The chemisorption of coronene on Si(001)-2 x 1

Coronene (C24H12) adsorption on the clean Si(001)-2 x 1 surface was investigated by scanning tunneling microscopy and by density-functional calculations. The coronene adsorbed randomly at 25 degrees C on the surface and did not form two-dimensional islands. The scanning tunneling microscopy measurements revealed three adsorption sites for the coronene molecule on the Si(001) surface at low coverage. The major adsorption configuration involves coronene bonding to four underlying Si atoms spaced two lattice spacings apart in a dimer row. The two minor adsorption configurations involve asymmetrical bonding of a coronene molecule between Si dimer rows and form surface species with a mirror plane symmetry to their chiral neighbor species. The two minor bonding arrangements are stabilized by a type-C defect on the Si(001) surface.