Molecular modeling of alkyl monolayers on the Si(111) surface

A computational approach has been delineated to model alkyl monolayers on h ydrogen-terminated silicon (111) surfaces by molecular mechanics calculatio ns. The monolayers can be properly described by making use of two-dimension ally repeating boxes with minimally similar to 30 alkyl chains. For two dif ferent substitution patterns on the Si surface, both with an overall substi tution percentage of 50%, good agreement between the computational and the available experimental data (FT-IR, X-ray, ellipsometry) was found. It is s hown that the thus formed layers are nearly stress-free and that different orientations of individual alkyl chains exist, which combined yield an over all uniformly ordered monolayer.