Magnetic bipolarity and other electronic aspects of (4,4) silicon carbide nanotubes ((4,4)SiCNT) decorated by light noble metals; (Cu, Ag)

Abstract

The changes in structural and electronic properties of (4,4)SiCNT, induced by decoration with copper or silver atoms, are investigated. To this end, the dispersion-corrected density functional theory and Quantum-Espresso computational package, in its spin-polarized mode, are employed. It is found that adsorption of Cu or Ag atoms onto (4,4)SiCNT is exothermic and chemical. From the corresponding geometrical and electronic characteristics, it is concluded that decoration of (4,4)SiCNT by Cu or Ag causes a bulging in the nanotube which breaks the structural symmetry of the compounds. It turns out that in both cases, Si atoms in the tube bulge more drastically in comparison with the C atoms. Consequently, space-dependent electric fields form in the vicinity of adsorption sites, causing the spin degeneracy removal and the two compounds become ferromagnetic bipolar semiconductors. The latter conclusion is further supported by the electronic energy band structures and densities of states. It is also shown that in both materials, the electronic effective masses are by far larger than that in pristine (4,4)SiCNT. The possibility of tuning the magnetic properties of the two compounds by applications of gate (side-wise) potentials is discussed too. The present results then demonstrate novel paths to generate electrically switchable spin-polarized currents.