The quality of SiC film formed by thermal reaction of C₆₀ monolayer on Si(111)-(7×7) surface

We have investigated the quality of SiC film formed by the thermal reaction of C₆₀ molecules on Si(111)-(7×7) surface by the combined measurements of high-resolution electron-energy-loss spectroscopy (HREELS) and scanning tunneling microscopy (STM), HREELS-STM. The surface phonon energy of SiC film, formed by heating the C₆₀ monolayer adsorbed Si(111)-(7×7) surface up to 1173 K, is observed at 114 meV. Moreover, new peaks are measured at 91, 102, 192, 205, 215 and 228 meV in high resolution measurements. STM image of SiC films shows the presence of many domains which surface areas are 10×10-35 nm². Taking into account of the areas of SiC islands, we attribute the electron energy loss peaks at 91, 102 and 114 meV to the Si-C bonding at the SiC surfaces, the low frequency Fuchs-Kliewer phonon mode and the high-frequency one, respectively. The electron energy loss peaks observed around 200 meV is estimated to be the combination bands of those at 91, 102 and 114 meV. Considering the redshift of Fuchs-Kliewer phonon, SiC film formed by the thermal reaction of Si substrate with 1 ML of C₆₀ is mainly composed of the "buffer" layer. The coupling of modes perpendicular and parallel to the surface indicate that the SiC surface is not idealy flat.