Watching (De)Intercalation of 2D metals in Epitaxial Graphene: Insight to Defect Healing

Nanostructured materials provide new opportunities to engineer novel phenomena. However, for 2D heterostructures to realize widespread integration, wafer-scale and chemically robust structures must be synthesized in a facile way. Confinement heteroepitaxy (CHet) is a method to achieve this goal [1]. While it has been demonstrated that many metals and compounds can be intercalated with CHet, the exact mechanism is not known.

Here, we follow the de- and re-intercalation of 2D Ag and Ga within epitaxial graphene (Gr) using photoemission electron microscopy (PEEM). In both cases, we initially start with a fully intercalated system by CHet, Gr/Ag/SiC and Gr/Ga/SiC, and in-situ anneal to nearly 600 K. For the Gr/Ag/SiC system, we find Ag clusters initially diffusing to the top Gr surface and finally re-intercalating through defects. We estimate the Ag intercalation front to be 0.5 nm s^-1 ± 0.2 nm s^-1. The Gr/Ga/SiC was de-intercalated and followed a much faster kinetic process. The Gr defects serve as intercalation “windows” and were observed in both systems, and we propose that Ag intercalation process heals Gr defects while Ga intercalation does not.



[1] N. Briggs et al., Nature Materials 19, 637-643 (2020).

This work was partially supported by the following grants: NSF DMR-1539916NSF 2D CC, PREP UMD - NIST 70NANB18H165, and PREP Georgetown – NIST 70NANB18H161.