2D materials have attracted great interest in research since the first exfoliation of graphene in 2004. [1] Unique properties (ultra-thin, flexible, conductive or insulating) make 2D materials promising candidates for new applications like flexible electronics and neuromorphic computing. [2] Chemical vapor deposition (CVD) is an industrial technique to deposit large-scale, uniform and high quality 2D layers. Silicon technology-compatible substrate materials such as sapphire are studied to overcome potential copper contamination issues.[3] In this work metal catalyst-free CVD of single layer graphene (SLG) was studied on c-plane sapphire (0001) using an AIXTRON CCS 6x2” cold-wall reactor.

CH4/H2 gas mixture was used for SLG growth at 1400 °C in argon ambient. Annealing of the sapphire at high temperature in hydrogen prior to the graphene growth causes an OH-surface termination and SLG-sapphire interaction by weak hydrogen bonds. [4] Detachment of SLG occurs first at the sapphire step edges, which leads to attached and detached SLG with slightly different electronic properties on the local scale. In addition, wrinkles cause local defects. Here, the influence of the flow ratio between CH4 and H2 during growth on the quality of the grown SLG layer is discussed in detail. In addition, the influence on the delamination process of the graphene from the sapphire during exposure to air is addressed. For this, the results from SEM, AFM, Raman spectroscopy, XPS, XRR, TEM and Hall-measurements will be discussed.