Doping (10,0)-Semiconductor Nanotubes with Nitrogen and Vacancy Defects

The electronic properties of (10, 0)-semiconducting single-walled carbon nanotubes (SWCNTs) containing structural defects such as vacancies (single and di-vacancies), and pyridinic Nitrogen atoms, are investigated using first-principles density functional theory. The band structure, electronic band gap, formation energy, structural relaxation, and HOMO-LUMO wave functions, were systematically calculated using various combinations of vacancies and nitrogen concentrations. It is found that depending on the concentration and location of Nitrogen atoms with respect to the vacancy-sites, semiconducting (10, 0)-SWCNTs could become metallic. After relaxation, di-vacancies, with pyridine-like Nitrogen atoms, undergo a reconstruction so as to form pentagonal and octagonal rings in which Nitrogen behaves as a substitutional atom (not pyridinic) within the graphitic lattice. Interestingly, some Nitrogen doped configurations exhibit a p-type doping characteristics. The possibility of having p-n junctions in SWCNTs by doping with just one element as dopant is also discussed.