Preparation and Characterization of Self-Assembled Monolayers on Germanium Surfaces

The formation of self-assembled monolayers (SAMs) by specific organic molecules with appropriate anchor groups on semiconductor surfaces may be used to probe the chemical state and quality of the surface or to achieve surface passivation. Molecules with thiol anchor groups are able to bond to hydrogen-terminated germanium surfaces (Ge-S bond). We have prepared SAMs of alkylthiols with different head groups on germanium. Since the surface preparation of germanium is neither well understood nor developed, the controlled preparation of an oxide-free completely H-terminated surface which is a prerequisite for SAM formation of alkylthiols turned out to be a major challenge. Several approaches have been studied. The characterization of the germanium surface prior to and after SAMs formation has been performed by AFM, XPS, Synchrotron-TXRF and -NEXAFS.