Transition of an adsorption state ofC60on a Si(111)7×7 surface revealed by high-resolution electron-energy-loss spectroscopy

The interaction between ${\mathrm{C}}_{60}$ molecules and a Si(111)7×7 surface has been investigated for various stages of ${\mathrm{C}}_{60}$ coverage by using high-resolution electron-energy-loss spectroscopy (HREELS). In the case of 0.2- and 0.6-ML films, their HREELS spectra indicate the formation of chemical bonds between ${\mathrm{C}}_{60}$ molecules and Si dangling bonds. After the completion of monolayer ${\mathrm{C}}_{60}$ coverage, an $R-19\mathrm{}°$ double-domain structure is formed and its HREELS spectrum is quite similar to that of a monolayer ${\mathrm{C}}_{60}$ film grown on a ${\mathrm{MoS}}_2$ surface. This suggests that bond breaking between ${\mathrm{C}}_{60}$ and Si triggers the transition of adsorption state from a low-coverage disordered structure to the $R-19\mathrm{}°$ ordered structure.