Incoherent Stem Imaging at 1.5 Å Resolution With A 200 Kv FEGTEM

1999 ◽  
Vol 5 (S2) ◽  
pp. 610-611
Author(s):  
E.M. James ◽  
N.D. Browning
Keyword(s):  
Spatial Resolution ◽  
Image Interpretation ◽  
Dark Field ◽  
Contrast Imaging ◽  
Contrast Method ◽  
Transmission Electron ◽  
Annular Dark Field ◽  
Z Contrast ◽  
First Time ◽  
Electron Energy Loss

Here we demonstrate sub- 1.5 Å resolution in compositionally sensitive high-angle annular dark-field (HAADF) (“Z-contrast”) imaging. For the first time this has been achieved on a 200 kV field-emission transmission electron microscope (FEGTEM), the JEOL JEM-2010F. With a Gatan imaging filter, this type of instrument is then capable of both analytical imaging and electron energy-loss spectroscopy at similar spatial resolution as in the 300 kV dedicated STEM.The Z-contrast imaging technique has a spatial resolution given by the size of the electron probe. When used to image periodic specimens and their defects, the effective incoherent nature of the Z-contrast method leads to higher resolution for given lens Cs, higher sensitivity to atomic number and easier qualitative image interpretation than in HRTEM.In practice, the ability to form a small (atomic resolution) probe depends on the brightness of the electron source, and achieving low enough levels of mechanical and electrical instabilities that otherwise incoherently broaden the probe.

Incoherent High-Resolution Z-Contrast Imaging of Silicon and Gallium Arsenide Using HAADF-STEM

1999 ◽  
Vol 589 ◽  
Author(s):  
Y Kotaka ◽  
T. Yamazaki ◽  
Y Kikuchi ◽  
K. Watanabe
Keyword(s):  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Contrast Imaging ◽  
High Spatial Resolution Image ◽  
Transmission Electron ◽  
Eigen Value ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Convergent Beam ◽  
Z Contrast

AbstractThe high-angle annular dark-field (HAADF) technique in a dedicated scanning transmission electron microscope (STEM) provides strong compositional sensitivity dependent on atomic number (Z-contrast image). Furthermore, a high spatial resolution image is comparable to that of conventional coherent imaging (HRTEM). However, it is difficult to obtain a clear atomic structure HAADF image using a hybrid TEM/STEM. In this work, HAADF images were obtained with a JEOL JEM-2010F (with a thermal-Schottky field-emission) gun in probe-forming mode at 200 kV. We performed experiments using Si and GaAs in the [110] orientation. The electron-optical conditions were optimized. As a result, the dumbbell structure was observed in an image of [110] Si. Intensity profiles for GaAs along [001] showed differences for the two atomic sites. The experimental images were analyzed and compared with the calculated atomic positions and intensities obtained from Bethe's eigen-value method, which was modified to simulate HAADF-STEM based on Allen and Rossouw's method for convergent-beam electron diffraction (CBED). The experimental results showed a good agreement with the simulation results.

Atomic resolution Z-contrast imaging of bulk crystal surfaces in Scanning Reflection Electron Microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 414-415
Author(s):  
Z. L. Wang ◽  
J. Bentley
Keyword(s):  
Electron Microscopy ◽  
Elastic Scattering ◽  
Dark Field ◽  
Contrast Imaging ◽  
Crystal Lattices ◽  
Small Probe ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Image Position ◽  
Z Contrast

The success of obtaining atomic-number-sensitive (Z-contrast) images in scanning transmission electron microscopy (STEM) has shown the feasibility of imaging composition changes at the atomic level. This type of image is formed by collecting the electrons scattered through large angles when a small probe scans across the specimen. The image contrast is determined by two scattering processes. One is the high angle elastic scattering from the nuclear sites,where ϕNe is the electron probe function centered at bp = (Xp, yp) after penetrating through the crystal; F denotes a Fourier transform operation; D is the detection function of the annular-dark-field (ADF) detector in reciprocal space u. The other process is thermal diffuse scattering (TDS), which is more important than the elastic contribution for specimens thicker than about 10 nm, and thus dominates the Z-contrast image. The TDS is an average “elastic” scattering of the electrons from crystal lattices of different thermal vibrational configurations,

Structure and Chemistry across Interfaces at Nanoscale of a Ge Quantum Well Embedded within Rare Earth Oxide Layers

2011 ◽  
Vol 17 (5) ◽  
pp. 759-765 ◽  
Author(s):  
Tanmay Das ◽  
Somnath Bhattacharyya
Keyword(s):  
Rare Earth ◽  
Solid Phase ◽  
Rare Earth Oxide ◽  
Dark Field ◽  
X Ray ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Annular Dark Field ◽  
Electron Energy Loss ◽  
Field Imaging

AbstractStructure and chemistry across the rare earth oxide-Ge interfaces of a Gd2O3-Ge-Gd2O3 heterostructure grown on p-Si (111) substrate using encapsulated solid phase epitaxy method have been studied at nanoscale using various transmission electron microscopy methods. The structure across both the interfaces was investigated using reconstructed phase and amplitude at exit plane. Chemistry across the interfaces was explored using elemental mapping, high-angle annular dark-field imaging, electron energy loss spectroscopy, and energy dispersive X-ray spectrometry. Results demonstrate the structural and chemical abruptness of both the interfaces, which is most essential to maintain the desired quantum barrier structure.

scholarly journals Z-Contrast STEM Imaging of Long-Range Ordered Structures in Epitaxially Grown CoPt Nanoparticles

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Kazuhisa Sato ◽  
Keigo Yanajima ◽  
Toyohiko J. Konno
Keyword(s):  
Intermediate Stage ◽  
Dark Field ◽  
Structural Domains ◽  
Ordered Structures ◽  
Axis Orientation ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Z Contrast ◽  
Variant Structure

We report on atomic structure imaging of epitaxial L10CoPt nanoparticles using chemically sensitive high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Highly ordered nanoparticles formed by annealing at 973 K show single-variant structure with perpendicularc-axis orientation, while multivariant ordered domains are frequently observed for specimens annealed at 873 K. It was found that the (001) facets of the multivariant particles are terminated by Co atoms rather than by Pt, presumably due to the intermediate stage of atomic ordering. Coexistence of single-variant particles and multivariant particles in the same specimen film suggests that the interfacial energy between variant domains be small enough to form such structural domains in a nanoparticle as small as 4 nm in diameter.

Electron Irradiation and Electron Tomography Studies of Glasses and Glass Nanocomposites

2008 ◽  
Vol 1107 ◽  
Author(s):  
G. Möbus ◽  
G. Yang ◽  
Z. Saghi ◽  
X. Xu ◽  
R.J. Hand ◽  
...  
Keyword(s):  
Fine Structure ◽  
Electron Tomography ◽  
Dark Field ◽  
Gradual Transition ◽  
Borosilicate Glasses ◽  
Redox Partner ◽  
Transmission Electron ◽  
Annular Dark Field ◽  
Microscopy Techniques ◽  
Electron Energy Loss

AbstractCharacterization of glasses and glass nanocomposites using modern transmission electron microscopy techniques is demonstrated. Techniques used include: (i) high-angle-annular dark field STEM for imaging of nanocomposites, (ii) electron tomography for 3D reconstruction and quantification of nanoparticle volume fractions, and (iii) fine structure electron energy loss spectroscopy for evaluation of boron coordination. Precipitation of CeO2nanoparticles in borosilicate glasses is examined as a function of glass composition and redox partner elements. A large increase in the solubility of Ce is found for compositions where Ce retains +IV valence in the glass. Irradiation experiments with electrons and λ-rays are summarized and the degree of damage is compared by using changes in the boron K-edge fine structure, which allows the gradual transition from BO4to BO3coordination to be followed.

scholarly journals Randomly oriented twin domains in electrodeposited silver dendrites

2015 ◽  
Vol 80 (1) ◽  
pp. 107-113 ◽  
Author(s):  
Evica Ivanovic ◽  
Nebojsa Nikolic ◽  
Velimir Radmilovic
Keyword(s):  
Electron Microscopy ◽  
Orientation Imaging Microscopy ◽  
Dark Field ◽  
High Angle ◽  
Orientation Imaging ◽  
Transmission Electron ◽  
Annular Dark Field ◽  
Silver Dendrites ◽  
Z Contrast ◽  
Scanning Electron

Silver dendrites were prepared by electrochemical deposition. The structures of Ag dendrites, the type of twins and their distribution were investigated by scanning electron microscopy (SEM), Z-contrast high angle annular dark field transmission electron microscopy (HAADF), and crystallografically sensitive orientation imaging microscopy (OIM). The results revealed that silver dendrites are characterized by the presence of randomly distributed 180? rotational twin domains. The broad surface of dendrites was of the {111} type. Growth directions of the main dendrite stem and all branches were of <112> type.

Z-Contrast Imaging of Heavy Metal Particles Supported in A Zeolitic Matrix Via High-Resolution Stem

1987 ◽  
Vol 45 ◽  
pp. 204-205
Author(s):  
J. H. Butler ◽  
G. M. Brown
Keyword(s):  
High Resolution ◽  
Incident Beam ◽  
Dark Field ◽  
Irradiation Damage ◽  
Contrast Imaging ◽  
Vacuum Oven ◽  
Annular Dark Field ◽  
Resolution Imaging ◽  
Beam Currents ◽  
Z Contrast

High resolution Imaging of zeolites is difficult because these materials are very susceptible to Irradiation damage. It is now well known that dehydrated samples are more stable under the electron beam. Thus the most successful high resolution studies of zeolites to date have been on samples which were freeze-fractured and subsequently dehydrated via heating in a vacuum oven. Electron microscopy was then performed using a combination of low Incident beam currents and sensitive detectors. One problem with this method is that zeolites fracture along cleavage planes and therefore are deposited on microscope grids In a particular orientation. This limits the range of viewing angles. Here we describe a method of sample preparation via ultramlctrotomy as well as the establishment of suitable FEG/STEM Imaging conditions which permit the observation of small (7-14 A diameter) Pt particles within Individual zeolite channels using the method of Z-contrast as applied with a high-angle annular dark field detector. This method allows observation over all crystalline orientations for relatively long exposures to the beam.

Analysis of Nanometer Sized Pyrogenic Particles by Scanning Transmission Electron Microscopy

1995 ◽  
Vol 53 ◽  
pp. 218-219
Author(s):  
DJ Wallis ◽  
ND Browning ◽  
CM Megaridis
Keyword(s):  
Operating Conditions ◽  
Atomic Scale ◽  
Contrast Imaging ◽  
Chemical Mechanisms ◽  
Transmission Electron ◽  
Angle Scattering ◽  
Scanning Transmission ◽  
Z Contrast ◽  
Physical And Chemical ◽  
Electron Energy Loss

Iron is a ubiquitous element on the earth's surface, and is thus involved in most naturally occurring fires. Iron organometalic compounds have also been known to suppress carbonaceous soot emissions under certain operating conditions of practical combustors. In order to unravel the physical and chemical mechanisms of influence, of iron on the emission of carbonaceous pyrogenic particles, finescale characterization techniques need to be implemented.The combined techniques of Z-contrast imaging and electron energy loss spectroscopy (EELS) in a VG HB-501 dedicated STEM are ideally suited to study such a system. The sensitivity of the Z-contrast imaging technique to high-Z materials makes it ideal for location of the iron particles within the much lower atomic number matrix. As only the high-angle scattering is used in the image formation, EELS can be performed simultaneously from a position defined in the image. This accurate positioning of the probe by the Z-contrast image permits both compositional and bonding information to be obtained with a spatial resolution approaching the atomic scale.

High-Resolution Bright-Field and Dark-Field Hollow Cone Illumination

1990 ◽  
Vol 48 (1) ◽  
pp. 36-37
Author(s):  
R.A. Herring ◽  
M.E. Twigg
Keyword(s):  
Large Angle ◽  
Dark Field ◽  
Hollow Cone ◽  
Contrast Imaging ◽  
Lattice Image ◽  
Dark Field Imaging ◽  
Annular Dark Field ◽  
Lattice Images ◽  
Z Contrast ◽  
Field Imaging

Hollow cone illumination using a large C2 blocked-aperture (bl apt) in the conventional TEM (CTEM) can remove the beams within the zero-order Laue zone (ZOLZ) thereby making lattice images more simply interpretable. Dark-field (DF) hollow cone illumination has the added advantage of enhancing the Z-contrast within the lattice image, since the electrons contributing to the image must be scattered over a large angle (approximately 10 mrad). Both of these imaging methods have been explored, using a 600 um C2 bl apt and objective aperture sizes of 70, 20 and 10 um, and are reported in this paper.Much interest has been generated by the report of Pennycook [1] on STEM Z-contrast imaging using annular dark-field. In earlier work ,it was noted that CTEM hollow cone imaging and STEM annular dark-field imaging are related via reciprocity [2] (Fig. 1). In addition, Zernike has shown the advantages of hollow cone illumination in optical phase-contrast microscopy [3]. The electron-optical analogues to these optical techniques are now possible because of the low Cs values achieved in modern TEMs.

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