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SYOF: Organische Festkörper

SYOF 5: Poster Session

SYOF 5.27: Poster

Dienstag, 27. März 2001, 17:00–19:00, Aula S3

The electronic properties of highly ordered organic thin films: PTCDA and HBC on Au(100) studied by STM/STS — •Michael Toerker, Torsten Fritz, Holger Proehl, Farid Sellam, and Karl Leo — Institut für Angewandte Photophysik, Technische Universität Dresden, 01062 Dresden

Highly ordered organic thin films on Au(100) single crystals have been investigated by Scanning Tunneling Microscopy (STM) and Scanning Tunneling Spectroscopy (STS) at room temperature. The organic dye molecule perylene-tetracarboxylic-dianhydride (PTCDA) has been deposited as submonolayer coverage. I-V-spectroscopy at fixed tip-sample-separations performed alternately on PTCDA islands and on uncovered areas of the Au(100) surface revealed a clear chemical contrast. The normalized derivatives of the I-V-curves corresponding to PTCDA islands have then been compared to inverse photoelectron spectroscopy data known from literature, indicating resonant tunneling via the lowest unoccupied molecular orbital of PTCDA. As a second molecule, peri-hexabenzocorone (HBC) has been investigated. The Au(100) surface has been fully covered by a 1..2 monolayers thick, highly ordered HBC film. The normalized derivatives of I-V-curves measured on these films show a pronounced local maximum at a voltage of about -1.4 V. By comparison with ultraviolet photoelectron spectroscopy (UPS) measurements of HBC on Au(111) we can show that this peak in the tunneling spectroscopy plot is due to resonant tunneling via the highest occupied molecular orbital of HBC.