Electronic and magnetic properties of stacked graphene quantum dots

The electronic properties of vertically coupled stacked graphene quantum dots (GQDs) of triangular shape are investigated using density functional theory, including the influence of applied electric field. Both bilayer and trilayer configurations with different sizes are considered, and quantum dot edges are assumed to be passivated with hydrogen atoms. The electric field has, indeed, an effect on the relative positions of atoms in the layers and also on the inter-layer distances, although it is very slight, just reaching up to half an Angstrom. Electronic states in the dots are not largely affected by the electric field in the case of AA and AAA stacks, but significant variations are induced by it in the case of AB and ABA structures, mainly in the states with energies in the vicinity if the Fermi level. Magnetic features are reported for zigzag structures via the calculation of total spin moment. No magnetic response associated with spin is present on the case of AA bilayer GQDs, whereas zigzag-edged trilayer ABA and AAA, and bilayer AB structures show a net magnetic polarization. In trilayer GQDs, the magnetization is significantly reduced as a result of the increment in electric field intensity, independently of the size. In contrast, for bilayer AB structures, total spin moment is only very slightly affected by the applied field.