Regulation of Graphene Growth by Nitrogen-Modified Copper Surfaces Probed with In Situ Raman Spectroscopy

The controllable synthesis of high-quality graphene by chemical vapor deposition (CVD) critically depends on the surface chemistry and catalytic activity of copper substrates, yet the dynamic evolution of these surface states during growth remains unclear. In this study, in situ high-temperature Raman spectroscopy combined with systematic structural characterization was employed to elucidate the coupled evolution of copper surface states and graphene growth during annealing, growth, and cooling. Ammonia plasma pretreatment was introduced to regulate graphene nucleation. After high-temperature annealing, an ultrathin nitrogen-pinned noncrystalline surface layer formed on copper, which passivated high-energy surface sites and suppressed excessive nucleation without altering the bulk lattice. Under hydrogen-containing growth conditions, partial reconstruction of this nitrogen-modified surface restored the catalytic activity for methane decomposition while maintaining a low nucleation density. Raman mapping and isotope-labeled growth experiments revealed that graphene growth proceeds via a surface-mediated epitaxial mechanism dominated by edge attachment. These findings clarify the structure-catalytic activity-growth relationship governing graphene synthesis on copper and provide mechanistic insight into nitrogen-mediated surface chemical regulation for controllable graphene manufacturing.