新型二维材料五边形石墨烯电子结构研究

发布时间：2018-05-06 20:15

本文选题：五边形石墨烯 + 第一原理计算　；参考：《长春大学》2017年硕士论文

【摘要】：自从2004年海姆和诺沃肖洛夫利用机械剥离法成功制备石墨烯以来,一系列新型二维材料(单层六方氮化硼、单层二硫化钼、锗烯、黑磷烯、硼烯等)的相关研究已成为材料科学和凝聚态物理学等领域的研究热点之一。2015年,研究人员又发现了一种新型的二维碳同素异形体五边形石墨烯,其完全由碳五元环构成,为准直接带隙半导体材料,具有较好的热稳定性和机械稳定性,具有负泊松比和超高的力学强度。随着计算机技术的飞速发展,计算材料学在材料科学研究中占有越来越重要的地位。为了进一步探讨五边形石墨烯在微电子器件领域的潜在应用,从理论上研究五边形石墨烯的电子结构调控就显得非常必要。在本论文中,我们采用第一原理密度泛函理论研究碱金属原子吸附和外加应变对五边形石墨烯几何结构和电子结构的影响,为进一步研究五边形石墨烯的性能提供理论指导。具体研究工作和主要结论概括如下。(1)研究了五边形石墨烯的几何结构和电子结构。研究表明五边形石墨烯呈褶皱结构,由sp3杂化碳原子和sp2杂化碳原子构成。电子结构计算表明五边形石墨烯为带隙宽度3.22 eV的准直接带隙半导体。(2)研究了碱金属原子(Li、Na和K)吸附对五边形石墨烯的几何结构和电子结构的影响。吸附能计算表明五边形石墨烯第三层碳原子之间的桥位(B33)是碱金属原子最稳定的吸附位置,电荷由吸附的碱金属原子转移到五边形石墨烯上。碱金属原子吸附后,五边形石墨烯的导带和价带都向下移动,这说明费米能级向上移动。随着吸附的碱金属原子的原子序数逐渐增大,五边形石墨烯的功函数单调降低。计算结果表明当K原子在五边形石墨烯表面吸附时,其吸附能最大,吸附最强,五边形石墨烯的功函数降低最多,K原子与五边形石墨烯之间的电荷转移最大。(3)研究了外加拉伸和压缩应变对五边形石墨烯的几何结构和电子结构的影响。研究表明外加应变对五边形石墨烯中的sp3杂化碳原子的影响最大,在-10%到25%的应变范围内五边形石墨烯发生的是弹性形变。施加应变后,五边形石墨烯由准直接带隙半导体完全转变为间接带隙半导体。在外加压缩应变下,五边形石墨烯的带隙逐渐变小;在外加拉伸应变下,带隙随拉伸应变的增大先缓慢增加后急剧减小。
[Abstract]:Since Heym and Novosholov successfully prepared graphene by mechanical stripping in 2004, a series of novel two-dimensional materials (monolayer hexagonal boron nitride, monolayer molybdenum disulfide, germanium enene, black phosphorene) have been prepared. In 2015, researchers discovered a new two-dimensional carbon isomorphism pentagonal graphene, which is composed entirely of carbon quintuple rings. Quasi-direct band-gap semiconductor material has good thermal stability and mechanical stability, with negative Poisson ratio and ultra-high mechanical strength. With the rapid development of computer technology, computational materials science plays an increasingly important role in material science research. In order to further explore the potential applications of pentagonal graphene in the field of microelectronic devices, it is necessary to study the electronic structure regulation of pentagonal graphene theoretically. In this thesis, we use the first principle density functional theory to study the effect of alkali metal atomic adsorption and applied strain on the geometry and electronic structure of pentagonal graphene, which provides theoretical guidance for further study on the properties of pentagonal graphene. The geometrical and electronic structures of pentagonal graphene are studied. The results show that pentagonal graphene has a fold structure consisting of sp3 hybrid carbon atom and sp2 hybrid carbon atom. The electronic structure calculation shows that pentagonal graphene is a quasi-direct band-gap semiconductor with a band gap width of 3.22 EV). The effect of the adsorption of alkaline-metal atoms on the geometric and electronic structures of pentagonal graphene was studied. The calculation of adsorption energy shows that the bridge position B33 between the third layer carbon atoms of pentagonal graphene is the most stable adsorption position of alkali metal atom and the charge is transferred from the adsorbed alkali metal atom to the pentagonal graphene. After alkali atom adsorption, the conduction band and valence band of pentagonal graphene move downward, which indicates that the Fermi energy level moves upward. The work function of pentagonal graphene decreases monotonously with the increase of atomic number of the adsorbed alkali metal atom. The results show that when K atom is adsorbed on the surface of pentagonal graphene, the adsorption energy is the largest and the adsorption is the strongest. The maximum charge transfer between pentagonal graphene and pentagonal graphene was studied. The effect of tension and compression strain on the geometry and electronic structure of pentagonal graphene was studied. The results show that the effect of applied strain on the sp3 hybrid carbon atoms in pentagonal graphene is the greatest, and the deformation of pentagonal graphene is elastic in the range of -10% to 25%. After applied strain, pentagonal graphene completely changed from quasi direct band gap semiconductor to indirect band gap semiconductor. The band gap of pentagonal graphene decreases gradually under the applied compressive strain, and the band gap increases slowly at first and then decreases sharply with the increase of tensile strain.
【学位授予单位】：长春大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O613.71

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