First-principles studies of the surface reaction of acetylene with H-Si(001)(1 X 1)

摘要

Recent experiments have shown that it is possible to grow a monolayer of 1-alkynes on hydrogenated Si(001)-(1 X 1) surfaces by thermal reaction of the organic compound with the Si surface. Infrared spectros-copy and x-ray reflectivity measurements have indicated that the alkynes form two Si-C bonds to the surface (per reacting molecule). We present the results of a first-principles study of the reaction of acetylene with the hydrogenated Si(001)-(1 X 1) surface. Our calculated minimum-energy path shows that the reaction is possible. In the proposed mechanism there are two metastable states (with a carbon-centered radical) and two hydrogen abstractions. In the final configuration, the organic molecule is attached to the surface with two Si-C bonds, and the system has a large binding energy. We have also investigated the adsorption of a second molecule, finding that this is a self-promoting reaction. However, we have also found that polymerization of the two molecules is another process with similar activation energy indicating that the reaction may not be very efficient, at least for C_2H_2.