Analysis Of High-resolution Electron Microscope Images Research Articles

Electron image contrast analysis of mosaicity in rutile nanocrystals using direct electron detection.

Direct electron detection provides high detective quantum efficiency, significantly improved point spread function and fast read-out which have revolutionized the field of cryogenic electron microscopy. However, these benefits for high-resolution electron microscopy (HREM) are much less exploited, especially for in situ study where major impacts on crystallographic structural studies could be made. By using direct detection in electron counting mode, rutile nanocrystals have been imaged at high temperature inside an environmental transmission electron microscope. The improvements in image contrast are quantified by comparison with a charge-coupled device (CCD) camera and by image matching with simulations using an automated approach based on template matching. Together, these approaches enable a direct measurement of 3D shape and mosaicity (∼1°) of a vacuum-reduced TiO2 nanocrystal about 50 nm in size. Thus, this work demonstrates the possibility of quantitative HREM image analysis based on direct electron detection.

Application of FFT Data from HREM images to Electron crystallography

We succesfully determined the 3D crystal structure of inorganic nano-crystalline material using fast fourier transform (FFT) data obtained from high-resolution electron microscopy (HREM) images. To extract the reliable structural information from nano-crystalline materials by HREM imaging, it is essential to minimize the dynamical scattering effects caused by interactions bewteen electrons and matters. To alleviate this restriction, we tried to solve the crystal structure by employing high voltage electron microscope (HVEM) which has excellent tilting capability, atomic resolution as well as higher penetration power. First, the allowed sample thickness for CaMoO4 crystal was evaluated by examining the existence of forbidden reflections in FFT data of HREM images obtained at various sample thicknesses. The kinematical scattering conditions were satisfied up to a sample thickness of about 28.2 nm. Second, we tried to extract the crystallographic data and determine the atomic structure of CaMoO4 crystal by FFT analysis of HREM images obtained from 15 different zone axes. Consequently, its cell parameters and space group were a = 5.24(3) A, c = 11.50(8) A and I41/a (#88), respectively. These values coincided with X-ray crystallography results within 0.002 ~ 0.080 A. Finally, the atomic structure could be determined with an accuracy of 0.16 A.

High-resolution electron-microscopy analysis of splitting patterns in Ni alloys

The late stages of coarsening of coherent solid particles is strongly influenced by the reduction of elastic strain energy. This produces migration and alignment of particles as well as some other effects. In this investigation, the origin of the so-called splitting pattern arrangement of γ′ precipitate particles, an arrangement which has often been interpreted as being due to splitting of a larger particle into smaller ones, has been studied. The two-particle relationship as to whether they are in-phase or out-of-phase is examined by means of a translation order domain analysis of high-resolution electron-microscopy images along a zone axis parallel to [001]. Ni alloys have been used for the investigation including a binary Ni–Al alloy (producing different volume fractions) and two commercial multicomponent alloys with high volume fraction. About 72% of two-particle pairs forming the splitting configuration are in the out-of-phase relationship, indicating that adjacent pairs are randomly formed and that they are not formed by the splitting of a large particle. In addition, an elasticity analysis shows that the elastic interaction energy of two γ′ particles exhibits a minimum at a certain separation distance along ⟨ 100⟩.

Microstructures and interfaces in directionally solidified oxide–oxide eutectics

This article reviews different studies carried out on the microstructures and oxide–oxide interfaces encountered in directionally solidified eutectics. Depending on the phase diagram and preparation conditions, lamellar, fibrous or three-dimensional network microstructures can be obtained. Interfaces between refractory oxides with various structural types (corundum, fluorite, rocksalt, perovskite and garnet) are investigated. Orientation relations and interface planes are reported and general features of the structure of interfaces are discussed from high-resolution electron microscopy (HREM) studies. The accommodation of lattice mismatch at the interface is investigated by geometric phase analysis of HREM images.

Direct high-resolution electron microscopy of BN nanotubes with hexagonal zigzag network

Hexagonal zigzag network of boron nitride (BN) nanotubes was investigated by high-resolution electron microscopy (HREM) and image processing. From the HREM image, lattice planes of {0 0 2} and hexagonal rings of BN nanotube were confirmed by comparing image simulation and nanostructure models. The present work indicated that arrangement of hexagonal rings of BN nanotubes could be confirmed by combination of HREM image analysis and simulation.

Catalyst-Free Synthesis of Single-Wall Boron Nitride Nanotubes via Laser Ablation

AbstractBoron nitride nanotubes (BN-NTs) were synthesized in “mass” quantities (∼0.6 g/h) using a continuous CO2 laser ablation reactor described in the literature [1]. High-resolution electron microscopy (HRTEM) analyses have shown the nanotubes to be organized in “ropes” comprising ∼10 tubes. Analysis of HRTEM images indicate that the majority of the tubes are zig-zag. The chemical composition of the tubes was confirmed using electron energy loss spectroscopy (EELS) analysis, which also determined that nanoparticles terminating tube ends were composed of pure boron covered by BN fullerene-like “cages”. The growth mechanism of the nanotubes seems to be “root-based” with tubes growing from boron nanoparticles dispersed throughout the samples; the non-particle-terminated ends of the tubes exhibit flat “caps” characteristic of BN-NTs [2].

Fuzzy logic approaches to the analysis of HREM images of III–V compounds

It is known that high‐resolution electron microscopy (HREM) can provide quantitative information on the properties of crystalline materials. The HREM patterns of layered structures of III–V semiconductors vary with the chemical composition of the latter within the sublattices, which is also influenced by interdiffusion. Local variations of the crystal cell similarity are recorded for image analysis and compared with templates of known material composition.Of the advanced theories of data interpretation, the now well‐established fuzzy logic is highly suited for corresponding image processing techniques. Combining neighbouring image cell similarities, the underlying chemical composition is evaluated by applying fuzzy logic criteria of inference to masks of about 1 nm × 1 nm in size.The new approach can be used to localize regions of significant changes in composition, i.e. edge detection, and to determine the composition across the interface region. The methods introduced prove successfully applicable to simulated as well as to experimental images of AlAs/AlxGa1−xAs. Similarity/composition relations of nonlinear as well as nonmonotonic characteristics are studied to establish an alternative fuzzy logic approach.

REVIEW: Quantitative Transmission Electron Microscopy with Imaging Plates

Recent quantitative transmission electron microscopy (TEM) performed with imaging plates was reviewed according to the experimental results obtained by the author and his colleagues. First of all, characteristics of imaging plates for high-energy electrons, such as S/N and DQE were discussed. Taking account of the characteristics and by combining the imaging plate system with the computer network system, quantitative analysis of high-resolution electron microscope (HREM) images and electron diffraction patterns could be extensively carried out. In the analysis of HREM images, residual indices between observed and calculated images of W 8 Ta 2 O 29 were evaluated to determine the experimental conditions accurately. As an example of the analysis of electron diffraction patterns, the change of the thermal diffuse scattering of an Au thin film was accurately evaluated as a function of temperature. Finally the weak diffuse scattering in Ga 0.47 In 0.53 As was analyzed by utilizing an energy filter to remove the background due to the plasmon scattering.

Quantitative criteria for the detection and characterization of nanocrystals from high-resolution electron microscopy images

Abstract A new method of high-resolution electron microscopy image analysis is presented which improves considerably the visibility of nanocrystals in amorphous materials. The technique is based on individual Bragg filtering of the lattice fringes in the image. The significant feature is that the amplitude and phase of the fringes as functions of position are calculated separately. This is similar to a holographic reconstruction with the Bragg interference representing the carrier wave. The phase information is shown to be particularly robust with respect to noise due to amorphous material. The images so produced are in a form suitable for statistical analysis, and criteria for judging quantitatively the extent of the crystal are proposed. The application of the technique to a wide range of similar problems concerning partially ordered materials is discussed.

Quantitative Electron Microscope with imaging plate

Imaging plate has good properties, i.e., a wide dynamic range and good linearity for the electron intensity. Thus the digital data (2048x1536 pixels, 4096 gray levels in log scale) obtained with the imaging plate can be used for quantification in electron microscopy. By using the image processing system (PIXsysTEM) combined with a main frame (ACOS3900), quantitative analysis of electron diffraction patterns and high-resolution electron microscope (HREM) images has been successfully carried out.In the analysis of HREM images observed with the imaging plate, quantitative comparison between observed intensity and calculated intensity can be carried out by taking into account the experimental parameters such as crystal thickness and defocus value. An example of HREM images of quenched Tl2Ba2Cu1Oy (Tc = 70K) observed with the imaging plate is shown in Figs. 1(b) - (d) comparing with a structure model proposed by x-ray diffraction study of Fig. 1 (a). The image was observed with a JEM-4000EX electron microscope (Cs =1.0 mm).

Stable decagonal Al-Cu-Co-Si phase: A phason-perturbed quasiperiodic crystal.

The analysis of high-resolution electron-microscopy images of the stable ${\mathrm{Al}}_{62}$${\mathrm{Cu}}_{20}$${\mathrm{Co}}_{15}$${\mathrm{Si}}_{3}$ decagonal quasicrystal shows a long-range aperiodic translation order similar to that of Penrose tiling. Thus this particular decagonal phase could be interpreted as a phason-perturbed quasiperiodic crystal.

Quantification in high-resolution electron microscopy with the imaging plate

By making good use of the excellent properties of the imaging plate (IP), i.e., high sensitivity, a wide dynamic range and good linearity for electron intensity, high-resolution electron microscope (HREM) images were quantitatively analyzed. In W 8 Ta 2 O 29, contrast changes due to the dynamical diffraction effect were quantitatively evaluated and compared with the simulated images. In Pb( Ba, Sr) 2( Eu, Ce) 2 Cu 3 O y , which is related to high- T c superconductors, atomic columns containing heavy elements such as Pb were clearly distinguished from those of relatively light elements such as Cu. Furthermore, quantitatively evaluated contour maps revealed vacant oxygen positions, which are important in characterization of both the structure and the electrical properties of the high- T c superconductors. These results demonstrate that the IP is effective and indispensable for the quantitative analysis of HREM images as well as for electron diffraction patterns.