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基于密度泛函理论的第一性原理方法, 研究了含单排线缺陷锯齿型石墨烯纳米带(ZGNR)的电磁性质, 主要计算了该缺陷处于不同位置时的能带结构、透射谱、自旋极化电荷密度、总能以及布洛赫态. 研究表明, 含单排线缺陷的ZGNR和无缺陷的ZGNR在非磁性态和铁磁态下都为金属. 虽然都为金属, 但其呈金属性的成因有差异. 在反铁磁态下, 单排线缺陷越靠近ZGNR的边缘, 对ZGNR电磁性质的影响越明显, 缺陷由ZGNR对称轴线向边缘移动过程中, 含单排线缺陷的ZGNR有一个半导体-半金属-金属的相变过程. 虽然线缺陷靠近中线的ZGNR为半导体, 但由于缺陷引入新的能带, 导致含单排线缺陷的ZGNR的带隙小于无缺陷ZGNR的带隙. 单排线缺陷紧邻边界时, 含缺陷ZGNR最稳定; 单排线缺陷位于次近邻边界位置时, 含缺陷ZGNR最不稳定. 在反铁磁态下, 对单排线缺陷位于对称轴线的ZGNR施加适当的横向电场, 可以实现半导体到半金属的转变. 这些研究结果对于发展基于石墨烯的纳米电子器件有重要的意义.In this paper, electromagnetic properties of the zigzag graphene nanoribbon (ZGNR) with a single-row line defect are studied by using the first-principles method based on the density functional theory. The energy band structures, transmission spectra, spin polarization charge densities, total energies, and Bloch states of the ZGNR are calculated when the line defect is located at different positions inside a ZGNR. It is shown that ZGNRs with and without a line defect at nonmagnetic and ferromagnetic states are metals, but the reasons for it to become different metals are different. At the antiferromagnetic state, the closer to the edge of ZGNR the line defect, the more obvious the influence on electromagnetic properties of ZGNR is. In the process of the defect moving from the symmetrical axis of ZGNR to the edge, the ZGNR has a phase transition from a semiconductor to a half metal, and then to a metal gradually. Although the ZGNR with a line defect close to the central line is a semiconductor, its band gap is smaller than the band gap of perfect ZGNR, owing to the new band introduced by the defects. When the line defect is located nearest to the boundary, the ZGNR is stablest. When the line defect is located next nearest to the boundary, the ZGNR is unstablest. When the line defect is located nearest or next nearest to boundary, the ground state of the ZGNR is a ferromagnetic state. However, if the line defect is located at the symmetric axis of ZGNR (M5) or nearest to the symmetric axis, the ground state would be an antiferromagnetic state. At the antiferromagnetic state, the phase transition of M5 from a semiconductor to a half metal can be achieved by applying an appropriate transverse electric field. Without a transverse electric field, M5 is a semiconductor, and the band structures of up-and down-spin states are both degenerate. With a transverse electric field, band structures of up-and down-spin states near the Fermi level are both split. When the electric field intensity is 2 V/nm, M5 is a half metal. These obtained results are of significance for developing electronic nanodevices based on graphene.
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Keywords:
- graphene nanoribbon /
- line defect /
- spin polarization
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[1] Novoselov K S, Geim A K, Morozov S V, Jiang D, Zhang Y, Dubonos S V, Grigorieva I V, Firsov A A 2004 Science 306 666
[2] Zhang W X, Liu Y X, Tian H, Xu J W, Feng L 2015 Chin. Phys. B 24 076104
[3] Li J, Zhang Z H, Zhang J J, Tian W, Fan Z Q, Deng X Q, Tang G P 2013 Org. Electron. 14 958
[4] Li J, Zhang Z H, Wang D, Zhu Z, Fan Z Q, Tang G P, Deng X Q 2014 Carbon 69 142
[5] Westervelt R M 2008 Science 320 324
[6] Matulis A, Peeters F M 2008 Phys. Rev. B 77 115423
[7] Pedersen T G, Flindt C, Pedersen J, Mortensen N A, Jauho A P, Pedersen K 2008 Phys. Rev. Lett. 100 136804
[8] Xu H, Heinzel T, Zozoulenko I V 2009 Phys. Rev. B 80 045308
[9] Sahu B, Min H, MacDonald A H, Banerjeel S K 2008 Phys. Rev. B 78 045404
[10] Wimmer M, Adagideli I, Berber S, Tomanek D, Richter K 2008 Phys. Rev. Lett. 100 177207
[11] Yao Y X, Wang C Z, Zhang G P, Ji M, Ho K M 2009 J. Phys.: Condens. Matter 21 235501
[12] Son Y, Cohen M L, Louie S G 2006 Phys. Rev. Lett. 97 216803
[13] Wang D, Zhang Z H, Deng X Q, Fan Z Q 2013 Acta Phys. Sin. 62 207101 (in Chinese) [王鼎, 张振华, 邓小清, 范志强 2013 物理学报 62 207101]
[14] Ouyang F P, Xu H, Lin F 2009 Acta Phys. Sin. 58 4132 (in Chinese) [欧阳方平, 徐慧, 林峰 2009 物理学报 58 4132]
[15] Wang Z Y, Hu H F, Gu L, Wang W, Jia J F 2011 Acta Phys. Sin. 60 017102 (in Chinese) [王志勇, 胡慧芳, 顾林, 王巍, 贾金凤 2011 物理学报 60 017102]
[16] Zhang W X, He C, Li T, Gong S B 2015 RSC Adv. 5 33407
[17] Kan M, Zhou J, Sun Q, Wang Q, Kawazoe Y, Jena P 2012 Phys. Rev. B 85 155450
[18] Tang G P, Zhang Z H, Deng X Q, Fan Z Q, Zhu H L 2015 Phys. Chem. Chem. Phys. 17 638
[19] Tang G P, Zhou J C, Zhang Z H, Deng X Q, Fan Z Q 2013 Carbon 60 94
[20] Dai Q Q, Zhu Y F, Jiang Q 2013 J. Phys. Chem. C 117 4791
[21] Lahiri J, Lin Y, Bozkurt P, Oleynik I I, Batzill M 2010 Nat. Nanatechnol. 5 326
[22] Zeng M G, Shen L, Cai Y Q, Sha Z D, Feng Y P 2010 Appl. Phys. Lett. 96 042104
[23] Zhang Z H, Guo C, Kwong D J, Li J, Deng X Q, Fan Z Q 2013 Adv. Funct. Mater. 23 2765
[24] Zhang Z H, Deng X Q, Tan X Q, Qiu M, Pan J B 2010 Appl. Phys. Lett. 97 183105
[25] Pan J B, Zhang Z H, Deng X Q, Qiu M, Guo C 2011 Appl. Phys. Lett. 98 013503
[26] Pan J B, Zhang Z H, Deng X Q, Qiu M, Guo C 2011 Appl. Phys. Lett. 98 092102
[27] Zhang Z, Zhang J, Kwong G, Li J, Fan Z, Deng X, Tang G 2013 Sci. Rep. 3 2575
[28] Young W S, Marvin L C, Steven G L 2006 Nature 444 347
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