Nanostructured SiC films obtained by neutral-cluster depositions

Abstract

Nanosized neutral silicon-carbon compound clusters produced by a laser vaporization source have been analyzed in the gas phase and deposited at room temperature on various substrates in an ultrahigh vacuum environment to produce nanostructured thin films. The electronic structure has been probed by complementary techniques, such as x-ray photoemission and electron-energy-loss spectroscopies, and the vibrational structure investigated using Raman spectroscopy. The film presents a morphology close to an amorphouslike one. However, the main properties cannot be understood in terms of pure ${\mathrm{sp}}^{3}$ hybridization throughout the films. Due to the finite cluster size, the chemical order, which, is the key to ensuring the stability in the bulk phase, is counterbalanced by the trend for the dangling-bond saturation in the surface-reconstruction process. A partial phase separation is observed, consisting of silicon- and carbon-rich local phases. Theoretical results obtained within a simple tight-binding model are reported in order to qualitatively discuss the experimental results on the valence-band electronic structure.