High-resolution Transmission Electron Microscopy Micrographs Research Articles

Ultrathin Cr added Ru film as a seedless Cu diffusion barrier for advanced Cu interconnects

A 5nm thick Cr added Ru film has been extensively investigated as a seedless Cu diffusion barrier. High-resolution transmission electron microscopy micrograph, X-ray diffraction (XRD) pattern and Fourier transform-electron diffraction pattern reveal that a Cr contained Ru (RuCr) film has a glassy microstructure and is an amorphous-like film. XRD patterns and sheet resistance data show that the RuCr film is stable up to 650°C, which is approximately a 200°C improvement in thermal stability as compared to that of the pure Ru film. X-ray photoelectron spectroscopy depth profiles show that the RuCr film can successfully block Cu diffusion, even after a 30-min 650°C annealing. The leakage current of the Cu/5nm RuCr/porous SiOCH/Si stacked structure is about two orders of magnitude lower than that of a pristine Ru sample for electric field below 1MV/cm. The RuCr film can be a promising Cu diffusion barrier for advanced Cu metallization.

Fermi level positioning in organic semiconductor phase mixed composites: The internal interface charge transfer doping model

Photoemission data, taken on co-sublimed films and on bilayers of the prototypical small molecule semiconductor CuPc and p-type dopants TCNQ or WO3 show similar electronic trends that have to be interpreted by phase separation of the dopant within the matrix material forming a phase mixed composite. High resolution TEM micrographs for CuPc:WO3 co-deposited films clearly prove such phase separation. Therefore the doping models developed for singly dispersed dopant molecules cannot be applied. For the mechanism of the doping induced variations of the host matrix Fermi level in such phase mixed semiconductor:dopant composites we propose the internal interface charge transfer doping model. According to this model the Fermi levels of two mixed phases align at the internal interfaces and the doping limit is defined by the work function difference of matrix and dopant minus the potential drops induced by dipole formation at the internal matrix/dopant interfaces. It is shown that the magnitude of the internal interface dipole potential drops may be estimated from the dipoles measured at matrix/dopant bilayer interfaces and that the maximum dopant induced Fermi level shift may be estimated from the difference of work functions measured on thick films of matrix and of dopant, minus a mean value for the interface dipole.

Structure, optical properties and synthesis of Co-doped ZnO superstructures

Co-doped ZnO nanoparticles were synthesized by a simple chemical method at low temperature with Co:Zn atomic ratio from 0 to 7 %. The synthesis process is based on the hydrolysis of zinc acetate dihydrate and cobalt acetate tetrahydrate heated under reflux to 65 °C using methanol as a solvent. X-ray diffraction analysis reveals that the Co-doped ZnO crystallizes in a wurtzite structure with crystal size of 12–5 nm. These nanocrystals self-aggregated themselves in a highly spherical superstructure of broad size distribution. High-resolution transmission electron microscopy image also shows that each sphere is made up of numerous nanocrystals with average interfringe distance of ~0.28 nm. The X-ray diffraction patterns, energy dispersive X-ray, scanning electron microscopy and high-resolution transmission electron microscopy micrographs of doping of Co in ZnO confirmed the formation of spherical superstructure and indicated that the Co2+ is successfully substituted into the ZnO host structure of the Zn2+ site. The optical band gap of ZnO nanoparticles was remarkably from 3.32 to 4.12 eV with increase of Co doping levels from 0 to 7 %. Photoluminescence measurements confirm these results.

Effects of phosphorous-doping and high temperature annealing on CVD grown 3C-SiC

The integrity and property behavior of the SiC layer of the Tri-isotropic (TRISO) coated particle (CP) for high temperature reactors (HTR) are very important as the SiC layer is the main barrier for gaseous and metallic fission product release. This study describes the work done on un-irradiated SiC samples prepared with varying phosphorus levels to simulate the presence of phosphorus due to transmutation. 30Si transmutes to phosphorous (31P) and other transmutation products during irradiation, which may affect the integrity of the SiC layer. The P-doping levels of the SiC samples used in this study cover the range from 1.1×1015 to 1.2×1019atom/cm3 and are therefore relevant to the PBMR operating conditions. Annealing from 1000°C to 2100°C was performed to study the possible changes in nanostructures and various properties due to temperature. Characterization results by X-ray diffraction (XRD), secondary ion mass spectrometry (SIMS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM), are reported in this article. As grain boundary diffusion is identified as a possible mechanism by which 110mAg, one of the fission activation products, might be released through intact SiC layer, grain size measurements is also included in this study. Temperature is evidently one of the factors/parameters amongst others known to influence the grain size of SiC and therefore it is important to investigate the effect of high temperature annealing on the SiC grain size. The ASTM E112 method as well as electron back scatter diffraction (EBSD) was used to determine the grain size of various commercial SiC samples and the SiC layer in experimental PBMR Coated Particles (CPs) after annealing at temperatures ranging from 1600°C to 2100°C. The HRTEM micrograph of the decomposition of SiC at 2100°C are shown and discussed. Nanotubes were not identified during the TEM and HRTEM analysis although graphitic structures were identified. The preliminary conclusion reached is that the P-content at these experimental levels (1.1×1015 to 1.2×1019atom/cm3) does not have a significant influence on the nanostructure of SiC at high temperatures without irradiation.

Structural Refinement and Photoluminescence Properties of MnWO4 Nanorods Obtained by Microwave-Hydrothermal Synthesis

Manganese tungstate (MnWO4) nanorods were prepared at room temperature by the co-precipitation method and synthesized after processing in a microwave-hydrothermal (MH) system at 140 °C for 6–96 min. These nanorods were structurally characterized by X-ray diffraction (XRD), Rietveld refinements and Fourier transform (FT)-Raman spectroscopy. The growth direction, shape and average size distribution of nanorods were observed by means of transmission electron microscopy (TEM) and high resolution TEM (HR-TEM). The optical properties of the nanorods were investigated by ultraviolet visible (UV-vis) absorption and photoluminescence (PL) measurements. XRD patterns, Rietveld refinement data and FT-Raman spectroscopy indicate that the MnWO4 precipitate is not a single phase structure while the nanorods synthesized by MH processing have a wolframite-type monoclinic structure without deleterious phases. FT-Raman spectra exhibited the presence of 17 Raman-active modes from 50 to 1,000 cm−1. TEM and HR-TEM micrographs indicated that the nanorods are aggregated due to surface energy by Van der Waals forces and grow along the [100] direction. UV–vis absorption measurements confirmed non-linear values for the optical band gap (from 3.2 to 2.72 eV), which increased as the MH processing time increased. The structural characterizations indicated that the presence of defects in the MnWO4 precipitate promotes a significant contribution to maximum PL emission, while MnWO4 nanorods obtained by MH processing decrease the PL emission due to the reduction of defects in the lattice.

Orientation Relationship between the TRIP Steel Substrate and the ZrO2 thin Film

Distinct orientation relationships between face-centred cubic austenite (γ-Fe) and cubic c-ZrO2 were found and assigned using high-resolution transmission electron microscopy (HRTEM) that was complemented by the Fast Fourier Transform (FFT) of the HRTEM micrographs. These orientation relationships were described as [110] γ-Fe || [111] c-ZrO2 and () γ-Fe || () c-ZrO2. They imply the heteroepitaxial growth of the counterparts that improved substantially the adhesion between γ-Fe and c-ZrO2. The analysed specimens were prepared by magnetron sputtering from an unstabilized ZrO2 ceramic target in argon atmosphere on TRIP steel substrate. The microstructure of the thin zirconia films was analysed using glancing-angle x-ray diffraction (GAXRD), scanning electron microscope (SEM) and TEM.

Effect of annealing temperature on the structural, photoluminescence and magnetic properties of sol–gel derived Magnetoplumbite-type (M-type) hexagonal strontium ferrite

Magnetoplumbite-type (M-type) hexagonal strontium ferrite particles were synthesized via sol–gel technique employing ethylene glycol as the gel precursor at two different calcination temperatures (800 and 1000 °C). Structural properties were systematically investigated via X-ray diffraction (XRD), field emission scanning electron microscopy, high resolution transmission electron microscopy (HRTEM), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), photoluminescence spectrophotometry and superconducting quantum interference device magnetometer. XRD results showed that the sample synthesized at 1000 °C was of single-phase with a space group of P6 3/mmc and lattice cell parameter values of a=5.882 Å and c=23.048 Å. EDS confirmed the composition of strontium ferrite calcined at 1000 °C being mainly of M-type SrFe 12O 19 with HRTEM micrographs confirming the ferrites exhibiting M-type long range ordering along the c-axis of the crystal structure. The photoluminescence (PL) property of strontium ferrite was examined at excitation wavelengths of 260 and 270 nm with significant PL emission peaks centered at 350 nm being detected. Strontium ferrite annealed at higher temperature (1000 °C) was found to have grown into larger particle size, having higher content of oxygen vacancies and exhibited 83–85% more intense PL. Both the as-prepared strontium ferrites exhibited significant oxygen vacancies defect structures, which were verified via TGA. Higher calcination temperature turned strontium ferrite into a softer ferrite.

Quantitative analysis of layering and in-plane structural ordering at an alumina–aluminum solid–liquid interface

Real-time observations of Al–Al 2O 3 dynamic liquid–solid interfaces on the atomic scale indicate the presence of structural ordering in the liquid at the solid–liquid interface. The main problem with direct high resolution transmission electron microscopy (HRTEM) interpretation is that the imaging conditions and aberrations in the imaging system have a significant influence on the contrast in the image, and may lead to inaccurate conclusions about the structure examined. New quantitative results based on using a single image iterative wave function reconstruction are presented. This technique requires only a single experimental image, and allows extraction of reliable and aberration-free structural information from experimental HRTEM micrographs. This numerical phase retrieval method was successful in analysis of the experimental data and allowed, for the first time, direct extraction of quantitative information regarding the degree of ordering (parallel and perpendicular to the interface) at liquid–solid interfaces. The degree of ordering at the Al 2O 3–Al interface at 750 °C was quantified and both layering and in-plane ordering were found. The layering in the liquid extends to about four to five layers (about 1 nm from the edge of the crystal). The in-plane ordering, which was observed only in the first three layers of the liquid, decays faster than the layering. In addition, the interlayer spacings measured in the liquid indicate that the liquid atoms at the interface are influenced by the structure of the crystal, while further away the ordering of the liquid atoms gradually disappears, until they adopt the characteristics of the bulk liquid.

MEGACELL: A nanocrystal model construction software for HRTEM multislice simulation

Image simulation has an invaluable importance for the accurate analysis of High Resolution Transmission Electron Microscope (HRTEM) results, especially due to its non-linear image formation mechanism. Because the as-obtained images cannot be interpreted in a straightforward fashion, the retrieval of both qualitative and quantitative information from HRTEM micrographs requires an iterative process including the simulation of a nanocrystal model and its comparison with experimental images. However most of the available image simulation software requires atom-by-atom coordinates as input for the calculations, which can be prohibitive for large finite crystals and/or low-symmetry systems and zone axis orientations. This paper presents an open source citation-ware tool named MEGACELL, which was developed to assist on the construction of nanocrystals models. It allows the user to build nanocrystals with virtually any convex polyhedral geometry and to retrieve its atomic positions either as a plain text file or as an output compatible with EMS (Electron Microscopy Software) input protocol. In addition to the description of this tool features, some construction examples and its application for scientific studies are presented. These studies show MEGACELL as a handy tool, which allows an easier construction of complex nanocrystal models and improves the quantitative information extraction from HRTEM images.

Green luminescence from triphenylphosphine functionalized single-wall carbon nanotubes

In a simple wet chemical process, purified single-wall carbon nanotubes (SWCNTs) are treated with triphenylphosphine (Ph 3P) at room temperature. The functionalized material is characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy. HRTEM micrograph clearly reveals that triphenylphosphine nanocrystals of nearly uniform size are attached to the surfaces of SWCNTs. The hybrid structure shows remarkable green luminescence with peak emission at around 500 nm, under UV excitation. The photoluminescence may be attributed to charge transfer from the electron-donating phosphorous atoms to the carbon nanotubes.

Direct synthesis and stabilization of Bi-sized cysteine-derived gold nanoparticles: Reduction catalyst for methylene blue

Bi-sized and separable gold nanoparticles (AuNps) with smaller sizes were synthesized by treatment of cysteine with tetrachloroauric acid solution. These nanoparticles were made stable with further reduction in size after adding very small volume of NaOH solution before controlled heating. In NaOH treated solution the AuNps stopped precipitation as compared to untreated solution. Various methods such as UV-Vis spectroscopy, Transmission Electron Microscopy (TEM), X-ray Diffractometry (XRD), FTIR and Raman spectroscopy were used for characterization of surface properties and interaction between AuNps and cysteine. The results showed good correlation with literature regarding the interaction but interesting differences in size distribution as evident from high resolution TEM micrograph. Zeta potential studies revealed that these particles are negatively charged. Surprisingly, the Raman of the cysteine-derived AuNps without NaOH showed tremendous enhancement as compared to pure cysteine and cysteine-derived AuNps treated with NaOH. The NaOH treated Cyst-AuNps sol proved as excellent homogeneous catalyst for reduction of methylene blue (MB).

Crystallization Behaviour and Nanostructuring in Alkali Niobiosilicate Glasses

23K2O(27Nb2O5(50SiO2((KNS), 13K2O(10Na2O(27Nb2O5(50SiO2 (KNaNS) and 15K2O(12Li2O(27Nb2O5(46SiO2 (KLiNS) transparent glasses were synthesized by melt-quenching technique, and studied by differential thermal analysis (DTA), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) to reveal the effect of the devitrification behaviour on transparent nanostructure. Just above the glass transition temperature Tg in the KNS glass, an unidentified phase was formed, while in KNaNS and KLiNS, mixed-alkali niobate phases with tungsten bronze structure were obtained by bulk crystallization. Heat treatments at Tg performed on the KNS glass resulted in the transparent nanostructure with second order harmonic generation (SHG) activity. Heat treatment for 10 h on KNaNS and KLiNS decreased the first DTA exothermic peaks (at least 24°C), indicating the bulk nucleation, which was confirmed by the DTA in comparison with the powdered as-quenched samples. KNaNS and KLiNS showed similar XRD profiles as the K3Li2Nb5O15 crystal with the five most intense peaks at 22.7, 29.4, 32.3, 46.3 and 52.0 deg. HRTEM micrograph showed clear-cut nano-sized circular domains and spherical nanocrystals dispersed into the amorphous matrix.

Mechanical and Thermal Properties of Nano-Titanium Dioxide-Reinforced Polyetheretherketone Produced by Optimized Twin Screw Extrusion

Polyetheretherketone (PEEK), an attractive matrix for highly loaded parts in terms of temperature and mechanical performance, is applied in many engineering applications. However, its improvement in the mechanical properties by, for example, nanoparticles is sometimes necessary to fulfill actual requirements. In this case, the nanoparticles need to be deagglomerated, wetted by the polymer matrix, and equally distributed. Excellent results can be achieved by a second extrusion step applied on the masterbatch. Theoretical calculations of processing parameters (e.g., shear energy) explain the reason for a better dispersion and distribution of nanoparticles inside the matrix for the multipass extrusion process. PEEK compounds reinforced with 15 nm titanium dioxide (TiO2) nanoparticles are compared with PEEK reinforced with 300 nm particles. The incorporation of the nanoparticles into the PEEK matrix was realized by a corotating twin screw extruder (ZE25x44, Berstorff GmbH) with 10 heating barrels. The mechanical and thermal properties of the materials were characterized at room temperatures by tensile and impact testing, differential scanning calorimetry, and dynamic mechanical thermoanalysis. The important distribution quality of the nano-sized particles and corresponding fracture surfaces are shown in high-resolution scanning and transmission electron microscopy micrographs. It becomes visible that the 15 nm particles enhance the polymer properties much better than the 300 nm particles. The 15 nm particles improve the stiffness and the strength as a function of filler content. Highest values of impact energy can be achieved at a filler content of 2.2 vol. %.

Synthesis of Gold Nanoparticles by Leaves of Zero-Calorie Sweetener Herb (Stevia rebaudiana) and Their Nanoscopic Characterization by Spectroscopy and Microscopy

ABSTRACT In this research work, gold nanostructures with different shapes, such as octahedrons, hexagons and triangles, have been synthesized within 20 min by reducing gold chloride (HAuCl4) with dried, powdered Stevia rebaudiana, leaves, previously not exploited for the synthesis of gold nanoparticles. The nanoparticles were characterized and investigated by ultraviolet-visible (UV-Vis) spectrophotometry, high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray (EDX) spectroscopy, and X-ray diffraction (XRD). The UV-Vis spectrum of the aqueous medium containing gold nanostructures showed a peak at 539 nm corresponding to the surface plasmon resonance band (SPR) of gold nanoparticles. HR-TEM micrograph showed the formation of well-dispersed octahedral gold nanoparticles of size 8–20 nm. XRD spectrum of the gold nanoparticles “exhibited Bragg's pattern of reflection.”

Microstructure and microhardness analysis of the hexagonal oxides formed on the surface of the AISI 304 stainless steel after Nd:YAG pulsed laser surface melting

The laser surface melting (LSM) technique was adopted to modify the surface layer microstructure of the AISI 304 stainless steel in this paper. The results showed that the hexagonal morphologies have been successfully fabricated on the surface after LSM. These hexagons had side lengths of about 0.5–1 μm and were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM). It was proved by the XRD that the stainless steel surface mainly consisted of γ-Fe, Cr 2O 3, Fe 2O 3 and some manganese oxides. The FESEM micrographs showed that the hexagonal oxides were regular hexagons in geometry. The HRTEM micrographs also indicated the presence of the hexagons on the surface of the stainless steel. The spacing values were calculated from the HRTEM micrograph and the SAED pattern, and the hexagonal oxide phases determined by these spacing values were consistent with those verified by the XRD. After LSM, the microhardness of the stainless steel was significantly improved.

Room temperature ferromagnetism in ZnO (core)/graphite (shell) nanowires fabricated by a one-step method

ZnO (core)/graphitic (shell) nanowires were successfully fabricated by a one-step method. Morphology of the as-grown nanowires was studied in detail by scanning electron microscopy, transmission electron microscopy (TEM), and energy dispersive X-ray analysis (EDS). High resolution TEM micrographs and selected area electron diffraction patterns reveal the core/shell morphology of the nanowires that grew along the c -axis of ZnO. EDS study of the nanowires confirms that there are no impurities within the detectable limit. Superconducting quantum interference device magnetometer measurements show room temperature ferromagnetic ordering in these core/shell nanowires.

Plasma-Modified SnO2 Nanowires for Enhanced Gas Sensing

Tin oxide (SnO2) nanowires grown by chemical vapor deposition were modified by Ar/O2 plasma treatment through preferential etching of the lattice oxygen atoms, which produced nonstoichiometric surface compositions that imparted a manyfold higher sensitivity toward gas absorption on such surfaces. Microstructures of as-grown and plasma-treated SnO2 nanowires confirmed the gradual change in the chemical composition and morphologies. Surficial disorder caused by the bombardment of argon and oxygen ions present in the plasma was visible as a disordered overlayer in high-resolution TEM micrographs, when compared to single crystalline as-grown SnO2 nanowires. Gas-sensing experiments on modified SnO2 nanostructures showed higher sensitivity for ethanol gas at lower operating temperatures and exhibited an improved transduction response toward changing gas atmospheres, attributed to the increased concentration of oxygen vacancies on the surface of SnO2 nanowires. Modulation of surface chemistry was also supported ...

Growth of Co ultrathin films on MgO(0 0 1)

Cobalt ultrathin films with nominal thicknesses varying between 2 and 10 nm have been grown by DC sputtering process on MgO(0 0 1) substrate at room and high temperatures (650, 750 °C). Transmission electron microscopy (TEM) has been used to study the crystallographic structure, strain and morphology of the Co films. The TEM images demonstrate the three-dimensional growth of cobalt at all temperatures, with only fcc structure in low thicknesses, and cobalt islands with hcp and fcc structure at greater layer thicknesses when the temperature is below 650 °C. At 750 °C cobalt islands present only fcc structure for the whole studied thicknesses. The Co islands started to coalesce at nominal film thicknesses greater than 2 nm with pyramidal shape for hcp grains and flatter mesa shape for fcc grains. Quantitative analysis of high resolution TEM micrographs reveal that whatever the temperature and thickness the Co lattice is relaxed.

Glycolic acid assisted one-step synthesis of Cu–Ni–Fe metal oxide nanocomposites by sol–gel-combustion method: Structural, spectroscopic and magnetic studies

The present article reports the synthesis of copper, nickel and iron-based metal oxide nanocomposites by sol–gel method using disproportion of Cu(II) and Fe(III) in basic media. The synthesized nanocomposites were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Raman spectroscopy (RS), differential scanning calorimetery (DSC)/thermogravemetric analysis (TGA), field-emission scanning electron microscope (FE-SEM), high-resolution transmission electron microscope (HR-TEM) and vibrating sample magnetometer (VSM). The XRD patterns of nanocomposites confirm the presence of spinel, CuO and FeO phases. The particle size of the nanocomposite has been calculated using HR-TEM micrographs and found to be in the range of 10–120 nm. The magnetic properties of nanocomposites were measured at room temperature. The values of saturation magnetization (Ms) and remanent magnetization (Mr) were increasing with increase of iron concentration.

Synthetic near Σ5 (210)/[100] grain boundary in YAG fabricated by direct bonding: structure and stability

Several macroscopic physical and chemical properties, such as rheology, elasticity, or transport properties are governed by grain boundary processes. An improved understanding of the structure and evolution of grain boundaries has thus become a key challenge in geosciences and material sciences. Here, we report the structure of near Σ5 (210)/[100] grain boundaries in Y3Al5O12 (YAG), which were synthesised by the wafer direct bonding method. The produced grain boundaries were annealed at different temperatures, ranging from 673 to 1,873 K. The grain boundaries annealed at different temperatures are not distinguishable based on their flatness and apparent cohesiveness in high resolution TEM (HRTEM) micrographs, but show a considerable step in their mechanical stability at around 1,273 K, a temperature that corresponds to roughly half the melting temperature of YAG. This study further focuses on the effect of a slight misorientation of the two crystals on the grain boundary structure and we discuss if the boundary can reach a state of minimum energy configuration during annealing. Along the grain boundaries, we observed a long-range strain contrast with a periodicity of 40 nm, which has not been reported for high-angle grain boundaries so far. We conclude that this contrast is caused by faceting along the grain boundary plane, which is needed to achieve minimum energy configuration of the grain boundary plane.