First-principles study of electronic transport properties of graphene nanoribbons with pentagon-heptagon (5-7) line defe
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First-principles study of electronic transport properties of graphene nanoribbons with pentagon-heptagon (5-7) line defects Yasutaka Nishida, Takashi Yoshida, Fumihiko Aiga, Yuichi Yamazaki, Hisao Miyazaki, Akihiro Kajita, Tadashi Sakai Low-power Electronics Association & Project (LEAP), Tsukuba, Ibaraki 305-8569, Japan ABSTRACT In this study, we investigated the influence of line defects consisting of pentagonheptagon (5-7) pairs on the electronic transport properties of zigzag-edged and armchair-edged graphene nanoribbons (GNRs). Using the first-principles density functional theory, we study their electronic properties. To investigate their current-voltage (I-V) characteristics at low bias voltage (~ 1 meV), we use the nonequilibrium Green’s function method. As a result, we found that the conductance of the GNRs having a connected line defect between source and drain shows better performance than that of the ideal zigzag-edged GNRs (ZGNRs). A detailed investigation of the transmission spectra and the wave function around the Fermi level reveals that the line defects arranged along the transport direction work similar to an edge state of the ZGNRs and can be an additional conduction channel. Our results suggest that such a line defect can be effective for low-resistance GNR interconnects. INTRODUCTION In nanotechnology, graphene has been extensively studied for promising electronic applications [1] both theoretically and experimentally. A planar graphene is a special kind of semimetal with a density of states equal to zero at the Fermi level. Thus, it shows characteristic properties, for instance, high carrier mobility [2,3] because of massless Dirac electron. Since the development of innovative techniques [4] for the fabrication of single-sheet graphene, twodimensional nanometric carbon materials have attracted considerable interest in application in view of their potential for application in low-power-consumption devices. Among these materials, graphene nanoribbons (GNRs) have attracted much attention in regard to interconnect applications [5,6,7,8]. An interesting point concerning GNRs is that they exhibit a quite different property from a planar graphene; their electronic properties depend on the width and edge structure [9,10], namely, zigzag-edged (ZGNRs) or armchair-edged graphene nanoribbons (AGNRs). Whereas the ZGNRs exhibit unique transport properties originating from a high density of states at the Fermi level, AGNRs have a band gap. Accordingly, from an engineering viewpoint, controlling the edge states of GNRs is important for the fabrication of low-resistance interconnects. Theoretically, a typical approach for modifying the edge states in GNRs is substitutional doping with, for example, boron or nitrogen. The edge-doped ZGNRs [11,12,13,14,15] and AGNRs [16,17,18,19] with B or N atoms have been investigated by many authors using first-principles calculation. An alternative approach is to introduce topological line defects. For example, self-doping induced by the electron-hole symmetry breaking, in whi
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