Invisible vapor catalysis in graphene growth by chemical vapor deposition

Vapor catalysis was recently found to play a crucial role in superclean graphene growth via chemical vapor decomposition (CVD). However, knowledge of vapor-phase catalysis is scarce, and several fundamental issues, including vapor compositions and their impact on graphene growth, are ambiguous. Here, by combining density functional theory (DFT) calculations, an ideal gas model, and a designed experiment, we found that the vapor was mainly composed of Cu_i clusters with tens of atoms. The vapor pressure was estimated to be ~ 10⁻¹²–10⁻¹¹ bar under normal low-pressure CVD system (LPCVD) conditions for graphene growth, and the exposed surface area of Cu_i clusters in the vapor was 22–269 times that of the Cu substrate surface, highlighting the importance of vapor catalysis. DFT calculations show Cu clusters, represented by Cu₁₇, have strong capabilities for adsorption, dehydrogenation, and decomposition of hydrocarbons. They exhibit an adsorption lifetime and reaction flux six orders of magnitude higher than those on the Cu surface, thus providing a sufficient supply of active C atoms for rapid graphene growth and improving the surface cleanliness of the synthesized graphene. Further experimental validation showed that increasing the amount of Cu vapor improved the as-synthesized graphene growth rate and surface cleanliness. This study provides a comprehensive understanding of vapor catalysis and the fundamental basis of vapor control for superclean graphene rapid growth.