Transmission Scanning Electron Microscopy and Energy Analysis with the Siemens ELMISKOP 101

1972 ◽  
Vol 30 ◽  
pp. 450-451
Author(s):  
H. M. Thieringer
Keyword(s):  
Objective Lens ◽  
Transmission Microscopy ◽  
Image Recording ◽  
Mode Of Operation ◽  
Scanning Transmission ◽  
Electron Microscopes ◽  
And Performance ◽  
Convergent Beam ◽  
Ray Path ◽  
Beam Diffraction

It has repeatedly been show that with conventional electron microscopes very fine electron probes can be produced, therefore allowing various micro-techniques such as micro recording, X-ray microanalysis and convergent beam diffraction. In this paper the function and performance of an SIEMENS ELMISKOP 101 used as a scanning transmission microscope (STEM) is described. This mode of operation has some advantages over the conventional transmission microscopy (CTEM) especially for the observation of thick specimen, in spite of somewhat longer image recording times.Fig.1 shows schematically the ray path and the additional electronics of an ELMISKOP 101 working as a STEM. With a point-cathode, and using condensor I and the objective lens as a demagnifying system, an electron probe with a half-width ob about 25 Å and a typical current of 5.10-11 amp at 100 kV can be obtained in the back focal plane of the objective lens.

Reduction of Specimen Contamination in Electron-Beam Instruments

1976 ◽  
Vol 34 ◽  
pp. 576-577
Author(s):  
G. Lehmpfuhl ◽  
P. J. Smith
Keyword(s):  
Electron Beam ◽  
Cold Trap ◽  
Beam Diameter ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Hydrocarbon Molecules ◽  
Electron Microscopes ◽  
Combination Of Methods ◽  
Convergent Beam ◽  
Very High

Specimens being observed with electron-beam instruments are subject to contamination, which is due to polymerization of hydrocarbon molecules by the beam. This effect becomes more important as the size of the beam is reduced. In convergent-beam studies with a beam diameter of 100 Å, contamination was observed to grow on samples at very high rates. Within a few seconds needles began forming under the beam on both the top and the underside of the sample, at growth rates of 400-500 Å/s, severely limiting the time available for observation. Such contamination could cause serious difficulty in examining a sample with the new scanning transmission electron microscopes, in which the beam is focused to a few angstroms.We have been able to reduce the rate of contamination buildup by a combination of methods: placing an anticontamination cold trap in the sample region, preheating the sample before observation, and irradiating the sample with a large beam before observing it with a small beam.

A High Resolution Dual Gun Electron Miscroscope for TEM and SEM

1974 ◽  
Vol 32 ◽  
pp. 422-423
Author(s):  
P. S. Ong ◽  
C. L. Gold
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Spot Size ◽  
Resolving Power ◽  
Objective Lens ◽  
Scanning System ◽  
Transmission Electron ◽  
Mode Of Operation ◽  
Electron Microscopes ◽  
Scanning Electron

Transmission electron microscopes (TEM) have the capability of producing an electron spot (probe) with a diameter equal to its resolving power. Inclusion of the required scanning system and the appropriate detectors would therefore easily convert such an instrument into a high resolution scanning electron microscope (SEM). Such an instrument becomes increasingly useful in the transmission mode of operation since it allows the use of samples which are considered too thick for conventional TEM. SEM accessories now available are all based on the use of the prefield of the objective lens to focus the beam. The lens is operated either as a symmetrical Ruska lens or its asymmetrical version. In these approaches, the condensor system of the microscope forms part of the reducing optics and the final spot size is usually larger than 20Å.

Practical Examples of Point and Space Group Determination in Convergent Beam Diffraction

1980 ◽  
Vol 38 ◽  
pp. 188-191 ◽  
Author(s):  
J.W. Steeds ◽  
N.S. Evans
Keyword(s):  
Stacking Faults ◽  
Objective Lens ◽  
High Symmetry ◽  
Space Group ◽  
Thermal Disorder ◽  
Order Of Magnitude ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Unambiguous Assignment

The high quality of diffraction information generated by convergent beam electron microscopy provides many ways of arriving at an unambiguous assignment of a space group to a crystal under investigation. One method of space group determination involves tilting the crystal to a number of different zone axes and combining the information derived from each. However, it is often possible to obtain the same information more efficiently by concentrating on just one high symmetry zone axis and it is this approach which will be illustrated here. The prerequisites for the application of the technique are a good crystal and a microscope which offers a large angular view of the back focal plane of the objective lens. Specimen cooling is generally advantageous but has not been used in most of our work and, in particular, was not used for the results used as illustrations here. By the term 'good' crystal is meant a homogeneous and strain-free crystal without planar disorder (stacking faults, antiphase boundaries) linear disorder (dislocations) or point disorder. The requirements are certainly stringent but they need only operate over a cube of side approximately 1OO nm. Point disorder which produces an effect of the same order of magnitude as thermal disorder can be tolerated and strains less than 10-4are not detected. An angular view of 20° or so in the diffraction plane is generally acceptable although a larger view would be helpful for certain crystal structures and for low-specimen temperatures.

Multi-dimensional and multi-signal approaches in scanning transmission electron microscopes

2009 ◽  
Vol 367 (1903) ◽  
pp. 3845-3858 ◽  
Author(s):  
C. Colliex ◽  
N. Brun ◽  
A. Gloter ◽  
D. Imhoff ◽  
M. Kociak ◽  
...  
Keyword(s):  
Energy Resolution ◽  
Spherical Aberration ◽  
Objective Lens ◽  
Performance Limits ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Successful Design ◽  
Electron Microscopes ◽  
Data Acquisition And Processing ◽  
Available Information

Developments in instrumentation are essential to open new fields of science. This clearly applies to electron microscopy, where recent progress in all hardware components and in digitally assisted data acquisition and processing has radically extended the domains of application. The demonstrated breakthroughs in electron optics, such as the successful design and practical realization and the use of correctors, filters and monochromators, and the permanent progress in detector efficiency have pushed forward the performance limits, in terms of spatial resolution in imaging, as well as for energy resolution in electron energy-loss spectroscopy (EELS) and for sensitivity to the identification of single atoms. As a consequence, the objects of the nanoworld, of natural or artificial origin, can now be explored at the ultimate atomic level. The improved energy resolution in EELS, which now encompasses the near-IR/visible/UV spectral domain, also broadens the range of available information, thus providing a powerful tool for the development of nanometre-level photonics. Furthermore, spherical aberration correctors offer an enlarged gap in the objective lens to accommodate nanolaboratory-type devices, while maintaining angström-level resolution for general characterization of the nano-object under study.

The Application of SEM Techniques to the Study of Crystal Defects

1973 ◽  
Vol 31 ◽  
pp. 154-155
Author(s):  
M.N. Thompson
Keyword(s):  
Scanning Transmission Electron Microscopy ◽  
Crystal Defects ◽  
Scanning Probe ◽  
Objective Lens ◽  
Scattered Electron ◽  
Backscattered Electrons ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Viewing Screen ◽  
Convergent Beam

The present study is directed to the imaging of dislocations using backscattered electrons and verification that defect analysis procedures established using TEM techniques can also be applied to scanning transmission electron microscopy (STEM). A SEM attachment based on the design of Ong coupled to a Philips EM300 microscope equipped with goniometer stage was used in this investigation. Fundamental to the design of this TEM/STEM system, which utilises a Riecke-Ruska condenser-objective lens, is the formation of a convergent beam diffracttion pattern whose intensity distribution is dependent only on the scattering processes in the crystal and independent of the scanning probe position. The presence of this stationary diffraction pattern allows the crystal orientation to be monitored on the TEM viewing screen during STEM operation and assists accurate collection of a specific scattered electron fraction for image formation.

Combined CTEM and STEM using a condenser-objective lens and 100kv LaB6 gun

1978 ◽  
Vol 36 (1) ◽  
pp. 2-3
Author(s):  
S.P. Beaumont ◽  
H. Ahmed
Keyword(s):  
Electron Microscopy ◽  
Scanning Transmission Electron Microscopy ◽  
Objective Lens ◽  
Magnetic Vector Potential ◽  
Schematic Diagram ◽  
Magnetic Vector ◽  
Modes Of Operation ◽  
Transmission Electron ◽  
Mode Of Operation ◽  
Scanning Transmission

In order to study the differences in contrast that are observed in conventional and scanning transmission electron microscopy, a new microscope has been designed and constructed to examine the same area of a specimen in either mode of operation at a resolution of lnm or better.A schematic diagram of the instrument is shown in Fig.1 for each of its modes of operation. It operates at voltages of up to 100kV and uses an LaB6 gun that provides a 10 micron source which may be aligned using the coils marked A1. In the STEM mode this source is demagnified by two strong condenser lenses Cl & C2 (fp,min = 1.75mm) and finally by the prefield of a saturated condenser-objective lens (CO) in the centre of which the specimen is immersed. These lenses were designed with the aid of magnetic vector potential programs. A further program was written to calculate the characteristic trajectories and aberration coefficients of the condenser-objective.

Improving the accuracy of convergent-beam thickness measurements

1988 ◽  
Vol 46 ◽  
pp. 520-521
Author(s):  
K. K. Christenson
Keyword(s):  
Objective Lens ◽  
Fringe Spacing ◽  
Underlying Assumption ◽  
Angular Scale ◽  
Beam Thickness ◽  
Extinction Length ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Thickness Measurements ◽  
Beam Diffraction

Convergent-beam diffraction patterns taken at appropriate “two-beam” conditions allow simple, rapid determinations of a specimen's thickness, extinction length and even its anomalous absorption coefficient (1,2). We here note three points to consider when obtaining the pattern.First, in thickness measurements the ratio of the fringe spacing to the spacing between the disks is utilized; there is an underlying assumption that the two distances are on the same angular scale. This assumption is incorrect if the illumination crossover is not in the plane of the specimen and simultaneously, the diffraction lens is focused incorrectly. If the crossover is at the specimen (Fig. 1a), varying the focus of the diffraction lens (changing w) varies the distance between the disks and the sizes of features within the disks in the same way, only the magnification of the pattern is changed. Likewise, if the diffraction lens is focused correctly, on the back focal plane of the objective lens, the angular scale within the disks matches that between the disks and neither scale is affected by variations in the illumination.

High-Resolution Analysis of Rapidly Frozen Biological Specimens: Capabilities and Limitations

1999 ◽  
Vol 5 (S2) ◽  
pp. 412-413
Author(s):  
S.B. Andrews ◽  
N.B. Pivovarova ◽  
J. Hongpaisan ◽  
R.D. Leapman
Keyword(s):  
Low Temperature ◽  
Low Dose ◽  
Biological Tissues ◽  
Transmission Microscopy ◽  
Energy Filtering ◽  
Freeze Dried ◽  
Scanning Transmission ◽  
Analytical Microscopy ◽  
Electron Microscopes ◽  
Mapping Techniques

The past decade has seen major advances in the analytical capability and utility of both fixed beam and scanning beam electron microscopes. In particular, scanning transmission electron microscopy (STEM) and energy-filtering transmission microscopy (EFTEM) have benefited from the development of devices and techniques—including improved electron optics, sensitive solid-state detectors and new software for imaging and electron energy loss spectroscopy (EELS)—that optimize detection of weak spectroscopic signals arising from biological specimens while minimizing specimen damage. Here we discuss and illustrate some of these advances, especially in the context of structural imaging, detection limits and mapping techniques for the biologically important elements phosphorus and calcium. Analytical microscopy of biological tissues is absolutely dependent on cryotechniques. It is generally agreed that rapid freezing and subsequent low-temperature processing, e.g., cryosectioning or direct cryotransfer of frozen-hydrated specimens, is the most reliable way to preserve the native distribution and organization of biological structures. Equally important, however, as an adjunct to spectroscopic analysis is the use of established low-temperature, low-dose techniques for recording optimized images. By limiting beam exposure, low-dose methods greatly improve the quality of images from fragile, freeze-dried preparations. In this case, the quality and information content of, e.g., cryosections are virtually as good as conventional preparations (Fig 1).

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.

Enhancement of Contrast in the CEM and STEM Using Bumpy Specimens and Employing the “Dappled Field” Mode of Operation

1974 ◽  
Vol 32 ◽  
pp. 552-553 ◽  
Author(s):  
L. Gandolfi ◽  
J. Reiffel
Keyword(s):  
Operating Mode ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Specimen Preparation ◽  
Field Mode ◽  
Preparation Methods ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Mode Of Operation ◽  
Scanning Transmission

Calculations have been performed on the contrast obtainable, using the Scanning Transmission Electron Microscope, in the observation of thick specimens. Recent research indicates a revival of an earlier interest in the observation of thin specimens with the view of comparing the attainable contrast using both types of specimens.Potential for biological applications of scanning transmission electron microscopy has led to a proliferation of the literature concerning specimen preparation methods and the controversy over “to stain or not to stain” in combination with the use of the dark field operating mode and the same choice of technique using bright field mode of operation has not yet been resolved.

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