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O: Fachverband Oberflächenphysik

O 60: Time-Resolved Spectroscopies

O 60.2: Talk

Thursday, March 29, 2007, 16:00–16:15, H42

Photoemission Electron Microscopy Study of Anthracene Thin Film Growth on Si(111) — •Niemma Buckanie and Frank Meyer zu Heringdorf — Universität Duisburg-Essen, Lotharstraße 1, 47057 Duisburg

The organic molecule anthracene consists of three linearly fused aromatic rings and has been successfully used in Organic Light Emitting Devices (OLED).The efficiency of the OLEDs depends strongly on the crystalline structure of the anthracene films. The frequency (color) of the emitted light is determined by an Exciton in the molecule.

We used linear and non-linear Photoemission Electron Microscopy (PEEM)to study the growth and the electronic properties of anthracene thin films on Si(111). Anthracene forms fractal-shaped islands with standing up molecules on top of a wetting layer that consists of flat-lying molecules. The illumination of the films with fs-laser pulses (E = 3.1 eV ) enables us to determine the azimuthal alignment of the molecules in the textured films by using two photon-photoemission (2PPE). In 2PPE, a first photon excites the singlet exciton S1. The absorption of a second photon leads to the photoemission. The S1 state can only be excited with an electric field along the b-axis of the anthracene unit cell.