Initial stage of flourofullerene molecules adsorption on Si surface

Spatially resolved images of an individual C$_{60}$F$_{18}$ fluorofullerene molecule on Si$(100)-2\times1$ surface have been obtained using scanning tunneling microscopy (STM). STM results and ab initio calculations show that the fluorofullerene molecules interact with the Si$(100)-2\times1$ surface with $F$ atoms pointing down towards the surface. The adsorption energy of a C$_{60}$F$_{18}$ molecule on Si$(100)-2\times1$ surface is $\sim12\,$leV, which is much higher than the adsorption energy of the same molecule on Si$(111)-7\times7$ surface ($6.65$ eV). C$_{60}F_{18}$ molecules are located in the troughs in-between the dimer rows occupying the four-dimer site on Si$(100)-2\times1$ surface.