Scanning Electron Microscopy Transmission Electron Microscopy Research Articles

Solid and Liquid State Dewetting of Thin Silicon Films Sandwiched between Two Silicon Carbide Substrates

Silicon carbide (SiC) is a very promising material for power electronics thanks to its wide band gap and high thermal conductivity. Stacking of SiC substrates of different crystalline quality and/or doping levels through wafer bonding is of particular interest for applications. Although a direct SiC/SiC bonding may result in an unstable interface, a layer of intermediate material playing a role of a “glue” can be sandwiched between the SiC substrates to ensure their good attachment. However, the processing of the power electronics devices at a high temperature may degrade the properties of this material which evolution under high temperature annealing must be studied in advance.In this work, we exploited the possibility to use silicon (Si) as a bonding material. We studied the structure evolution of a nanometer-thick polycrystalline Si layer sandwiched between two monocrystalline SiC substrates with a high temperature annealing. We focused our attention on understanding the impact of as-bonded Si layer thickness and the temperature of annealing on the eventual Si layer morphology. Tests were conducted for Si films of as-bonded thickness of 8 nm, 20 nm and 40 nm at temperatures ranging from 950°C to 1400°C, i.e. below Si melting temperature of 1414°C, and above it up to 1700°C. The experiments were realized using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and high-resolution X-ray diffraction techniques. Cross-sectional TEM images were used to describe the structure and morphology of the interface. SEM was used to observe the inner surface of one of the SiC substrates once the other was removed by a cleavage. X-ray measurements were carried out to determine Si film thickness and texture as well as the strain in Si and SiC.We show that annealing at temperatures ranging from 950°C to 1400°C results in pitting, i.e. creation of voids, at the Si/SiC interfaces which are observed for any studied as-bonded thickness of a Si layer. We attribute this effect to a solid state dewetting of Si from SiC. This dewetting effect evolves into complete piercing of the silicon film and formation of cylindrical voids within the Si layer which grow in diameter with annealing temperature. We also observe a thickening of the silicon layer. The driving force for a solid state dewetting will be discussed in terms of SiC/Si interface energy, vacancies precipitation and Si atoms diffusion.When annealed to relatively higher temperatures allowing for Si melting followed by its solidification, we put into evidence the formation of step bunching on the internal surfaces of both SiC substrates. Regarding Si, it is concentrated along the SiC steps. The mechanism of the reconstruction of SiC internal surfaces resulting in the creation of step bunching will be discussed in relation to Si liquid state dewetting, carbon atoms dissolution, recondensation and migration within liquid Si.The effect of as-bonded silicon film thickness on the Si dewetting process is not pronounced after annealing at 950°C: all samples contain pits of a similar size and density. When the annealing temperature is slightly increased above 1000°C, the pits in the Si films of a lower initial thickness transform into cylindrical voids piercing the layers. The thicker layers contain both pits and cylindrical voids. At a high enough temperature of 1400°C only cylindrical voids were observed in all samples. The thicker layers present the lowest densities of voids.For the annealing at temperatures higher than 1400°C, the as-bonded thickness of a Si layer had a direct impact on the height of the steps formed on the internal surfaces of the SiC substrates. The eventual steps were higher the thicker the Si layer was used for bonding.The role of the diffusion and interaction of Si and C atoms and vacancies during annealing will be discussed in relation to the dynamics of solid and liquid state Si dewetting, size and density of pits and cylindrical voids and eventual Si layer morphology.Figure 1, on the left, SEM images showing the evolution of Si solid state dewetting with annealing temperature, from pitting to the formation of cylindrical voids. On the right, SEM and cross-sectional TEM images showing the step bunching on the SiC internal surfaces and the Si accumulation at the steps obtained after Si liquid state dewetting. Figure 1

Lattice Oxygen Lability of La-Hexaaluminates Substituted by Different Metals and Their Effects on the Thermal Stability of Supported Nano-Ir Particles.

Oxide supports with high lattice oxygen lability can stabilize the supported nanoparticles at high temperatures. The lattice oxygen lability of lanthanum hexaaluminates (LHAs) substituted with other metals (such as Mg and Fe) as well as their effects on the thermal stability of supported Ir particles were investigated via CO chemisorption, hydrogen temperature-programmed reduction (H2-TPR), oxygen temperature-programmed desorption (O2-TPD), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma (ICP), and scanning electron microscopy/transmission electron microscopy (SEM/TEM) techniques. The H2-TPR results showed that the lattice oxygen lability of lanthanum iron hexaaluminate (LFA) was much higher than that of lanthanum magnesium hexaaluminate (LMA). This variation could be attributed to the difference in the reducibility of Fe/Mg atoms and their substitution sites in the crystallographic lattice. Under the reductive condition, the H2-TPR presented that the amount of reducible lattice oxygen of LFA supported by metallic Ir decreased significantly, implying the existence of the migration of lattice oxygen and formation of oxygen vacancies, as revealed by O2-TPD and XPS results. After thermal aging at 1200 °C, the amount of residual Ir in LFA was about 4 times that of LMA, as shown in the ICP results. The mean size and dispersion of Ir particles in LFA were better than those in LMA, as revealed by the SEM/TEM results, showing the superior thermal stability of the Ir particles in LFA support. Hence, this study concludes that the lattice oxygen lability plays an important role in improving the thermal stability of the Ir@LHAs at high temperatures. Based on characterization results, a model was proposed to explain the interaction between Ir and LHAs and its effect on the thermal stability of the Ir particles.

Electrochemical Performance of Fe2O3@PPy Nanocomposite as an Effective Electrode Material for Supercapacitor

Herein, we offer the study on the conductive polymer of polypyrrole and iron oxide (Fe2O3@PPy) nanocomposites, which are prepared via a simple chemical oxidation method for energy storage applications. The synthesized nanocomposites are confirmed by the physico-chemical properties through Fourier Transform Infra-red Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS) results along with Electrochemical Impedance Spectroscopy (EIS), Cyclic Voltammetry (CV), Galvanostatic Charge–Discharge (GCD) and stability analyses. The surface morphological studies of SEM and high TEM images substantiated the formation of Fe2O3@PPy nanocomposite via the polymerization process. The prepared Fe2O3@PPy nanocomposites deliver at a specific capacity of 395.45 C g−1 at 5 mV s−1 scan rate. Moreover, Fe2O3@PPy nanocomposite shows outstanding cycling stability of capacity 94.3% even after 10000 cycles of charge-discharge at the highest current density value of 10 A g−1. The remarkable electrochemical energy storage manner of as-synthesized Fe2O3@PPy nanocomposite is considered a potential electrode for supercapacitor application. The higher electrochemical performance of this Fe2O3@PPy nanocomposite it’s suitable for numerous applications like batteries, sensors, photocatalysts, solar cells and commercial requirements.

Structural Restoration of Degraded LiFePO 4 Cathode with Enhanced Kinetics Using Residual Lithium in Spent Graphite Anodes

Structural Restoration of Degraded LiFePO ₄ Cathode with Enhanced Kinetics Using Residual Lithium in Spent Graphite Anodes

Enhanced cadmium removal from water by hydroxyapatite subjected to different thermal treatments

AbstractHydroxyapatite powders were synthesized according to a wet precipitation route and then subjected to heat treatments within the temperature range of 200–800 °C. The prepared samples were tested as sorbents for cadmium in an aqueous medium. The best performances were obtained with the material treated at 200 °C (HAp200), as the relevant sorbent textural features (SBET – specific surface area and Vp – total volume of pores) were least affected at this low calcination temperature. The maximum adsorption capacity at standard ambient temperature and pressure was 216.6 mg g−1, which increased to 240.7 mg g−1 by increasing the temperature from 25 to 40 °C, suggesting an endothermic nature of the adsorption process. Moreover, these data indicated that a thermal treatment at 200 °C enhanced the ability of the material in Cd2+ uptake by more than 100% compared to other similar studies. The adsorption kinetic process was better described by the pseudo-second-order kinetic model. Langmuir, Freundlich, and Dubinin–Kaganer–Radushkevich isotherms were applied to describe the sorption behaviour of Cd2+ ions onto the best adsorbent. Furthermore, a thermodynamic study was also performed to determine ΔH°, ΔS°, and ΔG° of the sorption process of this adsorbent. The adsorption mechanisms were investigated by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy-transmission electron microscopy (SEM-TEM) observations.

BiOCl/AgCl-BiOI/AgI quaternary nanocomposite for the efficient photodegradation of organic wastewaters and pathogenic bacteria under visible light

Sheet-like BiOCl/AgCl-BiOI/AgI quaternary nanocomposites were prepared by a facile single-step co-precipitation method using 1-methyl-3-(oxiran-2ylmethyl)-1H-imidazolium-3-chloride ([MOYI]Cl) ionic liquid (IL) and tetrabuthyl ammonium iodide (TBAI) as Cl and I sources and template agents as well. The products were comprehensively characterized by X-ray diffraction powder (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Diffuse Reflectance Spectroscopy (DRS), nitrogen adsorption-desorption isotherms (BET), and Fourier Transform Infrared spectroscopy (FTIR). The XRD pattern well confirmed the presence of BiOX and AgX (X = Cl and I) crystalline phases in the structure. In addition, the SEM micrographs and TEM image indicated that the sample had sheet-like morphology and the thickness was below 100 nm. Photoactivity of the sample was evaluated by photodegradation of Acid Blue 92 (AB92, an azo dye) and 3-methyl-4-nitrophenol (3M4N, from the semivolatile organic compounds (SVOCs) family) aqueous solutions. According to the results, the product was incredibly efficient for the removal of the contaminants during 120 min of the reaction time. Antibacterial experiments were also conducted and the obtained results showed that the prepared nanostructure had high capacity to decrease the concentration of both gram-negative (E. coli) and gram-positive (S. aureus) pathogenic bacteria after 5 h of the treatment time.

POSS Nanofiller-Induced Enhancement of the Thermomechanical Properties in a Fluoroelastomer Terpolymer

The present study reports on the use of three types of polyhedral oligomeric silsesquioxanes (POSS) nanoparticles with various organic substituents as fillers in a fluoroelastomer (FKM). A series of/POSS elastomer composite thin films is prepared. Microstructural SEM/TEM (scanning electron microscopy/transmission electron microscopy) imaging reveals a dispersion state allowing the presence of micron-sized domains. The influence of POSS content is studied in order to optimize thermal stability and mechanical properties of the composite thin films. Both POSS-A (with an acryloyl functional group and seven isobutyl substituents) and POSS-P (with eight phenyl substituents) lead to higher thermal stability and modulus of the composites, with respect to the unfilled FKM terpolymer matrix. covalent grafting of POSS-A onto the FKM network is found to play a critical role. Enhanced storage modulus in the rubbery plateau region (+210% at 200 °C for 20 phr) suggests that POSS-A is particularly suitable for high temperature applications.

Preparation, characterization and antibacterial activity of octenyl succinic anhydride modified inulin

Octenyl succinic anhydride modified inulin (In-OSA) was synthesized via chemical modification of inulin with octenyl succinic anhydride (OSA). The esterification of inulin with OSA was confirmed by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and degree of substitution (DS) calculation. Antibacterial activity of In-OSA against Staphylococcus aureus and Escherichia coli was investigated by minimum inhibitory concentration (MIC) and inhibition rate determination. The results showed that inhibition rates against both E.coli and S. aureus increased with the increase of the In-OSA concentration. And the MICs against E. coli and S. aureus were 1% and 0.5% (w/v), respectively. The antibacterial mechanism was analyzed with the results of the proteins and nucleic acids leakage, SEM and negative staining transmission electron microscopy (TEM). Both the leakages of proteins and nucleic acids increased with the increase of the In-OSA concentration. The leakage occurred mainly in the early stage which indicated that cell membrane and wall were destroyed by In-OSA quickly. The images of SEM and negative staining TEM suggested that the cell membranes and cell walls of S. aureus were damaged more severely and even destroyed completely; but only pores appeared on the surface of E. coli.

Synthesis of dumbbell shaped ZnO crystals using one-pot hydrothermal method and their characterisations

A highly monodispersed dumbbell like ZnO mesostructure has been synthesized by a one pot surfactant assisted hydrothermal method using zinc acetate dihydrate as a precursor and dodecylamine as a surfactant. The crystalline, structural, morphology and optical properties of synthesized ZnO mesostructure were observed using powder X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and transmission electron microscopy (TEM) and their optical properties characterized using UV–visible (UV–vis) and photoluminescence spectroscopy. XRD results revealed that the prepared ZnO sample is highly crystalline having wurtzite crystal structure. The dumbbell like morphological features of ZnO structure is observed from SEM micrographs and TEM measurements. The bandgap energy of ZnO mesostructure was calculated as 3.50eV using optical absorbance spectrum. Photoluminescence spectrum of prepared ZnO crystals showed the emissions peak in UV region at 395nm attributed to near-band-edge emission of recombined holes with an energy state of a specific defect.

Synthesis and characterization of In2O3nanoparticles

Metal-oxide nanostructures have elicited increasing interest in both fundamental and applied sciences. Among metal oxide nanostructures, In2O3 has the potential for use asa semiconductor material. This article provides details on studies carried out thus far for the synthesis and the characterization of In2O3 nanostructures. In this research, various techniques were investigated for the fabrication of diverse and fascinating spherical shaped In2O3 nanostructures. Brunauer- Emmett-Teller (BET) analyses of the In2O3 nanostructures through detailed refinements of the structure of the In2O3 nanoparticles by using the Rietveld method, followed by microstructural analyses using scanning electron microscopy/ transmission electron microscopy (SEM/TEM) and a chemical composition analysis are presented and discussed. Decreasing crystallinity with an improvement in specific surface area was observed from the structural characterization. The energy dispersive analysisresults showed that the as-prepared In2O3 powder sample was stoichiometric, containing almost equal proportions of indium and oxygen. The microstructural analysis (TEM and SEM) demonstrated precise control over the diameters of the nanoparticles, which is an important advantage of the solution combustion approach.

Preparation of nano-porous AlN micro-rods

In this paper, nano-porous AlN micro-rods were prepared and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emett-Teller (BET) method of nitrogen adsorption at low temperature, UV-via absorption spectrometry and Raman spectrometry. The SEM images and TEM images showed that the AlN samples were micro-size rods with pores in their surfaces evenly. The length of the rod was in the range of a few microns to tens of micron, the diameter of the rods was about one micron, the diameter of the pore was about hundreds of nanometer and the wall thickness of the pore about tens of nanometer. The BET surface area of the sample was 41.424 m2/g. The optical spectra showed that the optical properties of the AlN samples almost agreed with that of AlN bulk or film.

Structural and physical properties of SrMn2As2

SrMn2As2 single crystals were grown by the Sn flux method. Structural features of these crystals were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD results show that the single crystal has a rhombohedral structure and grows along the c-axis direction. The microstructure and layered structural features of this material have been examined by SEM and high-resolution TEM observations. The measurements of in-plane resistivity as a function of temperature demonstrate that SrMn2As2 undergoes a phase transition of semiconductor–insulator at a low temperature; the active energies are estimated to be Δ=0.64 and 0.29eV for two distinct regions. Magnetic measurements show a clear antiferromagnetic (AFM) transition at about TN=125K. Therefore, the SrMn2As2 material is an AFM insulator at low temperatures and could be a potential parent compound for superconductors.

Structural and chemical characterisation of titanium deuteride films covered by nanoscale evaporated palladium layers

Thin titanium deuteride (TiD(y)) films, covered by an ultra-thin palladium layer, have been compared with the corresponding titanium and palladium films using a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The TiD(y) layers were prepared under ultra-high vacuum (UHV) conditions by precisely controlled deuterium sorption at 298 K on a Ti film evaporated onto a Si(100) substrate. Both Ti and TiD(y) films were then covered in situ by a nanoscale Pd layer. It was found that a 10- to 12-nm-thick Pd layer protects the TiD(y) films efficiently against extensive air interaction. The morphology of both the surface and bulk Pd/TiD(y) (Ti) films have been observed using SEM and cross-sectional TEM analysis, respectively. A polycrystalline bulk morphology in both Ti and TiD(y) films accompanied by a fine-grained Pd surface was observed. High-magnification cross-sectional TEM images reveal the TiD(y) film to be plastically deformed leading to an increase in the roughness of the top Pd layer. Complex structures, including Moiré patterns, have been identified within the Pd/TiD(y) interface. The chemical nature of this interface has been analysed after partial sputtering of the Pd top layer using XPS. Besides TiD(y) and Pd, TiO and PdO were found to be the main chemical species in the interface region of the Pd/TiH(y) film. The XPS valence-band spectra of the Pd/TiD(y) interface reveal electronic features characteristic of a Pd-Ti bimetallic structure.

アルミニウム合金板上に形成させたＴｉＯ２薄膜の光触媒活性に対する陽極酸化皮膜の影響

The photocatalytic activity of TiO2 thin film formed on 5083 aluminum alloy (TiO2/5083) sheets by using the advanced sol-gel method, and the effect of anodic oxide film between TiO2 thin film and 5083 alloy sheets were investigated by evolution of photocatalytic activity, X-ray diffraction (XRD) technique, transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The photocatalytic activity of TiO2/5083 sheet was low and MgO was detected by XRD and TEM. The photocatalytic activity of TiO2/5083 sheet with anodic oxide was improved and was higher than that of TiO2/5083 sheet without anodic oxide film. It was confirmed by XRD, SEM and high resolution TEM that MgO was not detected in the TiO2 thin film with anodic oxide film between TiO2 thin film and 5083 sheet. It has been considered that the sheet which has anodic oxide film between TiO2 and 5083 sheet did not have MgO.

Heteroepitaxial silicon-carbide nitride films with different carbon sources on silicon substrates prepared by rapid-thermal chemical-vapor deposition

Cubic crystalline silicon-carbon nitride (Si1−x−yCxNy) films have been grown successfully using various carbon sources by rapid-thermal chemical-vapor deposition (RTCVD). The characteristics of the Si1−x−yCxNy films grown with SiH3CH3, C2H4, and C3H8 are examined and compared by x-ray photoelectron spectroscopy (XPS) spectra, scanning electron microscopy (SEM) images, and transmission electron microscopy (TEM) patterns. The XPS spectra show that the differences of chemical composition and chemical-bonding state are co-related to the C bonding type of the different carbon source. The SEM images and TEM analysis indicate that the better Si1−x−yCxNy film can be obtained using C3H8 gas as the carbon source. In addition, correlations between the growing stages to the microstructure of the cubic-crystalline Si1−x−yCxNy films have been illustrated in detail.

TEM and SEM studies of microstructural transformations of thin iron films during annealing

High-temperature induced transformations of the bulk structure as well as the surface and bulk morphology of thin polycrystalline iron films have been investigated using a combination of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The polycrystalline Fe films were evaporated onto a quartz substrate at 78K under UHV conditions and then annealed in situ within a temperature range 330–1000K. The morphology of both the surface and bulk Fe films have been observed ex situ after successive annealing steps of the Fe film using SEM and cross-sectional TEM analysis, respectively. An anisotropic polycrystalline bulk morphology accompanied by a fine-grained surface and the formation of microvoids was observed after heating the Fe film at 330K. The iron films annealed at higher temperatures, exhibit large grain size surface morphology. Polycrystalline Fe film transformation occurred at an annealing temperature of 700–1000K, resulting in the formation of a columnar microstructure of the bulk phase. The crystallites formed as a result of annealing at 1000K revealed a monocrystalline structure characterised by low-index Fe bcc diffraction patterns.

Ultrastructure of Bone Mineralization and Osseointegration with Hydroxyapatite-Coated Bone Implants in Vivo

Abstract The need to optimize adhesion between the femoral stem and surrounding tissue has led to the development of plasma-sprayed HA (PSHA) coatings as attachment facilitators for hip prostheses. The mechanisms underlying this facilitation are incompletely understood, and the long-term efficacy of HA coatings in maintaining bonding to bone remains largely unexplored. in this study, two in vivo models—canine and human—were employed for study by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to elucidate the sequence of early bone mineralization and the longer term fate of HA coatings. High-resolution SEM and TEM of whole bone and anorganic bone were employed to establish the structure of mature bone for comparison. Whole and Anorganic Bone.Anorganic bone derived from bovine trabecular bone was examined in low-voltage field-emission SEM(LV-FESEM) and high-resolution TEM to establish the morphology of the mineral component of bone [1,2]. Trabeculae were seen to comprise oriented fiber bundles (Fig. 1), each fiber comprising an array of oriented apatite platelets (Fig. 2) arranged like a sheared stack of dominoes with approximately the 64-nm stagger of collagen hole zones.

Correlation of freeze-fracture and scanning electron microscopy of epiphyseal chondrocytes.

Chondrocytes in epiphyseal cartilage were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) using freeze-fracture techniques. Freeze-fracture replicas showed large numbers of fingerlike, 0.11-0.15 micrometer diameter, projections from the chondrocyte surface, with numerous 95-180 A diameter intramembranous particles associated with both the cell membrane surface and these projections. With SEM, these cytoplasmic projections were also obvious, but appeared collapsed into clusters of globular-shaped projections on the surface of the chondrocytes. With freeze-fracture techniques, in which shrinkage artifacts were essentially eliminated, the cytoplasmic projections were often seen in intimate contact with the extracapsular matrix. However, with chondrocytes prepared by both SEM and conventional TEM, there was evidence of shrinkage, the cytoplasmic projections having little contact with the extracapsular matrix. These findings show that the cytoplasmic processes are not artifacts of tissue processing and provide morphological evidence in support of the hypothesis that matrix vesicles are of cellular origin.

Electron microscopy on etched thin foils. A comparative SEM, STEM and TEM analysis

During the last decade, much effort has been devoted to relations between structure and mechanical properties, particularly in metals. The need for sophisticated structure studies has increased accordingly. Combinations of different types of microscope methods have been tried, for example by performing optical and scanning electron microscopy (SEM) on etched metallographic sections.Particularly in the case of more intricate phase analyses, it is often necessary to add information about the internal structure by means of transmission electron microscopy (TEM). The scope of the present work has been to combine the advantages of the “classical” methods of studying etched surfaces with those of transmission studies of the same field of observation. For that purpose, the scanning transmission electron microscope (STEM) technique is ideal, and has been applied on thin foils, which, after ordinary electro-polishing, were etched (nital, 10 sec.) and thereby given a structure-related surface topography. The microscope used was a JEOL 200B TEM with scanning attachment, operated at 200 kV in emissive SEM, STEM and conventional TEM mode.