Review of ZrO/W Schottky Cathode

Swanson, L. W.; Schwind, G. A.

doi:10.1201/9781420045550.ch1

Cited by 23 publications

(32 citation statements)

References 35 publications

(35 reference statements)

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“…At the center of the 0.5 kV pattern there still is the end facet emission spot, but it is very faint and small. Figure 2.6 gives a similar emission pattern from [Swa08] but with a bright central spot. It is expected that the latter has been recorded at a larger extraction voltage, for an extractor with a much larger aperture.…”

Section: Applying a Biasmentioning

confidence: 58%

Physics of Schottky Electron Sources

Bronsgeest¹

2016

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Section: Applying a Biasmentioning

confidence: 58%

Physics of Schottky Electron Sources

Bronsgeest¹

2016

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“…The work function of the ZrO/W(100) facet surface is approximately 2.8 eV while that of the other surfaces is 4.5 eV. Angular intensity distribution of the Swanson's Schottky emission gun is analyzed and indicates good agreement with Swanson's experimental data, as shown in Figure 4 [5]. Simulation of the multi-detector system Figure 6 shows a multi-detector electron signal system installed in the SU8200 FE-SEM [7].…”

Section: Simulation Of the Electron Gunmentioning

confidence: 72%

Simulation for the Development of Electron Guns and Detection Systems of Modern Field Emission Scanning Electron Microscopes

et al. 2015

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IntroductionThe latest Field Emission (FE) Scanning Electron Microscopes (SEM) have been developed to meet the increasing demands of leading-edge users for the analysis of nanomaterials. In order to achieve optimum imaging resolution and contrast, modern SEMs incorporate innovative technologies in the FE Gun, stabilized primary electron optics, and advanced multi-detector systems for selective detection of specific electron signals. Electron optics simulators are indispensable for characterizing these functions. An axially symmetric simulator is critical for designing the primary electron optics, and a three dimensional (3D) simulator is particularly helpful for engineering and optimizing the detector system. Presented here is the theoretical basis of an axially symmetric simulator with demonstrated application results. The application and utility of a 3D simulator will also be introduced.

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“…If tunneling were present, electrons would go both over the top of the workfunction barrier as well as through the barrier, and the energy width of the emitted beam would grow to several eV Martin 1975, Swanson andSchwind 2009). This needs to be avoided in a practical source of electrons, and a practical Schottky gun is therefore never run at an applied field high enough to allow electrons of the Fermi energy to tunnel out of the tip.…”

Section: Cold Field Emission and Schottky Sourcesmentioning

confidence: 99%

“…Fig. 2 shows a schematic comparison of the emission mechanism from a cold field emission gun (Crewe et al 1968b), and the Schottky gun (Swanson and Schwind 2009). In the CFEG, the electric field at the surface of the emission tip is typically about 10x higher than in the Schottky gun.…”

Section: Cold Field Emission and Schottky Sourcesmentioning

confidence: 99%

“…In the Schottky gun, the temperature required to excite electrons over a lower workfunction barrier is lower, and this decreases the width of the tail of the energy distribution extending above the barrier. The workfunction is typically lowered in the Schottky gun case, by building up a layer of ZrO or a similar oxide covering a (100) W tip (Swanson and Schwind 2009). Attempts to do the same for the CFEG (e.g.…”

Section: Cold Field Emission and Schottky Sourcesmentioning

confidence: 99%

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Atomic-Resolution STEM at Low Primary Energies

Krivanek

Chisholm

Dellby

et al. 2010

Scanning Transmission Electron Microscopy

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Abstract. Aberration correction of the scanning transmission electron microscope (STEM) has made it possible to reach probe sizes close to 1 Å at 60 keV, an operating energy that avoids direct knock-on damage in materials consisting of light atoms such as B, C, N and O. The improved resolution is allowing individual atoms to be imaged in various novel materials including graphene, monolayer boron nitride and carbon nanotubes. Some radiation damage remains even at the lower energies, and this limits the maximum usable electron dose. Elemental identification by electron energy loss spectroscopy (EELS) is then usefully supplemented by annular dark field (ADF) imaging, for which the signal is much greater. Because of its strong Z dependence, ADF allows the chemical identification of individual atoms, both heavy and light. We review the instrumental requirements for atomic resolution imaging at 60 keV and lower energies, and we illustrate the kinds of observations that have now become possible by ADF images of graphene, monolayer BN and single wall carbon nanotubes, and by ADF images and EELS spectra containing nanopods filled with single atoms of Er. We then discuss likely future developments.

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Review of ZrO/W Schottky Cathode

Cited by 23 publications

References 35 publications

Physics of Schottky Electron Sources

Physics of Schottky Electron Sources

Simulation for the Development of Electron Guns and Detection Systems of Modern Field Emission Scanning Electron Microscopes

Atomic-Resolution STEM at Low Primary Energies

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