Fisrt-Principles Study Of The Boundray Modulation Of Graphene Ribbon

The special structures and physical properties of graphene has aroused widespread concern in many fields such as condensed matter physics. The nature of graphene ribbon has a close relationship with the boundary structure and morphology. For example, ribbon with Zigzag or Armchair boundary has different band structures. Modulating the boundary's shape of the ribbon naturally becomes a way of changing the nature of ribbon. In this thesis, using first-principles calculation we have systematically studied the nature of ribbon which affected from the boundary modulation of the shape.By introducing several defects with a certain depth and width on the boundaries of graphene ribbons, we studied the atomic and electronic structures of ribbons which were turned by changing the depths, widths and symmetry of the defects. We found that:the shapes of defects have a large impact upon the electronic structures of ribbons'boundaries. They can significantly modulate the electronic structures in the vicinity of the Fermi level and the spin polarization. The existence of defects have a larger impact on the bonds near the boundaries, which make them have a tendency of reconstruct and form the pentagon. Increasing the depth of the defects, the ribbon have a tendency of turning a conductor, while accompanied by the spin polarization. In contrast, the changing width of defects have a less impact upon the electronic structures but withdrawal the magnetization of the ribbon. And it seems that the affection of the changing symmetry of the defects is weak.