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

Abstract

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 are 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 with FLG having a concentric layered structure formed by interfacial nucleation (nucleation at the graphene/Cu interface) using a 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.

Spiral Growth of Adlayer Graphene

“…This structure is different from the spiral FLG reported by Tay who fabricated graphene spirals by screw dislocation. [ 28 ]…”

3D Porous Graphene Films with Large‐Area In‐Plane Exterior Skins

“…This ratio measures at ≈2–3 for single‐layer graphene (SLG), ≈1 for bilayer graphene (BLG), ≈0.6–0.3 for 3–5 layers (few‐layer graphene, FLG) and becomes indistinguishable for 5 layers and above (multilayer graphene, MLG). [ 20a,21 ] From the I 2D / I G map in Figure 4b, one can observe that the top surface comprises a distribution ranging from 1 to >5 layers of graphene. The corresponding histogram plot shows that the mapped region has an average I 2D / I G of 0.565 ± 0.224, which correlates to ≈3–5 layers of graphene in good agreement with TEM characterization (Figure S15a, Supporting Information).…”

Novel strategies for chemical vapor deposition growth and engineering of two-dimensional materials

“…The intensity ratio of 2D over G bands (I2D/IG) is ~2, signaling it was a single layer. 131 The Raman intensity ratio map (I2D/IG) was performed over the domain (Figure 4-3d). The uniform color contrast indicates the high uniformity…”

“…For monolayer graphene, the intensity ratio of I2D/IG is ~2, while bilayer graphene corresponds to a value of ~ 1. 131 Therefore, Raman spectroscopy is also used as a convenient tool to identify the layer number of graphene.…”

“…Raman spectra of mono-, bi-, tri-, and four-layer graphene and corresponding Raman intensity ratio of 2D band over G band. 131 For the Raman spectrum of h-BN, peaks between 1365 cm -1 and 1370 cm -1 are assigned to the E2g vibrational mode (Figure 3-10). 132 Since the Raman signals of atomically thin h-BN is relatively weak, they are normally only used for indicating the presence of h-BN, while other information such as number of layers and defects require additional characterization techniques.…”