Open AccessStructure and electronic properties of closed-ring defects in epitaxial graphene
Author(s) -
Yan Cui,
Mengchen Li,
Qiming Wang,
Guosheng Wang,
Xin Wei,
Guofeng Song,
Xiao Kong,
Yun Xu,
Ying Li
Publication year - 2020
Publication title -
materials research express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.383
H-Index - 35
ISSN - 2053-1591
DOI - 10.1088/2053-1591/ab8ee6
Subject(s) - graphene , materials science , scanning tunneling microscope , ring (chemistry) , grain boundary , condensed matter physics , epitaxy , scattering , spectroscopy , lattice (music) , scanning tunneling spectroscopy , molecular physics , crystallography , nanotechnology , layer (electronics) , chemistry , optics , physics , composite material , microstructure , quantum mechanics , organic chemistry , acoustics
A number of past studies have focused on point and line defects in graphene epitaxially grown on SiC substrates. However, few studies have investigated closed-ring defects formed within grain boundary loops. The present study addresses this issue by applying low-temperature scanning tunneling microscopy/spectroscopy to investigate the atomic structures of closed-ring defects in graphene epitaxially grown on 4H-SiC, and to evaluate their effects on the electron state density. The results indicate that the orientations of the graphene lattice inside and outside of grain boundary loop structures are rotated uniformly by an angle of 30° relative to each other, suggesting that closed-ring defects are highly ordered and are mainly composed of clusters of pentagon-heptagon carbon rings and highly ordered pentagon-heptagon chains. In addition, the spectroscopy results reveal for the first time that the density of electron states inside a closed-ring defect is strongly localized and position-dependent. Moreover, these closed-ring defects can eliminate intervalley scattering while maintaining intravalley scattering. These findings are not only helpful for contributing to a deeper understanding of the effects of closed-ring defects in graphene, but also present a potentially useful valley-filtering mechanism for charge carries that can be applied to the practical development of all-electric valley-based devices.