Hydrocarbon adsorption on Si(001): When does the Si dimer bond break?

We have used ab initio calculations to study the structural and electronic properties of two simple hydrocarbons, C2H4 and C2H2, adsorbed on the Si(001) surface. The hydrocarbons adsorb above surface dimers, saturating the dangling bonds and in the process weakening the carbon-carbon bond of the molecule. We found that the σ-bond of the silicon dimer remains intact but may be broken by post-hydrogenation of the surface. This resolves an apparent conflict between previous calculations and recent experiments. © 1997 Elsevier Science B.V. All rights reserved.