Adsorption of transition metal atoms (Co and Ni) on zigzag graphene nanoribbon
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- Wang, Z., Xiao, J. & Li, M. Appl. Phys. A (2013) 110: 235. doi:10.1007/s00339-012-7119-8
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The geometry structures and electronic properties of zigzag graphene nanoribbon (ZGNR) with the adsorption of transition metal atoms (Co and Ni) are investigated by using the density functional theory. The calculated results show that the interaction between Ni atom and ZGNR are stronger than that between Co atom and ZGNR. It is found that the ZGNR with Co adatom adsorbing has more possibility to show the character from semiconducting to the half-metallic one than that of the ZGNR with Ni adatom adsorbing. It is hoped that it may be valuable for investigating the GNR-based electronic devices.
Graphene has recently attracted much attention in both theoretical [1, 2, 3, 4, 5, 6, 7, 8, 9] and experimental [10, 11, 12] fields. Graphene nanoribbons (GNRs), which are slices of graphene, are quasi-one-dimensional (1D) structures. They can have different edge geometries, including zigzag and armchair. The electronic structure of the ribbon depends on the edge geometry [13, 14, 15]. The possibility to alter their electronic properties is via the adsorption or doping by external atoms or molecules [16, 17, 18, 19]. V.A. Rigo et al.  have investigated the electronic and transport properties of Ni-doped GNR, and Mayuko Ushiro et al.  have investigated the X-ray absorption of fine structure analyses of Ni trapped in graphene sheet of carbon nanofibers in experiment. Narjes Gorjizadeh et al.  have investigated the electronic and magnetic properties of the GNR whose edges are doped by s-, p-, and d-type atoms. Santos et al.  have investigated the magnetic properties of a graphene monolayer substitutionally doped with Co atom. Cao et al.  have carefully investigated the induced magnetization and electronic structures of graphene with transition metal adatom and dimmer adsorbed. However, the different Co/Ni-adsorbing configurations have not been investigated, yet. So, in this paper, we will investigate the geometry structures and electronic properties of 6-ZGNRs (6 zigzag chain) with Co/Ni-adsorbing.
2 Calculation method
3 Results and discussion
Using a periodic boundary condition, the geometry and electronic band structures of the 6-ZGNRs with Co/Ni-adsorbing have been investigated. The calculated results show that the most stable site for Co/Ni atom adsorption is on the edge of the 6-ZGNR compared with the adsorption site in the middle of the 6-ZGNR. In this paper, Per refers to the perfect 6-ZGNR. As shown in Fig. 1, (a) configuration refers to one Ni atom adsorbing on the edge of the 6-ZGNR, (b) configuration refers to two Ni atoms adsorbing on the two edges of the 6-ZGNR, (c) configuration refers to one Co atom adsorbing on the edge of the 6-ZGNR, (d) configuration refers to two Co atoms adsorbing on the two edges of the 6-ZGNR, and (e) configuration refers to one Ni atom adsorbing on one edge and one Co atom adsorbing on the other edge of the 6-ZGNR.
Bond lengths of Co–C (or Ni–C) for different adatom adsorbing on the 6-ZGNR. The lengths are in Å
Bond length (Co–C or Ni–C): Å
The transferred charge from adatom to the GNRs for different adsorption configurations. The unit is e
The transferred charge from adatom to GNRs (e)
The bandgap of both spins for the Per configuration and different adsorption configurations. The unit is eV
α spin (eV)
β spin (eV)
In conclusion, we present a systematic investigation of the properties of the GNRs with Co/Ni atom adsorbing on the edge in terms of geometry structures and electronic properties. For these adsorption configurations, the formed six Co–C or Ni–C bonds on the edge of the GNR affect the electronic properties of these configurations. The geometry structures, electronic band structures, and charge transfer suggest that the interaction between Ni atom and the 6-ZGNR are stronger than that between Co atom and the 6-ZGNR. The calculated results show that the 6-ZGNR with Co-adsorbing has more possibility to show the character from semiconducting to the half-metallic one than that of the 6-ZGNR with Ni adatom adsorbing. It is hoped that the theoretical results may be useful for designing the GNR-based devices.
This study is financially supported by the Scientific Research Foundation of Guilin University of Technology (Grant No. 002401003326), and the Natural Science Foundation of China (Grant No. 11147194 and 11064003), and Scientific Research Fund of Guangxi Provincial Education Department of China (Grant No.201203YB091).