• Single-layer graphene islands were synthesized on Cu via the Boudouard reaction. • Growth kinetics exhibit sigmoidal behaviour and discussed in autocatalytic terms. • 2D Percolation threshold is identified at ∼65% surface coverage • Simulations and experiment (micro- and THz analyses) show agreement for the 2D percolation • The transition from localized hopping to Drude-type conductivity demonstrated post-percolation. Due to its unique qualities, graphene is a potential material for future electronic and photonic technologies. Morphological and electrical properties of graphene are determined by the growth kinetics of the synthesis process. This work reveals that graphene chemical vapor deposition growth on copper via the Boudouard reaction exhibits an autocatalytic kinetics, where the graphene edges facilitate the decomposition of CO, thereby self-accelerating the growth. The feedback between the product (graphene edge) and the growth rate leads to a characteristic sigmoidal evolution of surface coverage. We fabricated a single layer of graphene islands and transferred the graphene islands onto free-standing parylene-N films. After the shape characterization of the graphene islands using atomic force microscopy, we present and validate the mechanistic model that quantitatively explains the sigmoidal surface coverage and provides a powerful lever to control the growth process. By combining the autocatalytic growth model with a computational percolation threshold simulation, we demonstrate the electrical percolation threshold on a parylene-N dielectric substrate to reach approximately 65% surface coverage or a synthesis duration time of approximately 6 minutes under continuous CO flow, where the system operates at nearly atmospheric pressure and the synthesis is carried out at 1045 °C. With the distinct percolation threshold, the synthesis time increase results in the change of localized hopping to delocalized Drude-type conductivity, allowing tunable THz surfaces. We establish autocatalytic growth as a fundamental principle that enables precise prediction and control of the percolation threshold, opening the path toward rational device design for graphene-based materials and applications.
Salehpoor et al. (Sun,) studied this question.