The equilibrium geometry, energetic, and electronic properties of antisites and vacancies in BC2N nanotubes were studied by spin density-functional calculations. An investigation was made of these defects in both the zigzag (4,0) and the armchair (3,3) nanotubes. It was found that B and N, occupying non-equivalent C sites (BCII and NCI) in both tubes, had the lowest formation energies; showing that they were energetically favorable to form under B-rich and N-rich growth conditions. They also exhibited acceptor and donor properties, suggesting the formation of defect-induced p-type and n-type BC2N nanotubes. In addition, C at B and N sites (CB and CN) also exhibited p-type and n-type properties, respectively, as well as low formation energies. Vacancies were less favorable defects with high formation energies as compared to the most stable antisites. Once a vacancy was formed, a strong reconstruction occurred, resulting in an under-coordinated atom which typically gives rise to deep levels in the band gap, changing the electronic properties of the nanotube. The results suggested that, with suitable growth conditions, it would be possible to synthesize BC2N nanotubes with intrinsic donor and acceptor character by inducing selective antisite defects.

Stability and Electronic Properties of Vacancies and Antisites in BC2N Nanotubes. J.Rossato, R.J.Baierle, W.Orellana: Physical Review B, 2007, 75[23], 235401 (7pp)