Intercalation in two-dimensional materials is an important degree of freedom to modify the structural and electronic properties. In this paper, the atomic arrangements at the interface between single-layer graphene and Co(0001) with intercalated Ag and Au atoms were investigated using total-reflection high-energy positron diffraction. A structure analysis on the basis of dynamical diffraction theory demonstrates that by intercalation at annealing temperatures above $400{}^{\circ }\mathrm{C}$, the graphene height from the underlying atoms is shifted from 2.04 Å to 3.24 Å for Ag and 3.32 Å for Au. The Debye temperatures of graphene are changed from 430 K to 320 K for Ag and 368 K for Au by the intercalation. These changes indicate that intercalation results in the transformation to quasifreestanding graphene via a van der Waals interaction. For Ag, further annealing at $700{}^{\circ }\mathrm{C}$ enables the graphene height and the Debye temperature to restore the pristine values by Ag deintercalation. However, for Au, the graphene height remains high up to $900{}^{\circ }\mathrm{C}$, which indicates the absence of deintercalation. The obtained results reveal a reversible structure change in the graphene/Co(0001) interface by Ag intercalation and deintercalation. The difference in the deintercalation between Ag and Au atoms can be explained by the activation energy of thermal desorption.

• Received 12 July 2023
• Accepted 1 October 2023

DOI:https://doi.org/10.1103/PhysRevB.108.155422