Graphene on Pt(111): Growth and substrate interaction

Abstract

In situ low-energy electron microscopy (LEEM) of graphene growth combined with measurements of the graphene structure and electronic band structure has been used to study graphene on Pt(111). Growth by carbon segregation produces macroscopic monolayer graphene domains extending continuously across Pt(111) substrate steps and bounded by strongly faceted edges. LEEM during cooling from the growth temperature shows the propagation of wrinkles in the graphene sheet, driven by thermal stress. The lattice mismatch between graphene and Pt(111) is accommodated by moiré structures with a large number of different rotational variants, without a clear preference for a particular interface geometry. Fast and slow growing graphene domains exhibit moiré structures with small [e.g., ${\left(3\times 3\right)}_{\text{G}}$, $\left(\sqrt{6}\times \sqrt{6}\right)\text{R}{2}_{\text{G}}$, and $\left(2\times 2\right)\text{R}{4}_{\text{G}}$] and large unit cells [e.g., $\left(\sqrt{44}\times \sqrt{44}\right)\text{R}{15}_{\text{G}}$, $\left(\sqrt{52}\times \sqrt{52}\right)\text{R}{14}_{\text{G}}$, and ${\left(8\times 8\right)}_{\text{G}}$], respectively. A weak substrate coupling, suggested by the growth and structural properties of monolayer graphene on Pt(111), is confirmed by maps of the band structure, which is close to that of isolated graphene aside from minimal hole doping due to charge transfer from the metal. Finally, the decoupled graphene monolayer on Pt(111) appears impenetrable to carbon diffusion, which self-limits the graphene growth at monolayer thickness. Thicker graphene domains, which can form at boundaries between monolayer domains, have been used to characterize the properties of few-layer graphene on Pt(111).