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We use the density functional theory B3LYP/6-31G(d) to study the graphene quantum dots with zigzag edges. The result shows that the ground states of different size graphene quantum dots are all ferromagnetic spin-triplet states. The magnetic properties orignate both from the boundary carbon atom occuping protruding position, and from the carbon atom with unpaired electron. On the whole, the energy gap of other structures decreases with the increase of the number of benzene rings as excepted for the structure of 6b, and the system energy gap decreases significantly by the added charges. In addition, using time-dependent density functional theory (TD-DFT), the excited states of the triangular structure composed of six carbon rings which have an energy gap is 3.83 eV are calculated, and the results show that the 17th excited state has the greatest excitation strength, the excitation energy is 3.93 eV, corresponding to a wavelength of 315.8 nm, close to experimental result.
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Keywords:
- graphene quantum dots /
- magnetism /
- energy gap /
- excited state
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[7] Berger C, Song Z, Li T, Li X, Ogbazghi A, Feng R, Dai Z, Marchenkov A, Conrad E, First P, deHeer W 2004 Phys. Chem. B 108 19912
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[21] Nakada K, Fujita M, Dresselhaus G, Dresselhaus M S 1996 Phys. Rev. B 54 17954
[22] Ouyang F P, Xu H, Wei C 2007 Acta Phys. Sin. 56 1073 (in Chinese) [欧阳方平、徐 慧、魏 辰 2007 物理学报 56 1073]
[23] Kusakabe K, Maruyama M 2003 Phys. Rev. B 67 092406
[24] Son Y W, Cohen M L, Louie S G 2006 Nature (London) 444 347
[25] Pisani L, Chan J A, Montanari B, Harrison N M 2007 Phys. Rev. B 75 064418
[26] Huang B, Liu F, Wu J, Gu B L, Duan W 2008 Phys. Rev. B 77 153411
[27] Yu D, Lupton E M, Liu M, Liu W, Liu F 2008 Nano Res. 1 56
[28] Toshiaki E, Kazuyuki T 2009 Solid State Communications 149 1144
[29] Kusakabe K, Maruyama M 2003 Phys. Rev. B 67 092406
[30] Yoshioka H 2003 J. Phys. Soc. Jpn. 72 2145
[31] Ljubisa R Radovic, Bradley B 2005 J. Am. Chem. Soc. 127 5917
[32] Zhao X H, Liu F Y, Zhou L C, Li Y Z, Chen M D 2010 J. Lumin. 3 7
[33] Wei Y, Tong G P 2009 Acta Phys. Sin. 58 3 (in Chinese) [韦 勇、童国平 2009 物理学报 58 3]
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[1] Novoselov K S, Jiang Z, Zhang Y, S V Morozov, Stormer H L, Zeitler U, Maan J C, Boebinger G S, Kim P, Geim A K 2007 Science 315 1379
[2] Novoselov K S, McCann E, Morozov S V, Falko V I, Katsnel-son M I, Zeitler U, D Jiang, F Schedin, Geim A K 2006 Nat. Phys. 2 177
[3] Morozov S V, Novoselov K S, Katsnelson M I, Schedin F, Ponomarenko L A, Jiang D, Geim A K 2006 Phys. Rev. Lett. 97 016801
[4] Katsnelson M I, Novoselov K S, Geim A K 2006 Nat. Phys. 2 620
[5] Hill E W, Geim A K, Novoselov K, Schedin F, Blake P 2006 IEEE Trans. Magn. 42 2694
[6] Schedin F, Geim A K, Morozov S V, Hill E W, Blake P, Katsnelson M I, Novoselov K S 2007 Nat. Mater. 6 652
[7] Berger C, Song Z, Li T, Li X, Ogbazghi A, Feng R, Dai Z, Marchenkov A, Conrad E, First P, deHeer W 2004 Phys. Chem. B 108 19912
[8] Eda G, Lin Y Y, Mattevi C, Yamaguchi H, Chen H A, Chen I-S, Chen C W, Chhowalla M 2009 Adv. Mater. 21 1
[9] Somnath Bhowmick, Vijay B Shenoy 2008 Chem. Phys. 128 244717
[10] Son Y W, Cohen M L, Louie S G 2006 Phys. Rev. Lett. 97 216803
[11] Tan C L, Tan Z B, Ma L, Chen J, Yang F, Qu F M, Liu G T, Yang H F, Yang C L, Lu L 2009 Acta Phys. sin. 58 8 (in Chinese) [谭长玲、谭振兵、马 丽、陈 军、杨 帆、屈凡明、刘广同、杨海方、杨昌黎、吕 力 2009 物理学报 58 8]
[12] Li X, Wang X, Zhang L, Lee S, Dai H 2008 Science 319 1229
[13] Ponomarenko L A, Schedin F, Katsnelson M I, Yang R, Hill E W, Novoselov K S, Geim A K 2008 Science 320 356
[14] Pan D Y, Zhang J C, Li Z, Wu M H 2010 Adv. Mater. 22 734
[15] Rothberg L J, Lovinger A J 1996 J. Mater. Res. 11 3174
[16] Wang W L, Meng S, Kairas E 2008 Nano Lett. 8 241
[17] Fernandez-Rossier J, Palacios J J 2007 Phys. Rev. Lett. 99 177204
[18] Wang W L, Meng S, Kairas E 2008 Nano Lett. 8 241
[19] Ezawa M 2007 Phys. Rev. B 76 245415
[20] Hod O, Barone V, Scuseria G E 2008 Phys. Rev. B 77 035411
[21] Nakada K, Fujita M, Dresselhaus G, Dresselhaus M S 1996 Phys. Rev. B 54 17954
[22] Ouyang F P, Xu H, Wei C 2007 Acta Phys. Sin. 56 1073 (in Chinese) [欧阳方平、徐 慧、魏 辰 2007 物理学报 56 1073]
[23] Kusakabe K, Maruyama M 2003 Phys. Rev. B 67 092406
[24] Son Y W, Cohen M L, Louie S G 2006 Nature (London) 444 347
[25] Pisani L, Chan J A, Montanari B, Harrison N M 2007 Phys. Rev. B 75 064418
[26] Huang B, Liu F, Wu J, Gu B L, Duan W 2008 Phys. Rev. B 77 153411
[27] Yu D, Lupton E M, Liu M, Liu W, Liu F 2008 Nano Res. 1 56
[28] Toshiaki E, Kazuyuki T 2009 Solid State Communications 149 1144
[29] Kusakabe K, Maruyama M 2003 Phys. Rev. B 67 092406
[30] Yoshioka H 2003 J. Phys. Soc. Jpn. 72 2145
[31] Ljubisa R Radovic, Bradley B 2005 J. Am. Chem. Soc. 127 5917
[32] Zhao X H, Liu F Y, Zhou L C, Li Y Z, Chen M D 2010 J. Lumin. 3 7
[33] Wei Y, Tong G P 2009 Acta Phys. Sin. 58 3 (in Chinese) [韦 勇、童国平 2009 物理学报 58 3]
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