Role of intrinsic carbon in copper and its hydrogen-assisted depletion during growth of graphene by chemical vapor deposition

Official URL: https://risc01.sabanciuniv.edu/record=b2102508 _(Table of contents)

Growth of graphene on Cu by chemical vapor deposition (CVD) method is a multidimensional process. Therefore, a comprehensive understanding of the parameters involved in this process is essential to achieve a reproducible and optimized growth recipe. In this work, the role of intrinsic carbon in the bulk of Cu on nucleation of graphene is revealed and it is disclosed that CVD growth of graphene on Cu foil is not a pure surface process. We uncovered that hydrogen-assisted carbon depletion (HACD) effect causes carbon content within Cu bulk to diffuse out during annealing under hydrogen atmosphere and is a critical mechanism in the nucleation of graphene crystals. Additionally, we investigated the role of hydrogen on the diffusion of carbon toward the Cu surface during annealing. We showed that this interplay is not a linear mechanism, but depending on its concentration hydrogen either can boost or diminish the surface density of segregated carbon atoms from bulk. From that, we managed not only to grow a graphitic film on Cu foil but also and more importantly, illustrate spontaneous nucleation of graphene crystals during hydrogen annealing in the absence of external carbon precursor. To our knowledge, this is the first time such a growth has been realized. This finding can clarify the role of intrinsic carbon on the nucleation mechanism of graphene in the CVD process. We also showed that intrinsic carbon in Cu can effect the formation of ad-layers under as-grown graphene layer