Study of adsorption structure of benzene and toluene on Si(1 1 1)7 × 7 surfaces

The adsorption of benzene and toluene on Si(1 1 1)7 × 7 was investigated using scanning tunneling microscopy (STM) and theoretical calculations. For both aromatic molecules, bright spots in the STM images and populations of the subunits, each consisting of three reacted adatoms, indicated that an adsorbed molecule is involved in a configuration with an adatom and its adjacent rest atom. The structures of adsorbed benzene and toluene were also examined using theoretical calculations involving the cluster model of Si30H28. Several structures were obtained as energetically favorable structures using geometrical optimization calculations. By comparing the binding energies of each structure, the 1,4-cyclohexadiene-like adsorption structure was found to be most energetically favorable for benzene and toluene adsorption. These calculated adsorption structures are in good agreement with the experimental results.