Stoichiometry and interface effects on the electronic and optical properties of SiC nanoparticles
Résumé
The physical properties of nanosized SiC particles are investigated as a function of the C/Si ratios. The synthesis by the laser pyrolysis process monitors the particle stoichiometry by the initial fluxes of the reactants (SiH4 and C2H2) and leads to Si- or C-rich batches. Spectroscopic methods such as EPR and Raman are used to probe the paramagnetic active electronic centres as well as the role played by the external surface composition on the effective vibrational and optical properties of the nanoparticles. Numerical methods are undertaken in order to point out the role played by the carbon or silicon excess on the interface properties. In particular, simulations by quantum chemistry codes within the configuration interaction and the parametric method (PM3) evidence the relevant features of the Raman spectra induced by a suitable distribution of C or Si excess within the SiC nanoparticles.