Vacancies in SiC nanopowders

Origin of vacancies in the large-sized SIC nanocrystals (higher than 10 nm) has been investigated using theoretical band structure calculations and ex perimental electronic paramagnetic resonance (EPR) measurements. Influence of geometry sizes on appearance of concrete vacancy has been studied. The t heoretical approach includes self-consistent norm-conserving pseudopotentia l band energy calculations and geometry structure optimisation. The perform ed calculations show that the presence of the vacancies is a necessary attr ibute of the SiC nanocrystallites. Moreover, the type and concentration of the vacancies are dependent on the nanoparticle geometry. We have revealed that spin-polarised states of intracrystallite vacancies differ essentially from vacancies in the bulk crystals. A comparison between the performed th eoretical simulations and obtained EPR experimental data shows the possibil ity of using the proposed methods for prediction of vacancy appearance in t he binary nanocrystallites and possibility for their operation. (C) 2000 El sevier Science S.A. All rights reserved.