Concentric and Spiral Few-Layer Graphene: Growth Driven by Interfacial Nucleation vs Screw Dislocation

Spiral growth of various nanomaterials including some two-dimensional (2D) transition metal dichalcogenides had recently been experimentally realized using chemical vapor deposition (CVD). However, such growth that is driven by screw dislocation remained elusive for graphene and is rarely discussed because of the use of metal catalysts. In this work, we show that formation of few-layer graphene (FLG) with a spiral structure driven by screw dislocation can be obtained alongside FLG having a concentric layered structure formed by interfacial nucleation (nucleation at the graphene/Cu interface) using Cu-catalyzed ambient pressure CVD. Unlike commonly reported FLG grown by interfacial nucleation where the second layer is grown independently beneath the first, the growth of a spiral structure adopts a top growth mechanism where the top layers are an extension from the initial monolayer which spirals around an axial dislocation in self-perpetuating steps. Since the same atomic orientation is preserved, the subsequent spiraling layers are stacked in an oriented AB-stacked configuration. This contrasts with FLG formed by interfacial nucleation where turbostratic stacking of the entire adlayer may exist. In both growth scenarios, the second layer (either top or bottom) can grow across the grain boundaries of the initial monolayer domains, forming partial regions with turbostratic stacking configuration due to weak interlayer van der Waals interactions. The unique interlayer coupling of FLG spirals, which enable superior conductivity along the normal of the 2D crystal with spiraling trajectories, are expected to have new and interesting nanoscale applications.