Electronic and structural properties of vacancies and antisites of silicon carbide and CS₁ nanotubes

We have studied the energetic, stability, equilibrium geometries and electronic properties of neutral native defects in S_iC nanotubes and Cs_i. We found that calculations show that silicon carbon nanotubes are always semiconducting. The energy band gap of these tubes is weakly dependent on their chirality with direct band gaps for zigzag tubes (n, 0) and indirect gaps for armchair and chiral tubes. Silicon carbon nanotubes are produced by S_iD reaction with carbon nanotubes at about 1200°C and the formation by numerous native defect are found. The calculations were made by first principles density function theory, using the local spin density approximation for the exchange correlation term. We found that S_iC defects, C-rich exhibit the lowest formation energies followed by CS_i at Si-rich conditions. Electronic structure of these defects is an empty electronic level close to the bottom of the conduction band. The use of nonzero electronic temperature promotes a partial occupation of the almost degenerate levels within the nanotube gap.