Ring-cathode focused electron beam columns
1 : Department of Electrical and Computer Engineering, National University of Singapore
(NUS)
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Website
Department of Electrical and Computer Engineering Block E4, Level 5, Room 45 4 Engineering Drive 3 Singapore 117576 National University of Singapore -
Singapore
This paper describes the aberration characteristics of ring-cathode electron beam focused columns. Ring-cathodes are expected to have emission currents that are several orders of magnitude higher than their conventional single-tip counterparts, due to their larger area of emission. A wide-variety of different cold field emitter geometries can for instance be fabricated from Carbon Nanotubes (CNTs) [1], and it should be possible to fabricate nano-size CNT ring-cathode cold field emitters, ones that have radii in the tens to hundreds micron range and edge thicknesses that are less 100 nm. On the other hand, new techniques of electron beam focusing are required in order to form a nano-meter size electron probe from a ring-cathode. Direct ray tracing simulation results in this paper show how electron beam focused columns can be designed to use ring-cathodes. There are certain situations where the chromatic and geometric aberrations of lenses in such columns can be made to cancel, greatly minimizing the spot diameter of the electron probe. Simulation results predict that it should in principle be possible to focus microamperes of electron beam current into nanometer probe diameters with such techniques.
