Three-fold astigmatism: An important TEM aberration

1993 ◽  
Vol 51 ◽  
pp. 972-973 ◽  
Author(s):  
O.L. Krivanek ◽  
M.L. Leber
Keyword(s):  
High Resolution ◽  
Spatial Frequency ◽  
Field Emission ◽  
Azimuthal Angle ◽  
Hollow Cone ◽  
Small Probe ◽  
Wide Range ◽  
High Resolution Images ◽  
Image Position

Three-fold astigmatism resembles regular astigmatism, but it has 3-fold rather than 2-fold symmetry. Its contribution to the aberration function χ(q) can be written as:where A3 is the coefficient of 3-fold astigmatism, λ is the electron wavelength, q is the spatial frequency, ϕ the azimuthal angle (ϕ = tan-1 (qy/qx)), and ϕ3 the direction of the astigmatism.Three-fold astigmatism is responsible for the “star of Mercedes” aberration figure that one obtains from intermediate lenses once their two-fold astigmatism has been corrected. Its effects have been observed when the beam is tilted in a hollow cone over a wide range of angles, and there is evidence for it in high resolution images of a small probe obtained in a field emission gun TEM/STEM instrument. It was also expected to be a major aberration in sextupole-based Cs correctors, and ways were being developed for dealing with it on Cs-corrected STEMs.

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.

Development of a conical anode Fe-gun for low voltage SEM

1988 ◽  
Vol 46 ◽  
pp. 978-979
Author(s):  
T. Miyokawa ◽  
S. Norioka ◽  
S. Goto
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Low Voltage ◽  
Irradiation Damage ◽  
Cold Cathode ◽  
Virtual Source ◽  
Source Position ◽  
Electrostatic Lens ◽  
Electrostatic Lenses ◽  
Wide Range

Field emission SEMs (FE-SEMs) are becoming popular due to their high resolution needs. In the field of semiconductor product, it is demanded to use the low accelerating voltage FE-SEM to avoid the electron irradiation damage and the electron charging up on samples. However the accelerating voltage of usual SEM with FE-gun is limited until 1 kV, which is not enough small for the present demands, because the virtual source goes far from the tip in lower accelerating voltages. This virtual source position depends on the shape of the electrostatic lens. So, we investigated several types of electrostatic lenses to be applicable to the lower accelerating voltage. In the result, it is found a field emission gun with a conical anode is effectively applied for a wide range of low accelerating voltages.A field emission gun usually consists of a field emission tip (cold cathode) and the Butler type electrostatic lens.

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.

scholarly journals Introduction to the Joint Commission Meeting on High Resolution Imaging from the Ground

1989 ◽  
Vol 8 ◽  
pp. 545-546
Author(s):  
John Davis
Keyword(s):  
High Resolution ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
High Resolution Imaging ◽  
Wide Range ◽  
High Resolution Images ◽  
Resolution Imaging ◽  
Optical Wavelengths ◽  
To Come ◽  
Very High

As a result of advances in instrumentation and techniques, from radio through to optical wavelengths, we have before us the prospect of producing very high resolution images of a wide range of objects across this entire spectral range. This prospect, and the new knowledge and discoveries that may be anticipated from it, lie behind an upsurge in interest in high resolution imaging from the ground. Several new high angular resolution instruments for radio, infrared, and optical wavelengths are expected to come into operation before the 1991 IAU General Assembly.

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.

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 New Developments in Gemini® Fesem Technology

2005 ◽  
Vol 13 (2) ◽  
pp. 8-11 ◽  
Author(s):  
H. Jaksch ◽  
J-P Vermeulen
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
High Stability ◽  
Beam Instability ◽  
New Developments ◽  
Voltage Range ◽  
Analytical Applications ◽  
Wide Range ◽  
Imaging Resolution ◽  
Stable Source

The Field Emission SEM was introduced to improve imaging resolution available with conventional SEMs with a tungsten source. Thermal assisted or Schottky Field Emission SEMs were introduced in s the nineties by a number of companies as a stable source to overcome the beam instability of the cold FESEMs introduced earlier. The Gemini® based Field Emission SEM launched by Zeiss 12 years ago has been designed from the beginning as a high stability FESEM with a relatively large multi-ported chamber. The drive to develop Gemini® technology was the need for a FESEM capable of ultra-high resolution performance over the entire accelerating voltage range that also possessed the flexibility needed for a wide range of analytical applications.

scholarly journals biPACT: a method for three-dimensional visualization of mouse spinal cord circuits of long segments with high resolution

2021 ◽  
Author(s):  
Katsuyuki Nakanishi ◽  
Munehisa Shinozaki ◽  
Narihito Nagoshi ◽  
Masaya Nakamura ◽  
Hideyuki Okano
Keyword(s):  
Spinal Cord ◽  
High Resolution ◽  
Spinal Cord Injuries ◽  
Neural Circuit ◽  
Three Dimensional ◽  
Special Equipment ◽  
Thoracic Spinal Cord ◽  
Thoracic Spinal ◽  
Wide Range ◽  
High Resolution Images

Background: The spatial complexity of neuronal circuits in the central nervous system is an hurdle in understanding and treating brain and spinal cord injuries. Although several methods have recently been developed to render the spinal cord transparent and label specific neural circuits, three-dimensional visualization of long segments of spinal cord with high resolution remains challenging. New Method: We have established a method that combines tissue staining of neuronal tracts traced with biotinylated dextran amine (BDA) and a modified passive clarity clearing protocol. Results: BDA was injected into the unilateral sensorimotor cortex of a mouse model of thoracic spinal cord contusional injury. Ten days later, the spinal cord was removed and immersed first in staining solution and then in hydrogel solution. The spinal cord was then sealed with a syringe and underwent gelation process, followed by clearing with clearing solution and observation solution. Staining and clearing took a total of two weeks. The samples were observed with a lightsheet microscope, and three-dimensional reconstruction was performed with ImageJ software. With the lightsheet microscope, high resolution-images comparable with tissue sections were obtained continuously and circumferentially. By tiling, it was possible to obtain high-resolution images of long segments of the spinal cord, in which each fiber could be traced. The tissue could be easily re-stained in case of fading. Comparison with Existing Methods: The present method does not require special equipment, can label specific circuits without genetic technology, and re-staining rounds can be easily implemented. It enables to visualize specific neural circuit of long spinal cord segments with high resolution up to individual nerve fiber. Conclusions: By using simple neural labeling, staining, and transparency methods, it was possible to acquire a wide range of high-resolution three-dimensional images of the spinal cord.

Yorktown display architecture

1984 ◽  
Vol 42 ◽  
pp. 554-555
Author(s):  
Satish Gupta
Keyword(s):  
High Resolution ◽  
Computer Aided Design ◽  
Memory Systems ◽  
Display System ◽  
The Past ◽  
Wide Range ◽  
Raster Scan ◽  
Watson Research ◽  
High Resolution Images ◽  
Aided Design

The advances in VLSI and CRT technology over the past ten years have resulted in feasible implementations of raster-scan displays capable of displaying complex images with reasonably high resolutions. Single chips capable of storing 64 Kilobits can be used to build memory systems capable of storing such high resolution images. The ability to manipulate these high resolution images interactively requires the ability to change a large amount of information rather rapidly.At the IBM Thomas J. Watson Research Center, we have built a display system which addresses the problem of changing high resolution display images rapidly. The system was design to allow the rapid manipulating of images in wide range of applications. The applications planned include text formatting, computer aided design, and image processing applications which process digitized images.

A field-emission SEM optimized for operation at low beam voltage

1993 ◽  
Vol 51 ◽  
pp. 630-631
Author(s):  
JB Pawley ◽  
J Ximen ◽  
PS-D Lin ◽  
M. Schippert
Keyword(s):  
High Resolution ◽  
Radiation Damage ◽  
Field Emission ◽  
Secondary Electron ◽  
Structural Features ◽  
Objective Lens ◽  
Beam Diameter ◽  
Beam Voltage ◽  
High Resolution Images ◽  
Topographic Imaging

The advantages of operating the SEM at low beam voltage (V0 ) have been recognized for some time. They include: less specimen charging, greater contrast in the fine topographic component of the secondary electron (SE) signal and reduced radiation damage. Although initially it was difficult to obtain high resolution images when using low V0, this limitation can be essentially overcome by employing both a FE source and an immersion objective lens. In an instrument employing both of these features it is possible to produce a beam diameter of about 3 nm @ 1.5 kV. When insulating specimens are viewed under these conditions, the resolution in the image is limited more by the structure of the coating material than by the beam diameter, while on conductors, small structural features produce useful contrast only at low V0.The remaining obstacle to more widespread use of LVSEM for high resolution topographic imaging is the high cost of the equipment.

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