Transmission Electron Microscopy Measurements Research Articles

The Impact of Microstructure on Filament Growth at the Sodium Metal Anode in All‐Solid‐State Sodium Batteries

AbstractIn recent years, all‐solid‐state batteries (ASSBs) with metal anodes have witnessed significant developments due to their high energy and power density as well as their excellent safety record. While intergranular dendritic lithium growth in inorganic solid electrolytes (SEs) has been extensively studied for lithium ASSBs, comparable knowledge is missing for sodium‐based ASSBs. Therefore, polycrystalline Na‐β″‐alumina is employed as a SE model material to investigate the microstructural influence on sodium filament growth during deposition of sodium metal at the anode. The research focuses on the relationship between the microstructure, in particular grain boundary (GB) type and orientation, sodium filament growth, and sodium ion transport, utilizing in situ transmission electron microscopy (TEM) measurements in combination with crystal orientation analysis. The effect of the anisotropic sodium ion transport at/across GBs depending on the orientation of the sodium ion transport planes and the applied electric field on the current distribution and the position of sodium filament growth is explored. The in situ TEM analysis is validated by large field of view post‐mortem secondary ion mass spectrometer (SIMS) analysis, in which sodium filament growth within voids and along grain boundaries is observed, contributing to the sodium network formation potentially leading to failure of batteries.

Tuning of exchange bias by regulating the microstructural parameters in Ni81Fe19 (5, 8, 11, 14, 17, and 20 nm)/Ir7Mn93(10 nm) bilayers probed using magnetoresistance

The investigation and tunning of positive exchange bias (PEB) and negative exchange bias (NEB) are reported at room temperature (RT) and low temperature (20 K), respectively, in a series of top-pinned Ni81Fe19(tFM = 5, 8, 11, 14, 17, and 20 nm)/Ir7Mn93(10 nm) polycrystalline heterostructure thin films grown in the presence of a 1 kOe in situ magnetic field by systematically controlling the microstructural parameters such as thickness, roughness, and crystallite/grain size. On decreasing the thickness (roughness) of NiFe from 20 nm (0.49 nm) to 5 nm (0.28 nm), an enhancement in PEB and NEB is observed from +12 to +22 Oe and −300 to −556 Oe at RT and 20 K, respectively. It is observed that both exchange bias and coercivity substantially depend on the atomic scale roughness of the interface width (NiFe/IrMn). The representative plane-view of transmission electron microscopy (TEM) measurements revealed the enhanced antiferromagnet (AF) grain size on decreasing the thickness of ferromagnetic, whereas cross-sectional TEM studies exhibited the sharp interfaces in the bilayer samples after magnetic annealing. A unique correlation between the training mechanism and the degree of asymmetry is established. Further, the training measurement data are fitted with various theoretical models that support the fact that not only interfacial but also bulk AF spins play a vital role in the exchange bias. Thus, the present study reveals the microstructural insights by varying the thickness of NiFe to address the unresolved issues of the EB by directly correlating it with interface roughness and the crystallite/grain size of AF in it, probed using the magnetoresistance technique.

Zn-Al layered double hydroxide/zeolitic imidazolate framework-8 nanocomposite as a high-performance sorbent for adsorption and desorption of anticancer drugs from aqueous media

Zn-Al layered double hydroxide/zeolitic imidazolate framework-8 (Zn-Al LDH/ZIF-8) nanocomposite was synthesized through growing zeolitic imidazolate framework-8 (ZIF-8) on Zn-Al layered double hydroxide and employed as an effective pollutant adsorbent. The nanocomposite was utilized for the removal of Ifosfamide (IF) and cyclophosphamide (CK) anticancer drugs from aqueous matrices. Zn-Al LDH/ZIF-8 nanocomposite was characterized via different analyses such as Brunauer-Emmett-Teller, X-ray diffraction, X-ray photoelectron spectroscopy, Energy-dispersive X-ray spectroscopy, Elemental mapping, Fourier-transform infrared spectroscopy, Field emission scanning electron microscopy, Transmission electron microscopy, Thermogravimetric analysis, and Contact angle measurement. Batch experiments were implemented to investigate the parameters affecting the adsorption process, including adsorbent loading, pH value, ionic strength, initial pollutant concentration, temperature, and impurity. The experimental results were analyzed using various models to determine the adsorption mechanism, thermodynamics, isotherm, and kinetics. The Langmuir isotherm model presented higher consistency with the experimental data (R2 >0.990). The saturation adsorption capacity of the nanocomposite for IF and CK drugs, obtained as 929.66 and 888.94 mg/g, respectively, was found to be higher than those for ZIF-8 (759.70 and 724.53 mg/g, respectively) at a temperature of 298 ± 1 K and pH of 7.5 ± 0.1. The kinetic data had a better fit with the pseudo-second-order kinetic model (R2 >0.980). Thermodynamic studies revealed that the adsorption process was exothermic and spontaneous. The mechanism of adsorption was attributed to electrostatic interactions, hydrophobic forces, H-bonding, π-π stacking, and π-π electron-donor acceptor. Additionally, after performing four adsorption-desorption cycles, the nanocomposite indicated only a 9.3% reduction in the adsorption capacity, demonstrating the promising potential of this, for industrial applications.

Photocatalytic degradation performance of antibiotics by WO3/α-Fe2O3/zeolite type II heterojunction with core-shell structure.

The accumulation of antibiotics in the environment can be harmful to human health, and research on their disposal technologies is of increasing interest. In this study, WO3/α-Fe2O3/zeolite (WFZ) type II heterojunction composites with core-shell structures were prepared by coupling WO3 semiconductors with visible-light photocatalytic activity with α-Fe2O3 via hydrothermal synthesis using zeolite as a carrier for the adsorption of synergistic photocatalytic degradation of antibiotics in wastewater. X-ray diffraction, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), specific surface, and porosity measurements were used to characterize the structure of WFZ type II heterojunction. The performance of WFZ heterojunction for the visible photocatalytic degradation of antibiotics (tetracycline hydrochloride (TCH), ciprofloxacin (CIP), and levofloxacin hydrochloride (LVF)) was investigated. Through four photocatalytic cycles, the catalyst exhibited excellent durability and stability. This was attributed to the core-shell structure and type II heterojunction promoting the effective separation of photogenerated carriers and the extended visible light response range, which resulted in the best photocatalytic activity of the catalyst under visible light irradiation. Radical trapping experiments showed that superoxide radicals (•O2-) and hydroxyl radical (•OH) were the main active species that played a major role in the photocatalytic degradation. These findings show that the synthesized WFZ type-II heterojunction can be used as a reliable visible-light-responsive photocatalyst for the treatment of antibiotics in wastewater.

Photocatalytic degradation of tetracycline antibiotics by RGO-CdTe composite with enhanced apparent quantum efficiency

RGO-CdTe composite was synthesized using a straightforward, easy-to-realize, one-pot solvothermal technique. The synthesized composite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller method (BET), Raman spectra, UV-Vis absorption, and photoluminescence measurement. The RGO-CdTe composite exhibited 83.6% photocatalytic degradation efficiency for the aqueous tetracycline (TC) antibiotic solution and the apparent quantum yield (AQY) for the same was as high as 22.29% which is 2.63 times higher than that of CdTe. The scavenger investigation demonstrated that although hole acts as the leading active species, despite that, superoxide and hydroxyl radicals have also played crucial roles. The initial pH-dependent photocatalytic performance was measured. The zeta potential of the composite at different pH values was evaluated to establish the photocatalytic performance of the RGO-CdTe towards TC degradation at different pH. The recycling experiment depicts that only a 10% degradation performance declines after 5 times recycle use of the RGO-CdTe photocatalyst. An efficient photocurrent generation in RGO-CdTe thin film device has also been observed. Our study establishes as-synthesized composite of RGO-CdTe as a highly potential, and stable photocatalyst for the degradation of antibiotics from the polluted aqueous environment with a very good photoinduced charge generation efficiency in its solid phase.

Characterization after aging of Si nanoparticles synthesized by picosecond laser ablation of solids in liquids

Colloidal silicon nanoparticle suspensions have been synthesized by the laser ablation of solids in liquids technique. We employed a picosecond laser to irradiate a silicon wafer immersed into distilled water at different fluences. After 30 months of aging, the optical properties of the nanoparticle suspensions were studied by photoluminescence spectroscopy, revealing the existence of visible light emissions arising from quantum confinement effects due to size reduction. Raman microspectroscopy was used to further observe size reduction of Si by analyzing shifts to lower frequencies of the Si-Si main vibrational mode associated to quantum confinement of phonons in silicon at nanoscale dimensions. Transmission electron microscopy measurements corroborated the presence of Si nanoparticles in the suspensions. Furthermore, the stability of these aged nanoparticles was confirmed by measuring their zeta potential. Results are analyzed and discussed in terms of the influence of the per pulse laser fluence on the nanoparticle features.

Nanocomposite Hydrogels with Self-Assembling Peptide-Functionalized Carbon Nanostructures.

Carbon nanostructures (CNSs) are attractive components to attain nanocomposites, yet their hydrophobic nature and strong tendency to aggregate often limit their use in aqueous conditions and negatively impact their properties. In this work, carbon nanohorns (CNHs), multi-walled carbon nanotubes (CNTs), and graphene (G) are first oxidized, and then reacted to covalently anchor the self-assembling tripeptide L-Leu-D-Phe-D-Phe to improve their dispersibility in phosphate buffer, and favor the formation of hydrogels formed by the self-organizing L-Leu-D-Phe-D-Phe present in solution. The obtained nanocomposites are then characterized by transmission electron microscopy (TEM), oscillatory rheology, and conductivity measurements to gain useful insights as to the key factors that determine self-healing ability for the future design of this type of nanocomposites.

Fabrication of Aligned Alanine Functionalized Hydroxyapatite Nanorods Embedded in Electrospun Gelatin Scaffolds as a Coating Material for Titanium Bone Implant Application

Aligned calcium phosphate nanorods embedded in gelatin nanofibers were fabricated to be applied as a coating material on the Ti bone implant using the conventional electrospinning method. Calcium phosphate nanorods with a strong positively charged surface were prepared by modifying with alanine (alanine/HA) to facilitate the arrangement of nanoparticles under the electric field in the electrospinning process, followed by mild hydrothermal treatment to preserve the structure of fibers. Scanning electron microscope, atomic force microscope, and transmission electron microscope measurements confirmed that the composite fibers were smooth without the presence of particles on the surface and alanine/HA was aligned within the fiber. The tensile strength of the prepared scaffolds was identical to that of the cancellous bone (2 to 12 MPa). According to MTT assay, the scaffold coated Ti showed a significant improvement on cell adhesion and biocompatibility compared to uncoated Ti.

Synthesis and Characterization of a Novel Nanocomposite Polymer

One-dimensional nanostructures of PANI: PVA-g-EI nanocomposite are prepared by the interfacial polymerization method. The properties of a resulting green powder are studied by the X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), and infrared spectroscopy (FTIR). Prepared thin films were characterized by UV-Vis and photoluminescence (PL) spectroscopies. The XRD pattern of the nanocomposite shows that the higher volume fraction of crystalline phases corresponds to the PANI polymer with the accepted monoclinic unit cell of PVA. Nano-sized irregular particles arranged in clusters appear in the TEM measurements and SEM images, which testifies to the agglomeration without uniform packing. EDX confirms that the PVA-g-EI is incorporated in the structure of the polymer nanocomposite. A significant shift in the absorption edge with three PL independent emission peaks again confirms that PANI/PVA-g-EI form a nanocomposite.

The beneficial role of nano-sized Fe3O4 entrapped in ultra-stable Y zeolite for the complete mineralization of phenol by heterogeneous photo-Fenton under solar light

Highly efficient, separable, and stable magnetic iron-based-photocatalysts produced from ultra-stable Y (USY) zeolite were applied, for the first time, to the photo-Fenton removal of phenol under solar light. USY Zeolite with a Si/Al molar ratio of 385 was impregnated under vacuum with an aqueous solution of Fe2+ ions and thermally treated (500–750 °C) in a reducing atmosphere. Three catalysts, Fe-USY500°C-2h, Fe-USY600°C-2h and Fe-USY750°C-2h, containing different amounts of reduced iron species entrapped in the zeolitic matrix, were obtained. The catalysts were thoroughly characterized by absorption spectrometry, X-ray powder diffraction with synchrotron source, followed by Rietveld analysis, X-ray photoelectron spectroscopy, N2 adsorption/desorption at −196 °C, high-resolution transmission electron microscopy and magnetic measurements at room temperature.The catalytic activity was evaluated in a recirculating batch photoreactor irradiated by solar light with online analysis of evolved CO2. Photo-Fenton results showed that the catalyst obtained by thermal treatment at 500 °C for 2 h under a reducing atmosphere (FeUSY-500°C-2h) was able to completely mineralize phenol in 120 min of irradiation time at pH = 4 owing to the presence of a higher content of entrapped nano-sized magnetite particles. The latter promotes the generation of hydroxyl radicals in a more efficient way than the Fe-USY catalysts prepared at 600 and 750 °C because of the higher Fe3O4 content in ultra-stable Y zeolite treated at 500 °C. The FeUSY-500°C-2h catalyst was recovered from the treated water through magnetic separation and reused five times without any significant worsening of phenol mineralization performances. The characterization of the FeUSY-500°C-2h after the photo-Fenton process demonstrated that it was perfectly stable during the reaction. The optimized catalyst was also effective in the mineralization of phenol in tap water. Finally, a possible photo-Fenton mechanism for phenol mineralization was assessed based on experimental tests carried out in the presence of scavenger molecules, demonstrating that hydroxyl radicals play a major role.

Degradation mechanism of high-voltage single-crystal LiNi0.5Co0.2Mn0.3O2 cathode material

Layered cathode materials have been successfully commercialized and applied to electric vehicles. To further improve improve the energy density of these marterials is still the main efforts in the market. Therefore, developing high-voltage LiNi x Co y Mn z O2 (x + y + z = 1, NCM) to achieve high energy density is particularly important. However, under high voltage cycling, NCM often exhibits rapid capacity degradation, which can be attributed to oxygen release, structural phase transition and particle cracking. In this work, the representative single-crystal LiNi0.5Co0.2Mn0.3O2 (NCM523) was studied under various high charge cut-off voltages. Analysis by x-ray diffraction (XRD), transmission electron microscope (TEM) and electron back scatter diffraction (EBSD) measurements indicated that the rock-salt phase is formed on the surface of the particles after high voltage cycling, which is responsible for the increase of impedance and the rapid decay of capacity. Therefore, inhibiting the formation of rock-salt phase is believed an effective strategy to address the failure of NCM under high voltages. These findings provide effective guidance for the development of high-voltage NCM.

Low driving-voltage four-armed pentaerythritol and coumarin based compounds as potential materials for LCDs

The electro-optical properties of some four-armed liquid crystalline materials with pentaerytrithol core based on coumarin as mesogenic moiety is investigated. The mesogenic moiety is connected to the core via spacers with various chain lengths differing. The compounds are investigated via differential scanning calorimetry (DSC) and polarizing optical microscopy (POM) equiped with a temperature controlled hot-stage. Field-Emission Scanning Electron Microscope (FESEM) and “High-Resolution Transmission Electron Microscope (HRTEM) measurements are exhibited a relatively spherical morphology with particle sizes of 145–174 nm. The electro-optical performance of the materials as thin films coated on indium-tin-oxide (ITO) glass substrates are investigated via applied voltage versus transmittance plots, exhibiting relatively low driving voltage values as low as 2.5–3 V. The ordinary (no) and extraordinary (ne) refractive indexes of the compounds at different temperatures are measured showing a good correspondence with the POM results. In conclusion, the studied materials have exhibited proper physicochemical and electro-optical properties as materials for liquid crystal displays (LCD).

Unusual gold nanoparticle-antibody interactions

The formation of an antibody (Ab) protein corona surrounding gold nanoparticles (AuNPs) is a crucial step in the design of immunological assays. The Ab corona stabilizes AuNPs, preventing their aggregation even at high ionic strength, and can be achieved by simply mixing Abs and AuNPs. In this paper, we report the unusual interactions between AuNPs and the antibody against L1 Cell Adhesion Molecule (L1CAM) purified from rabbits. We have observed that at low ionic strength, the addition of a wide range of concentrations of rabbit monoclonal Abs against L1CAM protein immediately causes the coagulation of citrate-capped gold nanoparticles. This finding is surprising since the addition of proteins to colloidal gold usually forms a stable protein corona. The combination of extinction spectra, dynamic light scattering (DLS), and transmission electron microscopy (TEM) measurements reveals the presence of small clusters of AuNPs coated by the antibodies, as well as micron-sized antibody aggregates. Furthermore, static light scattering measurements demonstrate that Ab self-interactions are attractive (with a negative second virial coefficient, B2) and induce very slow Ab self-aggregation over several months. Overall, these results indicate that, at low ionic strength, the presence of AuNPs enhances Ab-Ab interactions, leading to their rapid aggregation. Simultaneously, the self-aggregation of the antibodies coating the AuNPs results in the formation of nanoparticle clusters. The addition of NaCl to increase the ionic strength fully reverses the coagulation of AuNPs (the Ab-coated AuNPs repel each other) and dissolves the Ab aggregates (the Ab interactions become repulsive, with a positive B2). The AuNPs-induced enhancement of the aggregation process can be explained by considering that the highly favorable binding of Abs on the gold surface compensates for the entropic penalty associated with Ab-Ab aggregation. The phenomenon we observed is specific to anti-L1CAM purified from rabbits and aligns with very old reports on AuNP coagulation induced specifically by the immunoglobulins present in the cerebrospinal fluid of patients suffering from neurosyphilis or multiple sclerosis (C. Lange Zeitschr. Chemotherap., 1912, 1, 44). It is reasonable to hypothesize that other antibodies exhibit this unusual behavior, so this work may aid in the interpretation of “anomalous” results that might otherwise be attributed to errors in fine-tuning AuNPs-Abs conjugation protocols.

Acoustic stimulation during sleep improves cognition and ameliorates Alzheimer's disease pathology in APP/PS1 mice

Nonpharmacological therapies for Alzheimer's disease (AD) have become a popular research topic, and acoustic stimulation during sleep is one such promising strategy for the clinical treatment of AD. Some animal experiments have illustrated that acoustic stimulation at a specific frequency can ameliorate AD-related pathology or improve cognition in mice, but these studies did not explore the effective time window of auditory stimulation. Here, we explored the effects of acoustic stimulation during wakefulness and acoustic stimulation during sleep on cognition and AD-related pathology in APP/PS1 mice and the underlying mechanisms. In this study, forty APP/PS1 mice were equally divided into the following 4 groups and treated for 28 days: the chronic sleep deprivation (CSD) group (exposed to sleep deprivation from zeitgeber time [ZT] 0 to ZT 12 each day), the normal sleep and stress exposure (NSS) group (exposed to a stressor from ZT 0 to ZT 12 each day), the acoustic stimulation during wakefulness (ASW) group (exposed to sleep deprivation and 40 Hz acoustic stimulation from ZT 0 to ZT 12 each day) and the acoustic stimulation during sleep (ASS) group (exposed to sleep deprivation from ZT 0 to ZT 12 and 40 Hz acoustic stimulation from ZT 12 to ZT 24 each day). After the intervention, cognition was assessed by behavioural experiments. The amyloid-β burden was analysed by Western blotting, immunofluorescence and enzyme-linked immunosorbent assay. Tau pathology was assessed by Western blotting. Mitochondrial function was evaluated by transmission electron microscopy, Western blotting and fluorescence intensity measurement. We found that the NSS and ASS groups had better cognitive functions than the CSD and ASW groups. The Aβ burden and tau phosphorylation were lower in the NSS and ASS groups than in the CSD and ASW groups. Mitochondrial function was better in the NSS and ASS groups than in the CSD and ASW groups. However, the differences in these parameters between the NSS and ASS groups and between the CSD and ASW groups were not significant. Our findings suggest that acoustic stimulation at a specific frequency during sleep, but not during wakefulness, reduces the amyloid-β burden by inhibiting amyloid beta precursor protein-binding protein 2, hinders tau phosphorylation by blocking glycogen synthase kinase 3 beta, and restores mitochondrial function by elevating mitophagy and promoting mitochondrial biogenesis.

Three-dimensional reconstruction of Y-IrNi rhombic dodecahedron nanoframe by STEM/EDS tomography

The structural analysis of nanocrystals via transmission electron microscopy (TEM) is a valuable technique for the material science field. Recently, two-dimensional images by scanning TEM (STEM) and energy-dispersive X-ray spectroscopy (EDS) have successfully extended to three-dimensional (3D) imaging by tomography. However, despite improving TEM instruments and measurement techniques, detector shadowing, the missing-wedge problem, X-ray absorption effects, etc., significant challenges still remain; therefore, the various required corrections should be considered and applied when performing quantitative tomography. Nonetheless, this 3D reconstruction technique can facilitate active site analysis and the development of nanocatalyst systems, such as water electrolysis and fuel cell. Herein, we present a 3D reconstruction technique to obtain tomograms of IrNi rhombic dodecahedral nanoframes (IrNi-RFs) from STEM and EDS images by applying simultaneous iterative reconstruction technique and total variation minimization algorithms. From characterizing the morphology and spatial chemical composition of the Ir and Ni atoms in the nanoframes, we were able to infer the origin of the physical and catalytic durability of IrNi-RFs. Also, by calculating the surface area and volume of the 3D reconstructed model, we were able to quantify the Ir-to-Ni composition ratio and compare it to the EDS measurement result.

Structural and Thermomagnetic Properties of Gallium Nanoferrites and Their Influence on Cells In Vitro.

Magnetite and gallium substituted cuboferrites with a composition of GaxFe3-xO4 (0 ≤ x ≤ 1.4) were fabricated by thermal decomposition from acetylacetonate salts. The effect of Ga3+ cation substitution on the structural and thermomagnetic behavior of 4-12 nm sized core-shell particles was explored by X-ray and neutron diffraction, small angle neutron scattering, transmission electron microscopy, Mössbauer spectroscopy, and calorimetric measurements. Superparamagnetic (SPM) behavior and thermal capacity against increasing gallium concentration in nanoferrites were revealed. The highest heat capacity typical for Fe3O4@Ga0.6Fe2.4O4 and Ga0.6Fe2.4O4@Fe3O4 is accompanied by a slight stimulation of fibroblast culture growth and inhibition of HeLa cell growth. The observed effect is concentration dependent in the range of 0.01-0.1 mg/mL and particles of Ga0.6Fe2.4O4@Fe3O4 design have a greater effect on cells. Observed magnetic heat properties, as well as interactions with tumor and healthy cells, provide a basis for further biomedical research to use the proposed nanoparticle systems in cancer thermotherapy (magnetic hyperthermia).

Reversible tuning of charge Carrier's polarity of MoTe2 FETs enabled by laser and high temperature

The transition metal dichalcogenides (TMDs) materials exhibit variety of crystal phase structures and vulnerable to extrinsic doping for phase transformation, leading diverse electronic applications. Here we demonstrate the controlled charge carrier's polarity in the phase transition of molybdenum ditelluride (MoTe2) based field effect transistors (FETs) affected by laser irradiations in ambient environment. The conductivity in MoTe2-based FETs was measured before and after laser irradiations in a range of temperatures (77, 100, 150, 200, 250, 300, 350 and 400 K). The devices achieved reversible charge polarity by changing its 2H phase to semimetal 1Tʹ phase upon laser irradiations and returned to its original state once treated with high temperature 400 K. Since, the 1Tʹ phase is confirmed by Raman spectroscopy, transmission electron microscopy (TEM) and electrical transport measurements. Thus, our finding provides an effective approach in controlling charge carrier's modulation in laser-doped 2D materials for electronic and optoelectronic applications.

Formation of vesicular structures from fatty acids formed under simulated volcanic hydrothermal conditions

Microscopic compartmentalization is beneficial in synthetic chemistry and indispensable for the evolution of life to separate a reactive “inside” from a hydrolyzing “outside”. Here, we show compartmentalization in aqueous solution containing mixtures of fatty acids up to 19 carbon atoms which were synthesized by one-pot reactions of acetylene and carbon monoxide in contact with nickel sulfide at 105 °C, reaction requirements which are compatible to Hadean Early Earth conditions. Based on confocal, dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements, vesicle-like structures with diameters of 10–150 nm are formed after solvent extraction and resolubilisation. Moreover fluorescent dye was encapsulated into the structures proving their vesicular properties. This self-assembly could also have occurred on Early Earth as a crucial step in establishing simple membranes of proto-cells as a prerequisite in the evolution of metabolism and life.

High-density, spontaneous magnetic biskyrmions induced by negative thermal expansion in ferrimagnets.

Magnetic skyrmions are topologically protected quasiparticles that are promising for applications in spintronics. However, the low stability of most magnetic skyrmions leads to either a narrow temperature range in which they can exist, a low density of skyrmions, or the need for an external magnetic field, which greatly limits their wide application. In this study, high-density, spontaneous magnetic biskyrmions existing within a wide temperature range and without the need for a magnetic field were formed in ferrimagnets owing to the existence of a negative thermal expansion of the lattice. Moreover, a strong connection between the atomic-scale ferrimagnetic structure and nanoscale magnetic domains in Ho(Co,Fe)3 was revealed via in situ neutron powder diffraction and Lorentz transmission electron microscopy measurements. The critical role of the negative thermal expansion in generating biskyrmions in HoCo3 based on the magnetoelastic coupling effect is further demonstrated by comparing the behavior of HoCo2.8Fe0.2 with a positive thermal expansion.

Low damage atomic layer etching technology for gate recessed fabrication

In this work, the damage induced by etching to AlGaN surface employing atomic layer etching (ALE), which use Cl2 plasma and Ar plasma for etching and removal, compared with conventional etching method was investigated. The Hall-effect measurements indicate that a higher two-dimensional electron gas (2DEG) concentration of 1.54 × 1013 cm−2 is achieved and an electron mobility of 1756 cm2/V is obtained on the ALE sample by reducing the bombardment of BCl2+ and BCl + on the surface. Simultaneously, the damage caused by ALE to the etching surface is lower than the conventional etching method according to Raman spectroscopy analyses and atomic force microscopy (AFM) scans. The X-ray photoelectron spectroscopy (XPS) spectrum and Transmission Electron Microscope (TEM) measurements were further carried out to prove that ALE process results in a higher 2DEG concentration due to maintaining stable Al composition and inducing lower damage on the surface.