Local structure and chemical reaction of C60 films on Si(111)7 × 7 studied by HREELS-STM

We have investigated the thermal stability and the chemical reactions of C60 thin films on Si(111)7 × 7 surfaces by the combined measurements of the high-resolution electron-energy-loss spectroscopy (HREELS) and the scanning tunneling microscopy (STM), HREELS-STM. After heating the Si up to 400 °C, the molecules did not align perfectly but made local arrangements. The energy shifts of the inelastic electrons indicate that the electrons in the Si dangling bond transfer to the C60 molecules. The value of the charge transfer is estimated to be 1 ± 1 electron(s). After heating the Si up to 800 °C, the smooth C60 monolayer film aggregates and forms islands. The nearest neighbouring distance between the C60 molecules is shortened from 10 إ to 9.3 إ. The intensity of the 92 and 101 meV peaks drastically increase. These results indicate the formation of a covalent bond between the C60 molecules. After heating the Si up to 1100 °C, an SiC film grows.