新型二维材料的自旋极化、量子自旋霍尔效应和半导体性质的电子结构及调控

发布时间：2018-01-24 11:35

  本文关键词： 第一性原理 二维纳米材料 自旋极化 量子自旋霍尔效应 半导体性质　出处：《山东大学》2017年博士论文　论文类型：学位论文

【摘要】：二维纳米材料由于原材料丰富以及性质优良等突出特点,是当今科学研究领域的热点。尤其是在石墨烯成功制备后,人们发现这种二维单层材料具有良好的机械性能和物理化学性质。石墨烯的成功问世,进一步激发了人们探索新型二维纳米材料的研究热情。目前,已有诸多二维纳米材料被成功预测甚至合成,它们优异的性能在不同领域都表现出重要的应用价值。如,在自旋电子学应用方面,二维磁性纳米材料体系具有较稳定的自旋极化性质和优良的结构-性能稳定性,能够满足当今时代越来越高的存储和处理能力与越来越小的器件尺寸的双重需求,可以作为新一代高性能自旋纳米器件;在新奇物理效应方面,二维拓扑绝缘体材料体系具有奇异的量子自旋霍尔效应,即边缘态受到拓扑保护,并且自旋在边缘态中可以无耗散的高速迁移,在进一步提高新一代自旋电子设备性能、降低能耗等方面表现出重要的应用潜力;在半导体应用方面,二维半导体纳米材料体系通常具有超高的比表面积、外场可控的能带结构、较高的载流子迁移率和合适的半导体带边位置,为我们寻找新型高效的纳米半导体材料,实现电子器件和光催化等方面的应用提供了新途径。在本论文中,我们借助第一性原理计算系统地研究了一系列新型二维纳米材料体系的电子结构和相关性质,并对其微观物理机制进行了深入探讨,研究了二维纳米材料在自旋电子学、量子自旋霍尔效应和半导体电子结构及调控等多方面的性质,为二维纳米材料在节约能源、降低能耗和能源转换等多方面的应用提供了系统的理论指导。本文第一章介绍二维纳米材料的发展现状与应用以及本论文主要研究内容。第二章介绍第一性原理计算的理论基础和软件包。第三章研究基于过渡金属的二维磁性纳米材料体系的电子结构和自旋极化性质,并探讨了体系自旋极化性质的调控。第四章详细地展示了二维纳米材料体系中的量子自旋霍尔效应,设计了一系列室温二维拓扑绝缘体体系。第五章详细研究了二维纳米材料和其复合体系的半导体电子结构调控以及在电子器件、光解水等方面的潜在应用。第六章对本论文的主要结论和创新点进行了总结,并对新型二维纳米材料的理论研究做了展望。本论文的主要研究内容和结果如下:(1)研究了二维 TM(TM = Ti、Zr、Hf、V、Nb 和 Ta)单层材料以及 TM(TM= Ti、V、Cr、Mn和Fe)与锗环构成的纳米分子链[(Ge5)TM]∞的电子结构和自旋极化性质。研究表明Ti、Zr、Hf单层以及[(Ge5)TM]∞(TM=Ti和Fe)具有铁磁基态,其铁磁性来源于TM原子的d电子。此外,TM单层的居里温度大于580 K,在室温下也能保持较高的自旋极化率。这些结果为新型自旋电子器件的发展开辟了道路。(2)探索了一系列二维纳米材料体系中的量子自旋霍尔效应,其中包括g-TlA(A = N、P、As和Sb)和TMC6(TM = Mo和W)体系。结果表明这些体系中较强的自旋轨道耦合作用(SOC)能够在费米能级附近引入能带反转,同时产生拓扑保护的边缘态。且这些二维体系的带隙宽度均大于室温下电子的跃迁能(26 meV),是室温下理想的二维拓扑绝缘体材料。(3)研究了二维复合拓扑绝缘体体系GeI/MoTe2的电子结构和拓扑性质。并且证实MoTe2都是二维拓扑绝缘体GeI单层的理想衬底。以MoTe2为衬底的GeI单层,其带隙宽度是240 meV,比室温下电子跃迁能(26 meV)大了将近一个数量级。同时,SOC作用下费米能级附近非平庸的能带反转机制可以通过直接计算体系的自旋陈数Cs= 1得到证实。我们解决了目前二维拓扑绝缘体和衬底相互作用过强使得边缘态与衬底能带相耦合,导致实验中不能观测到拓扑态的关键科学问题。(4)探索了二维复合半导体材料体系graphene/g-C3N4和MoS2/MXene(MXene = Ti2C02、Zr2C02和Hf2C02)的电子结构和能带调控。研究结果表明层间弱范德瓦尔斯相互作用能够使得体系的电荷重新分布,导致复合体系的能带结构兼备两种不同单层的性质。Graphene/g-C3N4复合体系是带隙宽度为106meV的半导体,而其费米能级附近仍能够保持类似石墨烯体系中的较小的有效质量和较大的费米速度。MoS2/MXene体系形成了 Type-II半导体能带对齐方式,使得电子和空穴分别分布在MXene和MoS2上,实现了载流子的空间分离。另外,研究还发现这些二维复合纳米材料体系的能带结构均可以通过外场(电场、应力等)进行有规律地调控。(5)研究了一系列新型非金属硅基二维材料p-SiX(X = B、C和N)以及无机非金属螺旋纳米链体系XYP(X = Si、Ge和Sn;Y = Cl、Br和I)。结果表明p-SiC和无机非金属螺旋纳米链体系XYP是带隙宽度在2.21～2.96 eV之间的半导体体系,其带隙宽度恰好对应太阳光谱的可见光波段。进一步研究表明这些材料具有较高的载流子迁移率,并且其带隙宽度与带边位置均能满足光解水的氧化还原电势。这一研究为实验制备新型高效的光催化剂提供了重要的理论基础。
[Abstract]:Two dimensional nano materials due to abundant raw materials and other excellent properties of outstanding features, is a hot spot in the field of scientific research. Especially in graphene was successfully prepared, people found that the two-dimensional single-layer material has excellent physical and chemical properties and mechanical properties. Graphene successfully come out, to further stimulate the enthusiasm of the people to explore a new two-dimensional nano materials. At present, there are many two-dimensional nano materials are successfully predicted even their synthesis, excellent performance in different areas are showing important application value. For example, in spintronics applications, two dimensional magnetic nanomaterials spin polarization system has stable properties and excellent structure stability, can meet the dual requirements of storage and the ability to deal with more and more nowadays more and more small size of the device, can be used as a new generation of high performance spin nano meter In the novel; physical effect, 2D topological insulator material system with spin quantum Holzer effect of singularity, namely edge state by topology protection, and high-speed non dissipative spin migration at the edge of state, to further enhance the performance of a new generation of spin electronic devices, reduce the energy consumption and show great potential applications in; the application of two-dimensional semiconductor, semiconductor nano material system usually has a high specific surface area, the band structure of field controlled, high carrier mobility and appropriate semiconductor band edge position, looking for new and efficient nano semiconductor materials for us, provides a new way to realize the application of electronic devices and catalysis fields. In in this paper, we use the first principle calculation system to study the electronic structure of a series of novel two-dimensional nano material system and related properties, and the micro The concept of physical mechanism in-depth discussion, study the two-dimensional nano materials in spintronics, the spin properties of quantum Holzer effect and semiconductor electronic structure and control and other aspects of the two-dimensional nano materials in energy conservation, provides a theoretical guidance for system application in many aspects of reducing energy consumption and energy conversion. The first chapter is the introduction of two dimensional nano material development and application as well as the main content of this thesis. The second chapter introduces the first principle calculation theory and software package. The third chapter studies on the electronic structure and spin polarization properties of two-dimensional magnetic nano materials, transition metal, and discusses the regulation of spin polarization properties of the system. The fourth chapter shows quantum spin Holzer effect of two-dimensional nano materials in the system, the design of a series of room temperature 2D topological insulator system. The fifth chapter studies two 缁寸撼绫虫潗鏂欏拰鍏跺�嶅悎浣撶郴鐨勫崐瀵间綋鐢靛瓙缁撴瀯璋冩帶浠ュ強鍦ㄧ數瀛愬櫒浠�,鍏夎В姘寸瓑鏂归潰鐨勬綔鍦ㄥ簲鐢，

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