Binding geometry of furan on Si(5 5 12) − 2 × 1

The adsorption configuration of furan molecules on a Si(5 5 12) − 2 × 1 surface was investigated using scanning tunneling microscopy and density functional theory calculations. The molecules nondissociatively and exclusively chemisorbed onto the adatom rows. The adsorption binding structure formed a di-σ bond without the involvement of the oxygen atoms, indicating a [4 + 2] cycloaddition process. Adsorption at other sites, including at the dimer, tetramer, or honeycomb rows, was observed much less frequently. Our calculations predicted that the adsorption energies of the furan molecules were 1.31-2.05 eV at the adatom, dimer, tetramer, and honeycomb rows.