Effect of intrinsic defects on the electronic structure of BN nanotubes

The effect of intrinsic defects on the electronic structure of boron-nitrogen nanotubes (5, 5) and (9, 0) is investigated by the method of linearized associated cylindrical waves. Nanotubes with extended defects of substitution N _B of a boron atom by a nitrogen atom and, vice versa, nitrogen by boron B N with an impurity concentration of 1.5 to 5% are considered. It is shown that the presence of such defects significantly affects the band structure of boron-nitrogen nanotubes. A defect band D ^π(B, N) is formed in the bandgap, which sharply reduces the width of the gap. The presence of impurities also affects the valence band: the widths of s, sp, and p _π bands change and the gap between s and sp bands is partially filled. These effects may be detected experimentally by, e.g., optical and photoelectron spectroscopy.