Thermal reactions at the interface between Si and C nanoparticles: nanotube self-assembling and transformation into SiC

The thermal reactions induced in C nanoparticles films deposited on Si substrates were followed by high resolution C 1s and Si 2p core level spectroscopy. These particles, when annealed at ∼1300 K transform into single wall carbon nanotubes [Appl. Phys. Lett. 80 (2002) 1441; Chem. Phys. Lett. 355 (2002) 395]. With increasing temperature a progressive re-hybridization of the sp3 into the sp2 carbon phase was observed. At 1270 K the C 1s core level showed a major component at 284.29 eV related to the graphitic tubes, and minor one at 283.75 eV, attributed to CSi bonds at the interface, which however do not seem to participate in the nanotube self-assembling. A strong reaction between Si atoms evaporated from the substrate and nanotube walls was observed at 1400 K, which led to the formation of stoichiometric SiC, occurring as a site-confined reaction.