Journal
SCIENTIFIC REPORTS
Volume 12, Issue 1, Pages -Publisher
NATURE PORTFOLIO
DOI: 10.1038/s41598-022-22889-4
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Funding
- German Federal Ministry of Education and Research (BMBF) [16ME0398K, 16ME0399, 16ME0403, 03ZU1106AB]
- Projekt DEAL
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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.
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.
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