The self-assembly of alkyl-trichlorosilanes on model surfaces of biphenylthiols

Despite of its technological relevance, the self assembly of alkyl-trichlorosilanes onto oxidized metal or semiconductor surfaces is still not fully understood. Phenomena, such as island formation and polymerization, hamper the formation of densely packed and well-ordered self assembled monolayers (SAM). To elucidate the influence of the distribution of OH groups on the surface, we have used 4-mercaptobiphenyls (MBP) to prepare stable, molecularly engineered surfaces and used them as substrates for the assembly of alkyl-trichlorosilanes. The monolayers of MBP as well as the bilayer assemblies were characterized by contact angle, ellipsometry, IR spectroscopy, X-ray photoelectron spectroscopy, sum frequency generation, and AFM. In combination with the results of ab initio calculations, a detailed picture of the film formation of the silane overlayer could be achieved.