Study On The Electronic Structure Of The Interface Between Metal-organic Semiconductor

Organic semiconductors on metal surfaces are interesting for their potential application in the production of highly scaled and highly efficient electronic device Many studies have in fact shown that well-ordered films grown with high structural quality are the most relevant for these devices. So it is necessary to study the electronic and geometry structure of adsorbed molecular films which are responsible for the charge injection ability, the charge transport, and light emission/absorption processes. The self-assemble of layers of molecules on a solid surface has been shown to represent a balance between molecule-substrate and molecule-molecule interaction. The molecule-substrate interaction controls both the electrical properties and the conformation and the arrangement of individual and/or groups of molecules on the substrate.The fluorescein molecule, in most favorable structure, is on hollow site, and the adsorption energy is 2.34 eV. Here the adsorption sites refer to the positions at the first layer of the substrate where the middle carbon atom of the fluorescein molecule is located. Our results showed that the interface structure of fluorescein/Ag(110) is determined largely by the molecule-substrate interaction i.e., the O-Ag bonds. The electron charge flows mainly from the metal to the molecule, and this transfer leads to a slight positive charging of the silver atoms in the topmost layer, enhancing the local electrostatic interaction between Ag atoms and oxygens. The O-Ag attraction distorts the Triring plane of fluorescein from planarity.The changes in binding energy of the Ag d band and the emission feature from the organic molecule FePc indicate an interaction between the organic molecule FePc and the Ag(110) substrate. There is an electron transformation and distribution between the organic molecules and the substrate. ARUPS measurements show that the molecular plane is parallel to the substrate surface in the case of one monolayer. The theoretical calculation confirms the experimental results and indicates that the top site is the most stable adsorption configuration.With the deposition rate beyond 0.5 ML per min, the FePc molecules are not deposited dispersedly, but are deposited as the molecular cluster. After the heat treatment (the temperature higher than 420 K), the ordered organic structures of p(2×5) or p(5x2) are obtained from STM. The ordered adsorption structures are in the tilt adsorption model. The FePc molecules in the different domain are aligned along the [011] or [011] azimuth, respectively, the molecules are tilted.