Materials Synthesis from Atoms to Systems
Revealing the rapid isothermal growth of graphene on catalytic substratesJuly 01, 2013
Optical reflectivity tracks the rapid growth of graphene on Ni at 800°C following an acetylene gas pulse, revealing flux-dependent autocatalytic kinetics where subsurface carbon supplies surface graphene nuclei after an induction period.
Real-time optical diagnostics reveal that graphene nucleates and grows rapidly and isothermally on Ni substrates by dissolution and precipitation of carbon; the flux-dependent kinetics indicate autocatalytic reactions. Understanding the mechanisms by which graphene grows on different catalytic metal films is essential to synthesize graphene with the well-defined numbers of layers and ordered stacking required by many potential applications.
Sub-second pulses of acetylene combined in situ with real-time Raman spectroscopy, optical reflectivity, and microscope videography unambiguously detect graphene and measure its growth kinetics, including the fraction of graphene that precipitates upon cooldown. Both the growth kinetics and the fractional isothermal precipitation were found to be governed by the acetylene partial pressure in the CVD-pulse for a given film thickness and temperature. Up to 94% of graphene was found to grow isothermally within 1 second at 800°C for high partial pressures. The flux-dependent growth kinetics were described in the context of a dissolution/precipitation model, where carbon rapidly dissolves into the Ni film and later precipitates at surface nuclei driven by gradients in the chemical potential.
A. A. Puretzky, D. B. Geohegan, S. Pannala, C. M. Rouleau, M. Regmi, N. Thonnard, and G. Eres, “Real-time optical diagnostics of graphene growth induced by pulsed chemical vapor deposition,” Nanoscale 5, 6507 (2013). DOI:10.1039/c3nr01436c.
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