF-SIMS demonstrated that the distribution of F, while observed primarily in the new mineral phase, was widespread throughout the lesion with 44Ca substantially limited to the remineralizing mineral. Both penetrated the inter-rod spaces of the sound enamel illustrating how acid damage propagates into the native mineral as the caries lesion deepens. HR-TEM examination revealed different regions within the lesion characterized by distinct micro- and ultrastructures. Importantly, HR-TEM revealed a return of crystallinity following remineralization. F dose-response observations verified the ability of these high-resolution techniques to differentiate remineralization efficacy. Conclusion: The collective results provided new insights such as the visualization of F or calcium penetration pathways, as well as new tools to study the caries process.

Simultaneous secondary electron microscopy in the scanning transmission electron microscope with applications for in situ studies.

Scanning/transmission electron microscopy (STEM) is a powerful characterization tool for a wide range of materials. Over the years, STEMs have been extensively used for in situ studies of structural evolution and dynamic processes. A limited number of STEM instruments are equipped with a secondary electron (SE) detector in addition to the conventional transmitted electron detectors, i.e. the bright-field (BF) and annular dark-field (ADF) detectors. Such instruments are capable of simultaneous BF-STEM, ADF-STEM and SE-STEM imaging. These methods can reveal the 'bulk' information from BF and ADF signals and the surface information from SE signals for materials <200 nm thick. This review first summarizes the field of in situ STEM research, followed by the generation of SE signals, SE-STEM instrumentation and applications of SE-STEM analysis. Combining with various in situ heating, gas reaction and mechanical testing stages based on microelectromechanical systems (MEMS), we show that simultaneous SE-STEM imaging has found applications in studying the dynamics and transient phenomena of surface reconstructions, exsolution of catalysts, lunar and planetary materials and mechanical properties of 2D thin films. Finally, we provide an outlook on the potential advancements in SE-STEM from the perspective of sample-related factors, instrument-related factors and data acquisition and processing.

Stacking pressure homogenizes the electrochemical lithiation reaction of silicon anode in solid-state batteries

Several tens of MPa stacking pressure is usually necessary to fully utilize the capacity of energy-dense silicon anode in solid-state batteries, presenting significant hurdles for real applications. It is thus critical to establish the link between the macroscopic stacking pressure and the microscopic electrochemical processes. In this work, we used titration gas chromatography to quantify the capacity-loss processes of silicon anodes under different stacking pressures. Furthermore, time-of-flight secondary ion mass spectrometry, electron microscopy, and phase-field modeling techniques were used to map the spatial distribution of chemical species (e.g., LixSi alloys), stress, and electrochemical overpotential upon (de)lithiation processes of the silicon anode. High stacking pressure was observed to significantly increase the extent that a Si anode can be lithiated because of the increased reaction homogeneity resulting from the strong electro-mechanical coupling, while its impact over lithium loss during the first cycle is rather limited. Our work provides a basis to unlock the full potential of Si-anode based solid-state batteries at near-ambient stacking pressure and calls for innovative strategies to minimize or compensate for the lithium loss at the first cycle.

Zircon (U-Th)/He impact crater thermochronometry and the effects of shock microstructures on He diffusion kinetics

Accurate age determination of impact cratering events remains difficult and controversial. Less than a quarter of all documented impact craters are regarded as accurately and precisely age dated. Zircon (U-Th)/He (ZHe) dating of impactites has received recent attention as a novel technique to date impact structures. Complicated and localized post-impact hydrothermal systems could also affect the reliability of ZHe impact ages. We quantitatively define the effects of shock-induced microstructures on He diffusion kinetics in zircon with different shock microstructures characterized by Secondary Electron Microscopy (SEM) and electron backscatter diffraction (EBSD). We investigated samples from the Chicxulub and Ries impact craters, to compare diffusion kinetics from structures of different sizes, ages, and hydrothermal activity. Step-heating fractional-release experiments were used to quantify He diffusion kinetics of variably shocked zircon and examine the relationship of the experimentally derived diffusion domain sizes to the EBSD-defined subgrains. The diffusion data show a consistent activation energy independent of shock level, while shock microstructures, such as planar deformation bands (PDBs) and granular textures systemically and dramatically lower the He retentivity due to the microstructural reduction of the effective diffusion domain size. Shocked zircon were dated by ZHe and the less deformed grains yield ages within error of the accepted impact ages as determined by other methods (40Ar/39Ar and U-Pb), whereas the grains with PDBs or granular textures commonly exhibited younger ages. Thus, the characterization of impact-induced zircon microstructures is critical for determining accurate impact ages because shocked grains are less suitable for reliable impact dating, but potentially powerful for exploring temperature–time history of hydrothermal activity.

Analysis of adhesion characteristics of steel back plates and encapsulants for fire-proof BIPV modules

Recently, researchers are actively exploring the use of steel plates as replacements for the backs of building integrated photovoltaic (BIPV) modules to achieve improved workability, reduced weight, and enhanced maintainability. It is crucial to note that the adhesion between steel plates and encapsulants must match the high level observed between conventional backsheets and glass surfaces. In this study, we assessed the adhesion between steel plates and encapsulants and proposed a method to enhance adhesion to the level of existing materials, such as backsheets and glass, by improving the surface of the steel plates and the lamination process. When steel plates were laminated with ethylene vinyl acetate (EVA) encapsulant at 150 °C (as per the preset process), the peel force measured by the 180° peel test was significantly low at 0.045 N/mm. However, it increased nearly 40 times to 1.70 N/mm due to the formation of a structure capable of physical interlocking through surface treatment and an increase in the lamination temperature by 20 °C. Furthermore, we evaluated the adhesion performance of polyolefin elastomer (POE) encapsulant, which demonstrated high adhesion of over 6.0 N/mm, comparable to that between the currently used encapsulants and backsheets. When we examined the surface-treated sample using a confocal microscope and a secondary electron microscope (SEM), the surface-treated sample exhibited a considerably rough surface with a high Rku value of 5 compared to the untreated sample. These modules can maintain high outputs even when exposed to the external environment for extended periods with fire-resistant properties.

Spontaneous pattern of orthogonal ferroelectric domains in epitaxial KNN films

Lead-free piezoelectric (K, Na)NbO3 (KNN) is considered one of the promising candidates for the replacement of Pb(ZrxTi1−x)O3. Several studies underlined the issue of K and Na volatility with increasing deposition temperatures, leading to high leakage currents in thin films, which still represents a major drawback for applications. This paper shows how epitaxial growth with concomitant preferred orientation of KNN films on niobium-doped strontium titanate (Nb:STO) depends on growth temperature and substrate strain. A preferred out-of-plane polar (001) orientation of KNN is obtained at high temperatures (&amp;gt;600 °C), while (100) orientation is dominant for lower ones. The (001) orientation is forced out-of-plane due to the sizeable in-plane stress derived from a negative lattice mismatch of pseudo-cubic KNN with respect to the underlying cubic (001) Nb:STO substrate. Moreover, we show that K-Na deficiency and high leakage of epitaxial KNN films deposited at high temperatures are accompanied by the appearance of a pattern of orthogonal spontaneous ferroelectric domains aligned to the [100] and [010] directions of Nb:STO. This pattern, visible in secondary electron microscopy, piezoforce response microscopy, and conductive atomic force microscopy images, is uncorrelated to the surface morphology. Supported by reciprocal space mapping by x-ray diffraction, this phenomenon is interpreted as the result of strain relaxation via ferroelectric domain formation related to K-Na deficient films displaying a sizable and increasing compressive strain when grown on Nb:SrTiO3. Our findings suggest that strain engineering strategies in thin films could be used to stabilize specific configurations of piezo- and ferroelectric domains.

Modeling the Osteogenic Potential of Decellularized Human Bone Particles by Tuning their Size Distribution Through a Sonic Microfragmentation Approach

AbstractHuman decellularized bone fragments are commonly used in clinics to perform allograft surgeries. To reduce the immunological response in the recipient and ensure their safety, these fragments underwent decellularization, a procedure that greatly reduces their osteogenicity (the ability to induce differentiation into osteoblast). In this work, by the introduction of an ultrasonication step to fragment the human bone, the size distribution of the resulting demineralize bone particles can be controlled, tuning their osteogenic potential. The sonication protocol is optimized by a response surface method, using 12 different sonication protocols, allowing to model the relationship between the sonication parameters and the outcoming particles properties in terms of dimensions, physical/chemical properties, and biological activity. The size distribution is extrapolated by a deep learning image segmentation while the structure is characterized by infrared and thermal analysis. The particles are combined with methacrylated silk gel to test in vitro their biological response on adipose‐derived stromal cells. The ultrasonication fragmented the bone particles, revealing their internal organic matrix as proved by secondary electron microscopy and confocal microscopy. An inverse linear correlation is found between the particles’ sizes and their osteogenic activity, thus proving the efficacy of the proposed ultrasonication treatment in tuning the biological response.

The Ferrar Continental Flood Basalt: A ∼1.6 Ma long duration evidenced by high-precision 40Ar/39Ar ages suggest a potential role in the Pliensbachian-Toarcian extinction event

One of the most impassioned topics in large igneous province (LIP) research is how prolonged the duration of these large-scale magmatic events are, as LIP magmatism has considerable impact on models of associated reconstructions, of climate variability or tectonic events. High-precision geochronology is pivotal to LIP basalt emplacement rate, and thus to unravel the role these enormous magmatic events have throughout Earths geological and environmental history. Four high-precision 40Ar/39Ar plagioclase plateau ages for the Tasmanian dolerites (Ferrar) indicate ∼1.6 ± 0.4 Ma of resolvable, continuous magmatic activity; 184.27 ± 0.24 to 182.69 ± 0.54 Ma (2σ). The 40Ar/39Ar results provide evidence of distinctly older intrusions and a more prolonged duration than the observed 182.4-182.9 Ma age range and duration indicated by the main zircon record. Moreover, the precision of our 40Ar/39Ar results coupled with secondary electron microscopy analyses provide evidence of plagioclase crystal inheritance from slightly older magmatism entrained into younger magmatic pulses by exploiting pre-existing conduits. Numerical diffusion models, calculated for a theoretical age spectrum resulting from two slightly different plagioclase ages, provide an excellent match for measured data. Coupling geochemical data to the new age data indicates a silica and incompatible element evolution of the Ferrar magmatic system through time. The older generation of intrusions (ca. Zr: 92 ppm, SiO2: 53.67 wt.%) are seemingly less enriched in incompatible elements and silica than the youngest generation (ca. Zr: 147 ppm, SiO2: 56.5 wt.%). Here, we suggest that the magma chambers differentiated to more incompatible/silica-rich compositions saturating zircon only at evolved magmatic stages. This implies that plagioclase dates the full duration of magmatic Ferrar LIP activity of ca. 1.6 Myrs whilst zircon ages might be naturally biased and restricted to post-Zr saturation stage. The extended duration of Ferrar magmatism indicates that it is coeval with the Pliensbachian-Toarcian boundary. Therefore, we speculate that Ferrar (±Karoo) magmatism triggered the Pliensbachian-Toarcian extinction event and contributed to the Toarcian oceanic anoxic event, from which the environment did not begin to recover until only after the waning and cessation of Ferrar magmatic activity at ∼182 Ma, with zircon crystals recording the final flux of magma.

Novel Fe‐Based Amorphous Brazing Foils in the Quinary System Fe–Ni–Cr–Si–B

Amorphous brazing foils are increasingly used on a wide variety of component geometries because of their flexibility and the resulting ease of application. Due to the recent rapid rise in Ni prices, there is an enormous need for research into the substitution of nickel with iron within conventionally used nickel‐based amorphous brazing foils. To avoid time‐consuming series of experiments, newly developed thermodynamic databases will be used to predict alloy compositions with a high glass forming ability. Foils should be produced with the melt‐spin process and characterized with differential scanning calorimetry and secondary electron microscopy. Novel iron‐based brazing foils with different compositions are successfully produced in the alloying system iron–nickel–chromium–silicon–boron. The characterization of these foils indicates the presence of a partly amorphous or nanocrystalline structure. The novel iron‐based brazing foils are characterized by a simple and cost‐efficient alloying concept. Furthermore, newly developed thermodynamic databases in the iron–nickel–chromium–silicon–boron system are validated by the successful production of these foils. The prediction of further iron‐based amorphous foils with the aid of thermodynamic calculations can thus be made possible.

Characterization of dissipative regions of a N-doped superconducting radio-frequency cavity

We report radio-frequency measurements of quality factors and temperature mapping of a nitrogen doped Nb superconducting RF cavity. Cavity cutouts of hot and cold spots were studied with low temperature scanning tunneling microscopy and spectroscopy, X-ray photoelectron spectroscopy and secondary electron microscopy. Temperature mapping revealed a substantial reduction of the residual resistance upon cooling the cavity with a greater temperature gradient and hysteretic losses at the quench location, pointing to trapped vortices as the dominant source of residual surface resistance. Analysis of the tunneling spectra in the framework of a proximity effect theory shows that hot spots have a reduced pair potential and a wider distribution of the contact resistance between the Nb and the top Nb oxide. Alone, these degraded superconducting properties account for a much weaker excess dissipation as compared with the vortex contribution. Based on the correlation between the quasiparticle density of states and temperature mapping, we suggest that degraded superconducting properties may facilitate vortex nucleation or settling of trapped flux during cooling the cavity through the critical temperature.

Electromagnetic attenuation displayed by La-Co substituted Ba-Sr hexaferrite nanoparticles and multiwall carbon nanotubes in polyaniline and polythiophene matrix

Our presented research aims to provide a systematic study of electrical, magnetic and microwave absorption properties of La-Co substituted Ba-Sr hexaferrite nanoparticles and MWCNTs, encapsulated in conductive polymer matrix. La-Co substituted Ba-Sr hexaferrite nanoparticles were produced using Sol-Gel auto combustion, whereas carrier fluid ultrasonication dispersion and in-situ polymerization were used to synthesize their composites with multiwall carbon nanotubes (MWCNTs) and conductive polymers. Structural investigations were accomplished using X-rays diffraction, secondary electron microscopy, Infrared and Raman Spectroscopy. The dielectric measurements revealed increased dielectric losses (4.86 at 1 GHz for pure nanoparticles, which increases up to 11.59 and 13.36 for ternary composites within PANI and PTh matrix), indicating good energy dissipation behavior. The decrease in magnetism was observed due to the weakening of exchange coupling or domain wall pinning at the interface of Ferrite-MWCNTs and Ferrite-Polymer, resulting in lowered saturation magnetization, remanence and coercivity values. The microwave absorption of our samples was evaluated as a function of frequency and thickness, revealing its dependence on the quarter wavelength phenomenon with maximum reflection loss of − 40.4 dB observed for ternary composite with Polythiophene matrix at 7.54 GHz resonance frequency. The dependence of reflection loss peaks on matching thickness was analyzed using calculated thickness profiles, revealing their close agreement with simulated thickness. The study highlighted the potential of synthesized samples for electromagnetic signature reduction, in both commercial and military applications. The resonance bands were found to coincide with the operating frequency of military radars for shipborne and airborne surveillance and navigation in the X band (8–12 GHz).

A novel mesoporous CoMn2O4@rGO composite as an electrode material for hybrid supercapacitor for energy storage device applications

Cobalt‑manganese spinel oxide (CoMn2O4) was hybridized with reduced graphene oxide (rGO) via a facile hydrothermal process and a highly porous three-dimensional (3D) structure was constructed. The phase structure, chemical bands, morphology and chemical state of the synthesized powders were investigated by X-ray diffraction (XRD), Raman spectroscopy, field emission secondary electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS). CoMn2O4@rGO electrode delivered high specific capacitance of 1578 Cg−1at 1 Ag−1 in 1.0 M KOH electrolyte and an outstanding cycling stability with 94.2 % retention over 5000 cycles, suggesting the great potential application of this material in advanced energy storage device. The rGO makes great contributions to hybrid through supplying a conductive support for CoMn2O4, resulting in the prominent specific capacitances and outstanding cycle stability. Besides, the assembled CoMn2O4@rGO//AC asymmetric supercapacitor (ASC) displays the maximum energy density of 35.6 Whkg−1 at a power density of 8916.9 Wkg−1. Significantly, an ultralong cycling life of 98.2 % capacitance retention is achieved for the ASC device after 10,000 charge/discharge cycles at 1 Ag−1.

Non-Covalent Free-Standing Monolayer Nanoarchitectonics of Heterocoronene-Based Discotic Liquid Crystal Molecules

With excellent charge carrier mobility, tendency to form long-range assembly with self-healing ability, and remarkable chemical and mechanical stability, highly conjugated discotic molecules constitute an important class of materials for electronic applications. Here, we report formation of the stable free-standing molecular film of heterocoronene-based discotic liquid crystal (DLC) molecules, held solely by supra-molecular non-covalent interactions. The films of monolayer thickness (∼4 nm) were lifted from Langmuir trough directly onto a circular ring of diameter up to 2 mm as well as onto TEM grids. Films remain free-standing up to a macroscopic length scale, as revealed by optical and secondary electron microscopy, presumably due to the synergistic effect of intermolecular π–π interactions and the dispersion forces between the peripheral alkyl chains as well as their interdigitation. The monolayer is more than 97% transparent in the visible range. Further, resistive switching measurements carried out on the monolayer DLC film transferred on a silver substrate revealed electrochemical metallization to be the governing process. The switching time was found to decrease exponentially with voltage indicating nucleation to be a possible rate-limiting step. We anticipate that the method presented here will facilitate utilization of such non-covalent free-standing films in flexible memristor and nano-electromechanical systems.

Encapsulation of Ba–Sr hexaferrite nanoparticlesand MWCNTs in conductive polymer matrix for improved dielectric spectroscopy, electromagnetic shielding and microwave absorption applications

Ba–Sr hexaferrite nanoparticles were produced using Sol-Gel auto combustion, whereas carrier fluid ultrasonication dispersion and in-situ polymerization were used to synthesize their composites with MWCNTs and conductive polymers. Structural investigations were accomplished using X-rays diffraction, secondary electron microscopy, Infrared and Raman Spectroscopy. The low frequency dielectric measurements revealed increased dielectric losses (304 at 100 Hz for pure nanoparticles, which increases up to 2721 and 7861 for ternary composites within polyaniline and Polythiophene matrix), indicating good energy dissipation behavior. The diminishing magnetism resulted from the weakening of exchange coupling or domain wall pinning at the interface of Ferrite-MWCNTs and Ferrite-Polymer, causing the shifting of magnetic resonance peak towards lower frequency in the shielding effectiveness (Absorption) plots. Increasing DC conductivity adds to the nominal increase of Shielding effectiveness (Reflection) values owing to the rise in charge carrier conduction. The maximum total shielding effectiveness, perceived for the composition of Ba0.5Sr0.5Fe12O19/MWCNTs/Polythiophene, was −34 dB and −33 dB at 8.1 GHz and 16.2 GHz, respectively. The microwave absorption of our samples was evaluated as a function of frequency and thickness, revealing its dependence on the quarter wavelength phenomenon with maximum reflection loss of −39 dB observed for ternary composite with Polythiophene matrix at 7.4 GHz resonance frequency. The resonance bands coincide with the operating frequency of military radars for shipborne and airborne surveillance and navigation in the X band.

Self-marked preparation of site-specific transmission electron microscope lamellae of nanodevices using focusing ion beam technique.

The precise extraction of a thin slice (lamellae) from nano electronic devices using a focused ion beam (FIB) is crucial for transmission electron microscopy analysis, but it remains a challenge for 100nm and beyond scale device components. In this study, we introduce a new method that utilises the device's own features as markers during FIB thinning process by continuously monitoring the intermediate structures with secondary electron scanning electron microscopy (SE-SEM) imaging. This allows for the targeted extraction of the desired device component with high precision. We successfully demonstrate the effectiveness of this approach by extracting lamellae from 100nm length channel in arrayed carbon nanotube film field-effect transistors using FIB lift-out.

P-type nickel oxide deposited by reactive hollow cathode gas flow sputtering for the potential usage in thin-film transistors

Thin Nickel Oxide film were deposited by reactive pulsed-direct current hollow cathode gas flow sputtering. This unique technique allows for sputtering magnetic target materials with very high rates without magnetron. Deposition was carried out from a nickel target at room temperature. The influence of process parameters on optical, electrical, and structural film properties are investigated. High deposition rates of 6 nm/s and 2 nm/s are achieved for both direct current and pulsed-direct current power supply. All films are highly resistive and show p-type conduction that is tunable with oxygen flow. The films exhibit optical band gap around 3,8 eV depending on process parameters like oxygen flow and pulsing parameter. Secondary electron microscopy shows pillar-like growth perpendicular to the surface, while grazing incidence X-ray diffraction reveals smaller, randomly oriented crystals. Electrical properties of the films were tested by Hall measurements, revealing mobilities in the range of 1 cm2Vs. The nano crystalline thin films were tested in staggered bottom gate Thin-Film Transistor structures for potential use as channel layer.