Berlin 2005 – wissenschaftliches Programm

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O: Oberflächenphysik

O 41: Elektronische Struktur III

O 41.5: Vortrag

Dienstag, 8. März 2005, 11:45–12:00, TU EB107

Polarization-Dependent Domain Contrast on cesiated Si(100) in Photoemission Electron Microscopy — •D. Thien, M. Horn-von Hoegen, and F.-J. Meyer zu Heringdorf — Institut für Laser und Plasmaphysik, Universität Duisburg-Essen (Campus Essen), 45117 Essen

On the Si(100) surface, two types of terraces are present with either (2x1) or (1x2) reconstruction. In Low Energy Electron Microscopy (LEEM) dark-field contrast can be observed if a diffraction spot of only one of the two superstructures is used for imaging of the related domain. In Photoelectron Emission Microscopy (PEEM), however, such contrast has not yet been observed. Using a polarized light source such as a 532nm-laser (2.4eV) for illumination of a Cs covered Si(100) surface, however, we observe a polarization dependent photoemission signal of the two different terraces. Ultraviolet Photoemission Spectroscopy (UPS) and Medium Energy Ion Spectroscopy (MEIS) studies of Cs on Si(100) indicate the transfer of the Cs 6s electron to the previously unoccupied upper dangling bond state of the Si(100) surface [1], which acts as initial state for the photoemission process. This lowers the work function while leaving the geometry of the silicon substrate unchanged. The polarization dependence of this contrast is strong enough to be observed even with a green laser pointer.

[1] J.Günster et al., Surf.Sci.359(1996)155-162