Band gap tunability and structural stability of metal/nonmetal codoped group-IV tin nanotubes: Effect of spin-orbit coupling

By using the first principles calculations, the structural and electronic properties of substitutionally group III/V elements codoped buckled tin nanotubes were investigated in details. The dopants (B, N, Al, P, Ga, As) were substituted at different patterns into the structure of armchair and zigzag nanotubes. The results of formation energies indicate that the doped stanene based nanotubes are thermodynamically stable. The band structure calculations indicate that both pristine armchair (8, 8) and zigzag (8, 0) nanotubes act as semiconductors, which can be attributed to opening of band gap around the Fermi energy. For the B, Al and Ga doped nanotubes, the Fermi level shifts to the valence band edge, whereas in the N, P and As doped systems, the Fermi level shifts towards the conduction band edge. By including spin-orbit coupling in the calculations, the band gaps of the considered nanotubes get narrower. Thus, the mono-doped systems exhibit metallic characteristics. However, there is a direct band gap at the Fermi level for B/N-codoped, Al/P-codoped and Ga/As-codoped structures, suggesting the semiconductor property of these systems. Therefore, B/N, Al/P and Ga/As pair doping improves the electronic properties of stanene based nanotubes by opening the band gap at the Fermi energy. Total charge density distribution plots show that there is non-zero charge density between the dopants and Sn atoms, representing the covalent bonds formation between the considered atoms.