Recent Progress and Plans in Computer-Controlled High Resolution Electron Microscopy

1990 ◽  
Vol 48 (1) ◽  
pp. 154-155
Author(s):  
W.J. de Ruijter ◽  
Peter Rez ◽  
David J. Smith
Keyword(s):  
Electron Microscopy ◽  
Digital Processing ◽  
High Resolution Electron Microscopy ◽  
Objective Lens ◽  
Linear Filter ◽  
Contrast Transfer Function ◽  
Image Displacement ◽  
Spatially Resolved ◽  
Wide Range ◽  
On Line

Digital computers are becoming widely recognized as standard accessories for electron microscopy. Due to instrumental innovations the emphasis in digital processing is shifting from off-line manipulation of electron micrographs to on-line image acquisition, analysis and microscope control. An on-line computer leads to better utilization of the instrument and, moreover, the flexibility of software control creates the possibility of a wide range of novel experiments, for example, based on temporal and spatially resolved acquisition of images or microdiffraction patterns. The instrumental resolution in electron microscopy is often restricted by a combination of specimen movement, radiation damage and improper microscope adjustment (where the settings of focus, objective lens stigmatism and especially beam alignment are most critical). We are investigating the possibility of proper microscope alignment based on computer induced tilt of the electron beam. Image details corresponding to specimen spacings larger than ∼20Å are produced mainly through amplitude contrast; an analysis based on geometric optics indicates that beam tilt causes a simple image displacement. Higher resolution detail is characterized by wave propagation through the optical system of the microscope and we find that beam tilt results in a dispersive image displacement, i.e. the displacement varies with spacing. This approach is valid for weak phase objects (such as amorphous thin films), where transfer is simply described by a linear filter (phase contrast transfer function) and for crystalline materials, where imaging is described in terms of dynamical scattering and non-linear imaging theory. In both cases beam tilt introduces image artefacts.

Recent Applications of High Resolution Electron Microscopy to Crystalline Arrays of Virus Particles

1978 ◽  
Vol 36 (3) ◽  
pp. 470-482 ◽  
Author(s):  
R.W. Horne
Keyword(s):  
Electron Microscopy ◽  
Image Processing ◽  
Analytical Techniques ◽  
Staining Technique ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
Full Potential ◽  
Virus Particles ◽  
Resolution Electron ◽  
Wide Range

The technique of surrounding virus particles with a neutralised electron dense stain was described at the Fourth International Congress on Electron Microscopy, Berlin 1958 (see Home & Brenner, 1960, p. 625). For many years the negative staining technique in one form or another, has been applied to a wide range of biological materials. However, the full potential of the method has only recently been explored following the development and applications of optical diffraction and computer image analytical techniques to electron micrographs (cf. De Hosier & Klug, 1968; Markham 1968; Crowther et al., 1970; Home & Markham, 1973; Klug & Berger, 1974; Crowther & Klug, 1975). These image processing procedures have allowed a more precise and quantitative approach to be made concerning the interpretation, measurement and reconstruction of repeating features in certain biological systems.

Limits for high-resolution electron microscopy of inorganic materials?

1987 ◽  
Vol 45 ◽  
pp. 4-5
Author(s):  
David J. Smith
Keyword(s):  
Electron Microscopy ◽  
Spherical Aberration ◽  
High Resolution Electron Microscopy ◽  
Inorganic Materials ◽  
Atomic Scale ◽  
Resolution Limit ◽  
Contrast Transfer Function ◽  
Existing Problems ◽  
Resolution Electron ◽  
Electron Microscopes

The era of atomic-resolution electron microscopy has finally arrived. In virtually all inorganic materials, including oxides, metals, semiconductors and ceramics, it is possible to image individual atomic columns in low-index zone-axis projections. A whole host of important materials’ problems involving defects and departures from nonstoichiometry on the atomic scale are waiting to be tackled by the new generation of intermediate voltage (300-400keV) electron microscopes. In this review, some existing problems and limitations associated with imaging inorganic materials are briefly discussed. The more immediate problems encountered with organic and biological materials are considered elsewhere.Microscope resolution. It is less than a decade since the state-of-the-art, commercially available TEM was a 200kV instrument with a spherical aberration coefficient of 1.2mm, and an interpretable resolution limit (ie. first zero crossover of the contrast transfer function) of 2.5A.

Voltage-center COMA-free alignment for high-resolution Electron Microscopy

1994 ◽  
Vol 52 ◽  
pp. 410-411
Author(s):  
K. Ishizuka ◽  
K. Shirota
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Incident Beam ◽  
Chromatic Aberration ◽  
High Resolution Electron Microscopy ◽  
Beam Deflection ◽  
Objective Lens ◽  
Main Magnetic Field ◽  
Beam Direction ◽  
Resolution Electron

In a conventional alignment for high-resolution electron microscopy, the specimen point imaged at the viewing-screen center is made dispersion-free against a voltage fluctuation by adjusting the incident beam direction using the beam deflector. For high-resolution works the voltage-center alignment is important, since this alignment reduces the chromatic aberration. On the other hand, the coma-free alignment is also indispensable for high-resolution electron microscopy. This is because even a small misalignment of the incident beam direction induces wave aberrations and affects the appearance of high resolution electron micrographs. Some alignment procedures which cancel out the coma by changing the incident beam direction have been proposed. Most recently, the effect of a three-fold astigmatism on the coma-free alignment has been revealed, and new algorithms of coma-free alignment have been proposed.However, the voltage-center and the coma-free alignments as well as the current-center alignment in general do not coincide to each other because of beam deflection due to a leakage field within the objective lens, even if the main magnetic-field of the objective lens is rotationally symmetric. Since all the proposed procedures for the coma-free alignment also use the same beam deflector above the objective lens that is used for the voltage-center alignment, the coma-free alignment is only attained at the sacrifice of the voltage-center alignment.

scholarly journals 2.7 Å cryo-EM structure of vitrified M. musculus H-chain apoferritin from 200 keV “screening microscope”

2019 ◽  
Author(s):  
Farzad Hamdi ◽  
Christian Tüting ◽  
Dmitry A. Semchonok ◽  
Fotis L. Kyrilis ◽  
Annette Meister ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Stability ◽  
Objective Lens ◽  
List Type ◽  
Constant Power ◽  
Contrast Transfer Function ◽  
Microscopy Imaging ◽  
Detection Technology ◽  
High Emission ◽  
Solvent Molecules

AbstractHere we present the structure of mouse H-chain apoferritin at 2.7 Å (FSC=0.143) solved by single particle cryogenic electron microscopy (cryo-EM) using a 200 kV device. Data were collected using a compact, two-lens illumination system with a constant power objective lens, without the use of energy filters or aberration correctors. Coulomb potential maps reveal clear densities for main chain carbonyl oxygens, residue side chains (including alternative conformations) and bound solvent molecules. We argue that the advantages offered by (a) the high electronic and mechanical stability of the microscope, (b) the high emission stability and low beam energy spread of the high brightness Field Emission Gun (x-FEG), (c) direct electron detection technology and (d) particle-based Contrast Transfer Function (CTF) refinement have contributed to achieving resolution close to the Rayleigh limit. Overall, we show that basic electron optical settings for automated cryo-electron microscopy imaging, widely thought of as a “screening cryo-microscope”, can be used to determine structures approaching atomic resolution.HighlightsThe 2.7 Å structure of mouse apoferritin was solved using a 200 keV screening cryo-microscopeThe apoferritin reconstruction was resolved without an energy filter, aberration correctors, or constant-power condenser lensesComparison to available crystallographic and cryo-EM structures from high-end cryo-microscopes demonstrates consistency in resolved water molecules, metals and side chain orientationsAlthough radiation damage is more prominent at 200 keV compared to 300 keV, this type of instrumentation is more accessible to research laboratories due to its compactness and simplicity

Instrumentation at the National Center for Electron Microscopy: The atomic resolution microscope

1983 ◽  
Vol 41 ◽  
pp. 310-311 ◽  
Author(s):  
R. Gronsky ◽  
G. Thomas
Keyword(s):  
Electron Microscopy ◽  
Atomic Resolution ◽  
Objective Lens ◽  
Contrast Transfer Function ◽  
Voltage Electron ◽  
Variable Voltage ◽  
New Instrument ◽  
Performance Specifications ◽  
Electron Microscopes ◽  
Point To Point

The Atomic Resolution Microscope (ARM) is one of two unique high voltage electron microscopes at the Lawrence Berkeley Laboratory's National Center for Electron Microscopy (NCEM). This paper reports on the latest results from this new instrument which was manufactured by JEOL, Ltd. to the performance specifications of the NCEM, delivered in January of 1983, and soon to be open to access by the entire microscopy community. Details of its history and development are given in reference 1; its performance specifications are reviewed below.Adopting as a design definition for resolution the first zero crossover of th% phase contrast transfer function at Scherzer defocus, the ARM (Fig. 1) maintains 1.7Å point-to-point resolution over its 400kV to 1000kV operating range. Consequently the microscope can be tuned to a voltage which is below the threshold for knock-on damage in a specimen and used to directly image its contiguous-atom structure. The key to this variable-voltage, high-resolution performance is a top-entry objective stage, which, in addition to ± 40° biaxial tilting, incorporates a height (Z)-control to alter specimen position within the objective lens.

Combined High Resolution Electron Microscopy and X-Ray Microanalysis

1970 ◽  
Vol 28 ◽  
pp. 552-553 ◽  
Author(s):  
C. J. Cooke ◽  
I. K. Openshaw
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Easy Access ◽  
Objective Lens ◽  
X Ray ◽  
Chart Recorder ◽  
Resolution Electron ◽  
Better Than ◽  
Rear Panel

The Analytical Microscope EMMA-4 combines the function of high resolution electron microscopy with the facility of x-ray microanalysis. The microscope is a commercially available version of similar instruments which have been previously described. The design of the main console is based on the AEI EM802 with the rear panel suitably modified to house extra controls. An additional console houses the spectrometer controls and affords easy access to the pulse counting electronics. A chart recorder is mounted separately on a mobile trolley.The Figure shows the electron optical column of the instrument and the position of the two x-ray spectrometers. The objective lens accommodates a side entry specimen stage which permits six specimens or standards to be loaded into the instrument at any one time. By using the normal projector system of the EM802 a direct magnification of about 140,000 times is possible and the resolution is better than 10Å.

High-resolution electron microscopy of beam-sensitive specimens: Results with paraffin

1986 ◽  
Vol 44 ◽  
pp. 10-13
Author(s):  
F. Zemlin ◽  
E. Reuber ◽  
E. Beckmann ◽  
D. Dorset
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Radiation Damage ◽  
High Resolution Electron Microscopy ◽  
Objective Lens ◽  
Resolution Electron ◽  
Electron Microscopical

Many of the most interesting specimens are so severely damaged during the electron microscopical imaging that no useful image emerges from the electron noise. One method of reducing this radiation damage is to cool the specimen, and if this helps it seems reasonable to cool it down as far as possible. This goal is reached most straightforwardly by using the Siemens helium-cooled superconducting objective lens designed by I. Dietrich and co-workers.

Characterization of Ultrathin Multilayers for Applications in X-Ray Optics

1990 ◽  
Vol 48 (1) ◽  
pp. 20-21
Author(s):  
David J. Smith ◽  
Z.G. Li ◽  
S.-C.Y. Tsen ◽  
P. Boher ◽  
Ph. Houdy
Keyword(s):  
Electron Microscopy ◽  
Structural Information ◽  
Profile Analysis ◽  
Practical Importance ◽  
Rf Sputtering ◽  
Digital Processing ◽  
High Resolution Electron Microscopy ◽  
Interface Roughness ◽  
Ion Milling ◽  
X Ray

Ultrathin multilayers have unique physical properties which are of great practical importance. Our interest here is in layer systems suitable for X-ray optical devices, in particular for X-ray mirrors. Optimization of device performance depends upon such factors as the layer uniformity (thickness and composition), interface roughness, and structural irregularities. Techniques such as Rutherford backscattering, X-ray diffraction and Auger profile analysis provide valuable structural information but averaged over comparatively large specimen regions. High-resolution electron microscopy has been used in the present study to gain complementary insight into the local microstructure of various layer systems, based on combinations of Rh,W,C,B4C, grown by diode rf-sputtering. Samples suitable for electron microscopy were prepared in cross-section using standard grinding, dimpling and argon ion-milling techniques. Most observations were made with a JEM-4000EX HREM operated at 400kV, with selected area electron diffraction (SAED) to determine the average bilayer thickness by reference to the diffraction pattern of the Si (110) substrate. Optical diffractograms (ODMs) and digital processing were used for accurate measurement of the lattice spacings visible in the multilayers.

Relaxation of Metamorphic III-V Heterostructures Studied by Digital Processing of HREM Images

1998 ◽  
Vol 523 ◽  
Author(s):  
André Rocher ◽  
Etienne Snoeck ◽  
Léon Goldstein ◽  
Joël Jacquet ◽  
Catherine Fortin
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Transition Zone ◽  
Epitaxial Layer ◽  
Digital Processing ◽  
High Resolution Electron Microscopy ◽  
Dislocation Network ◽  
Misfit Dislocations ◽  
Misfit Stress ◽  
Resolution Electron

AbstractThe crystalline structure of metamorphic heterostructures grown by epitaxy has been studied by digital processing of High Resolution Electron Microscopy (HREM) images. Two systems have been investigated: the GaSb/(001)GaAs, known to be fully relaxed by a perfect Lomer dislocation network and the GaAs/(001)InP relaxed by partial and 60° dislocations randomly distributed. A transition zone can be defined between the perfect substrate and the relaxed epitaxial layer: its thickness is less than 20Å in GaSb/GaAs and more than 80Å in GaAs/InP. These results indicate that the misfit dislocations are only one of the elements involved in the relaxation of misfit stress.

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