Atomically resolved electronic properties in single layer graphene on α-Al2O3 (0001) by chemical vapor deposition

Metal-free chemical vapor deposition (CVD) of single-layer graphene (SLG) on c-plane sapphire has recently been demonstrated for wafer diameters of up to 300 mm, and the high quality of the SLG layers is generally characterized by integral methods. By applying a comprehensive analysis approach, distinct interactions at the graphene-sapphire interface and local variations caused by the substrate topography are revealed. Regions near the sapphire step edges show tiny wrinkles with a height of about 0.2 nm, framed by delaminated graphene as identified by the typical Dirac cone of free graphene. In contrast, adsorption of CVD SLG on the hydroxyl-terminated alpha-Al2O3 (0001) terraces results in a superstructure with a periodicity of (2.66 +/- 0.03) nm. Weak hydrogen bonds formed between the hydroxylated sapphire surface and the pi-electron system of SLG result in a clean interface. The charge injection induces a band gap in the adsorbed graphene layer of about (73 +/- 3) meV at the Dirac point. The good agreement with the predictions of a theoretical analysis underlines the potential of this hybrid system for emerging electronic applications.

Automated summary

Metal-free chemical vapor deposition allows for the high-quality synthesis of single-layer graphene. The interactions at the graphene-sapphire interface and the substrate topography affect the properties of graphene. Graphene near sapphire step edges forms tiny wrinkles, while adsorption on hydroxyl-terminated alpha-Al2O3 leads to a periodic superstructure. This hybrid system shows promise for emerging electronic applications.