Structure and binding energies of unsaturated hydrocarbons on Si(001) and Ge(001)

Abstract

The adsorption of acetylene, ethylene, and benzene on the Si(001) and Ge(001) surfaces is investigated by first-principles density-functional calculations within the generalized-gradient approximation. We find that the adsorption energies of the three hydrocarbons containing a triple bond, a double bond, and a π -conjugated aromatic ring decrease as the sequence of C 2 H 2 > C 2 H 4 > C 6 H 6 . We also find that the bondings of acetylene, ethylene, and benzene to Ge(001) are much weaker than those to Si(001). As a result, benzene is weakly bound to Ge(001) while it is chemisorbed on Si(001), consistent with temperature-programed desorption data.