[Zurück]

Hp. Winter, F. Aumayr, H. Winter:
"Recent progress in slow-ion induced kinetic electron emission from solid surfaces";
in: "Proc. Symp. on Surface Science 2004 (3S04)", F. Aumayr, P. Varga (Hrg.); Proc. Symp. on Surface Science 2004 (3S'04), 2004, S. 153 - 154.

We describe recent improvements in the understanding of kinetic electron emission
(KE) from bombardment of atomically clean, flat monocrystalline target surfaces by
slow (impactvelocity typically keV/amu) atoms and singly charged ions. Al(111) [1]
and LiF(001) [2] have been chosen as model targets for a free-electron metal and a
wide-band gap insulator,respectively. Relevant KE features were deduced from
ejected electron number statistics which have been measured in coincidence with
the time-of-flight distribution of specularlyscattered projectiles (Ho, Heo, He+)
impinging under grazing incidence (θ in â?Euro 2o) on the targetsurface. Our
experimental approach distinguishes between such electrons which are emitted from
thetarget selvage (region above the uppermost surface layer), and KE originating
from the first target layer and below. Total KE yields can be determined from the
coincidently measuredelectron number statistics down to 10-5 electrons per
projectile, i.e. at and near the KE impact velocity threshold [3] (cf. fig. 1). We
observe clearly different KE statistics for surfacescattering along random- and
channeling directions, which fact can be utilized [4] for surface structure
investigations (fig. 2).Distinctly different processes which contribute to KE from
metal- and insulator surfaces [5] clarify the longstanding question why KE from
contaminated metals is more effective thanfrom atomically clean metal surfaces.

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