Atomic-Scale Evidence for Potential Barriers and Strong Carrier Scattering at Graphene Grain Boundaries: A Scanning Tunneling Microscopy Study

• Published in: ACS nano 2013-01, Vol.7 (1), p.75-86
• Main Authors: Koepke, Justin C, Wood, Joshua D, Estrada, David, Ong, Zhun-Yong, He, Kevin T, Pop, Eric, Lyding, Joseph W
• Format: Article
• Language: English
• Subjects: Chemical vapor deposition; Electron Transport; Electronics; Grain boundaries; Graphene; Graphite - chemistry; Materials Testing; Microscopy, Scanning Tunneling - methods; Molecular Conformation; Nanostructure; Nanostructures - chemistry; Nanostructures - ultrastructure; Particle Size; Scanning tunneling microscopy; Scattering; Silicon dioxide; Surface Properties; Wave propagation
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/nn302064p

We use scanning tunneling microscopy and spectroscopy to examine the electronic nature of grain boundaries (GBs) in polycrystalline graphene grown by chemical vapor deposition (CVD) on Cu foil and transferred to SiO2 substrates. We find no preferential orientation angle between grains, and the GBs are continuous across graphene wrinkles and SiO2 topography. Scanning tunneling spectroscopy shows enhanced empty states tunneling conductance for most of the GBs and a shift toward more n-type behavior compared to the bulk of the graphene. We also observe standing wave patterns adjacent to GBs propagating in a zigzag direction with a decay length of ∼1 nm. Fourier analysis of these patterns indicates that backscattering and intervalley scattering are the dominant mechanisms responsible for the mobility reduction in the presence of GBs in CVD-grown graphene.