Revealing the surface and bulk regimes of isothermal graphene nucleation and growth on Ni with in situ kinetic measurements and modeling

Abstract

In situ optical diagnostics are used to reveal the isothermal nucleation and growth kinetics of graphene on Ni across a wide temperature range (560°C<T<840°C) by chemical vapor deposition from single, sub-second pulses of acetylene. An abrupt, two-orders of magnitude change in growth times (∼100–1s) is revealed at T=680°C. Above this temperature, sigmoidal kinetics are measured and attributed to autocatalytic nucleation and growth from carbon dissolved in the bulk of the Ni film. However, for T<680°C fast surface nucleation and growth occurring during the gas pulse appears responsible for the drastic alteration of the kinetics of subsequent dissolution-mediated growth. A simple and general kinetic model for isothermal graphene growth is developed that includes the nucleation phase and the effects of carbon solubility in metals, describes delayed nucleation, and allows the interpretation of the competition between surface- and bulk-nucleation and growth. The easily-implemented optical reflectivity diagnostics and the simple kinetic model described here allow a pathway to optimize the growth of graphene on metals with arbitrary carbon solubility.