Fig. 4: Characterization of K and Cs intercalation in graphite.
a ADF image of K intercalated highly oriented pyrolytic graphite (HOPG) revealing the honeycomb C6K2C6 structure in three domains with different numbers of graphene layers. The imaged region has an approximate thickness of 5 nm (Supplementary Fig. 15). The inset displays the corresponding FFT image (scale bar = 5 nm−1). b Cross-sectional ADF image of Cs intercalated HOPG. Bilayer Cs is found near the surface layers, while single layer Cs is found in the deeper layers of graphite. c Corresponding EELS Cs intensity mapping from the same area as in (b). d Schematic illustration of the top view of the AM intercalation in HOPG, highlighting the C6M2C6 domains in pink. e Schematic illustration of the side view of AM intercalation in HOPG, emphasizing the wrapping of the AM bilayer domain by the surface graphite layers and the single-layer AM intercalated in the deeper layer of graphite. The cross-sectional specimen, fabricated by focused ion beam (FIB), has a specimen thickness in y-direction of approximately 50 nm. The darker ADF contrast of the Cs intercalation domain is attributed to its incomplete intercalation within the graphite layers.
