Systematic zone-Axis orientation of NM-scale particles for microdiffraction

1990 ◽  
Vol 48 (4) ◽  
pp. 262-263
Author(s):  
E D Boyes ◽  
L Hanna
Keyword(s):  
Real Space ◽  
Dark Field ◽  
Zone Axis ◽  
High Symmetry ◽  
Lattice Imaging ◽  
Cell Level ◽  
Bright Field ◽  
Axis Orientation ◽  
Annular Dark Field ◽  
Target Designation

A VG HB501 FEG STEM has been modified to provide track whilst tilt [TWIT] facilities for controllably tilting selected and initially randomly aligned nanometer-sized particles into the high symmetry zone-axis orientations required for microdiffraction, lattice imaging and chemical microanalysis at the unit cell level. New electronics display in alternate TV fields and effectively in parallel on split [+VTR] or adjacent externally synchronized screens, the micro-diffraction pattern from a selected area down to <1nm2 in size, together with the bright field and high angle annular dark field [HADF] STEM images of a much wider [˜1μm] area centered on the same spot. The new system makes it possible to tilt each selected and initially randomly aligned small particle into a zone axis orientation for microdiffraction, or away from it to minimize orientation effects in chemical microanalysis. Tracking of the inevitable specimen movement with tilt is controlled by the operator, with realtime [60Hz] update of the target designation in real space and the diffraction data in reciprocal space. The spot mode micro-DP and images of the surrounding area are displayed continuously. The regular motorized goniometer stage for the HB501STEM is a top entry design but the new control facilities are almost equivalent to having a stage which is eucentric with nanometric precision about both tilt axes.

Identifying Hexagonal Boron Nitride Monolayers by Transmission Electron Microscopy

2012 ◽  
Vol 18 (3) ◽  
pp. 558-567 ◽  
Author(s):  
Michael L. Odlyzko ◽  
K. Andre Mkhoyan
Keyword(s):  
Boron Nitride ◽  
Hexagonal Boron Nitride ◽  
Dark Field ◽  
Zone Axis ◽  
Bright Field ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Annular Dark Field ◽  
Stem Image ◽  
Tilt Series

AbstractMultislice simulations in the transmission electron microscope (TEM) were used to examine changes in annular-dark-field scanning TEM (ADF-STEM) images, conventional bright-field TEM (BF-CTEM) images, and selected-area electron diffraction (SAED) patterns as atomically thin hexagonal boron nitride (h-BN) samples are tilted up to 500 mrad off of the [0001] zone axis. For monolayer h-BN the contrast of ADF-STEM images and SAED patterns does not change with tilt in this range, while the contrast of BF-CTEM images does change; h-BN multilayer contrast varies strongly with tilt for ADF-STEM imaging, BF-CTEM imaging, and SAED. These results indicate that tilt series analysis in ADF-STEM image mode or SAED mode should permit identification of h-BN monolayers from raw TEM data as well as from quantitative post-processing.

Local structure of Pb(Zr0.53Ti0.47)O3

2014 ◽  
Vol 47 (5) ◽  
pp. 1688-1698 ◽  
Author(s):  
K. Z. Baba-Kishi ◽  
A. M. Glazer
Keyword(s):  
Phase Boundary ◽  
Local Structure ◽  
Dark Field ◽  
Chemical Inhomogeneity ◽  
Monoclinic Space Group ◽  
High Angle ◽  
Cell Level ◽  
Bright Field ◽  
Atomic Column ◽  
Annular Dark Field

High-angle annular dark-field (HAADF) and annular bright-field (ABF) images recorded from the Pb(ZrxTi1−x)O3morphotropic phase boundary (PZTmpb) showB-site displacements along the 〈110〉 directions and prominent distortions in the oxygen cages surrounding both theBsites and the Pb environments. The measured range ofB-site displacements is about 0.25–0.4 Å. Oxygen cage distortions appear to be variable in shape and dimensions at the unit-cell level. Comparison of the observed displacements with the structural projections based on the established monoclinic space groupCm(Cs3) shows a good overall agreement. A qualitative match betweenCm(Cs3) and the reported observations is inconclusive because of inaccuracy in the measurements, originating from imprecise identification of atomic column centres inherent in the HAADF and ABF images. In most of the observed cases,B-site displacements in HAADF images, and oxygen cage distortions in ABF images, appear pronounced compared with the structural projections inCm(Cs3). Columnar chemical inhomogeneity has been commonly observed in bothB-site and Pb columns in PZTmpb. Weak 〈110〉 diffuse streaking along the [001], [110] and [111] zone axes has been imaged, suggestive of correlation with the systematic ion disorder along 〈110〉.

Imaging properties of bright-field and annular-dark-field scanning confocal electron microscopy

2010 ◽  
Vol 111 (1) ◽  
pp. 20-26 ◽  
Author(s):  
K. Mitsuishi ◽  
A. Hashimoto ◽  
M. Takeguchi ◽  
M. Shimojo ◽  
K. Ishizuka
Keyword(s):  
Electron Microscopy ◽  
Dark Field ◽  
Bright Field ◽  
Annular Dark Field ◽  
Imaging Properties

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.

Calculations of Z-Contrast for organic and biological specimens

1983 ◽  
Vol 41 ◽  
pp. 284-285
Author(s):  
R.F. Egerton ◽  
M. Misra
Keyword(s):  
Atomic Number ◽  
Cross Sections ◽  
Phase Contrast ◽  
Detection System ◽  
Dark Field ◽  
Single Atom ◽  
Bright Field ◽  
Annular Dark Field ◽  
Z Contrast ◽  
Increasing Function

So-called "atomic-number contrast" is obtained in STEM by displaying a ratio signal formed by dividing the annular-dark-field signal Iad by the inelastic component Ii of the bright-field intensity (isolated by means of an electron spectrometer; see Fig. 1). Originally used for single-atom imaging, the technique has more recently been applied to polymer samples and biological tissue.We report here estimates of the ratio signal from organic specimens, based on the following assumptions:(1) That the specimen is amorphous and that phase contrast may be neglected for the electron-optical conditions and specimen features being considered; (2) That atomic cross sections may be used to estimate the amount of elastic and inelastic scattering. Modern calculations differ from simple Lenz theory in predicting that the cross section is not a smoothly-increasing function of atomic number (see Fig. 2), particularly for the 1ighter elements. (3) We assume a slightly idealized detection system in which all elastically scattered electrons contribute to Iad, while all electrons which have been inelastically (but not elastically) scattered contribute to Ii.

High-angle annular dark-field STEM imaging of doped semiconductor layers

1991 ◽  
Vol 49 ◽  
pp. 704-705
Author(s):  
D.D. Perovic ◽  
J.H. Paterson
Keyword(s):  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
High Angle ◽  
Axis Orientation ◽  
Undoped Material ◽  
Transmission Electron ◽  
Ultrathin Layers ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
P Type

With the development of crystal growth techniques such as molecular beam epitaxy (MBE), it is now possible to fabricate modulation-doped superlattices consisting of alternating ultrathin layers of n-and/or p-type material abruptly separated by undoped material. At sufficiently high dopant concentrations these abrupt layers may be imaged in cross section by electron microscopy. Pennycook et al. and Treacy et al. have used high angle annular dark-field (HAAD) imaging in the scanning transmission electron microscope (STEM) to image low levels of dopants (∼1 at. %) in semiconductors. This work is concerned with imaging boron and arsenic doped layers in silicon at levels « 1 at.%.Fig. 1 shows a HAAD image of a B-Si superlattice at the <110> zone-axis orientation taken at 100 kV using a VG HB501UX STEM. The bright vertical layers are the B-doped regions, containing ∼4 x 1020 B/cm3. The horizontal lines are due to beam instability while the image was recorded. Fig.2 shows a line scan across the same superlattice, recorded by scanning the beam across the specimen in a direction perpendicular to the layers.

New detection system for HAADE and holography in STEM

1992 ◽  
Vol 50 (1) ◽  
pp. 102-103
Author(s):  
Marian Mankos ◽  
Shi Yao Wang ◽  
J.K. Weiss ◽  
J.M. Cowley
Keyword(s):  
High Efficiency ◽  
Detection System ◽  
Dark Field ◽  
Light Signal ◽  
Bright Field ◽  
Transmitted Beam ◽  
Wide Range ◽  
Annular Dark Field ◽  
Resolution Imaging ◽  
Diffraction Patterns

A novel detection system has been designed and realized experimentally on the HB5 STEM instrument. Shadow images, diffraction patterns as well as high-angle annular dark field and bright field images are observed simultaneously with high efficiency using CCD and TV cameras. The microscope can be operated in a wide range of instrument modes which includes the implementation of new techniques for high resolution imaging.As shown in Fig. 1, the detection system has three triple choice stages. Diffracted beams can be collected by three P47 fast phosphor annular detectors inclined at 45 degree to the axis and having different inner and outer acceptance angles, which can be adjusted by the postspecimen lenses. The detector is observed through a window by a photomultiplier. The annular detectors have been used also for a new bright field STEM technique which utilizes the inner rim of the detectors to collect only the outermost annular part of the central beam and promises an improvement in resolution by a factor of about 1.6. Initial results show some promise (Fig. 2). The transmitted beam is then converted into a light signal in YAG and P47 detectors; optionally the central part of the beam can be detected in the EELS spectrometer. The generated light signal is reflected through a system of mirrors, exits the vacuum chamber and is collected with high efficiency by high aperture optical lenses.

Improving the depth resolution of STEM-ADF sectioning by 3D deconvolution

Microscopy ◽  
2020 ◽  
Author(s):  
A Ishizuka ◽  
K Ishizuka ◽  
R Ishikawa ◽  
N Shibata ◽  
Y Ikuhara ◽  
...  
Keyword(s):  
Graphene Layer ◽  
Depth Resolution ◽  
Real Space ◽  
Dark Field ◽  
Entropy Method ◽  
Three Dimensions ◽  
Single Atom ◽  
Monolayer Graphene ◽  
Scanning Transmission ◽  
Annular Dark Field

Abstract Although the possibility of locating single atom in three dimensions using the scanning transmission of electron microscope (STEM) has been discussed with the advent of aberration correction technology, it is still a big challenge. In this report we have developed deconvolution routines based on maximum entropy method (MEM) and Richardson-Lucy algorithm (RLA), which are applicable to the STEM annular dark-field (ADF) though-focus images to improve the depth resolution. The new 3D deconvolution routines require a limited defocus-range of STEM-ADF images that covers a whole sample and some vacuum regions. Since the STEM-ADF probe is infinitely elongated along the optical axis, a 3D convolution is performed with a 2D convolution over xy-plane using the 2D fast Fourier transform (FFT) in reciprocal space, and a 1D convolution along the z-direction in real space. Using our new deconvolution routines, we have processed simulated focal series of STEM-ADF images for single Ce dopants embedded in wurtzite-type AlN. Applying the MEM, the Ce peaks are clearly localized along the depth, and the peak width is reduced down to almost one half. We also applied the new deconvolution routines to experimental focal series of STEM-ADF images of a monolayer graphene. The RLA gives smooth and high-P/B ratio scattering distribution, and the graphene layer can be easily detected. Using our deconvolution algorithms, we can determine the depth locations of the heavy dopants and the graphene layer within the precision of 0.1 and 0.2 nm, respectively, Thus, the deconvolution must be extremely useful for the optical sectioning with 3D STEM-ADF images.

Spatial resolution limits in EELS spectroscopy and imaging

1988 ◽  
Vol 46 ◽  
pp. 522-523 ◽  
Author(s):  
C. Colliex ◽  
C. Mory
Keyword(s):  
Spatial Resolution ◽  
Carbon Layer ◽  
Dark Field ◽  
Minimum Detectable Concentration ◽  
Bright Field ◽  
Atomic Size ◽  
Simultaneous Acquisition ◽  
Resolution Limits ◽  
Annular Dark Field ◽  
Detectable Concentration

In analytical problems, EELS is a powerful technique to locate, identify and measure the atoms contained within volumes of very small size. The present study is an experimental investigation of its resolution limits on a test specimen made of small metallic Tb and U clusters down to the atomic size and lying on a thin amorphous carbon layer. Several parameters have to be determined : the spatial resolution power (d), the minimum detectable concentration (Co) and the ultimate number of detectable atoms N = Co d2 tn within a specimen of local thickness t. The used instrument is a dedicated FEG-STEM VG HB 501 equipped with a Gatan spectrometer and governed by a home made digital acquisition system. This equipment offers unique capabilities for complete data quantification : the simultaneous acquisition for each pixel of two information channels (the annular dark field (adf) and the bright field one after the spectrometer) allows to discriminate the primary probe contribution from the inelastic effect. Sequences of up to 10 energy filtered images are acquired for different loss values covering the EELS range of interest from below the U-O45 edge (at 105 eV) to above the Tb-N4B edge (at 155 eV).

New imaging modes in STEM

1988 ◽  
Vol 46 ◽  
pp. 648-649
Author(s):  
A.V. Jones
Keyword(s):  
Energy Loss ◽  
Dark Field ◽  
Detector System ◽  
Objective Lens ◽  
Acceptance Angle ◽  
Bright Field ◽  
Dark Field Imaging ◽  
Annular Dark Field ◽  
Complex Forms ◽  
Field Imaging

The most often quoted advantage of STEM over conventional TEM is the ability to produce multiple simultaneous images by the use of multiple detector systems. In practice, this postulated advantage has seldom been fully utilised, mainly because of the practical difficulties in designing such detector systems.Most STEMs to date have been constructed as two-channel instruments combining annular dark-field imaging with either filtered bright-freld or inelastic imaging. More complex forms of bright-field detector have been employed1, as have parallel-readout systems for energy-loss spectra but the ability of the spectrometer to produce multiple simultaneous images has not been fully utilised.The basis of the problem lies in the fact that the objective lens and the detector system(s) have in most cases been designed by the manufacturers as separate entities in order to simplify the later addition of user-specific detectors. Since the acceptance angle of even the best spectrometers is relatively small, additional post-specimen lenses [with their attendant aberrations] had to be added in order to make full use of the spectrometer.

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