Theoretical And Practical Design Considerations for Ultra-High Resolution Electron Lenses

1980 ◽  
Vol 38 ◽  
pp. 266-269
Author(s):  
Y. Harada ◽  
K. Tsuno ◽  
Y. Arai
Keyword(s):  
Optical Properties ◽  
High Resolution ◽  
Chromatic Aberration ◽  
Point Of View ◽  
Pole Piece ◽  
Axial Field ◽  
Design Considerations ◽  
Resolution Electron ◽  
Practical Design ◽  
Peak Flux

Magnetic objective lenses, from the point of view of pole piece geometry, can he roughly classified into two types, viz., symmetrical and asymmetrical. In the case of the former, the optical properties have been calculated by several authors1-3) and the results would appear to suggest that, in order to reduce the spherical and chromatic aberration coefficients, Cs and Cc, it is necessary to decrease the half-width value of the axial field distribution and to increase the peak flux density. The expressions for either minimum Cs or minimum Cc were presented in the form of ‘universal’ curves by Mulvey and Wallington4).

Design of objective lens for 200-kV high-resolution electron microscopes

1983 ◽  
Vol 41 ◽  
pp. 314-315
Author(s):  
K. Tsuno ◽  
T. Honda ◽  
Y. Harada ◽  
M. Naruse
Keyword(s):  
Optical Properties ◽  
Computer Technology ◽  
Axial Magnetic Field ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Resolution Electron ◽  
Correction Of Astigmatism ◽  
Three Stages ◽  
Electron Microscopes ◽  
Stage 1

Developement of computer technology provides much improvements on electron microscopy, such as simulation of images, reconstruction of images and automatic controll of microscopes (auto-focussing and auto-correction of astigmatism) and design of electron microscope lenses by using a finite element method (FEM). In this investigation, procedures for simulating the optical properties of objective lenses of HREM and the characteristics of the new lens for HREM at 200 kV are described.The process for designing the objective lens is divided into three stages. Stage 1 is the process for estimating the optical properties of the lens. Firstly, calculation by FEM is made for simulating the axial magnetic field distributions Bzc of the lens. Secondly, electron ray trajectory is numerically calculated by using Bzc. And lastly, using Bzc and ray trajectory, spherical and chromatic aberration coefficients Cs and Cc are numerically calculated. Above calculations are repeated by changing the shape of lens until! to find an optimum aberration coefficients.

High-resolution electron microscopy of Cu2O surfaces

1986 ◽  
Vol 44 ◽  
pp. 396-397
Author(s):  
V. Castano ◽  
W. Krakow
Keyword(s):  
High Resolution ◽  
Natural Extension ◽  
High Resolution Electron Microscopy ◽  
Point Of View ◽  
Initial Oxidation ◽  
System A ◽  
Resolution Electron ◽  
Surface Reconstructions ◽  
Atomic Surface ◽  
Au Thin Films

In non-UHV microscope environments atomic surface structure has been observed for flat-on for various orientations of Au thin films and edge-on for columns of atoms in small particles. The problem of oxidation of surfaces has only recently been reported from the point of view of high resolution microscopy revealing surface reconstructions for the Ag2O system. A natural extension of these initial oxidation studies is to explore other materials areas which are technologically more significant such as that of Cu2O, which will now be described.

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.

Characterization of Tilt Boundaries by Ultra High Resolution Electron Microscopy

1984 ◽  
Vol 41 ◽  
Author(s):  
W. Krakow ◽  
J. T. Wetzel ◽  
D. A. Smith ◽  
G. Trafas
Keyword(s):  
High Resolution ◽  
Grain Boundary ◽  
Structural Information ◽  
Theoretical Work ◽  
High Resolution Electron Microscopy ◽  
Point Of View ◽  
Experimental Point ◽  
Structure Information ◽  
Resolution Electron ◽  
Tilt Boundaries

AbstractA high resolution electron microscope study of grain boundary structures in Au thin films has been undertaken from both a theoretical and experimental point of view. The criteria necessary to interpret images of tilt boundaries at the atomic level, which include electron optical and specimen effects, have been considered for both 200kV and the newer 400kV medium voltage microscopes. So far, the theoretical work has concentrated on two different [001] tilt bounda-ries where a resolution of 2.03Å is required to visualize bulk lattice structures on either side of the interface. Both a high angle boundary, (210) σ=5, and a low angle boundary, (910) σ=41, have been considered. Computational results using multislice dynamical diffraction and image simulations of relaxed bounda-ries viewed edge-on and with small amounts of beam and/or specimen inclina-tion have been obtained. It will be shown that some structural information concerning grain boundary dislocations can be observed at 200kV. However, many difficulties occur in the exact identification of the interface structure viewed experimentally for both [001] and [011] boundaries since the resolution required is near the performance limit of a 200kV microscope. The simulated results at 400kV indicate a considerable improvement will be realized in obtain-ing atomic structure information at the interface.

A microscopic system for high-resolution electron crystallography

1995 ◽  
Vol 53 ◽  
pp. 70-71
Author(s):  
Y. Fujiyoshi ◽  
K. Murata ◽  
K. Mitsuoka ◽  
T. Hirai ◽  
A. Miyazawa ◽  
...  
Keyword(s):  
High Resolution ◽  
Structure Analysis ◽  
Room Temperature ◽  
Point Of View ◽  
Irradiation Damage ◽  
High Resolution Data ◽  
Light Harvesting Complex ◽  
Resolution Electron ◽  
Structural Point ◽  
Resolution Data

High-resolution electron cryo-microscopy is one of good candidate for structure analysis of membrane-protein, and also actually analyzed the structure of membrane-proteins such as bacteriorhodopsin (bR) and plant light-harvesting complex (LHC). By developing an expeditious method for structure analysis up to atomic or near atomic resolution, we would like to interpret a function of protein from the structural point of view. However, there are some difficulties in electron microscopy for structure analysis of protein. Especially, the most serious problems are the specimen damage caused by electron irradiation, the denaturation of biomolecules caused by dehydration and missing high-resolution data on electron micrographs at high-tilted angle.The irradiation damage at 8K has been found to be reduced to 1/20 compared with that at room temperature. We have, therefore, developed a high-resolution electron cryo-microscope and improved it by which images can be recorded with higher resolution than 3 Å at a specimen-stage temperature of 4.2 K, even when the specimen is highly tilted. The highly tilted data are essential for reduction of the missing corn effect.

Transparent Sol-Gel Matrices Doped with Quantum Sized PbS Particles

1994 ◽  
Vol 358 ◽  
Author(s):  
T. Gacodin ◽  
J.P. Boilot ◽  
M. Gandais ◽  
C. Ricolleau ◽  
M. Chamarro
Keyword(s):  
Electron Microscopy ◽  
Optical Properties ◽  
Absorption Spectrum ◽  
High Resolution ◽  
Lead Sulfide ◽  
Sol Gel ◽  
High Resolution Electron Microscopy ◽  
Resolution Electron ◽  
Linear Optical Properties ◽  
Lead Sulfide Nanoparticles

ABSTRACTSol-gel matrices doped with lead sulfide nanoparticles showing a structured absorption spectrum were synthesized by using the procedure previously reported for CdS doped matrices. The morphology of the PbS aggregates was investigated by high resolution electron microscopy, and the observations are correlated with the absorption spectra. Finally, preliminary results concerning some linear optical properties of the materials are presented.

Holographic Image Deconvolution in High Resolution Electron Microscopy

1974 ◽  
Vol 32 ◽  
pp. 398-399
Author(s):  
G.W. Stroke ◽  
M. Halioua ◽  
F. Thon ◽  
D. Willasch
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Negative Contrast ◽  
Chromatic Aberration ◽  
High Resolution Electron Microscopy ◽  
Partial Coherence ◽  
Image Deconvolution ◽  
Contrast Transfer Function ◽  
Spatial Frequencies ◽  
Resolution Electron

The phase contrast transfer function (CTF) for imaging of weak phase objects in high resolution electron microscopy is well known. It is an oscillating function, generating transfer intervalls with positive and negative contrast. Due to the influence of chromatic aberration and partial coherence its amplitude decreases at higher spatial frequencies. Several attempts have been made to improve the CTF by a posteriori optical filtering, e.g. zonal filtering or the use of Tsujiuchi-type phase filters. The method of holographic deconvolution, as proposed by Stroke and Halioua, employs phase and amplitude filters in such a way that the CTF approaches nearly a constant value.

High resolution phase contrast electron microscopy:imaging of single atoms and “amorphous state”

1978 ◽  
Vol 36 (1) ◽  
pp. 252-253
Author(s):  
Sumio Iijima
Keyword(s):  
High Resolution ◽  
Transfer Functions ◽  
Amorphous State ◽  
Chromatic Aberration ◽  
Pole Piece ◽  
Image Transfer ◽  
Ideal Image ◽  
Similar Phase ◽  
Better Than ◽  
The Ideal

Using very thin films of graphite crystals as support films, we demonstrated some bright-field CTEM images of single tungsten atoms and surface structures of the graphite films. Theoretical calculation on these objects using phase object approximation supported the validity of our interpretation of the images.We made a further investigation on the similar phase objects by utilizing a JEOL-UHP objective pole-piece (Cs = 0.7mm) installed in a JEM-100B microscope. This lens gives an “interpretable resolution”, , of 2.6Å. Practically, however, the attainable resolution is restricted by chromatic aberration and illumination angle, barring operational faults. These parameters modify the ideal image transfer functions in the higher frequency region and thus become important for discussing the high resolution details. The resolution measured for the new lens from the optical diffractograms was around 3.2Å, which is slightly better than the value 3.8Å for our old lens (BLG-pole-piece, Cs = 2.0mm).

The crystal structure of 4Nb2O5.9WO3 studied by 1 MV high-resolution electron microscopy

1978 ◽  
Vol 34 (6) ◽  
pp. 939-946 ◽  
Author(s):  
S. Horiuchi ◽  
K. Muramatsu ◽  
Y. Matsui
Keyword(s):  
High Resolution ◽  
Tungsten Bronze ◽  
Chromatic Aberration ◽  
High Resolution Electron Microscopy ◽  
Resolving Power ◽  
Tungsten Bronze Structure ◽  
Tetragonal Tungsten Bronze ◽  
Resolution Electron ◽  
Computer Calculations ◽  
High Resolution Electron Microscope

Images of pale yellow crystals of 4Nb2O5. 9WO3, obtained with a 1 MV high-resolution electron microscope revealed twinned domains of a tetragonal tungsten bronze structure with a superlattice of 3 x 1 subcells. Comparison with computer calculations suggests that the cations filling the pentagonal tunnels include both Nb and W. Crystals darkened due to reduction on longer heating included no domains and were sensitive to electron irradiation; cations were knocked on from the filled to the vacant pentagonal tunnels. This suggests that some oxygens are released from the -M-O-M-O-M- strings in the tunnels on reduction to weaken the chemical bonding. The number of deficient oxygens is known from the weight gain on oxidizing the crystal. Some additional experiments reveal that there is no '6Nb2O5. 1 IWO3' phase. The resolving power of the present microscope is discussed on the basis of the analysis of the chromatic aberration.

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