Evolution of Graphene Growth on Ni and Cu by Carbon Isotope Labeling

TLDR

Large‑area graphene growth, essential for electronic device production, is pursued via CVD on metal substrates such as Ni and Cu, where Ni growth is thought to involve carbon segregation/precipitation and Cu growth occurs by surface adsorption. The study uses carbon isotope labeling combined with Raman spectroscopic mapping to trace carbon incorporation during graphene growth. Carbon isotope labeling and Raman mapping were employed to monitor carbon diffusion, mixing, segregation, and precipitation on Ni, and surface adsorption on Cu during CVD growth. At high temperatures, sequentially introduced isotopic carbon diffuses into Ni, mixes, segregates, and precipitates at the surface forming graphene/graphite with a uniform 12C/13C mixture, whereas on Cu growth proceeds by surface adsorption with spatial distribution following precursor timing and a linear growth rate of 1–6 μm/min depending on grain orientation, providing critical guidance for producing high‑quality graphene.

Abstract

Large-area graphene growth is required for the development and production of electronic devices. Recently, chemical vapor deposition (CVD) of hydrocarbons has shown some promise in growing large-area graphene or few-layer graphene films on metal substrates such as Ni and Cu. It has been proposed that CVD growth of graphene on Ni occurs by a C segregation or precipitation process whereas graphene on Cu grows by a surface adsorption process. Here we used carbon isotope labeling in conjunction with Raman spectroscopic mapping to track carbon during the growth process. The data clearly show that at high temperatures sequentially introduced isotopic carbon diffuses into the Ni first, mixes, and then segregates and precipitates at the surface of Ni forming graphene and/or graphite with a uniform mixture of 12C and 13C as determined by the peak position of the Raman G-band peak. On the other hand, graphene growth on Cu is clearly by surface adsorption where the spatial distribution of 12C and 13C follows the precursor time sequence and the linear growth rate ranges from about 1 to as high as 6 μm/min depending upon Cu grain orientation. This data is critical in guiding the graphene growth process as we try to achieve the highest quality graphene for electronic devices.