物理化学学报 >> 2019, Vol. 35 >> Issue (10): 1142-1149.doi: 10.3866/PKU.WHXB201810040

所属专题: 二维材料及器件

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点缺陷石墨烯的电导

刘南舒,周思*(),赵纪军   

  • 收稿日期:2018-10-18 录用日期:2019-02-03 发布日期:2018-12-07
  • 通讯作者: 周思 E-mail:sizhou@dlut.edu.cn
  • 基金资助:
    国家自然科学基金(11504041);中央高校基本科研业务费专项资金(DUT16LAB01);中央高校基本科研业务费专项资金(DUT17LAB19);大连理工大学超算中心资助

Electrical Conductance of Graphene with Point Defects

Nanshu LIU,Si ZHOU*(),Jijun ZHAO   

  • Received:2018-10-18 Accepted:2019-02-03 Published:2018-12-07
  • Contact: Si ZHOU E-mail:sizhou@dlut.edu.cn
  • Supported by:
    The project was supported by the National Natural Science Foundation of China(11504041);Fundamental Research Funds for the Central Universities of China(DUT16LAB01);Fundamental Research Funds for the Central Universities of China(DUT17LAB19);Supercomputing Center of Dalian University of Technology, China

摘要:

作为纳米材料中最有前途的的材料之一,石墨烯由于其超高的电导率、优异的热稳定性和机械强度受到了研究者的广泛关注。本文通过非平衡格林函数法结合密度泛函理论计算了石墨烯点缺陷(包括Stone-Waals,反Stone-Waals,单空位和双空位)及其浓度对石墨烯电输运性质的影响。石墨烯的电导在很大程度上依赖于点缺陷的类型及浓度。低浓度的Stone-Waals和反Stone-Waals缺陷不会显著地降低石墨烯的电输运,而双空位可使电导降低约50%左右。石墨烯中明显的电输运行为变化是由带缺陷石墨烯的能带结构决定的——由于点缺陷破坏了石墨烯蜂窝状晶格的对称性,会在费米能级附近引入局域态,进而导致狄拉克点处有能带劈裂。高缺陷浓度的双空位会在费米能级附近引入更多的平带以及在缺陷处更多的局域态,因此可能对载流子进行一定的散射,降低石墨烯的电导。此外,局部电荷密度表现出增强的局域性,阻碍了载流子的运动。石墨烯电导随着缺陷浓度和能带劈裂的增加呈指数下降。这些理论结果为研究真实单层石墨烯的电输运特性提供了重要的理解,并将有助于实验上控制石墨烯基器件的性能。

10.3866/PKU.WHXB201809013.F009  

关键词: 墨烯, 点缺陷, 电子输运, 电导, 能带劈裂

Abstract:

Graphene is one of the most promising materials in nanotechnology and has attracted worldwide attention and research interest owing to its high electrical conductivity, good thermal stability, and excellent mechanical strength. Perfect graphene samples exhibit outstanding electrical and mechanical properties. However, point defects are commonly observed during fabrication which deteriorate the performance of graphene based-devices. The transport properties of graphene with point defects essentially depend on the imperfection of the hexagonal carbon atom network and the scattering of carriers by localized states. Furthermore, an in-depth understanding of the effect of specific point defects on the electronic and transport properties of graphene is crucial for specific applications. In this work, we employed density functional theory calculations and the non-equilibrium Green's function method to systematically elucidate the effects of various point defects on the electrical transport properties of graphene, including Stone-Waals and inverse Stone-Waals defects; and single and double vacancies. The electrical conductance highly depends on the type and concentration of point defects in graphene. Low concentrations of Stone-Waals, inverse Stone-Waals, and single-vacancy defects do not noticeably degrade electron transport. In comparison, DV585 induces a moderate reduction of 25%–34%, and DV55577 and DV5555-6-7777 induce significant suppression of 51%–62% in graphene. As the defect concentration increases, the electrical conductance reduces by a factor of 2–3 compared to the case of graphene monolayers with a low concentration of point defects. These distinct electrical transport behaviors are attributed to the variation of the graphene band structure; the point defects induce localized states near the Fermi level and result in energy splitting at the Dirac point due to the breaking of the intrinsic symmetry of the graphene honeycomb lattice. Double vacancies with larger defect concentrations exhibit more flat bands near the Fermi energy and more localized states in the defective region, resulting in the presence of resonant peaks close to the Fermi energy in the local density of states. This may cause resonant scattering of the carriers and a corresponding reduction of the conductance of graphene. Moreover, the partial charge densities for double vacancies and point defects with larger concentrations exhibit enhanced localization in the defective region that hinder the charge carriers. The electrical conductance shows an exponential decay as the defect concentration and energy splitting increase. These theoretical results provide important insights into the electrical transport properties of realistic graphene monolayers and will assist in the fabrication of high-performance graphene-based devices.

Key words: Graphene, Point defect, Electron transport, Electrical conductance, Energy splitting

MSC2000: 

  • O649