Etching-Controlled Growth of Graphene by Chemical Vapor Deposition

Graphene growth and etching are reciprocal processes that can reach a dynamic balance during chemical vapor deposition (CVD). Most commonly, the growth of graphene is the dominate process, while the etching of graphene is a recessive process often neglected during CVD growth of graphene. We show here that through the rational design of low-pressure CVD of graphene in hydrogen-diluted methane and regulation of the flow rate of H₂, the etching effect during the growth process of graphene could be prominent and even shows macroscopic selectivity. On this basis, etching-controlled growth and synthesis of graphene with various morphologies from compact to dendritic even to fragmentary have been demonstrated. The morphology–selection mechanism is clarified through phase-field theory based on simulations. This study not only presents an intriguing case for the fundamental mechanism of CVD growth but also provides a facile method for the synthesis of high-quality graphene with trimmed morphologies

Fractal Etching of Graphene

An anisotropic etching mode is commonly known for perfect crystalline materials, generally leading to simple Euclidean geometric patterns. This principle has also proved to apply to the etching of the thinnest crystalline material, graphene, resulting in hexagonal holes with zigzag edge structures. Here we demonstrate for the first time that the graphene etching mode can deviate significantly from simple anisotropic etching. Using an as-grown graphene film on a liquid copper surface as a model system, we show that the etched graphene pattern can be modulated from a simple hexagonal pattern to complex fractal geometric patterns with sixfold symmetry by varying the Ar/H₂ flow rate ratio. The etched fractal patterns are formed by the repeated construction of a basic identical motif, and the physical origin of the pattern formation is consistent with a diffusion-controlled process. The fractal etching mode of graphene presents an intriguing case for the fundamental study of material etching