Dresden 2003 – wissenschaftliches Programm
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O: Oberflächenphysik
O 4: Elektronische Struktur I
O 4.3: Vortrag
Montag, 24. März 2003, 11:45–12:00, FOE/ANOR
Adsorbate Induced Work Function Change of Tungsten Surfaces — •C. Mosch1,2, J. Almanstötter1, P. Schade1, T. Fries1, and A. Groß2 — 1OSRAM GmbH, 86830 Schwabmünchen — 2Physik-Department, Technical University Munich, D-85747 Garching
The most important electrode material used in high pressure gas discharge lamps is tungsten. One key parameter for the efficiency of these lamps is their work function. In many lamps, thorium is added since it leads to a significant reduction of the work function. Unfortunately, thorium is slightly radioactive. Therefore there is a strong interest to find a replacement. The rare earth elements are among the most promising candidates for substituting thorium, however, only very little is known about the work function change of tungsten induced by rare-earth adsorption [1].
In order to contribute to a microscopic understanding of the adsorbate-induced work function change, we have performed electronic structure calculations based on density functional theory and the FLAPW method [2] for more than forty different adsorbates on tungsten. The chemical trends found in the induced work function change are addressed by a detailed analysis of the electronic structure. In particular, we will discuss the influence of spin-polarization, non-local functionals and coverage on the work function.
[1] E. Lassner, and W. Schubert, Tungsten, Kluver Academic (1999).
[2] P. Blaha, J. Luitz, and K. Schwarz, WIEN2k, TU-Wien (2001).