Properties of the cathode lens combined with a focusing magnetic/immersion-magnetic lens

0358594 - ÚPT 2012 RIV NL eng J - Journal Article
Konvalina, Ivo - Müllerová, Ilona
Properties of the cathode lens combined with a focusing magnetic/immersion-magnetic lens.
Nuclear Instruments & Methods in Physics Research Section A. Roč. 645, č. 1 (2011), s. 55-59. ISSN 0168-9002. E-ISSN 1872-9576
R&D Projects: GA ČR GAP102/10/1410; GA AV ČR IAA100650902; GA MŠMT ED0017/01/01
Institutional research plan: CEZ:AV0Z20650511
Keywords : cathode lens * compound objective lens * aberration coefficients * spot size * field calculations
Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering
Impact factor: 1.207, year: 2011

The cathode lens is an electron optical element in an emission electron microscope accelerating electrons from the sample, which serves as a source for a beam of electrons. Special application consists in using the cathode lens first for retardation of an illuminating electron beam and then for acceleration of reflected as well as secondary electrons, made in the directly imaging low energy electron microscope or in its scanning version discussed here. In order to form a real image, the cathode lens has to be combined with a focusing magnetic lens or a focusing immersion-magnetic lens, as used for objective lenses of some commercial scanning electron microscopes. These two alternatives are compared with regards to their optical properties, in particular with respect to predicted aberration coefficients and the spot size, as well as the optimum angular aperture of the primary beam. The important role of the final aperture size on the image resolution is also presented.
Permanent Link: http://hdl.handle.net/11104/0196579