Theoretical calculation of probe size of low-voltage scanning electron microscopes

1993 ◽  
Vol 170 (2) ◽  
pp. 119-124 ◽  
Author(s):  
J. XIMEN ◽  
Z. SHAO ◽  
P. S. D. LIN
Keyword(s):  
Theoretical Calculation ◽  
Low Voltage ◽  
Probe Size ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Voltage Scanning ◽  
Scanning Electron

Current State of Biological High-Resolution Scanning Electron Microscopy

1988 ◽  
Vol 46 ◽  
pp. 180-181 ◽  
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
High Performance ◽  
Low Voltage ◽  
Backscattered Electrons ◽  
Lens Position ◽  
Low Voltage Operation ◽  
Signal Collection ◽  
Probe Size ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

A new generation of high performance field emission scanning electron microscopes (FSEM) is now commercially available (JEOL 890, Hitachi S 900, ISI OS 130-F) characterized by an "in lens" position of the specimen where probe diameters are reduced and signal collection improved. Additionally, low voltage operation is extended to 1 kV. Compared to the first generation of FSEM (JE0L JSM 30, Hitachi S 800), which utilized a specimen position below the final lens, specimen size had to be reduced but useful magnification could be impressively increased in both low (1-4 kV) and high (5-40 kV) voltage operation, i.e. from 50,000 to 200,000 and 250,000 to 1,000,000 x respectively.At high accelerating voltage and magnification, contrasts on biological specimens are well characterized1 and are produced by the entering probe electrons in the outmost surface layer within -vl nm depth. Backscattered electrons produce only a background signal. Under these conditions (FIG. 1) image quality is similar to conventional TEM (FIG. 2) and only limited at magnifications >1,000,000 x by probe size (0.5 nm) or non-localization effects (%0.5 nm).

The Low Voltage Scanning Electron Microscope

1997 ◽  
Vol 3 (S2) ◽  
pp. 1213-1214
Author(s):  
David C Joy
Keyword(s):  
Materials Science ◽  
Low Voltage ◽  
Backscattered Electrons ◽  
Mode Of Operation ◽  
Low Energy Electron ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Enhanced Surface ◽  
Voltage Scanning ◽  
Scanning Electron

A majority of the scanning electron microscopes (SEMs) now in use are probably employed as low voltage SEMs (LVSEMs), that is to say they are operated to produce beams with energies below 5keV. This trend away from the more conventional mode of operation at 20 or 30keV has gathered momentum over the past decade and has been driven by both theoretical and practical considera-tions.Firstly, the distance travelled by an electron falls rapidly (in fact as about E1.6 ) as the incident ener-gy E is reduced. Images generated by low energy electron beams therefore contain enhanced surface information compared to those images recorded at higher energies. Since surfaces are of great inter-est in both the life sciences and in materials science this has been a persuasive factor. Secondly, both the secondary and the backscattered electrons now come from essentially the same interaction volume, rather than from volumes which are widely different in size and shape.

Chromatic aberration and low-voltage SEM

1987 ◽  
Vol 45 ◽  
pp. 546-547
Author(s):  
Zhifeng Shao ◽  
A.V. Crewe
Keyword(s):  
Electron Energy ◽  
Low Voltage ◽  
Spherical Aberration ◽  
Chromatic Aberration ◽  
Primary Electron ◽  
Probe Size ◽  
Non Local ◽  
Optical Treatment ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes

For scanning electron microscopes, it is plausible that by lowering the primary electron energy, one can decrease the volume of interaction and improve resolution. As shown by Crewe /1/, at V0 =5kV a 10Å resolution (including non-local effects) is possible. To achieve this, we would need a probe size about 5Å. However, at low voltages, the chromatic aberration becomes the major concern even for field emission sources. In this case, δV/V = 0.1 V/5kV = 2x10-5. As a rough estimate, it has been shown that /2/ the chromatic aberration δC should be less than ⅓ of δ0 the probe size determined by diffraction and spherical aberration in order to neglect its effect. But this did not take into account the distribution of electron energy. We will show that by using a wave optical treatment, the tolerance on the chromatic aberration is much larger than we expected.

scholarly journals Depth Information Available from the Backscattered Electron Signal

1995 ◽  
Vol 3 (6) ◽  
pp. 8-9
Author(s):  
V.N.E. Robinson
Keyword(s):  
Surface Topography ◽  
Atomic Number ◽  
Secondary Electron ◽  
Low Voltage ◽  
Depth Information ◽  
New Techniques ◽  
Backscattered Electron ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

Although the secondary electron (SE) signal is still the most commonly used signal in scanning electron microscopes (SEMs), the backscattered electron (BSE) signal is now in wide use. Imaging both atomic number and surface topography have been the major applications of BSE detectors, with some applications in channelling, magnetic contrast and similar specialized applications. Over the last few years, low voltage BSE imaging has been used for imaging surface features to a depth of a few nm. But the BSE signal contains much more information and new techniques are being developed to take advantage of its versatility.

Low-voltage high-resolution Scanning Electron Microscopy of semiconductors

1989 ◽  
Vol 47 ◽  
pp. 82-83
Author(s):  
S.J. Krause ◽  
G.N. Maracas ◽  
W.J. Varhue ◽  
D.C. Joy
Keyword(s):  
High Resolution ◽  
High Performance ◽  
Low Voltage ◽  
Image Recording ◽  
Surface Charging ◽  
New Information ◽  
Negative Surface ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

The advent of scanning electron microscopes (SEMs) with reliable, high performance field emission guns (FEG) has afforded many opportunities to obtain new information at low voltages not available at higher voltages in traditional SEMs equipped with tungsten hairpin or LaB6 filaments. The FEG SEMs are able to operate at low voltages with both high brightness and high resolution (HR) due to the small source size and low energy spread of the beam. Resolution of 4 nm down to 1.5 nm are routinely possible in the energy range from 1 to 5 keV along with standard image recording times of 1 to 2 minutes. The low voltage capabilities have allowed insulating materials, such as polymers, composites, and ceramics to be imaged at high resolutions at energies below the second crossover, usually around 1 to 2 keV, without experiencing image artifacts from negative surface charging normally found in uncoated insulators at higher operating voltages.

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