Electrical Conductance of Graphene with Point Defects

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.

Defects in graphene-based heterostructures: topological and geometrical effects

“…As a result, the conductivity of Gr gradually decreases, and carrier resonance scattering also occurs. 91 However, the defects and nanoholes are not all harmful. 92 The defects improve the semiconductor performance, ion-diffusion coefficient, dispersivity, and reaction activity of Gr-based materials.…”

Electron transport of one-dimensional non-conjugated (CH₂)_<i>n</i> molecule chain coupling to graphene electrode

“…Liu等针对(GaAs) n (n = 1-4)原子链 的研究, 发现了n值的不同导致的金属或负微分电 阻现象; 而针对Si原子链的电子输运研究却发现 了明显的奇偶电导振荡现象 [14] . 此外, 一维富电子 有机共轭分子链 [15,16] 、点缺陷石墨烯 [17] 、石墨烯层 数 [18] 等不同分子结的导电性质也被研究报道, 证 实石墨烯的输运机制主要来源于单层石墨烯的弹 道散射或少层石墨烯的声子散射作用. 烷烃分子由于不具有金属或分子导体的导电 性质, 同时也不属于富电子的共轭体系, 因此在分 子器件的研究中较少被探讨.…”

High Crystallinity Vertical Few-Layer Graphene Grown Using Template Method Assisted ICPCVD Approach

“…The measured thermal conductivity of VFLG is only 250 Wm −1 K −1 , which is much lower than the few-layer graphene film 1500 Wm −1 K −1 [ 6 , 7 ]. Furthermore, VFLG with defects and weak crystallinity also leads to a sharply decreased electrical conductivity [ 8 , 9 , 10 ]. Although doping is an efficient way to improve its electrical conductivity [ 11 , 12 ], it is hard to realize heteroatom uniform distribution and accurate doping quantity.…”