Phase contrast, contrast transfer function (CTF) and high‐resolution electron microscopy (HRTEM)

2011 ◽  
pp. 131-155
Author(s):  
Xiaodong Zou ◽  
Sven Hovmöller ◽  
Peter Oleynikov
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Transfer Function ◽  
Phase Contrast ◽  
High Resolution Electron Microscopy ◽  
Contrast Transfer Function ◽  
Resolution Electron

Possible applications of fraunhofer holography in high resolution electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 222-223 ◽  
Author(s):  
N. Bonnet ◽  
M. Troyon ◽  
P. Gallion
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Transfer Function ◽  
Radiation Damage ◽  
High Resolution Electron Microscopy ◽  
Far Field ◽  
Field Region ◽  
Crystalline Materials ◽  
Resolution Electron ◽  
The Ideal

Two main problems in high resolution electron microscopy are first, the existence of gaps in the transfer function, and then the difficulty to find complex amplitude of the diffracted wawe from registered intensity. The solution of this second problem is in most cases only intended by the realization of several micrographs in different conditions (defocusing distance, illuminating angle, complementary objective apertures…) which can lead to severe problems of contamination or radiation damage for certain specimens.Fraunhofer holography can in principle solve both problems stated above (1,2). The microscope objective is strongly defocused (far-field region) so that the two diffracted beams do not interfere. The ideal transfer function after reconstruction is then unity and the twin image do not overlap on the reconstructed one.We show some applications of the method and results of preliminary tests.Possible application to the study of cavitiesSmall voids (or gas-filled bubbles) created by irradiation in crystalline materials can be observed near the Scherzer focus, but it is then difficult to extract other informations than the approximated size.

HIGH RESOLUTION ELECTRON MICROSCOPE STUDY OF CdTe-Cd0.6Mn0.4 Te SUPERLATTICES

1985 ◽  
Vol 56 ◽  
Author(s):  
C. CHOI ◽  
N. OTSUKA ◽  
L. A. KOLODZIEJSKI ◽  
R. L. GUNSHOR-a
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Phase Contrast ◽  
Electron Microscope Study ◽  
Lattice Mismatch ◽  
Thick Layer ◽  
High Resolution Electron Microscopy ◽  
Misfit Dislocations ◽  
Resolution Electron ◽  
High Resolution Electron Microscope

AbstractStructures of CdTe-Cd0.6Mn0.4Te superlattices which are caused by the lattice mismatch between suterlattice layers have been studied by high resolution electron microscopy (HREM). In thin-layer superlattices, the crystal lattice in each layeris elastically distorted, resulting in the change of the crystal symmetry from cubic to rhombohedral. The presence of the small rhombohedral distrotion has been confirmed through a phase contrast effect in HREM images. In a thick-layer superlattice, the lattice mismatch is accommodated by dissociated misfit dislocations. Burgers vectors of partial misfit dislocations have been identified from the shift of lattice fringes in HREM images.

Fourier spectrum analysis of phase contrast of support film

1978 ◽  
Vol 36 (1) ◽  
pp. 170-171
Author(s):  
Tetsuo Oikawa ◽  
Fumiko Ishigaki ◽  
Kiichi Hojou ◽  
Koichi Kanaya
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Phase Shift ◽  
Phase Contrast ◽  
Fourier Transforms ◽  
Spherical Aberration ◽  
High Resolution Electron Microscopy ◽  
Spatial Frequencies ◽  
Resolution Electron ◽  
Atomic Phase

In high resolution electron microscopy, it is most important to determine the defocus of electron micrographs of amorphous support films. The variation of spatial frequencies of phase contrast of support films was obtained from the phase shift of the electron waves caused by defocus and spherical aberration as well as the atomic phase, which are demonstrated by use of optical Fourier transforms. The spatial frequencies of phase contrast of films of tungsten, prepared by ion bombardment, which are useful as support films for high resolution electron microscopy, has been discussed analytically.Taking account of atomic phase shift, the transfer function, which was originally presented by Thon (1966), was modified. Optical Fourier transforms are in similar to the calculated Fourier transforms of corre- sponding computed images. Accordingly, it turned out that the atomic phase shift should not be neglected. The thickness of tungsten film, in case of less than 2 nm thickness, can be determined by comparing the optical Fourier transforms with the calculated ones.

High Resolution Electron Microscopy Using Phase Plates

1971 ◽  
Vol 29 ◽  
pp. 38-39
Author(s):  
F. Thon ◽  
D. Willasch
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Focal Plane ◽  
Phase Contrast ◽  
High Resolution Electron Microscopy ◽  
Dominant Factor ◽  
Objective Lens ◽  
Resolution Electron ◽  
Optical Reconstruction ◽  
Transfer Properties

The phase contrast transfer properties of objective lenses used in electron microscopy are not at all satisfactory and therefore the interpretation of phase contrast images is quite limited in the high resolution field. Phase contrast, however, is the dominant factor in creating contrast in high resolution electron microscopy. This is why methods which promise to improve the transfer conditions are of great importance.A series of experiments has been reported to improve the contrast transfer conditions by zonal or semicircular filtering in the back focal plane of the objective lens or in subsequent light optical reconstruction. By these methods the transfer properties can be improved only to a certain degree.For ideal imaging a transfer function would be desirable that is of constant value for the whole spatial frequency spectrum relevant to high resolution microscopy. This should in principle be attainable by inserting a phase shifting foil of varying thickness into the back focal plane.

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.

scholarly journals Advancing conventional High-Resolution Electron Microscopy

1991 ◽  
Vol 49 ◽  
pp. 652-653
Author(s):  
Ronald Gronsky
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Phase Contrast ◽  
High Resolution Electron Microscopy ◽  
Phase Contrast Imaging ◽  
Contrast Imaging ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Imaging Resolution ◽  
Electron Microscopes

Due to the exceptional performance of most modern commercial transmission electron microscopes, the achievement of phase-contrast imaging resolution in the sub-2Å range is today a routine exercise, provided the samples are compliant. Nonetheless, there remains room for improvement, and the purpose of this manuscript is to highlight procedures that might be employed by the practicing microscopist for advancing conventional high resolution electron microscopy.

Phase contrast of tungsten support films for high resolution electron microscopy

Micron (1969) ◽  
1977 ◽  
Vol 8 (1-2) ◽  
pp. 63-76 ◽  
Author(s):  
K. Kanaya ◽  
T. Oikawa ◽  
K. Hojou ◽  
S. Ono ◽  
E. Watanabe ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Phase Contrast ◽  
High Resolution Electron Microscopy ◽  
Resolution Electron

Structural analysis of the surface-layer protein of spirillum serpens by high-resolution electron microscopy

1983 ◽  
Vol 41 ◽  
pp. 738-739
Author(s):  
W. H. Wu ◽  
R. M. Glaeser
Keyword(s):  
Electron Microscopy ◽  
Surface Layer ◽  
Structural Analysis ◽  
High Resolution ◽  
Low Dose ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
Surface Layer Protein ◽  
Morphological Unit ◽  
Resolution Electron

Spirillum serpens possesses a surface layer protein which exhibits a regular hexagonal packing of the morphological subunits. A morphological model of the structure of the protein has been proposed at a resolution of about 25 Å, in which the morphological unit might be described as having the appearance of a flared-out, hollow cylinder with six ÅspokesÅ at the flared end. In order to understand the detailed association of the macromolecules, it is necessary to do a high resolution structural analysis. Large, single layered arrays of the surface layer protein have been obtained for this purpose by means of extensive heating in high CaCl2, a procedure derived from that of Buckmire and Murray. Low dose, low temperature electron microscopy has been applied to the large arrays.As a first step, the samples were negatively stained with neutralized phosphotungstic acid, and the specimens were imaged at 40,000 magnification by use of a high resolution cold stage on a JE0L 100B. Low dose images were recorded with exposures of 7-9 electrons/Å2. The micrographs obtained (Fig. 1) were examined by use of optical diffraction (Fig. 2) to tell what areas were especially well ordered.

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