Effect of nitrogen impurities on the physical properties of ZnO nanowires: First-principles study

We present an analysis of the structural, electronic, and magnetic properties of nitrogen-doped ZnO nanowires (hexagonal and triangular shapes) as obtained by means of density functional theory calculations. We found that the lattice distortions induced by the presence of neutral defects are negligible in most doping cases and that the energy of the acceptor levels generated by nitrogen depends on the positions of the dopant within the nanowire and on its diameter. Both in hexagonal and triangular nanowires, the defect formation energy decreases when going from the bulk to the surface of the wire; thus, impurities tend to segregate at the surface of the nanostructure. The study of the ferromagnetic stability of the doped systems points to a spin-polarized ground state, particularly in the case of surface doping. Furthermore, a long-range magnetic coupling between dopants that oscillates between ferromagnetic and antiferromagnetic ordering as a function of the defect-defect distance within the nanowire was observed. The striking feature is that such coupling is likely sp, in which the d orbitals of zinc are not involved

Structural and electronic properties of ZnO nanowires: a theoretical study

AbstractZnO nanowires with different sizes and geometrical shapes have been studied by means of density functional theory (DFT) calculations. Atomic relaxation, energetic stability, and electronic properties of these nanostructures show a particular dependence on the shape of the nanowires. Our results indicate that the hexagonal shape nanostructures are more favorable than the triangular one due to lower total surface energy, whereas lattice relaxation and surface states appear to be more pronounced in the case of triangular nanowires

Effect of Vacancies on Electronic and Magnetic Properties of Hydrogen Passivated Graphene Nanoribbons

Using first-principles calculations we have demonstrated that electronic and magnetic properties of armchair graphene nanoribbons are modified by introducing vacancies defects. The equilibrium geometries, electronic, charge spin density distributions, electronic band structures, and magnetic moments were examined in the presence of vacancies. We have found that introducing vacancies into armchair graphene nanoribbons changes the spatial distribution of neighbor atoms, particularly those located around the vacancies. Our calculations showed that the vacancies have significant effect on the magnetization of armchair graphene nanoribbons. Magnetic moment values and electronic behavior in different configurations depend on the number of vacancies. These results suggest that vacancy defects can be used to modify the electronic and the magnetic properties of armchair graphene nanoribbons