In-Lens Low-Loss Electron Detector for the Upper Specimen Stage in the Scanning Electron Microscope

1990 ◽  
Vol 48 (1) ◽  
pp. 382-383
Author(s):  
Oliver C. Wells ◽  
Françoise K. LeGoues ◽  
Rodney T. Hodgson
Keyword(s):  
Magnetic Field ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Chromatic Dispersion ◽  
Incident Beam ◽  
Objective Lens ◽  
Low Loss ◽  
Backscattered Electrons ◽  
Energy Filtering ◽  
Scanning Electron

For the best resolution in either the scanning electron microscope (SEM) or the transmission electron microscope (TEM) the sample must be mounted in the high-field region of a condenser-objective lens. Detectors for either the secondary electrons (SE) or the backscattered electrons (BSE) in the SEM must allow for the fact that both of these are strongly deflected by the focusing magnetic field of the lens. Typically the SE are collected above the lens, while the BSE are collected using either diode(s) or scintillator(s) between the polepieces.Low-loss electrons (LLE) are scattered from a solid target with an energy loss of less than a few percent of the incident beam energy. These can be collected from a steeply tilted sample from below the exit polepiece of a condenser-objective lens. A suggestion to use the second half of the lens field as an energy filter was shown to by Munro to be unlikely to work because the chromatic dispersion of this part of the lens field is insufficient.The magnetic field of a condenser-objective lens can provide energy filtering as follows.A flat sample is mounted at typically 25° to 30° from the horizontal at or near the center of the lens. Figure 1 shows the trajectories of the electrons scattered with no loss of energy as calculated by Munro. These electrons are confined within a “containment region” with a well-defined boundary beyond which they cannot go. If a suitable detector is placed just inside the surface of this region then it will collect LLE. The slower BSE are confined within a smaller region and so are not collected.

Improved in-lens low-loss electron detector for the Scanning Electron Microscope

1991 ◽  
Vol 49 ◽  
pp. 480-481
Author(s):  
Oliver C. Wells ◽  
Eric Munro
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Beam Energy ◽  
High Field ◽  
Incident Beam ◽  
Objective Lens ◽  
Low Loss ◽  
Incident Beam Energy ◽  
The Magnetic Field ◽  
Scanning Electron

We have built an improved version of in-lens low-loss electron (LLE) detector for the scanning electron microscope (SEM) in which the LLE are energy-filtered by the focusing field. The sample is in the high-field region of a condenser-objective lens (Fig. 1). The fastest scattered electrons are then confined by the magnetic field of the lens into a region with a well-defined outer surface (Fig. 1(b)). A detector is moved under micrometer control to be just inside this surface. In this way, only the fastest scattered electrons (which are the LLE) are collected. In the earlier work, the detector was a flat aluminized garnet scintillator. This showed that the method did work but required that the incident beam energy E0 should be greater than the energy threshold of the scintillator.

Optimizing the collector solid angle for the low-loss electron image in the Scanning Electron Microscope

1987 ◽  
Vol 45 ◽  
pp. 548-549 ◽  
Author(s):  
Oliver C. Wells
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Solid Angle ◽  
Angle Of Incidence ◽  
Tungsten Filament ◽  
Low Loss ◽  
Backscattered Electrons ◽  
Glancing Angle ◽  
Electron Image ◽  
Scanning Electron

The low-loss electron (LLE) image in the scanning electron microscope (SEM) is formed by collecting backscattered electrons (BSE) that have lost less than a specified energy. Compared to the secondary electron (SE) image, these images are less affected by specimen charging and show the surface topography clearly when examining uncoated photoresist. However, LLE images sometimes contain dark shadows caused by the limited solid angle of the LLE detector. Here, we describe a way to position the sample (with a given LLE detector) so as to reduce these shadows as far as possible.The SEM was a Cambridge S-250 Mk. III with a tungsten filament. An experimental LLE detector was added. The SE image was obtained using the SE detector ordinarily present in the SEM.The LLE detector is shown in Fig. 1. The specimen is mounted close to the lens in the SEM with a glancing angle of incidence of 30°.

Observability of Very Thick Specimen by Using Transmission Scanning Electron Microscope

1971 ◽  
Vol 29 ◽  
pp. 26-27
Author(s):  
K. Shibatomi ◽  
T. Yamanoto ◽  
H. Koike
Keyword(s):  
Electron Microscope ◽  
Image Quality ◽  
Scanning Electron Microscope ◽  
Chromatic Aberration ◽  
Image Contrast ◽  
Objective Lens ◽  
Thick Specimen ◽  
Transmission Electron ◽  
Scanning Electron

In the observation of a thick specimen by means of a transmission electron microscope, the intensity of electrons passing through the objective lens aperture is greatly reduced. So that the image is almost invisible. In addition to this fact, it have been reported that a chromatic aberration causes the deterioration of the image contrast rather than that of the resolution. The scanning electron microscope is, however, capable of electrically amplifying the signal of the decreasing intensity, and also free from a chromatic aberration so that the deterioration of the image contrast due to the aberration can be prevented. The electrical improvement of the image quality can be carried out by using the fascionating features of the SEM, that is, the amplification of a weak in-put signal forming the image and the descriminating action of the heigh level signal of the background. This paper reports some of the experimental results about the thickness dependence of the observability and quality of the image in the case of the transmission SEM.

Resolution of a Transmitted Electron Image Formed by A Scanning Electron Microscope

1970 ◽  
Vol 28 ◽  
pp. 386-387
Author(s):  
S. Takashima ◽  
H. Hashimoto ◽  
S. Kimoto
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Specimen Thickness ◽  
Probe Diameter ◽  
Transmission Electron ◽  
Electron Image ◽  
Conventional Transmission Electron Microscope ◽  
Scanning Electron

The resolution of a conventional transmission electron microscope (TEM) deteriorates as the specimen thickness increases, because chromatic aberration of the objective lens is caused by the energy loss of electrons). In the case of a scanning electron microscope (SEM), chromatic aberration does not exist as the restrictive factor for the resolution of the transmitted electron image, for the SEM has no imageforming lens. It is not sure, however, that the equal resolution to the probe diameter can be obtained in the case of a thick specimen. To study the relation between the specimen thickness and the resolution of the trans-mitted electron image obtained by the SEM, the following experiment was carried out.

Edge Penetration Effects in the Low-Loss Electron Image in the SEM

1988 ◽  
Vol 46 ◽  
pp. 202-203
Author(s):  
Oliver C. Wells
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Beam Energy ◽  
Secondary Electron ◽  
Sharp Edge ◽  
Beam Diameter ◽  
Low Loss ◽  
Additional Information ◽  
Electron Image ◽  
Scanning Electron

The low-loss electron (LLE) image in the scanning electron microscope (SEM) is useful for the study of uncoated photoresist and some other poorly conducting specimens because it is less sensitive to specimen charging than is the secondary electron (SE) image. A second advantage can arise from a significant reduction in the width of the “penetration fringe” close to a sharp edge. Although both of these problems can also be solved by operating with a beam energy of about 1 keV, the LLE image has the advantage that it permits the use of a higher beam energy and therefore (for a given SEM) a smaller beam diameter. It is an additional attraction of the LLE image that it can be obtained simultaneously with the SE image, and this gives additional information in many cases. This paper shows the reduction in penetration effects given by the use of the LLE image.

Magnetic Domain Observation of an Amorphous Fe-Si-B Ribbon by Means of a High Voltage Scanning Electron Microscope

1981 ◽  
Vol 39 ◽  
pp. 320-321
Author(s):  
K. Tsuno ◽  
Y. Harada ◽  
T. Sato
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
High Voltage ◽  
Amorphous Ribbon ◽  
Image Resolution ◽  
Objective Lens ◽  
Magnetic Domains ◽  
Scattered Electron ◽  
Voltage Scanning ◽  
Scanning Electron

Magnetic domains of ferromagnetic amorphous ribbon have been observed using Bitter powder method. However, the domains of amorphous ribbon are very complicated and the surface of ribbon is not flat, so that clear domain image has not been obtained. It has been desired to observe more clear image in order to analyze the domain structure of this zero magnetocrystalline anisotropy material. So, we tried to observe magnetic domains by means of a back-scattered electron mode of high voltage scanning electron microscope (HVSEM).HVSEM method has several advantages compared with the ordinary methods for observing domains: (1) high contrast (0.9, 1.5 and 5% at 50, 100 and 200 kV) (2) high penetration depth of electrons (0.2, 1.5 and 8 μm at 50, 100 and 200 kV). However, image resolution of previous HVSEM was quite low (maximum magnification was less than 100x), because the objective lens cannot be excited for avoiding the application of magnetic field on the specimen.

Comparison of freeze-fractured yeast replicas using conventional TEM and low-voltage field-emission SEM

1989 ◽  
Vol 47 ◽  
pp. 74-75
Author(s):  
William P. Wergin ◽  
Eric F. Erbe ◽  
Terrence W. Reilly
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Field Emission ◽  
Low Voltage ◽  
Objective Lens ◽  
Specimen Preparation ◽  
Lens System ◽  
Air Drying ◽  
Preparation Techniques ◽  
Scanning Electron

Although the first commercial scanning electron microscope (SEM) was introduced in 1965, the limited resolution and the lack of preparation techniques initially confined biological observations to relatively low magnification images showing anatomical surface features of samples that withstood the artifacts associated with air drying. As the design of instrumentation improved and the techniques for specimen preparation developed, the SEM allowed biologists to gain additional insights not only on the external features of samples but on the internal structure of tissues as well. By 1985, the resolution of the conventional SEM had reached 3 - 5 nm; however most biological samples still required a conductive coating of 20 - 30 nm that prevented investigators from approaching the level of information that was available with various TEM techniques. Recently, a new SEM design combined a condenser-objective lens system with a field emission electron source.

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