Growth and characterization of thin PTCDA films on Si(001)

Abstract: The research presented in this thesis concerns experimental studies of the large aromatic semiconducting molecule 3,4,9,10 perylenetetracarboxylic dianhydride (PTCDA) on a clean and hydrogen passivated Si(001) substrate. Thin organic films have the potential use in various electronic and optical devices. The PTCDA/Si(001) is a model system for an organic/inorganic homo junction. The growth and electronic structure of thin PTCDA films was studied in situ at various film thickness ranging from sub-monolayer up to 10 monolayer thickness. The experimental methods used were photoelectron spectroscopy, X-ray absorption

spectroscopy and atomic force microscopy. On the passivated surface the film grows with flat lying molecules. At a coverage about 0.5-2 ML the growth mode changes from a layer by layer to a Stranski-Krastanov growth mode for thicker films. The interaction between the substrate is weak and the electronic structure of the film have only a very small dependence of the film thickness. On the clean surface the substrate-molecule interaction is strong. This give a Stranski-Krastanov growth mode with a change in the molecular orientation, the island size

and shape as well as the electronic structure of the film.