Solid-state graphene formation via a nickel carbide intermediate phase

Direct formation of graphene with a controlled number of graphitic layers on dielectric surfaces is highly desired for practical applications but still challenging. Distinguished from the conventional chemical vapor deposition methods, a solid-state rapid thermal processing (RTP) method can achieve high-quality graphene formation on dielectric surfaces without transfer. However, little research is available to elucidate the graphene growth mechanism in the RTP method (heating rate ∼15 °C s^-1). Here we show a solid-state transformation mechanism in which a metastable nickel carbide (Ni₃C) intermediate phase plays a critical role in transforming amorphous carbon to two dimensional crystalline graphene and contributing to the autonomous Ni evaporation in the RTP process. The formation, migration and decomposition of Ni₃C are confirmed to be responsible for graphene formation and Ni evaporation. The Ni₃C-assisted graphene formation mechanism expands the understanding of Ni-catalyzed graphene formation and provides insightful guidance for controlled growth of graphene through the solid-state transformation process.