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类石墨烯二硫化钼的第一性原理研究
Abstract
In this thesis, using the first-principles method within the framework of density functional theory, we have studied structures, electronic energy band properties and magnetic behavior of molybdenum disulfide sheet (2H-MoS2, monolayer and bilayer) with the adsorption of 3d transition metal adatom (TM) Fe to its surface and interlayer, and bilayer MoS2 with various 3d TM atoms (Cr, Mn, Fe, Co and Ni) doped in its interlayer, aiming to provide a theoretical basis for potential spintronic applications. At the same time, we also explore the band structure changes of monolayer MoS2 on top of 1-5 layers of hBN substrate (MoS2/n-h-BN heterostructures). The results show that different number layers of h-BN can provide different lattice strain in single-layer MoS2 so as to realize the effective control of band structure.
Firstly, functionalization of MoS2 sheet (monolayer and bilayer) by the adsorption of transition metal Fe adatom to its surface and interlayer has been investigated computationally by using the first-principles method within the framework of density functional theory. We find that the systems with absorption of Fe adatoms on the surfaces of both monolayer and bilayer MoS2 sheets are still semiconductors without spin polarization at the Fermi level. However, for the system with absorption of Fe adatom in the interlayer of bilayer MoS2 sheet, its electronic structure exhibits half-metal behavior, with 100 % spin polarization at the Femi level. Furthermore, on the basis of the first work, we continue to explore the structural, electronic band structure and magnetic properteies of bi-layer MoS2 with various 3d TM atoms (Cr, Mn, Fe, Co and Ni) doped in its interlayer. We find that local moments of the doping TM atoms are smaller than the magnetic moments of their free states and the Ni dopant shows zero magnetic moment. The spin polarization is found to be 100 % at the Fermi level for Cr and Fe or at the HOMO level for Mn and Co, which ensures a selective passage of the preferred spin. Our results suggest that bilayer MoS2 sheets with Cr, Mn, Fe and Co atoms interlayer doping are excellent candidates for spintronic devices.
In addition, we have carried out first-principles study within the framework of density functional theory and theoretical analysis to explore the structural and electronic energy band properties of MoS2/n-h-BN heterostructures consisting of monolayer MoS2 on top of h-BN substrates with one to five layers. We find that the MoS2/n-h-BN heterostructures show indirect band-gap features with both of CBM (in the K point) and VBM (in the Γ point) localized on the monolayer MoS2. We find that the band-gaps of
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万方数据湘潭大学博士学位论文
MoS2/n-h-BN heterostructures decrease with increasing number of h-BN layers, which is proposed to be resulted from the different strain distributions in MoS2 due to the varieties of lattice mismatch rates between MoS2 and h-BN layers. Our results suggest that the MoS2/n-h-BN heterostructure could serve as a prototypical example for band structure engineering of two-dimensional (2D) crystals with atomic layer precision.
Key Words: Density Functional Theory (DFT)；Molybdenum Disulfide；First-Principles
Calculation；Spin Polarization；Heterostructure
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万方数据类石墨烯二硫化钼的第一性原理研究
目 录
第1章 绪 论...................................................................................................................1
1.1 引言......................................................................................................................1 1.2 石墨烯与类石墨烯二维结构..............................................................................2
1.2.1 石墨烯和类石墨烯结构的概述................................................................3 1.2.2 类石墨烯结构的掺杂效应........................................................................6 1.2.3 类石墨烯结构的应变效应........................................................................7 1.3 二硫化钼的概述..................................................................................................8
1.3.1 MoS2的结构..............................................................................................8 1.3.2 MoS2的性质..............................................................................................9 1.3.3 MoS2的应用............................................................................................10 1.3.4 奇异形貌的MoS2低维结构...................................................................11 1.4 类石墨烯二硫化钼的物理性质与应用............................................................15
1.4.1 类石墨烯MoS2的Raman特征..............................................................15 1.4.2 类石墨烯MoS2的能带结构...................................................................16 1.4.3 类石墨烯MoS2的光电性质...................................................................18 1.4.4 类石墨烯MoS2的其它性质...................................................................21 1.4.5 类石墨烯MoS2在光电子器件中的应用...............................................21 1.5 本论文的选题依据和主要研究内容................................................................27 第2章 计算理论与方法...............................................................................................................................29
2.1 密度泛函理论....................................................................................................29
2.1.1 Born-Oppenheimer绝热近似..................................................................29 2.1.2 Hohenberg-Kohn 定理............................................................................30 2.1.3 Kohn-Sham方程......................................................................................30 2.1.4 交换关联泛函..........................................................................................33 2.2 第一性原理计算方法的应用............................................................................33
2.2.1 VASP软件包...........................................................................................33 2.2.2 体系的能量..............................................................................................34 2.2.3 电荷密度..................................................................................................34 2.2.4 电子态密度..............................................................................................35 2.2.5 能带结构计算..........................................................................................35 2.2.6 电荷布局分析..........................................................................................36
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万方数据湘潭大学博士学位论文
第3章 单层和双层MoS2的Fe原子吸附效应..............................................................................37
3.1 引言....................................................................................................................37 3.2 理论方法与模型................................................................................................39 3.3 单层和双层MoS2吸附Fe原子的结构特性...................................................40 3.4 单层和双层MoS2吸附Fe原子的电学特性...................................................41 3.5 小结....................................................................................................................45 第4章 双层MoS2的层间掺杂效应.............................................................................47
4.1 引言....................................................................................................................47 4.2 理论方法与模型................................................................................................48 4.3 双层MoS2层间掺杂过渡金属原子的结构特性.............................................48 4.4 双层MoS2层间掺杂过渡金属原子的电学特性.............................................50 4.5 小结....................................................................................................................55 第5章 六角氮化硼片（h-BN）对单层MoS2的调控效应........................................56
5.1 引言....................................................................................................................56 5.2 理论方法与模型................................................................................................57 5.3 MoS2/1-h-BN异质结的结构特性.....................................................................58 5.4 h-BN片层数对异质结构MoS2/n-h-BN的能带调控......................................59 5.5 小结....................................................................................................................63 第6章 总结与展望........................................................................................................65
6.1 总结....................................................................................................................65 6.2 展望....................................................................................................................66 参考文献............................................................................................................................67 致谢....................................................................................................................................82 个人简历、攻读博士学位期间完成的主要工作............................................................83
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