Structure and Electronic Transport in Graphene Wrinkles

Abstract

Wrinkling is a ubiquitous phenomenon in two-dimensional membranes. In particular, in the large-scale growth of graphene on metallic substrates, high densities of wrinkles are commonly observed. Despite their prevalence and potential impact on large-scale graphene electronics, relatively little is known about their structural morphology and electronic properties. Surveying the graphene landscape using atomic force microscopy, we found that wrinkles reach a certain maximum height before folding over. Calculations of the energetics explain the morphological transition and indicate that the tall ripples are collapsed into narrow standing wrinkles by van der Waals forces, analogous to large-diameter nanotubes. Quantum transport calculations show that conductance through these "collapsed wrinkle" structures is limited mainly by a density-of-states bottleneck and by interlayer tunneling across the collapsed bilayer region. Also through systematic measurements across large numbers of devices with wide "folded wrinkles", we find a distinct anisotropy in their electrical resistivity, consistent with our transport simulations. These results highlight the coupling between morphology and electronic properties, which has important practical implications for large-scale high-speed graphene electronics.

Structure of graphene and its disorders: a review

“…Unlike ripples having a modest aspect ratio of ~ 1 and feature sizes of peaks and valleys below 10 nm, wrinkles exhibit a high aspect ratio of 10, and the width ranges from 1 to 10 nm, the height below 15 nm and the length above 100 nm [193]. Wrinkles normally occur on metallic substrates due to the opposite thermal deformation [194,195] and the defect lines [196] on the substrates. Also, the thickness of growth substrate has an effect on the attributes and density of wrinkles.…”

“…More specifically, intrinsic ripples are expected to influence the electrical properties of graphene by changing band gap [239], creating polarized carrier puddles [240] and inducing pseudo-magnetic fields [241]. Whereas wrinkles and crumples result in several electronic phenomena, such as electron-hole puddles [189,242], carrier scattering [195,243], band gap opening [244], suppression of weak localization [245] and quantum corrections [246]. …”

Spatially Resolved Mapping of Electrical Conductivity across Individual Domain (Grain) Boundaries in Graphene

“…The growth of hexagonal graphene domains on Cu foil by atmospheric pressure CVD was described previously by Vlassiouk et al 11 The graphene islands are shown in SEM image in al. 35 The wrinkle at GB site is much narrower and only plays a secondary role in the increase of the GB resistance in comparison with GB itself. Table 2), at first glance there seems to be a positive correlation between misorientation angle and the GB resistance, and that wrinkles at GB seem to further increase the GB resistance.…”

Weighing graphene with QCM to monitor interfacial mass changes

“…4(a) and 4(b). 22 The wrinkles increase the surface area and mass density of graphene. Previously, high densities of wrinkles were observed in large-scale grown graphene on metallic substrates.…”

“…Previously, high densities of wrinkles were observed in large-scale grown graphene on metallic substrates. 22 These wrinkles are formed due to thermal contraction of the substrate during the cooling process. Besides, nanoscale holes, cracks, and organic/ inorganic residues alter the measured mass density of graphene.…”