[Zurück]

S. Cernusca, M Fürsatz, Hp. Winter, F. Aumayr:
"Ion-induced kinetic electron emission from differently oriented HOPG surfaces";
in: "Proc. Symp. on Surface Science 2004 (3S'04)", F. Aumayr, P. Varga (Hrg.); Proc. Symp. on Surface Science 2004 (3S'04), 2004, S. 70 - 71.

Electron emission from solid surfaces due to the impact of energetic ions
(i.e.kinetic electron emission (KE) is a well-investigated phenomenon [1, 2, 3]. Most
studies on KE have so far focused on the primary mechanism of exciting
electronswithin the target surface. However, before escaping into vacuum, these
electrons have to diffuse towards the surface [1, 4]. Therefore, the electron
transport can havea significant influence on the resulting total electron yield. For
example, it is commonly assumed that the mean free path of low energy electrons is
larger forinsulators than for metals. Thus also their escape depth and the total
electron yield are expected to be larger [1]. Because of quite different mechanisms
causing KEfrom insulating and conducting surfaces, it is however difficult to
separate the role of electron transport from the primary excitation
mechanism.Highly oriented pyrolytic graphite (HOPG) is a standard target used in
surface physics, easy to clean and handle. It consists of well-defined layered carbon
sheetswhich exhibit large differences in electrical and thermal conductivity
parallel to the layers (large conductivity) as compared to the perpendicular
direction (lowconductivity). Since electron transport in a conductor is related to
conductivity, a possible dependence of the electron emission on the orientation of
the layers withrespect to the surface would allow us to study the role of electron
transport in KE separated from the primary excitation mechanism. The latter is
expected to beindependent from the target orientation. We have therefore measured
electron emission yields induced by impact of singlycharged ions (H+, H 2+, C+, N+,
O+ and Ar+, impact energy between 2 and 10 keV) onclean HOPG of two different
orientations.

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