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Keywords:

  • density functional theory;
  • electronic properties;
  • graphene;
  • half-metallic nature;
  • quantum dots

Abstract

A comprehensive first-principles theoretical study of the electronic properties and half-metallic nature of zigzag edge-oxidized graphene quantum dots (GQDs) is carried out by using density functional theory (DFT) with the screened exchange hybrid functional of Heyd, Scuseria and Ernzerhof (HSE06). The oxidation schemes include -OH, -COOH and -COO groups. We identify oxidized GQDs whose opposite spins are localized at the two zigzag edges in an antiferromagnetic-type configuration, showing a spin-polarized ground state. Oxidized GQDs are more stable than the corresponding fully hydrogenated GQDs. The partially hydroxylated and carboxylated GQDs with the same size exhibit half-metallic state under almost the same electric-field intensity whereas fully oxidized GQDs behave as spin-selective semiconductors. The electric-field intensity inducing the half metal increases with the length of the partially oxidized GQDs, ranging from M=4 to 7.