Focal properties and spherical aberration of a field emission electron gun†

1969 ◽  
Vol 27 (1) ◽  
pp. 49-58 ◽  
Author(s):  
J. WORSTER
Keyword(s):  
Field Emission ◽  
Spherical Aberration ◽  
Electron Gun ◽  
Emission Electron

Observation of Phase Contrast Images in STEM and CTEM Modes by Using 100 kV Field Emission Electron Gun

1974 ◽  
Vol 32 ◽  
pp. 390-391
Author(s):  
Y. Harada ◽  
T. Goto ◽  
H. Koike ◽  
T. Someya
Keyword(s):  
Field Emission ◽  
Phase Contrast ◽  
Image Formation ◽  
Fresnel Diffraction ◽  
Experimental Results ◽  
Electron Gun ◽  
Scanning Microscopy ◽  
Emission Electron ◽  
Lattice Images

Since phase contrasts of STEM images, that is, Fresnel diffraction fringes or lattice images, manifest themselves in field emission scanning microscopy, the mechanism for image formation in the STEM mode has been investigated and compared with that in CTEM mode, resulting in the theory of reciprocity. It reveals that contrast in STEM images exhibits the same properties as contrast in CTEM images. However, it appears that the validity of the reciprocity theory, especially on the details of phase contrast, has not yet been fully proven by the experiments. In this work, we shall investigate the phase contrast images obtained in both the STEM and CTEM modes of a field emission microscope (100kV), and evaluate the validity of the reciprocity theory by comparing the experimental results.

Interference Experiments with a Field Emission Source

1970 ◽  
Vol 28 ◽  
pp. 534-535
Author(s):  
A. V. Crewe ◽  
J. Saxon
Keyword(s):  
Field Emission ◽  
Spherical Aberration ◽  
Electron Gun ◽  
Partial Coherence ◽  
Vacuum System ◽  
High Brightness ◽  
Small Spot ◽  
Tungsten Tip ◽  
Effective Source ◽  
Better Than

Field emission from a tungsten tip provides a source with very high brightness and high partial coherence. An electron gun of low spherical aberration is used to focus the electrons from the tip to a small spot about 100 Å in diameter. Since the voltages applied to the tip and gun are stable to better than 5 ppm, the temporal coherence is limited by the energy spread of the source, about 200 mv.Using the focused spot a few centimeters below the gun as an effective source, a metalized quartz fiber about 2 μ in diameter is positioned a few centimeters below the source, as shown in Fig. 1. Two cylindrica11y symmetric magnetic lenses are used to magnify the resulting Fresnel diffraction pattern. The image is produced on a fluorescent coating deposited on the vacuum side of a fiber optic window. The image is recorded directly on film placed against the window outside the vacuum system.

Development of a 1-MV Field-Emission Electron Microscope III. Electron Optical Design and Development of Field-Emission Electron Gun

2000 ◽  
Vol 6 (S2) ◽  
pp. 1142-1143
Author(s):  
Takaho Yoshida ◽  
Takeshi Kawasaki ◽  
Junji Endo ◽  
Tadao Furutsu ◽  
Isao Matsui ◽  
...  
Keyword(s):  
Electron Beam ◽  
Field Emission ◽  
Optical Design ◽  
Electron Gun ◽  
Electron Holography ◽  
Optimized Design ◽  
Emission Electron ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Aharonov Bohm

Bright and coherent electron beams have been opening new frontiers in science and technology. So far, we have developed several field-emission transmission electron microscopes (FE-TEM) with increasing accelerating voltages to provide higher beam brightness. By using a 200-kV FE-TEM and electron holography techniques, we directly confirmed the Aharonov-Bohm effect. A 350-kV FE-TEM equipped with a low-temperature specimen stage enabled us to observe moving vortices in superconductors.2 Most Recently, we have developed a new 1-MV FE-TEM with a newly designed FE gun to obtain an even brighter and more coherent electron beam.Electron beam brightness, Br, defined in Figure 1, is suitable for measuring the performance of electron guns, since both lens aberrations and mechanical/electrical vibrations contribute to a decrease in beam brightness, and beam coherency is proportional to (Br)1/2. Therefore, we optimized design of the illuminating system and its operation by maximizing the electron beam brightness.

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