Berlin 2005 – wissenschaftliches Programm

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O: Oberflächenphysik

O 15: Postersitzung (Adsorption an Oberfl
ächen, Epitaxie und Wachstum, Organische Dünnschichten, Oxide und Isolatoren, Rastersondentechniken, Zeitaufgelöste Spektroskopie, Methoden)

O 15.12: Poster

Freitag, 4. März 2005, 17:00–20:00, Poster TU D

’Pulse injection’: A non-destructive way of depositing large organic molecules under ultrahigh vacuum conditions — •Ingeborg Staß, Leonhard Grill, Francesca Moresco, and Karl-Heinz Rieder — Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin

A fundamental problem in the deposition of molecules from a Knudsen cell is the heating procedure: When the molecules are getting larger the temperature must be increased which results in the dissociation of molecular bonds. We present a low temperature STM study of porphyrin-based molecules on copper surfaces. In order to deposit intact molecules onto the substrate we have used the so-called pulse injection method. Molecules (in solution) are injected by a valve with very short aperture times (few ms). Residual solvent contamination can be desorbed from the surface by heating of the sample, but the chemical structure of the molecules must be maintained. We used various solvents, which differ in their chemical properties, and obtained information on the adsorption and desorption behaviour of the solvents on the metal substrate. The results are compared and discussed by means of the ideal deposition conditions.