内在缺陷与Cu掺杂共存对ZnO电磁光学性质影响的第一性原理研究
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摘要
采用基于自旋密度泛函理论的平面波超软赝势方法,研究了Cu掺杂ZnO (简称Cu_(Zn))与内在缺陷共存对ZnO电磁光性质的影响.结果表明,Cu是以替位受主的形式掺入的;制备条件对Cu_(Zn)及内在缺陷的形成起至关重要的作用,富氧条件下Cu掺杂有利于内在缺陷的形成,且Cu_(Zn)-O_i最易形成;相反在缺氧条件下,Cu掺杂不利于内在缺陷的形成.替位Cu的3d电子在价带顶形成未占据受主能级,产生p导电类型.与Cu_(Zn)体系相比,Cu_(Zn)-V_O体系中载流子浓度降低,导电性变差;Cu_(Zn)-V_(Zn)体系中载流子浓度几乎不变,对导电性没影响;Cu_(Zn)-O_i体系中载流子浓度升高,导电性增强.纯ZnO体系无磁性;而Cu掺杂ZnO体系,与Cu原子相连的O原子,电负性越小,键长越短,对磁矩贡献越大;Cu_(Zn)与Cu_(Zn)-O_i体系中的磁矩主要是Cu的3d电子与Z轴上O的2p电子耦合产生的;Cu_(Zn)中存在空位缺陷(V_O,V_(Zn))时,磁矩主要是Cu 3d电子与XY平面内O的2p电子强烈耦合所致;Cu_(Zn)中存在V_(Zn)时,磁性还包含V_(Zn)周围0(5, 6)号原子2p轨道自旋极化的贡献;所有体系中Zn原子自旋对称,不产生磁性.Cu_(Zn)-V_(Zn)和Cu_(Zn)-O_i缺陷能态中,深能级中产生的诱导态是0-0 2s电子相互作用产生的.Cu_(Zn)模型的光学带隙减小,导致吸收边红移;Cu_(Zn)-V_(Zn)模型中吸收和反射都增强,使得透射率降低.
For ZnO which is not magnetic itself, it is of great significance to study the source of ferromagnetism and its photoelectric properties when Cu doped ZnO coexists with internal defects. The effects of intrinsic defects on the electronic structures, magnetic and optical properties of Cu-doped ZnO(Cu_(Zn)) are studied by using first principle calculations based on the density functional theory combined with the Hubbard U(DFT+ U_d+ U_p).The results indicate that the doped Cu is a substitute acceptor, and the manufacturing environment plays an important role in forming the Cu_(Zn) with internal defects. Under the oxygen-rich condition, the doped Cu is favorable for forming internal defects, and the Cu_(Zn)-O_i bonds are easily formed. On the contrary, the Cu-doped ZnO is not conducive to forming internal defects under the O-poor condition. The 3 d electrons of the substitute Cu form the unoccupied accepter energy level at the top of valence band, generating p-type conduction.Comparing with Cu_(Zn) system, the carrier concentration of positive hole decreases in Cu_(Zn)-V_O system and the conductivity is poor. In the Cu_(Zn)-V_(Zn) system, the number of carrier holes is almost constant, and the conductivity has no effect. In the Cu_(Zn)-O_i model, the carrier concentration of positive holes increases and the conductivity gets better. The pure ZnO system exhibits non-magnetic behavior. The study also reveals that the smaller the electro-negativity, the greater the contribution to magnetic moment is when O atom is connected with Cu atom. The magnetic moments in Cu_(Zn) and Cu_(Zn)-O_i system are mainly generated by the coupling between the Cu 3 d and the O 2 p orbital on the c axis. When V_O and V_(Zn) exist in Cu_(Zn), the magnetic moment is mainly caused by the strong coupling of Cu 3 d with O 2 p in ab plane. In the presence of V_(Zn) in Cu_(Zn), the magnetism also contains the contribution of the spin polarization of O(5, 6) atoms around V_(Zn). In the defect states of Cu_(Zn)-V_(Zn) and Cu_(Zn)-O_i, the induced states in the deep energy levels are generated by the interaction between the O-O 2 s orbital electrons. The reduced optical band gap of the Cu_(Zn) model results in the red shift of absorption spectrum. The enhanced absorption and reflection of the Cu_(Zn)-V_(Zn) model reduce the transmission.
For ZnO which is not magnetic itself, it is of great significance to study the source of ferromagnetism and its photoelectric properties when Cu doped ZnO coexists with internal defects. The effects of intrinsic defects on the electronic structures, magnetic and optical properties of Cu-doped ZnO(Cu_(Zn)) are studied by using first principle calculations based on the density functional theory combined with the Hubbard U(DFT+ U_d+ U_p).The results indicate that the doped Cu is a substitute acceptor, and the manufacturing environment plays an important role in forming the Cu_(Zn) with internal defects. Under the oxygen-rich condition, the doped Cu is favorable for forming internal defects, and the Cu_(Zn)-O_i bonds are easily formed. On the contrary, the Cu-doped ZnO is not conducive to forming internal defects under the O-poor condition. The 3 d electrons of the substitute Cu form the unoccupied accepter energy level at the top of valence band, generating p-type conduction.Comparing with Cu_(Zn) system, the carrier concentration of positive hole decreases in Cu_(Zn)-V_O system and the conductivity is poor. In the Cu_(Zn)-V_(Zn) system, the number of carrier holes is almost constant, and the conductivity has no effect. In the Cu_(Zn)-O_i model, the carrier concentration of positive holes increases and the conductivity gets better. The pure ZnO system exhibits non-magnetic behavior. The study also reveals that the smaller the electro-negativity, the greater the contribution to magnetic moment is when O atom is connected with Cu atom. The magnetic moments in Cu_(Zn) and Cu_(Zn)-O_i system are mainly generated by the coupling between the Cu 3 d and the O 2 p orbital on the c axis. When V_O and V_(Zn) exist in Cu_(Zn), the magnetic moment is mainly caused by the strong coupling of Cu 3 d with O 2 p in ab plane. In the presence of V_(Zn) in Cu_(Zn), the magnetism also contains the contribution of the spin polarization of O(5, 6) atoms around V_(Zn). In the defect states of Cu_(Zn)-V_(Zn) and Cu_(Zn)-O_i, the induced states in the deep energy levels are generated by the interaction between the O-O 2 s orbital electrons. The reduced optical band gap of the Cu_(Zn) model results in the red shift of absorption spectrum. The enhanced absorption and reflection of the Cu_(Zn)-V_(Zn) model reduce the transmission.
引文
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[2] Ahn K S, Deutsch T, Yan Y, Jiang C S, Perkins C L, Turner J, Jassin M A 2007 J. Appl. Phys. 102 023517
[3] Wei M, Braddon N, Zhi D, Midgley P A, Chen S K, Blarmire M G, Driscoll J L M 2005 Appl. Phys. Lett. 86 072514
[4] Drmosh Q A, Rao S G, Yamani Z H, Gondal M A 2013 Appl.Surf. Sci. 270 104
[5] Suja M, Bashar S B, Morshed M M, Liu J 2015 ACS Appl.Mater. Interface, 7 8894
[6] Chakraborty M, Ghosh A, Thangavel R 2015 J. Sol-Gel Sci.Technol. 74 756
[7] Horzum S, Torun E, Serin T, Peeters F M 2016 Philos. Mag.96 1743
[8] Vachhani P S, Bhatnagar A K 2013 Phys. Scr. 8715 045702
[9] Xia C H, Wang F, Hu C L 2014 J. Alloys Compd. 589 604
[10] Hou Q Y, Xi Z C, Wu Y, Zhao E J 2015 Acta Phys. Sin. 64167201(in Chinese)[侯清玉,许镇潮,乌云,赵二俊2015物理学报64 167201]
[11] Iqbal J, Jan T, Shafiq M, Arshad A, Ahmad N, Badshah S,Yu R H 2014 Ceram. Int. 40 2091
[12] Li T J, Li G P, Gao X X, Chen J S 2010 Chin. Phys. Lett. 27211
[13] Nia B A, Shahrokhi M, Moradian R, Manouchehri I 2014Eur. Phys. J. Appl. Phys. 67 20403
[14] Keavney D J, Buchholz D B, Ma Q, Chang R P 2007 Appl.Phys. Lett. 91 012501
[15] Xu Q Y. Schmidt H, Zhou S Q, Potzger K, Helm M,Hochmuth H, Lorenz M, Setzer A, Esqtinazi P, Meinecke C,Grundmann M 2008 Appl. Phys. Lett. 92 082508
[16] Znu M Y, Zhang Z H, Zhong M, Tariq M, Li Y, Li W X, Jin H M, Skotnicova K, Li Y B 2017 Ceram. Int. 43 3166
[17] Luo J H, Liu Q, Yani L N, Sun Z Z, Li Z S 2014 Comput.Mater. Sci. 82 70
[18] Wang Q B, Zhou C, Wu J, L(u|¨)T 2013 Opt. Commun. 297 79
[19] Chen Y F, Song Q G, Yan H Y 2012 Comput. Theor. Chem.983 65
[20] Lee M H, Peng Y C, Wu H C 2014 J. Alloys Compd. 616 122
[21] Wu H C, Peng Y C, Chen H C 2013 Opt. Mater. 35 509
[22] Segall M D, Lindan P J D, Probert M J, Pickard C J, Hasnip P J, Clark S J, Payne M C 2002 J. Phys.:Condens. Matter14 2717
[23] Perdew J P, Burke K, Ernzerhof M 1996 Phys. Rev. Lett. 77 3865
[24] Ma X G, Lu B, Li D, Shi R, Pan C S, Zhu Y F 2011 J. Phys.Chem. C 115 4680
[25] Anisimov V V, Zaanen J, Andersen K 1991 Phys. Rev. B:Condens. Matter 44 943
[26] Monkhost H J, Pack J D 1976 Phys. Rev. B 13 5188
[27] Vanderbilt D 1990 Phys. Rev. B:Condens. Matter 41 7892
[28] Janotti A, van de Walle C G 2007 Phys. Rev. B 76 165202
[29] Guo T T, Dong G B, Chen Q, Diao X G, Gao F Y 2014 J.Phys. Chem. Solids 75 42
[30] Sun H G, Fan W L, Li Y L, Cheng X F, Li P, Hao J C, Zhao X 2011 Phys. Chem. Chem. Phys. 13 1379
[31] Chen Y, Xu X L, Zhang G H, X,e H, Ma S Y 2009 Physica B404 3645
[32] Duan Z F, Wang X Q, He A L, Cheng Z M 2011 J. At. Mol.Phys.28 343(in Chinese)[段壮芬,王新强,何阿玲,程志梅2011原子与分子物理学报28 343]
[33] Feriat M, Zaoui A, Ahuja R 2009 Appl. Phys. Lett. 94142502
[34] Yan Y F, Aljassim M M, Wei S H 2006 Appl. Phys. Lett. 89181912
[35] Narendra G L, Sreedhar B, Rao J L, Lakshman S V J 1991 J.Mater. Sci. 26 5342
[36] Lee H Y, Clark S J, Robertson J 2012 Phys. Rev. B 86075209
[37] Lin Q L, Li G P, Xu N N, Liu H, Wang C L 2017 Acta Phys.Sin.66 037101(in Chinese)[林俏露,李公平,许楠楠,刘欢,王苍龙2017物理学报66 037101]
[38] Zhao L, Lu P F, Yu Z Y, Liu Y M, Wang D L, Ye H 2010Chin. Phys. B 19 056104
[39] Xu Q Y, Wu X M, Zhuge L J, Chen X M, Wu Z F 2008MicroFabric.Tech. 12 16(in Chinese)[徐庆岩,吴雪梅,诸葛兰剑,陈学梅,吴兆丰2008微细加工技术12 16]