Tuning electronic properties of graphene heterostructures via controlled metal intercalation

The synthesis of heterostructures by intercalating layered materials like epitaxial graphene on SiC (Gr/SiC) is a promising strategy for producing high-quality 2D heterostructures. However, identifying the growth kinetics poses a challenge in achieving predictive synthesis. Here, we systematically study the intercalation of metals (Dy, Gd, Pb) in Gr/SiC as a function of temperature, time, and coverage using surface diffraction (SPA-LEED) and scanning tunneling microscopy (STM). Such a comprehensive approach identifies the intercalation locations throughout the process, which is crucial for the final electronic properties.

We demonstrate that Dy and Pb intercalate at different locations by monitoring diffraction spot intensities in SPA-LEED and examining the 6×6 moiré with STM. As for Gd intercalation, an intermediate "continent" phase is observed at 850 ℃, while homogeneous phase only forms at saturated θ and 1200 ℃ annealing. Recently, interests are growing towards a (10×10) moiré phase in Pb intercalation as moiré phases are promising for studying the physics of correlated electrons. In LEED, (10×10) moiré spots are faint and only visible at certain energies. In contrast, ARPES reveals distinct and strong bands, which is puzzling and requires further investigation.