Berlin 2018 – wissenschaftliches Programm
O 5.1: Hauptvortrag
Montag, 12. März 2018, 10:30–11:00, MA 042
In-situ studies of organic thin films — •Thorsten Wagner — Experimental Physics, Johannes Kepler University Linz, Austria
The performance of electronic devices based on organic thin films,. e.g. LEDs, field effect transistors and solar cells, correlates strongly with the crystalline structure and the morphology of the organic layer. To study the transition of ultrathin films from 2D to 3D growth, Photoelectron Emission Microscopy (PEEM) and Differential Reflectance Spectroscopy (DRS) are applied in situ and in real-time during the deposition of the molecules. The PEEM provides local information on the wetting layer and on µm sized crystallites with a lateral resolution in the 100 nm range. In spectroscopic mode, the electronic density of states is accessible like in conventional UPS but with a much better resolution. The application of linear polarized light for the excitation of the photoelectrons makes the PEEM also sensitive to the in-plane orientation of the molecules. DRS compares the reflectivity of the bare surface to the one of the surface after deposition of molecules. Due to the different environment of the molecules in the first, the second, and higher layers, these layers can be easily identified based on their spectral fingerprints. For anisotropic samples, linear polarized light (pol-DRS) can be used to obtain information about the orientation of the molecules. The combination of both techniques, applied synchronized in one experiment, turns out to be a very powerful tool to make a direct correlation of the morphology and the optical properties of the sample. As an example, the deposition of α-sexithiophene on different silver surfaces will be discussed throughout the entire presentation.