Neck formation processes of nanocrystalline silicon carbide: A tight-binding molecular dynamics study

Atomistic and electronic structures in the process of intergranular neck formation of nanocrystalline silicon carbide (SiC) have been investigated by a tight-binding molecular dynamics method. An order-N parallel algorithm is employed for efficient calculations of electronic energy and forces. We find that a defect-free neck is formed between SiC nanocrystals aligned along [112̄] axis at T = 1000 K. In the case of neck formation between tilted nanocrystals (with an orientation equivalent to a {122}, Σ = 9 grain boundary), surface reconstruction before sintering, that is Si-Si bond formation, significantly affects the grain-boundary formation. The spatial distribution of the electronic population and the electronic density of states show that structural defects, accompanied by gap states, are formed around the reconstructed regions after the sintering.