Possibility of Single Atom Resolution in Single-Sideband Imaging

1977 ◽  
Vol 35 ◽  
pp. 16-17
Author(s):  
K. H. Downin
Keyword(s):  
Electron Microscopy ◽  
Image Processing ◽  
Phase Contrast ◽  
Dark Field ◽  
Single Atom ◽  
Bright Field ◽  
Heavy Atoms ◽  
Single Atoms ◽  
Single Sideband ◽  
Light Components

The ability to distinguish between heavy and light components of a specimen, and especially to distinguish single heavy atoms, would be a great benefit in many instances. Even with the demonstrated ability of the STEM, and of the CTEM especially in dark field, to image single atoms, it is of interest to know the possibility of using bright field in a conventional microscope with subsequent image processing to obtain images of single heavy atoms separated from the image of a lighter supporting film.Single-sideband image reconstruction, involving the combination of two images obtained using opposite halves of the diffraction pattern, offers in principle the ability to separate images of heavy and light specimen components, or specimen components giving rise to amplitude and phase contrast, respectively. This has been demonstrated in electron microscopy^, but under conditions or low resolution, where inelastic scattering, as well as scattering outside the effective objective aperture, contribute heavily to the component with amplitude contrast.

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.

Application of Scanning Confocal Electron Microscopy to Nanomaterials and the Improvement in Resolution by Image Processing

2011 ◽  
Vol 675-677 ◽  
pp. 259-262
Author(s):  
X. Zhang ◽  
Masaki Takeguchi ◽  
Ayako Hashimoto ◽  
Kazutaka Mitsuishi ◽  
Masayuki Shimojo
Keyword(s):  
Electron Microscopy ◽  
Image Processing ◽  
Spherical Aberration ◽  
Depth Resolution ◽  
Dark Field ◽  
Nanometer Scale ◽  
Bright Field ◽  
Probe Size ◽  
Annular Dark Field ◽  
Vertical Probe

Scanning confocal electron microscopy (SCEM) is a novel technique for threedimensional observation with a nanometer-scale resolution. Annular dark field (ADF) SCEM imaging has been demonstrated to have better depth resolution than bright field (BF) SCEM imaging. However, the depth resolution of ADF-SCEM images is limited by the vertical probe size determined by spherical aberration and convergence angle. Therefore, we attempted to employ a deconvolution image processing method to improve the depth resolution of SCEM images. The result of the deconvolution process for vertically sliced SCEM images showed the improvement in the depth resolution by 35-40%.

Single Atom Image Contrast in Fixed Beam Dark Field Electron Microscopy

1974 ◽  
Vol 32 ◽  
pp. 366-367
Author(s):  
Wah Chi
Keyword(s):  
Scattering Amplitude ◽  
Present Report ◽  
Dark Field ◽  
Image Contrast ◽  
Single Atom ◽  
Optical Theorem ◽  
Hartree Fock ◽  
Heavy Atoms ◽  
Beam Stop ◽  
Fixed Beam

Resolution and contrast are the important factors to determine the feasibility of imaging single heavy atoms on a thin substrate in an electron microscope. The present report compares the atom image characteristics in different modes of fixed beam dark field microscopy including the ideal beam stop (IBS), a wire beam stop (WBS), tilted illumination (Tl) and a displaced aperture (DA). Image contrast between one Hg and a column of linearly aligned carbon atoms (representing the substrate), are also discussed. The assumptions in the present calculations are perfectly coherent illumination, atom object is represented by spherically symmetric potential derived from Relativistic Hartree Fock Slater wave functions, phase grating approximation is used to evaluate the complex scattering amplitude, inelastic scattering is ignored, phase distortion is solely due to defocus and spherical abberation, and total elastic scattering cross section is evaluated by the Optical Theorem. The atom image intensities are presented in a Z-modulation display, and the details of calculation are described elsewhere.

Removal of inelastically scattered electrons substantially increases phase contrast on frozen-hydrated molecules

1987 ◽  
Vol 45 ◽  
pp. 652-653
Author(s):  
John P. Langmore ◽  
Brian D. Athey
Keyword(s):  
Electron Diffraction ◽  
Phase Contrast ◽  
Low Dose ◽  
Dark Field ◽  
Biological Structure ◽  
Bright Field ◽  
Low Contrast ◽  
Negative Stain ◽  
The Difference ◽  
Better Than

Although electron diffraction indicates better than 0.3nm preservation of biological structure in vitreous ice, the imaging of molecules in ice is limited by low contrast. Thus, low-dose images of frozen-hydrated molecules have significantly more noise than images of air-dried or negatively-stained molecules. We have addressed the question of the origins of this loss of contrast. One unavoidable effect is the reduction in scattering contrast between a molecule and the background. In effect, the difference in scattering power between a molecule and its background is 2-5 times less in a layer of ice than in vacuum or negative stain. A second, previously unrecognized, effect is the large, incoherent background of inelastic scattering from the ice. This background reduces both scattering and phase contrast by an additional factor of about 3, as shown in this paper. We have used energy filtration on the Zeiss EM902 in order to eliminate this second effect, and also increase scattering contrast in bright-field and dark-field.

Imaging sub-micron objects with light microscopy: Visualization of the T-4 bacteriophage

1989 ◽  
Vol 47 ◽  
pp. 834-835
Author(s):  
Malcolm Brown ◽  
Reynolds M. Delgado ◽  
Michael J. Fink
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Focal Plane ◽  
Phase Contrast ◽  
Dark Field ◽  
E Coli ◽  
Polystyrene Beads ◽  
Television Camera ◽  
Transmission Electron ◽  
Universal Microscope

While light microscopy has been used to image sub-micron objects, numerous problems with diffraction-limitations often preclude extraction of useful information. Using conventional dark-field and phase contrast light microscopy coupled with image processing, we have studied the following objects: (a) polystyrene beads (88nm, 264nm, and 557mn); (b) frustules of the diatom, Pleurosigma angulatum, and the T-4 bacteriophage attached to its host, E. coli or free in the medium. Equivalent images of the same areas of polystyrene beads and T-4 bacteriophages were produced using transmission electron microscopy.For light microscopy, we used a Zeiss universal microscope. For phase contrast observations a 100X Neofluar objective (N.A.=1.3) was applied. With dark-field, a 100X planachromat objective (N.A.=1.25) in combination with an ultra-condenser (N.A.=1.25) was employed. An intermediate magnifier (Optivar) was available to conveniently give magnification settings of 1.25, 1.6, and 2.0. The image was projected onto the back focal plane of a film or television camera with a Carl Zeiss Jena 18X Compens ocular.

Coelomomyces canadense stat. et comb. nov. (Blastocladiales: Coelomomycetaceae) from Psectrocladius sp. G (Diptera: Chironomidae)

1978 ◽  
Vol 56 (18) ◽  
pp. 2303-2306 ◽  
Author(s):  
Richard A. Nolan
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Phase Contrast ◽  
Field Phase ◽  
Species Status ◽  
Bright Field ◽  
Latin Diagnosis ◽  
Taxonomic Criterion ◽  
Sporangial Wall ◽  
Scanning Electron

Resistant sporangia of Coelomomyces chironomi var. canadense Weiser and McCauley were examined by bright-field, phase-contrast, and scanning electron microscopy (SEM). The use of SEM facilitated the observation of previously undescribed complex furrows in the sporangial wall. The taxonomic criterion for varietal status is discussed, and the variety is elevated to species status. Coelomomyces canadense (Weiser and McCauley) Nolan stat. et comb. nov. is described with an emended Latin diagnosis.

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

Z Dependence of Electron Scattering by Single Atoms into Annular Dark-Field Detectors

2011 ◽  
Vol 17 (6) ◽  
pp. 847-858 ◽  
Author(s):  
Michael M.J. Treacy
Keyword(s):  
Elastic Scattering ◽  
Inelastic Scattering ◽  
Cross Section ◽  
Electron Scattering ◽  
Dark Field ◽  
Single Atom ◽  
Single Atoms ◽  
Annular Dark Field ◽  
Annular Detector ◽  
The Cross

AbstractA simple parameterization is presented for the elastic electron scattering cross sections from single atoms into the annular dark-field (ADF) detector of a scanning transmission electron microscope (STEM). The dependence on atomic number, Z, and inner reciprocal radius of the annular detector, q0, of the cross section σ(Z,q0) is expressed by the empirical relationwhere A(q0) is the cross section for hydrogen (Z = 1), and the detector is assumed to have a large outer reciprocal radius. Using electron elastic scattering factors determined from relativistic Hartree-Fock simulations of the atomic electron charge density, values of the exponent n(Z,q0) are tabulated as a function of Z and q0, for STEM probe sizes of 1.0 and 2.0 Å.Comparison with recently published experimental data for single-atom scattering [Krivanek et al. (2010). Nature464, 571–574] suggests that experimentally measured exponent values are systematically lower than the values predicted for elastic scattering from low-Z atoms. It is proposed that this discrepancy arises from the inelastic scattering contribution to the ADF signal. A simple expression is proposed that corrects the exponent n(Z,q0) for inelastic scattering into the annular detector.

Quantitative Annular Dark Field Electron Microscopy Using Single Electron Signals

2013 ◽  
Vol 20 (1) ◽  
pp. 99-110 ◽  
Author(s):  
Ryo Ishikawa ◽  
Andrew R. Lupini ◽  
Scott D. Findlay ◽  
Stephen J. Pennycook
Keyword(s):  
Electron Microscopy ◽  
Dynamic Range ◽  
Light Element ◽  
Dark Field ◽  
Atomic Scale ◽  
Single Electron ◽  
Single Atom ◽  
Intensity Level ◽  
Primitive Cell ◽  
Annular Dark Field

AbstractOne of the difficulties in analyzing atomic resolution electron microscope images is that the sample thickness is usually unknown or has to be fitted from parameters that are not precisely known. An accurate measure of thickness, ideally on a column-by-column basis, parameter free, and with single atom accuracy, would be of great value for many applications, such as matching to simulations. Here we propose such a quantification method for annular dark field scanning transmission electron microscopy by using the single electron intensity level of the detector. This method has the advantage that we can routinely quantify annular dark field images operating at both low and high beam currents, and under high dynamic range conditions, which is useful for the quantification of ultra-thin or light-element materials. To facilitate atom counting at the atomic scale we use the mean intensity in an annular dark field image averaged over a primitive cell, with no free parameters to be fitted. To illustrate the potential of our method, we demonstrate counting the number of Al (or N) atoms in a wurtzite-type aluminum nitride single crystal at each primitive cell over the range of 3–99 atoms.

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