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α-Fe2O3是一种重要的磁性半导体材料, 在电子器件中应用广泛, 具有重要的研究意义. 本文基于密度泛函理论, 采用GGA+U方法, 应用第一性原理对间隙H掺杂前后的六方相α-Fe2O3的晶格常数、态密度、Bader 电荷分布进行了计算分析. 研究了U值对结果的影响, 发现U=6 eV时, 体相α-Fe2O3的晶胞平衡体积、Fe原子磁矩、带隙值与实验值最符合. 在选取合适U值后, 第一性原理计算结果表明, H掺杂后, 间隙H部分被氧化, 其最近邻的Fe 和O部分被还原, H和O有一定程度的成键. 在费米面附近, 出现了新的杂化能级, 杂化能级扩展了价带顶的宽度, 同时导带底下移, 引起带隙减小, 表明H掺杂是一种有效的能带结构调控方法.Hexagonal α-Fe2O3 is one of the most common functional material used as magnetic semiconductor, and plays an important part in various applications, such as electronic devices etc. Based on the density functional theory, the lattice parameters, density of states and Bader charge analysis of α-Fe2O3 have been calculated using the first-principles calculation with GGA+U method. As Fe is a transition metal element, the value of U can be more accurate by considering the influence of the strong on-site Coulomb interaction between 3d electrons. First, the crystal equilibrium volume, the magnetic moment of Fe atom, and the band gap value of α-Fe2O3 are synthetically researched and compared with those with different U. Results indicate that the calculation model of α-Fe2O3 are in good agreement with the experimental model when the value of U is 6 eV. These parameters can also be adapted to the following doping calculaton. The α-Fe2O3 unit cell has both tetrahedral and octahedral interstitial sites. The calculation of doping formation energy shows that the α-Fe2O3 system is most stable when the doped hydrogen atom is in the tetrahedral interstitial site. The density of states show that the valence band and conduction band compositions are similar for the bulk and hydrogen-doped α-Fe2O3. That is, the valence bands are dominated mainly by both O 2p and Fe 3d orbitals with the O 2p orbitals playing a leading role, while the conduction band is dominated by Fe 3d orbitals. The band gap of α-Fe2O3 decreases from 2.2 to 1.63 eV after hydrogen doping. Also, a strong hybrid peak occurs near the Fermi level after hydrogen doping, which is chiefly composed of Fe 3d orbital, and the O 2p orbital also has a small contribution. The H 1s orbital is mainly in the lower level below the top valence band. Results of the Bader charge analysis and the density of states calculation for partial correlated atoms suggest that the new hybrid peak is chiefly caused by Fe atom which is closest to the hydrogen atom in the crystal cell. In this process, H atom loses electrons, and the nearest neighbors of H atom, i.e. O and Fe atoms, almost obtain all the electrons H atom loses, so H and O atoms are bonded together strongly, causing the hybrid peak, to expand the width of the top valence band and shift down the bottom of the conduction band, so that the band gap decreases and the electrical conductivity increases. Hydrogen doping is suggested to be an effective method to modify the band.
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[1] Droubay T, Rosso K M, Heald S M, McCready D E, Wang C M, Chambers S A 2007 Phys. Rev. B 75 104412
[2] Amrit B, Velev J, Butler W H, Sarker S K, Bengone O 2004 Phys. Rev. B 69 174429
[3] Pozun Z D, Henkelman G 2011 J. Chem. Phys. 134 224706
[4] Shinde S S, Bhosale C H, Rajpure K Y 2011 J. Alloys Compd. 509 3943
[5] Meng X Y, Qin G W, Li S, Wen X H, Ren Y P, Pei W L, Zuo L 2011 Appl. Phys. Lett. 98 112104
[6] Zhang L, Xu M, Yu F, Yuan H, Ma T 2013 Acta Phys. Sin. 62 027501 (in Chinese) [张丽, 徐明, 余飞, 袁欢, 马涛 2013 物理学报 62 027501]
[7] Zhang H, Liu Y J, Pan L H, Zhang Y 2009 Acta Phys. Sin. 58 7141 (in Chinese) [张晖, 刘拥军, 潘丽华, 张瑜 2009 物理学报 58 7141]
[8] Pan F, Ding B F, Fa T, Cheng F F, Zhou S Q, Yao S D 2011 Acta Phys. Sin. 60 108501 (in Chinese) [潘峰, 丁斌峰, 法涛, 成枫锋, 周生强, 姚淑德 2011 物理学报 60 108501]
[9] Wang B B, Zhou J, Zhang H P, Chen J P 2014 Chin. Phys. B 23 087303
[10] Xu Y, Jin Z M, Zhang Z B, Zhang Z Y, Lin X, Ma G H, Cheng Z X 2014 Chin. Phys. B 23 044206
[11] Wang C, Wang F F, Fu X Q, Zhang E D, Xu Z 2011 Chin. Phys. B 20 050701
[12] Praveen C S, Timon V, Valant M 2012 Comput. Mater. Sci. 55 192
[13] Zielinski J, Zglinicka I, Znak L, Kaszkur Z 2010 Appl. Catal. A:Gen 381 191
[14] Gaudon M, Pailhe N, Majimel J, Wattiaux A, Abel J, Demourgues A 2010 J. Solid States Chem. 183 2101
[15] Hahn N T, Buddie Mullins C 2010 Chem. Mater. 22 6474
[16] Lukowski M A, Song J 2011 J. Phys. Chem. C 115 12388
[17] Liu J, Liang C H, Zhang H M, Tian Z F, Zhang S Y 2012 J. Phys. Chem. C 116 4896
[18] Shwarsctein A K, Hu Y S, Forman A J, Stucky G D, McFarland E W 2008 J. Phys. Chem. C 112 15900
[19] Shwarsctein A K, Huda M N, Walsh A, Yan Y F, Stucky G D, Hu Y S, Al-Jassim M M, McFarland E W 2010 Chem. Mater. 22 510
[20] Zhang M L, Luo W J, Li Z S, Yu T, Zou Z G 2010 Appl. Phys. Lett. 97 042105
[21] Tang H W, Yin W J, Matin M A, Wang H L, Deutsch T, Al-Jassim M M, Turner J A, Yan Y F 2012 J. Appl. Phys. 111 073502
[22] Van de Walle C G, Neugebauer J 2003 Nature 423 626
[23] Van de Walle C G 2000 Phys. Rev. Lett. 85 1012
[24] Wardle M G, Goss J P, Briddon P R 2006 Phys. Rev. Lett. 96 1
[25] Cox S F J 2003 J. Phys. Con. Matt. 15 1727
[26] Peacock P W, Robertson J 2003 Appl. Phys. Lett. 83 2025
[27] Kilic C, Zunger A. 2002 Appl. Phys. Lett. 81 73
[28] Chang H, Wu J, Gu B L, Liu F, Duan W 2005 Phys. Rev. Lett. 95 196803
[29] Chen W P, Shen Z J, Yuan G L 2007 Mater. Lett. 61 4354
[30] Chen W P, Wang Y, Chan H L W 2008 Appl. Phys. Lett. 92 112907
[31] Rollmann G, Rohrbach A, Entel P, Hafner J 2004 Phys. Rev. B 69 165107
[32] Finger L W, Hazen R M 1980 J. Appl. Phys. 51 5362
[33] Mochizuki S 1977 Phys Status Solidi A 41 591
[34] Todorova M, Reuter K, Scheffler M 2004 J. Phys. Chem. B 108 14477
[35] Chen W P, Wang J, Wang D Y, Wang Y, Qi J Q, Chan H L W 2004 Physica B 353 41
[36] Cao J L, Wang X H, Zhang L, Liu M, Li L T 2003 Ceram. Int. 29 327
[37] Cao J L, Wang X H, Zhang L, Li L T 2002 Mater. Lett. 57 386
[38] Wang P, Liu Z R, Lin F, Zhou G, Wu J, Duan W H, Gu B L, Zhang S B 2010 Phys. Rev. B 82 193103
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