Control and Characterization of Individual Grains and Grain Boundaries in Graphene Grown by Chemical Vapor Deposition

TL;DR

This paper investigates the effects of grain boundaries in CVD-grown graphene on its electronic properties and introduces a seed-based method to control nucleation for scalable single-crystal graphene fabrication.

Contribution

It provides detailed characterization of grain boundaries in CVD graphene and demonstrates a seed patterning technique to produce large-area single-crystal graphene without grain boundaries.

Findings

Grain boundaries increase Raman D peak intensity.

They impede electrical transport and cause weak localization.

Seed patterning enables controlled nucleation of single-crystal graphene.

Abstract

The strong interest in graphene has motivated the scalable production of high quality graphene and graphene devices. Since large-scale graphene films synthesized to date are typically polycrystalline, it is important to characterize and control grain boundaries, generally believed to degrade graphene quality. Here we study single-crystal graphene grains synthesized by ambient CVD on polycrystalline Cu, and show how individual boundaries between coalescing grains affect graphene's electronic properties. The graphene grains show no definite epitaxial relationship with the Cu substrate, and can cross Cu grain boundaries. The edges of these grains are found to be predominantly parallel to zigzag directions. We show that grain boundaries give a significant Raman "D" peak, impede electrical transport, and induce prominent weak localization indicative of intervalley scattering in graphene. Finally, we demonstrate an approach using pre-patterned growth seeds to control graphene nucleation, opening a route towards scalable fabrication of single-crystal graphene devices without grain boundaries.