Photoemission study ofC60/Si(111)adsorption as a function of coverage and annealing temperature

We report core-level and valence-band (VB) photoemission data of ${\mathrm{C}}_{60}$ molecules adsorbed at room temperature (RT) on Si(111). The measurements have been carried out as a function of ${\mathrm{C}}_{60}$ coverage [from 0.20 monolayer (ML) up to 2.2 ML] and annealing temperature (from RT up to 1300 K). From the VB spectra no increasing of the Fermi-level photoemission intensity has been observed for all the coverages investigated thereby indicating that no charge transfer occurs at the interface. Remarkable changes take place on the 1-ML spectrum as the annealing temperature is increased up to the disruption of the ${\mathrm{C}}_{60}$ cages and the following formation of SiC.