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Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P276
Structural and electronic properties of highly ordered CuPc thin films on
differently passivated vicinal silicon surfaces revealed by Near- Edge X-Ray
Absorption Spectroscopy
Gianina Gavrila 1 , Stefan Seifert 1 , Walter Braun 2 , Dietrich R.T. Zahn 1
1 Chemnitz University of Technology, Semiconductors Physics Department, D-09107
Chemnitz – 2 BESSY GmbH, Albert-Einstein-Straße 15, D-12489, Berlin
Organic/inorganic interfaces have attracted considerable attention due to their potential
technological applications and because of fundamental research interest. Currently
research is not only limited to structural analysis but extended to intentional structural
control aiming at the fabrication of molecule based nano-structures on inorganic
substrates in order to take advantage of the anisotropic physical molecular properties,
for instance, the anisotropic conductivity and the anisotropic light emission. One intriguing
way of controlling the in-plane orientation of organic molecules on inorganic
substrates is by designing the geometric structure of the substrate surface, e.g. by
the steps and terraces of vicinal silicon. Near Edge X-ray Absorption Fine Structure
(NEXAFS) investigations of CuPc deposition on hydrogen passivated vicinal Si(111)-
7x7 clearly reveal that CuPc molecules form structures aligned parallel to the step edges
on the substrates with individual molecules laying flat on the terraces. On the other
hand, on antimony (Sb)-passivated vicinal Si(111) surfaces the individual molecules
are taking a standing upright geometry and the columns of CuPc lie predominantly
parallel to the step edge direction. The influence of structural and molecular orientation
on the electronic properties of such highly ordered CuPc thin films on differently
passivated vicinal silicon surfaces is revealed by core-level and valence PhotoEmission
Spectroscopy (PES). By comparison of NEXAFS and PES results with scanning
tunneling microscopy images we can state that the two different chemical passivation
techniques result in totally different electronic structures in the CuPc thin films on the
well-defined vicinal silicon surfaces. This provides an interesting perspective for better
control of the electronic properties of CuPc thin film on silicon surfaces with a view to
applications.