The Use of Phase and Amplitude Information of Reconstructed Exit Waves

1997 ◽  
Vol 3 (S2) ◽  
pp. 1029-1030
Author(s):  
H.W. Zandbergen
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
High Resolution ◽  
Field Emission ◽  
Software Package ◽  
Dynamic Range ◽  
Ccd Camera ◽  
Phase Object ◽  
High Resolution Images

Exit waves can be reconstructed from through focus series of HREM images or by off-axis holography [1]. We have applied the through focus method to reconstruct exit waves, using algorithms developed by Van Dyck and Coene [2]. Electron microscopy was performed with a Philips CM30ST electron microscope with a field emission gun operated at 300 kV. The high resolution images were recorded using a Tietz software package and a 1024x1024 pixel Photometrix CCD camera having a dynamic range of 12 bits. The reconstructions were done using 15-20 images with focus increments of 5.2 nm. The resulting exit waves were corrected posteriorly for the three fold astigmatism.The exit wave is complex; consequently it contains phase and amplitude. Since in the very thin regions the specimen acts as a thin phase object, such a thin area will show little contrast, an example of which is shown in Figure 1.

Field Emission SEM Equipped With Noise Compensator

1973 ◽  
Vol 31 ◽  
pp. 302-303
Author(s):  
S. Saito ◽  
H. Todokoro ◽  
S. Nomura ◽  
T. Komoda
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Scanning Electron Microscope ◽  
Field Emission ◽  
Low Contrast ◽  
Probe Current ◽  
High Resolution Images ◽  
Scanning Electron

Field emission scanning electron microscope (FESEM) features extremely high resolution images, and offers many valuable information. But, for a specimen which gives low contrast images, lateral stripes appear in images. These stripes are resulted from signal fluctuations caused by probe current noises. In order to obtain good images without stripes, the fluctuations should be less than 1%, especially for low contrast images. For this purpose, the authors realized a noise compensator, and applied this to the FESEM.Fig. 1 shows an outline of FESEM equipped with a noise compensator. Two apertures are provided gust under the field emission gun.

Application of hollow-cone illumination to High-resolution electron microscopy

1991 ◽  
Vol 49 ◽  
pp. 692-693
Author(s):  
R.A. Herring
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Objective Lens ◽  
Hollow Cone ◽  
Lattice Image ◽  
Resolution Electron ◽  
High Resolution Images ◽  
Z Contrast

TEM hollow cone illumination can produce high resolution images having atomic number (Z) contrast within a lattice image. Inorder to produce these images, the contribution of four sources of electrons should be considered. These are the main, inelastically scattered, elastically scattered, and diffracted beams. This abstract discusses these sources of electrons to the hollow cone (HC) image, and then goes further to propose a possible method of extending the resolution of the electron microscope by using diffracted HC beams to form holograms which should remove the limitation on resolution imposed by the objective lens and inelastically scattered electrons. A Philips EM 430T was used to take the electron micrographs.

scholarly journals Simulated Image Maps for Use in Experimental High-Resolution Electron Microscopy

1989 ◽  
Vol 159 ◽  
Author(s):  
Michael A. O'Keefe ◽  
Ulrich Dahmen ◽  
Crispin J.D. Hetherington
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Perfect Crystal ◽  
Phase Object ◽  
Simulated Image ◽  
Transmission Electron ◽  
Resolution Electron ◽  
High Resolution Images ◽  
Imaging Conditions

ABSTRACTA “map” of all possible high-resolution images may be simulated for a crystalline specimen in a chosen orientation for any particular transmission electron microscope (HRTEM). These maps are useful during experimental high-resolution electron microscopy and make it possible to locate optimum imaging conditions even for foil thicknesses beyond the weak-phase object limit. Although defects such as grain boundaries are not generally periodic, image maps of perfect crystal can be used to optimize defect contrast during operation of the microscope by reference to the image of the perfect crystal neighboring the defect.

Development of Field Emission Electron Gun for High Resolution 100KV Electron Microscope

1972 ◽  
Vol 30 ◽  
pp. 430-431 ◽  
Author(s):  
T. Someya ◽  
T. Goto ◽  
Y. Harada ◽  
M. Watanabe
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
High Resolution ◽  
Field Emission ◽  
High Resolution Electron Microscopy ◽  
Electron Gun ◽  
Emission Source ◽  
Resolving Power ◽  
Emission Electron ◽  
Resolution Electron

The field emission source is one of the most important factors to improve the image contrast in extremely high resolution electron microscopy since it provides high brightness, very small electron source and low energy spread of electrons. In scanning electron microscopy, although the field emission source has been proved to be advantageous in the range of relatively low accelerating voltages, those capable of operating at higher accelerating voltages are now in great demand in order to improve the resolving power up to 3Å or better. In the present work, we have developed a field emission electron gun which is used with an electron microscope of accelerating voltages up to 100KV.In this development, we first made efforts to improve the method of supplying high voltages in order to eliminate the surge influence on the field emission source which are easily destroyed by a high voltage surge produced by the discharge between electrodes constituting the electron gun.

Contrast in High Resolution Images of Crystals

1972 ◽  
Vol 30 ◽  
pp. 558-559
Author(s):  
P. L. Fejes
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Phase Change ◽  
Octahedral Site ◽  
Phase Object ◽  
Maximum Phase ◽  
Resolution Electron ◽  
Microscope Images ◽  
High Resolution Images ◽  
High Resolution Electron Microscope

An attempt is made to understand experimentally observed high resolution electron microscope images. Iijima has obtained images that are good representations of the crystal potentials for a resolution of about 3Å using a defocus corresponding to the “optimum defocus condition”. This is to be expected for a thin phase object. However, Iijima's images are obtained from crystals having thicknesses of 100Å and greater for which the maximum phase change is more than 10 radians, and so the thin phase object approximation is not expected to be valid. These images must therefore be explained by other means.Many beam calculations have been made on thick crystals using a trial crystals structure as shown in Fig. 1. A metal atom sits at the centre of each octahedral site with oxygen atoms at the corners. This structure contains blocks of 3 x 3 octahedra of the type found in disordered samples of Ti2Nb10O29 as shown in Fig. 2.

A Base Specific Single Heavy Atom Stain for Electron Microscopy

1972 ◽  
Vol 30 ◽  
pp. 184-185
Author(s):  
J. P. Langmore ◽  
N. R. Cozzarelli ◽  
A. V. Crewe
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
High Resolution ◽  
Elastic Scattering ◽  
Heavy Atom ◽  
High Vacuum ◽  
Heavy Atoms ◽  
Large Movement ◽  
Base Sequencing ◽  
Scanning Electron

A system has been developed to allow highly specific derivatization of the thymine bases of DNA with mercurial compounds wich should be visible in the high resolution scanning electron microscope. Three problems must be completely solved before this staining system will be useful for base sequencing by electron microscopy: 1) the staining must be shown to be highly specific for one base, 2) the stained DNA must remain intact in a high vacuum on a thin support film suitable for microscopy, 3) the arrangement of heavy atoms on the DNA must be determined by the elastic scattering of electrons in the microscope without loss or large movement of heavy atoms.

High Resolution Scanning Electron Microscopy

1991 ◽  
Vol 49 ◽  
pp. 478-479
Author(s):  
David Joy ◽  
James Pawley
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Beam ◽  
Electron Microscope ◽  
High Resolution ◽  
Scanning Electron Microscope ◽  
Electron Probe ◽  
Impact Point ◽  
Interaction Volume ◽  
Scanning Electron

The scanning electron microscope (SEM) builds up an image by sampling contiguous sub-volumes near the surface of the specimen. A fine electron beam selectively excites each sub-volume and then the intensity of some resulting signal is measured. The spatial resolution of images made using such a process is limited by at least three factors. Two of these determine the size of the interaction volume: the size of the electron probe and the extent to which detectable signal is excited from locations remote from the beam impact point. A third limitation emerges from the fact that the probing beam is composed of a finite number of discrete particles and therefore that the accuracy with which any detectable signal can be measured is limited by Poisson statistics applied to this number (or to the number of events actually detected if this is smaller).

Principle and practice of high-resolution imaging with a field-emission TEM

1992 ◽  
Vol 50 (1) ◽  
pp. 138-139
Author(s):  
Max T. Otten ◽  
Wim M.J. Coene
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Incidence Angle ◽  
Temporal Coherence ◽  
Energy Spread ◽  
High Resolution Imaging ◽  
Major Improvement ◽  
High Resolution Images ◽  
Resolution Imaging

High-resolution imaging with a LaB6 instrument is limited by the spatial and temporal coherence, with little contrast remaining beyond the point resolution. A Field Emission Gun (FEG) reduces the incidence angle by a factor 5 to 10 and the energy spread by 2 to 3. Since the incidence angle is the dominant limitation for LaB6 the FEG provides a major improvement in contrast transfer, reducing the information limit to roughly one half of the point resolution. The strong improvement, predicted from high-resolution theory, can be seen readily in diffractograms (Fig. 1) and high-resolution images (Fig. 2). Even if the information in the image is limited deliberately to the point resolution by using an objective aperture, the improved contrast transfer close to the point resolution (Fig. 1) is already worthwhile.

Electron holography of p-n junctions

1996 ◽  
Vol 54 ◽  
pp. 974-975
Author(s):  
B.G. Frost ◽  
D.C. Joy ◽  
L.F. Allard ◽  
E. Voelkl
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Field Emission ◽  
Ccd Camera ◽  
Image Plane ◽  
Reference Wave ◽  
Field Of View ◽  
Control Mode ◽  
Objective Lens ◽  
Electron Holography

A wide holographic field of view (up to 15 μm in the Hitachi-HF2000) is achieved in a TEM by switching off the objective lens and imaging the sample by the first intermediate lens. Fig.1 shows the corresponding ray diagram for low magnification image plane off-axis holography. A coherent electron beam modulated by the sample in its amplitude and its phase is superimposed on a plane reference wave by a negatively biased Möllenstedt-type biprism.Our holograms are acquired utilizing a Hitachi HF-2000 field emission electron microscope at 200 kV. Essential for holography are a field emission gun and an electron biprism. At low magnification, the excitation of each lens must be appropriately adjusted by the free lens control mode of the microscope. The holograms are acquired by a 1024 by 1024 slow-scan CCD-camera and processed by the “Holoworks” software. The hologram fringes indicate positively and negatively charged areas in a sample by the direction of the fringe bending (Fig.2).

Computers and diffraction analysis

1989 ◽  
Vol 47 ◽  
pp. 44-45
Author(s):  
J. A. Eades
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Diffraction Analysis ◽  
Electron Diffraction Analysis ◽  
Image Simulation ◽  
Correct Interpretation ◽  
High Profile ◽  
High Resolution Images ◽  
Image Simulations

For well over two decades computers have played an important role in electron microscopy; they now pervade the whole field - as indeed they do in so many other aspects of our lives. The initial use of computers was mainly for large (as it seemed then) off-line calculations for image simulations; for example, of dislocation images.Image simulation has continued to be one of the most notable uses of computers particularly since it is essential to the correct interpretation of high resolution images. In microanalysis, too, the computer has had a rather high profile. In this case because it has been a necessary part of the equipment delivered by manufacturers. By contrast the use of computers for electron diffraction analysis has been slow to prominence. This is not to say that there has been no activity, quite the contrary; however it has not had such a great impact on the field.

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