Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 42: Nanostructures at surfaces I

O 42.5: Talk

Wednesday, March 28, 2012, 11:30–11:45, MA 042

Surface optical and vibrational properties of Ge(001) at 300 K/40 K before and after Au nanowire deposition — •Jochen Räthel¹, Eugen Speiser¹, Christoph Cobet¹, Karsten Hinrichs¹, Utz Bass², Jean Geurts², and Norbert Esser¹ — ¹Leibniz-Institut für Analytische Wissenschaften – ISAS – e.V., Albert-Einstein-Str. 9, 12489 Berlin — ²Universität Würzburg, Physikalisches Institut, Am Hubland, 97074 Würzburg

The interest in self organized 1-dimensional metallic nanowires on semiconductor surfaces is driven by their extraordinary electronic properties, like Luttinger liquid behaviour for Au nanowires on Ge(001) as shown recently. Therefore, the aims of our study comprise (i) the vibrational properties and the underlying surface structure and dynamics, and (ii) the anisotropic optical properties, arising from surface electronic transitions. For these purposes, we employed in-situ Raman spectroscopy as well as reflectance anisotropy spectroscopy (RAS) on self-organized Au nanowires, grown under UHV conditions on a flash-prepared Ge(001) c(4×2)/(2×1) surface. The Au chain order was identified by the expected c(8×2) LEED symmetry, with two orthogonal domain orientations. The clean Ge(001) shows surface vibration modes, whose energy values agree well with calculated mode patterns found in literature. These surface phonons vanish partly upon cooling to 40 K and completely upon Au deposition, indicating for both cases surface structure changes. RAS spectra in the range from 0.5 to 5 eV show several characteristic features before and after the Au deposition, assigned to electronic surface transitions.