Transmission Electron Microscopy Studies of Crystal Lattice Growth in Atomic Resolution

1976 ◽  
Vol 34 ◽  
pp. 596-597
Author(s):  
H. Hashimoto ◽  
A. Kumaol ◽  
A. Ono ◽  
E. Watanabe ◽  
E. Endoh
Keyword(s):  
Spherical Aberration ◽  
Dark Field Image ◽  
Dark Field ◽  
Objective Lens ◽  
Image Method ◽  
Bright Field Image ◽  
Electron Microscopic ◽  
Single Atoms ◽  
Transmission Electron ◽  
Small Crystals

The present authors showed that the image of single atoms in Th-pyromellitate molecules and Th02 small crystals supported on graphite films could be observed in the dark field transmission electron microscopic images with tilted illumination (TDF image). The achievement of the observation of single atoms can be attributed not only to the high contrast of the dark field image but also to the two times higher resolution of the TDF image than that of the bright field image with axial illumination.Using the TDF image method, the growth process of small ThO2 crystals formed by the electron irradiation in the vacuum has been studied.Th - pyromellitate of 10-4 mol which was placed on graphite flakes was observed by JEM 100-C electron microscope with an objective lens of spherical aberration coefficient Cs = 0. 7 mm. Objective aperture and illumination tilt angles were 9 x 10-3 rad and 16 x 10-3 rad respectively .

Resolution in the Scanning Transmission Electron Microscope

1972 ◽  
Vol 30 ◽  
pp. 454-455
Author(s):  
M. G. R. Thomson
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Spherical Aberration ◽  
Signal To Noise Ratio ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Objective Lens ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

The variation of contrast and signal to noise ratio with change in detector solid angle in the high resolution scanning transmission electron microscope was discussed in an earlier paper. In that paper the conclusions were that the most favourable conditions for the imaging of isolated single heavy atoms were, using the notation in figure 1, either bright field phase contrast with β0⋍0.5 α0, or dark field with an annular detector subtending an angle between ao and effectively π/2.The microscope is represented simply by the model illustrated in figure 1, and the objective lens is characterised by its coefficient of spherical aberration Cs. All the results for the Scanning Transmission Electron Microscope (STEM) may with care be applied to the Conventional Electron Microscope (CEM). The object atom is represented as detailed in reference 2, except that ϕ(θ) is taken to be the constant ϕ(0) to simplify the integration. This is reasonable for θ ≤ 0.1 θ0, where 60 is the screening angle.

Design of a new objective lens for an HB-501A STEM

1991 ◽  
Vol 49 ◽  
pp. 416-417
Author(s):  
Earl J. Kirkland ◽  
Robert J. Keyse
Keyword(s):  
High Resolution ◽  
Spherical Aberration ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Objective Lens ◽  
Specimen Holder ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
High Resolution Microscopy

An ultra-high resolution pole piece with a coefficient of spherical aberration Cs=0.7mm. was previously designed for a Vacuum Generators HB-501A Scanning Transmission Electron Microscope (STEM). This lens was used to produce bright field (BF) and annular dark field (ADF) images of (111) silicon with a lattice spacing of 1.92 Å. In this microscope the specimen must be loaded into the lens through the top bore (or exit bore, electrons traveling from the bottom to the top). Thus the top bore must be rather large to accommodate the specimen holder. Unfortunately, a large bore is not ideal for producing low aberrations. The old lens was thus highly asymmetrical, with an upper bore of 8.0mm. Even with this large upper bore it has not been possible to produce a tilting stage, which hampers high resolution microscopy.

Aberration-Corrected STEM: the Present and the Future

2001 ◽  
Vol 7 (S2) ◽  
pp. 896-897
Author(s):  
O.L. Krivanek ◽  
N. Dellby ◽  
P.D. Nellist ◽  
P.E. Batson ◽  
A.R. Lupini
Keyword(s):  
Spherical Aberration ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Objective Lens ◽  
High Angle ◽  
Successful Operation ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Full Speed ◽  
Aberration Corrected

Surprising as it may seem, aberration correction for the scanning transmission electron microscope (STEM) is now a practical proposition. The first-ever commercial spherical aberration corrector for a STEM was delivered by Nion to IBM Research Center in June 2000, and other deliveries have taken place since or are imminent. At the same time, the development of corrector hardware and software is still proceeding at full speed, and our understanding of what are the most important factors for the successful operation of a corrector is deepening continuously.Fig. 1 shows two high-angle dark field (HADF) images of [110] Si obtained with the IBM VG HB501 STEM operating at 120 kV, about 2 weeks after we fitted a quadrupole-octupole corrector into it. Fig. 1(a) shows the best HADF image that could be obtained with the corrector's quadrupoles on but its octupoles off. Sample structures were captured down to about 2.5 Å detail, easily possible in a STEM with a high resolution objective lens with a spherical aberration coefficient (Cs) of 1.3 mm. Fig. 1(b) shows a HADF image obtained after the Cs-correcting octupoles were turned on and the corrector tuned up. The resolution has now improved to 1.36 Å. This is sufficient to resolve the correct separation of the closely-spaced Si columns.

Dark Field Procedures in Electron Microscopy of Particulate Biological Material

1971 ◽  
Vol 29 ◽  
pp. 426-427
Author(s):  
E. de Harven ◽  
K. R. Leonard ◽  
A. K. Kleinschmidt
Keyword(s):  
Dark Field Image ◽  
Dark Field ◽  
Carbon Films ◽  
Objective Lens ◽  
Uranyl Ions ◽  
E Coli ◽  
Transmission Electron ◽  
Beam Stop ◽  
Electron Microscopes ◽  
Horse Spleen Ferritin

The dark field image of a specimen is obtained by allowing elastically scattered electrons to pass along the optic axis of the objective lens. Most of the inelastically scattered and the undeflected electrons are eliminated by various procedures, three of which have been found practical in conventional transmission electron microscopes. These three procedures are based on the use of: i) “beam stop” dark field apertures positioned in the back focal plane of the objective lens, as described by Thon; ii) electron beam tilted mechanically, or by a deflecting magnetic coil system between the condenser lens and the object; iii) a “cone mantle” illumination of the object obtained by an annular condenser aperture of appropriate dimension. Our observations have been made with Siemens Elmiskop 1A and 101 electron microscopes, equipped with pointed cathodes (single crystal or lancet-shaped). All samples were supported by ultrathin (2 to 3 nm) carbon films. They included: (a) various viral DNA-cytochrome c monolayers, (b) horse spleen ferritin, (c) B. Subtilis SP 50 bacteriophages, and (d) 50 S E. Coli ribosomal particles. Samples (c) and (d) were stained with uranyl ions.

Image resolution in conventional transmission electron microscopy

1991 ◽  
Vol 49 ◽  
pp. 468-469
Author(s):  
Mehmet Sarikaya ◽  
James M. Howe
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Phase Contrast ◽  
Spherical Aberration ◽  
Dark Field ◽  
Image Resolution ◽  
Objective Lens ◽  
Contrast Imaging ◽  
Conventional Transmission Electron Microscopy ◽  
Transmission Electron

The image resolution in bright-field (BF) and dark-field (DF) conventional transmission electron microscopy (TEM) is given by: r = 0.66 CS¼¾¾, where Cs and ¾ are the spherical aberration coefficient of the objective lens and electron wavelength, respectively. Based on this formula, it should be possible to resolve single atoms or clusters of atoms by phase contrast imaging with a highly coherent electron beam and a properly defocused objective lens; this has been demonstrated for both BF and DF imaging. However, for most situations encountered in conventional TEM, the type of information that can be obtained about the specimen is the most important, rather than the instrumental resolution. Atomicresolution microscopy of crystalline specimens relies on phase contrast produced when two or more beams interfere to form an image and this is discussed elsewhere in this symposium. This paper discusses the contrast and resolution when either a single beam or diffuse scattering is used to form an image.

Observation of Atom Images by Means of Field Emission Stem

1976 ◽  
Vol 34 ◽  
pp. 500-501
Author(s):  
H. Todokoro ◽  
S. Nomura ◽  
T. Komoda
Keyword(s):  
Electron Microscope ◽  
Carbon Film ◽  
Dark Field Image ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Single Atom ◽  
Bright Field Image ◽  
Contrast Effects ◽  
Transmission Electron ◽  
Scanning Transmission

A number of studies of single atom image observation utilizing either scanning transmission electron microscope ( STEM ) or conventional electron microscope ( OEM ) have been reported. For this purpose, the dark field image observation seems more promising because the scattering cross-section of an atom is extremely small. Much attention has been paid to decreasing background noises resulting from the supporting film. A thin amorphous carbon film is often utilized as a supporting film. However, many high contrast spots appear even in the dark field image when OEM is used. Matsuda and Nagata3 applied an incoherent illumination technique to the bright field image observation of OEM, and succeeded, in removing the phase contrast effects from the image.

scholarly journals Authors' Response

2005 ◽  
Vol 11 (2) ◽  
pp. 113-115 ◽  
Author(s):  
Chun-Lin Jia ◽  
Markus Lentzen ◽  
Knut Urban
Keyword(s):  
Oxygen Atom ◽  
Spherical Aberration ◽  
Objective Lens ◽  
Electron Microscopic ◽  
Image Intensity ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Letter Comment ◽  
Z Contrast ◽  
Local Image

The authors are grateful to the Editor for the opportunity to reply to the letter by Lupini et al. The authors of the above letter comment on a set of recent articles in which the novel technique of imaging at a negative value of the spherical aberration coefficient of the objective lens in an aberration-corrected transmission electron microscope (NCSI technique) is methodically described and applied to the measurement of the occupancy of atomically resolved oxygen columns in perovskites. In particular, the authors raise doubts about the possibility of inferring quantitative data from measurements of the local image intensity at the position of the oxygen atom columns. With reference to the study by Jia et al. (2003a), the letter authors present an image simulation on the basis of which it is stated that the observed effect of a reduced intensity at the oxygen atomic columns should not be interpreted in terms of reduced oxygen occupancy but can, as the authors claim, be “better” explained on the basis of the effect of surface roughness on contrast. In addition, the authors emphasize the work of Kim et al. (2001) with respect to the nonstoichiometry of the oxygen occupancy in grain boundaries of SrTiO3and criticize our reference to the literature in which it is reported that oxygen cannot be observed by the scanning transmission electron microscopy (STEM) technique in Z-contrast. In the following, we shall demonstrate that in spite of the fact that a nonideal surface morphology can—as in the application of any (!) electron microscopic technique whether used in TEM or in STEM—have an effect on local image intensity, meaningful quantitative measurements of relative oxygen-atom site occupancies can be carried out employing the NCSI technique.

Comparison of Deterministic and Linear Cosine Spatial Filtering of Transmission Electron Micrographs

1972 ◽  
Vol 30 ◽  
pp. 596-597
Author(s):  
David A. Ansley
Keyword(s):  
Spherical Aberration ◽  
Focal Length ◽  
Chromatic Aberration ◽  
Spatial Filter ◽  
Operating Conditions ◽  
Objective Lens ◽  
List Type ◽  
Spatial Filters ◽  
Transmission Electron ◽  
Wide Range

The coherence of the electron flux of a transmission electron microscope (TEM) limits the direct application of deconvolution techniques which have been used successfully on unmanned spacecraft programs. The theory assumes noncoherent illumination. Deconvolution of a TEM micrograph will, therefore, in general produce spurious detail rather than improved resolution.A primary goal of our research is to study the performance of several types of linear spatial filters as a function of specimen contrast, phase, and coherence. We have, therefore, developed a one-dimensional analysis and plotting program to simulate a wide 'range of operating conditions of the TEM, including adjustment of the:(1) Specimen amplitude, phase, and separation(2) Illumination wavelength, half-angle, and tilt(3) Objective lens focal length and aperture width(4) Spherical aberration, defocus, and chromatic aberration focus shift(5) Detector gamma, additive, and multiplicative noise constants(6) Type of spatial filter: linear cosine, linear sine, or deterministic

Effets of surfaces on precipitate morphology in irradiated thin foils

1978 ◽  
Vol 36 (1) ◽  
pp. 654-655
Author(s):  
D.I. Potter ◽  
A. Taylor
Keyword(s):  
Ion Irradiation ◽  
Dark Field Image ◽  
Thin Foil ◽  
Dark Field ◽  
Al Alloy ◽  
Bright Field Image ◽  
Dislocation Loops ◽  
Precipitate Morphology ◽  
Thin Foils

Thermal aging of Ni-12.8 at. % A1 and Ni-12.7 at. % Si produces spatially homogeneous dispersions of cuboidal γ'-Ni3Al or Ni3Si precipitate particles arrayed in the Ni solid solution. We have used 3.5-MeV 58Ni+ ion irradiation to examine the effect of irradiation during precipitation on precipitate morphology and distribution. The nearness of free surfaces produced unusual morphologies in foils thinned prior to irradiation. These thin-foil effects will be important during in-situ investigations of precipitation in the HVEM. The thin foil results can be interpreted in terms of observations from bulk irradiations which are described first.Figure 1a is a dark field image of the γ' precipitate 5000 Å beneath the surface(∿1200 Å short of peak damage) of the Ni-Al alloy irradiated in bulk form. The inhomogeneous spatial distribution of γ' results from the presence of voids and dislocation loops which can be seen in the bright field image of the same area, Fig. 1b.

Towards 1-Ångstrom-resolution STEM

1993 ◽  
Vol 51 ◽  
pp. 996-997
Author(s):  
H.S. von Harrach ◽  
D.E. Jesson ◽  
S.J. Pennycook
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Phase Contrast ◽  
Spherical Aberration ◽  
A Priori ◽  
Dark Field ◽  
Image Resolution ◽  
Objective Lens ◽  
Annular Dark Field ◽  
First Results

Phase contrast TEM has been the leading technique for high resolution imaging of materials for many years, whilst STEM has been the principal method for high-resolution microanalysis. However, it was demonstrated many years ago that low angle dark-field STEM imaging is a priori capable of almost 50% higher point resolution than coherent bright-field imaging (i.e. phase contrast TEM or STEM). This advantage was not exploited until Pennycook developed the high-angle annular dark-field (ADF) technique which can provide an incoherent image showing both high image resolution and atomic number contrast.This paper describes the design and first results of a 300kV field-emission STEM (VG Microscopes HB603U) which has improved ADF STEM image resolution towards the 1 angstrom target. The instrument uses a cold field-emission gun, generating a 300 kV beam of up to 1 μA from an 11-stage accelerator. The beam is focussed on to the specimen by two condensers and a condenser-objective lens with a spherical aberration coefficient of 1.0 mm.

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