Berlin 2008 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 12: Thin Film Characterisation: Structure Analyse and Composition (XRD, TEM, XPS, SIMS, RBS, ...)

DS 12.1: Vortrag

Dienstag, 26. Februar 2008, 11:45–12:00, H 2013

Experimental determination of the IMFP of electrons in organic molecular solids — •Tina Graber, Stefan Krause, Achim Schöll, and Friedrich Th. Reinert — Universität Würzburg, Experimentelle Physik II, Am Hubland, 97074 Würzburg

A precise knowledge of the inelastic mean free path (IMPF) of electrons in matter is of crucial interest in many respects. If electron spectroscopic techniques are applied in surface and interface science the attenuation length of the involved electrons has to be well-known in order to gain information on, e.g., adsorbate film thickness or growth modes. The IMFP certainly depends on the respective material and on the electron kinetic energy. Whereas some experimental information is available for inorganic compounds the data is very scarce for organic materials. Moreover, there is not yet a uniform theoretical description of the IMPF and the loss mechanisms of electrons in organic films, although some calculations have been performed [1]. In this work we present a systematic experimental study on the IMFP of electrons in condensed PTCDA films by means of photo electron spectroscopy (PES) and applying the overlayer method. Since the control of the adlayer growth mode it is mandatory for a precise determination, the attenuation length PTCDA/Ag(111) was chosen as a model system. The results indicate a significant deviation of the experimental IMPF values from the universal curve, which is generally utilized as a zeroth order approximation for the electron mean free path, particularly for low electron energies. [1] Tanuma, S.,Powell, C. J., Penn, D. R., Surf. Int. Anal. 21, 165, 1993