Ab initio study of native defects in SiC nanotubes

Spin-polarized density functional theory is used to investigate the electronic and structural properties of vacancies and antisites in zigzag, armchair, and chiral SiC nanotubes. Antisites present lower formation energies compared to vacancies, introducing an empty electronic level close to the bottom of the conduction band for both cases Si-C and C-Si. A carbon vacancy introduces a pair of electronic levels (bonding and antibonding) within the band gap. A silicon vacancy presents the highest formation energy and introduces one occupied level (spin up) resonant within the valence band and three nearly degenerate spin-polarized levels, one for spin up and two for spin down, within the nanotube band gap.