Design of a Field-Emission Gun for the Phillips CM20/STEM microscope

1990 ◽  
Vol 48 (2) ◽  
pp. 100-101
Author(s):  
P.M. Mul ◽  
B.J.M. Bormans ◽  
L. Schaap
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Analytical Electron Microscopy ◽  
Emission Region ◽  
Attractive Alternative ◽  
Electron Holography ◽  
Field Emitter ◽  
Field Emitters ◽  
Resolution Electron ◽  
High Resolution Tem

The first Field Emission Guns (FEG) on TEM/STEM instruments were introduced by Philips in 1977. In the past decade these EM400-series microscopes have been very successful, especially in analytical electron microscopy, where the high currents in small probes are particularly suitable. In High Resolution Electron Holography, the high coherence of the FEG has made it possible to approach atomic resolution.Most of these TEM/STEM systems are based on a cold field emitter (CFE). There are, however, a number of disadvantages to CFE’s, because of their very small emission region: the maximum current is limited (a strong disadvantage for high-resolution TEM imaging) and the emission is unstable, requiring special measures to reduce the strong FEG-induced noise. Thermal field emitters (TFE), i.e. a zirconiated field emitter source operating in the thermal or Schottky mode, have been shown to be a viable and attractive alternative to CFE’s. TFE’s have larger emission regions, providing much higher maximum currents, better stability, and reduced sensitivity to vacuum conditions as well as mechanical and electrical interferences.

High Resolution Tem Study of Diamond Formation on Silicon and Molybdenum Field Emitter Surfaces

1994 ◽  
Vol 354 ◽  
Author(s):  
A. F. Myers ◽  
J. Liu ◽  
W. B. Choi ◽  
G. J. Wojak ◽  
J. J. Hren
Keyword(s):  
High Resolution ◽  
Diamond Film ◽  
Microwave Plasma ◽  
Chemical Vapor ◽  
Polycrystalline Diamond ◽  
Plasma Chemical Vapor Deposition ◽  
Field Emitters ◽  
High Resolution Tem ◽  
Diffraction Patterns ◽  
Polycrystalline Diamond Film

AbstractDiamond is an attractive material for coating microfabricated metal and semiconductor field emitters, since it enhances the stability and emission characteristics of the emitter. In the present study, polycrystalline diamond thin films were grown on silicon and molybdenum field emitters by microwave plasma chemical vapor deposition, using the bias-enhanced nucleation technique. High resolution transmission electron microscopy (TEM) was used to analyze the morphology of the diamond film and the structure of the diamond/emitter interface. Electron diffraction patterns and high resolution images indicate the presence of a polycrystalline diamond film, as well as a polycrystalline SiC layer between the diamond film and the Si emitter. A carbide interlayer was also found to exist between the diamond and the Mo emitter surface. Parallel electron energy loss spectroscopy confirms the TEM identification of a polycrystalline diamond film.

High Resolution TEM Studies On Palladium, Rhodium Nanoparticles

2001 ◽  
Vol 7 (S2) ◽  
pp. 1100-1101
Author(s):  
M. José-Yacamán ◽  
M. Marín-Almazo ◽  
J.A. Ascencio
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Indirect Evidence ◽  
High Resolution Electron Microscopy ◽  
Dark Field ◽  
Rhodium Nanoparticles ◽  
Resolution Electron ◽  
Annular Dark Field ◽  
High Resolution Tem ◽  
Important Field

The field of catalysis is one of the most important areas of the nano-sciences for many years. in deed the goal of having a catalyst, with the maximum active area exposed to a chemical reaction, has produced enormous amount of research in nanoparticles. Particularly, the metal nanoparticles study is a very important field in catalysis. Electron Microscopy is one of the techniques that have played a mayor role on studding nanoparticles. Since bright field images, dark field techniques, to the high-resolution atomic images of nanoparticles and more recently the High Angle Annular dark field images or Z-contrast. However this technique provides only indirect evidence of the atomic arrangements on the particles. High Resolution Electron Microscopy (HREM) still appears as a very powerful technique to study nanoparticles and their internal structure. Among the most interesting metals to study is the palladium, which acts for instance as excellent catalyst for hydrogenation of unsaturated hydrocarbons and has many other applications such as environmental catalysts.

Interpretation of high-resolution TEM images of substitutional systems with a column structure

1983 ◽  
Vol 41 ◽  
pp. 236-237
Author(s):  
G. Van Tendeloo ◽  
D. Van Dyck ◽  
S. Amelinckx
Keyword(s):  
High Resolution ◽  
Structural Features ◽  
Crystal Thickness ◽  
Contrast Transfer Function ◽  
Resolution Electron ◽  
High Resolution Tem ◽  
Direct Interpretation ◽  
High Resolution Electron Microscope ◽  
Electron Microscopes ◽  
Almost All

Direct interpretation of high resolution electron microscope images in terms of the projected potential or projected charge density is only possible for very thin specimens and at a properly chosen defocus value. In most of the substitutional alloy systems such as those based on the fee basic lattice in which electron diffraction is strongly dynamical the useful crystal thickness is limited to the order of 1 nm which is rearly met in practice. Furthermore for almost all of the available electron microscopes the Scherzer plateau of the contrast transfer function is not large enough to contain even the first Bragg beams that carry information about the fee lattice. Nevertheless it has been shown in a number of papers on ordering in fcc-based Au-Mn alloys as well as in other heavy metal fee based alloys that under suitable conditions the images represent the structural features of these alloys in a directly interpretable manner. In particular the configuration of the minority atom columns can be imaged as bright dots. We shall indicate here semi-analytically why and under which conditions this conclusion is justified.

Investigation of biogenic magnetite particles by high-resolution electron microscope

1984 ◽  
Vol 42 ◽  
pp. 216-217
Author(s):  
T. Matsuda ◽  
J. Endo ◽  
N. Osakabe ◽  
A. Tonomura ◽  
T. Arii
Keyword(s):  
High Resolution ◽  
Permanent Magnets ◽  
Fine Particles ◽  
Electron Holography ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Water Pond ◽  
High Resolution Electron Microscope ◽  
Magnetite Particles ◽  
Mössbauer Analysis

In 1975, Blakemore found aquatic bacteria that swim along earth's magnetic lines of force [1]. They have permanent magnets of iron-rich fine particles within them. Such particles were found by Mössbauer analysis to consist of magnetite in the case of magnetospirilla [2]. In addition, Towe et al confirmed by electron diffraction that the particles were crystalline [3]. The purpose of the present investigation is to determine the crystal and magnetic structure of these particles by both high-resolution lattice imaging and electron holography; however only the former is reported here.Magnetotactic bacteria were gathered in a fresh-water pond. The specimens were peanut-shaped, and approximately 3um in length. Transmission electron micrographs, such as that shown in Fig. 1, reveal that approximately 30 fine particles are aligned within each bacterium.

Digital imaging for high-resolution electron holography

1992 ◽  
Vol 50 (2) ◽  
pp. 944-945
Author(s):  
L. F. Allard ◽  
T. A. Nolan ◽  
D. C. Joy ◽  
T. Hashimoto
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Digital Imaging ◽  
Electron Holography ◽  
Digital Recording ◽  
Original Image ◽  
Ccd Array ◽  
Resolution Electron ◽  
Phase Images ◽  
High Resolution Images

It is a goal of electron microscopy to eliminate film as the recording medium for electron microscope images in favor of direct digital recording. At present, there are commercially available digital TV systems (e.g. ref. [2]) based on CCD slow scan technology that provide 1M pixel images (i.e. 1k × 1k arrays). Such systems have proven useful for recording standard high resolution images and are sufficient to replace film for most standard electron microscopy. However, the newly developing technique of electron holography requires an advanced digital imaging capability, because the process of reconstruction of amplitude and phase images from a hologram necessarily gives final images that are only one-quarter the size of the original image. For a minimum desired 512 × 512 pixel reconstructed image, the original image should be 2k × 2k, requiring a CCD array with 4M pixels.Electron holograms which are recorded for reconstruction of aberration-corrected images with improved resolution (approaching 0.1 nm) require hologram fringes spaced on the order of 0.3 nm.

EM of diamond-coated molybdenum field emission cathodes

1995 ◽  
Vol 53 ◽  
pp. 440-441
Author(s):  
A. F. Myers ◽  
W. B. Choi ◽  
M. T. McClure ◽  
J. J. Hren ◽  
E. Voelkl ◽  
...  
Keyword(s):  
Field Emission ◽  
Nucleation Mechanism ◽  
Diamond Coating ◽  
Emitter Surface ◽  
Diamond Nucleation ◽  
Field Emitters ◽  
Nanocrystalline Particles ◽  
High Resolution Tem ◽  
Extended Operation ◽  
Field Emission Cathodes

Molybdenum is a common metal used to fabricate field emission devices.1-2 However, during extended operation, Mo cathodes exhibit current instabilities, which are thought to arise from adsorption of contaminants on the emitter surface. Coating Mo field emitters with diamond may enhance the current stability, as well as the total emission current. An understanding of the diamond nucleation mechanism is crucial for depositing consistent, uniform coatings on the emitters, and therefore producing reliable devices. To the author's knowledge, little information exists about the mechanism of diamond nucleation on these highly curved Mo surfaces.In order to study the diamond nucleation mechanism, the morphology of the diamond coating and the structure of the diamond/Mo interface were analyzed by high resolution TEM. Emitters make excellent TEM specimens, since no further sample preparation is required after the diamond deposition; artifacts thus do not become an issue in interpreting the TEM results. Figure 1 shows that the films have a general morphology of clustered nanocrystalline particles.

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