Rare earth modified silicon surfaces as templates for organic layer growth

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The ordered growth of thin organic layers on silicon surfaces is currently of high interest because of their fascinating physical properties as well as in view of possible applications including the integration of organics into the silicon technology. However, pure silicon surfaces are highly reactive because of their unsaturated dangling bonds, usually leading to rather disordered organic films. An interesting alternative are silicon surfaces modified by thin layers of atoms such as hydrogen, boron, or metal atoms, which have been studied intensively. Recently, we observed for the first time that Si(111) surfaces covered by rare earth silicide monolayers are a promising template for the highly ordered growth of thin organic films, in this case of cobalt phthalocyanine molecules. In the present project we plan a detailed study of selected organic molecules deposited on these rare earth modified silicon surfaces in order to determine the atomic structure and morphology of the films, the mechanisms for ordered growth, and their electronic and chemical properties. For this purpose, we employ scanning tunneling microscopy and spectroscopy, low energy electron diffraction, photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy. By selecting molecules with different structure and different characteristics of potentially reactive sites, we may vary the balance between the less local van-der-Waals interaction and the local chemical bonding in order to tune the mobility of the molecules and therewith their trend to form ordered layers.