Sodium intercalation of graphene films on Re(10$\bar1$0)

It is shown that during low-temperature (300–500 K) intercalation of sodium atoms into thin multilayer graphene and graphite films on rhenium the first graphene layer plays the role of a trap to which atoms coming on the surface diffuse through a graphite film. The intercalation phase of the interlayer space in the graphite bulk is actively filled at a sodium atoms concentration under the first graphene layer close to the maximum possible (2 $\pm$ 0.5) $\times$ 10$^{14}$ cm$^{-2}$. This phase capacity is proportional to the graphite film thickness that can be varied in this work from one graphene layer to 50 atomic layers. The diffusion energy $E_d$ of Na atoms through the graphite film was estimated to be $E_d\approx$ 1.4 eV.