Fig. 1: Scanning transmission electron microscopy (STEM) image and atomic structure of Cs bilayer in bilayer graphene (BLG) (C6Cs2C6).
a A STEM annular dark-field (ADF) image of Cs-intercalated BLG displaying the C6Cs2C6 structure. b, c Fast Fourier transform (FFT) image of BLG and Cs domains in (a) (scale bar = 5 nm−1). BLG exhibits a twist angle of 2.7° between its two graphene layers. The [100] and [110] spots of C6Cs2C6 domain correspond to interplanar d-spacings of 3.70 Å and 2.14 Å in real space, with the Cs [110] spots overlapping with the graphene [100] spots. d Top-view atomic model of C6Cs2C6. The yellow rhombus highlights a graphene (1 × 1) unit cell with a = b = 2.46 Å, while the red rhombus highlights the unit cell of the Cs lattice with\(\,\left(\sqrt{3}\times \sqrt{3}\,\right)R{30}^{\circ }\) lattice, where a = b = 4.26 Å. e Side and perspective view of the C6Cs2C6. The Cs atoms in different atomic planes are color-coded with two different shades of red. f ADF profile of the hexagonal Cs layer along the pink and light green boxes in (a). The red profile displays the shortest distance between two Cs atoms as 0.25 nm, consistent with the atomic model shown in (d). The green profile shows the shorter distance between the Cs atoms, indicating the lateral displacement of the two Cs atomic plans.
