Evolution of copper step beams during graphene growth by CVD method

Abstract

Cu step beams (CSBs) are common products obtained when growing graphene by chemical vapor deposition (CVD), which markedly affects the quality of graphene. Although considerable progress has been made in the preparation of large-area graphene on Cu, the growth behavior of CSBs has not been fully understood. This study investigated the main factors influencing the CSBs caused by thermal stress between graphene and Cu foil. The results showed that the copper crystal orientation, number of graphene layers, and surface undulation of the Cu foil influence the morphology of CSBs. It was found that Cu foils with high-index surfaces are more prone to form distinct CSBs, with more than a 50% increase in roughness average (Ra). The orientation of CSBs is closely related to the Cu crystal orientation. Bilayer graphene and trilayer graphene were found to cause deeper and wider CSBs than single-layer graphene, while its Ra increased significantly to about twice that of single-layer graphene. The thermal stress between graphene and Cu foil was studied through Raman spectral analysis. It was confirmed that CSBs are products resulting from the thermal stress released between grown graphene and Cu foil. This study offers new insights for high-quality graphene growth.