Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 5: Electronic structure I

O 5.6: Talk

Monday, March 27, 2006, 12:30–12:45, WIL A317

Scanning Tunneling Microscopy (STM) and Spectroscopy (STS) Investigation of Ultra-thin Epitaxial Nobel Metal Films on Sapphire — •Christof Dietrich, Berndt Koslowski, Gerd Kästle, Hans-Gerd Boyen, and Paul Ziemann — Abteilung Festkörperphysik, Universität Ulm, D-89069 Ulm

Ultra-thin epitaxial Au(111) and Ag(111) films have been prepared on (0001)-oriented sapphire with a niobium buffer layer. Despite their thickness of just 2nm, the nobel metal films are electrically conductive and, according to XRD, exhibit excellent epitaxial properties as well as outstanding smoothness over macroscopic scales [1,2]. Room temperature STM measurements revealed highly ordered smooth surfaces with large terraces and mono-atomic steps. STS measurements on these samples reproducibly showed prominent signatures which can be nicely explained by quantum well states due to the confinement of the electrons perpendicular to the film. Additionally, a thickness-dependent shift of the onset of the Shockley-like surface state was observed in the I(V) spectra possibly indicating a thickness dependent strain in the films.

[1] Growth of thin, smooth, epitaxial (111) oriented Gold films on c-cut Sapphire; G.Kästle, H.-G. Boyen, B. Koslowski, A. Plettl, F. Weigl and P. Ziemann, Surf. Sci. 498, 168 (2002). [2] Size-Effect of the resistivity of thin epitaxial Gold Films, G. Kästle, H.-G. Boyen, A. Schröder, P. Ziemann, Phys. Rev. B 70, 165414 (2004).