Contrast Effects in High Resolution, Low Voltage SEM

1974 ◽  
Vol 32 ◽  
pp. 452-453
Author(s):  
L. M. Welter
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Scanning Electron Microscope ◽  
Field Emission ◽  
Low Voltage ◽  
Electron Source ◽  
Scanning Microscopy ◽  
Contrast Effects ◽  
Probe Current ◽  
Scanning Electron

A scanning electron microscope using a field emission electron source and a single electromagnetic lens can produce a resolution of less than 180Å using an accelerating voltage of only 900v. High resolution, low voltage (0.1-2kV) scanning microscopy offers a number of advantages over the use of higher accelerating voltages. Specimen damage may be reduced because the power (P≃IV) which must be absorbed by the specimen for operation at a given probe current (I) is decreased in proportion to the reduction in accelerating voltage (V).

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.

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.

Field Emission SEM with a Newly Developed FEGUN and Conical Strongly Excited Objective Lens

2000 ◽  
Vol 6 (S2) ◽  
pp. 764-765
Author(s):  
H. Kazumori ◽  
A. Yamada ◽  
M. Mita ◽  
T. Nokuo ◽  
M. Saito
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Scanning Electron Microscope ◽  
Secondary Electron ◽  
Objective Lens ◽  
Probe Current ◽  
Large Samples ◽  
Low Emission ◽  
Working Distance ◽  
Scanning Electron

A newly developed cold FE-GUN which enables to us to obtain large probe current and low emission noise, and conical strongly excited objective lens has been installed on the JSM-6700F Scanning Electron Microscope (SEM). In the range of accelerating voltages from 0.5 to 15kV, this instrument has got much better resolution as compared with in-lens type SEM (Ohyama et al 1986)(Fig. 1). We can obtain high-resolution secondary electron images with large samples (ex. 150mm ϕ×10mmH).Our old type objective lens (Kazumori et al 1994) has the limitation of working distance (WD), but the new lens enables us to work at very short WD at accelerating voltage of 15kV. As a result the spherical (Cs) and chromatic (Cc) aberration constants are 1.9mm and 1.7mm respectively at a WD of 3mm.In order to get large probe current, we increased emission current and got near the distance between the t ip of emi tter and the pr inciple plane of condenser lens.

Variation With Voltage of Probe Current in the Scanning Electron Microscope

1972 ◽  
Vol 30 ◽  
pp. 420-421
Author(s):  
V. E. Cosslett
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Spherical Aberration ◽  
Electron Source ◽  
Operating Voltage ◽  
Probe Current ◽  
Probe Diameter ◽  
Maximum Current ◽  
Scanning Electron

As the operating voltage Vp of a scanning electron microscope is raised, with an electron source of given emission brightness βE, the current delivered into the probe will increase. The extent of the increase will depend on whether it is the Gaussian probe diameter dG or the total probe diameter dT (determined by the lens aberrations) that is kept constant. It will also depend on whether the probe is limited by spherical aberration alone or also by diffraction.If the Gaussian probe diameter is constant the maximum current imax into a diffraction limited probe is found by setting the diameter of the disc of least confusion due to spherical aberration dS equal to the diameter of the Airy diffraction disc dD.

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