Conversion between two binding states of benzene on Si(001)

초록

The adsorption and reaction of benzene on the Si(001) surface are investigated by first-principles density-functional calculations within the generalized gradient approximation. We find that the "tight-bridge" configuration in which benzene bonds across two adjacent Si dimers is more stable than the "butterfly" configuration in which benzene bonds on top of a single Si dimer. Upon benzene adsorption the latter configuration is initially formed but is converted to the former one with an energy barrier of 0.87 eV. As the coverage increases, such a convertion will be blocked if the butterfly configuration is formed at a single Si dimer site between two tight-bridge benzenes. Therefore we suggest that both the butterfly and tight-bridge configurations could coexist at saturation coverage, providing an explanation for recent high-resolution core-level photoelectron spectroscopy data.