First-principles study of the adsorption of C2H2 and C2H4 on Si(100) -: art. no. 073306

The adsorption of acetylene and ethylene on the Si(100) surface is studied by first-principles density-functional calculations within the generalized gradient approximation. Both molecules are found to adsorb identically on the top of Si dimers, forming two sigma bonds between C and Si atoms. This result does not support a recent photoelectron imaging observation where the adsorption sites of the two molecules differ from each other. Controversial issues, such as the intactness of the Si dimer bond and the saturation coverages of both adsorbed molecules, are discussed.