Dresden 2009 – scientific programme
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O: Fachverband Oberflächenphysik
O 27: Poster Session I (Methods: Scanning probe techniques; Methods: Atomic and electronic structure; Methods: Molecular simulations and statistical mechanics; Oxides and Insulators: Clean surfaces; Oxides and Insulators: Adsorption; Oxides and Insulators: Epitaxy and growth; Semiconductor substrates: Clean surfaces; Semiconductor substrates: Epitaxy and growth; Semiconductor substrates: Adsorption; Nano- optics of metallic and semiconducting nanostructures; Electronic structure; Methods: Electronic structure theory; Methods: other (experimental); Methods: other (theory); Solutions on surfaces; Epitaxial Graphene; Surface oder interface magnetism; Phase transitions; Time-resolved spectroscopies)
O 27.27: Poster
Tuesday, March 24, 2009, 18:30–21:00, P2
Auger spectroscopy of the ion neutralization at epitaxial transition metal surfaces — •Christian Tusche and Jürgen Kirschner — MPI für Mikrostrukturphysik, D-06120 Halle, Germany
The neutralization of ground state He+ at a metal surface proceeds by Auger neutralization, emitting an Auger electron from the conduction band of the metal. In ion-neutralization-spectroscopy (INS), developed by Hagstrum [1], the distribution of emitted electrons is related to the surface density of states (DOS). In contrast, He++ neutralization starts with a double electron capture into the outer He-2s and -2p shells, forming double excited He**. Subsequent auto-ionization (AI) emits a He-KLL Auger electron from the projectile.
We prepared clean surfaces of the transition metals Mn, Fe, and Ni by epitaxial growth on a W(110) substrate. He+ and He++ ions (Ekin≤ 30eV) were scattered at the clean surface and after adsorption of sub-monolayers of carbon, oxygen, or caesium. INS provides detailed information on changes of the work-function and electronic structure. All adsorbates are found to reduce the number of electrons emitted close to the Fermi energy. In the He** AI decay we observe a changed spectral weight of triplet and singlet terms with adsorbate coverage, like reported before by Busch et al. [2]. Our experiments give evidence that this can be related to the adsorbate induced changes in the DOS. We hope that our experiments will stimulate detailed theoretical studies of the electron transfer processes in ion-neutralization.
[1] Hagstrum: Phys. Rev. 150, p. 495-515 (1966)
[2] Busch, Wethekam, Winter: : Phys. Rev. A 78, 010901 (2008)