Figure 3

(a) Low loss EELS spectra obtained as a function of distance from the Bi₂Se₃/graphene/aC interface. The scanned region spans 60 nm with the positive direction running left to right in the images in (b). Blue lines indicate spectra from the bulk Bi₂Se₃ up to a position of − 13 nm, while red indicates spectra from the bulk aC up to a position of +13 nm. Green indicates the interface. The inset shows a zoom in of the \(\pi\) plasmon mode. (b) Spectral maps and HAADF collected from the spectral image. For the \(\pi\) plasmon, the red channel is the integrated spectral density between 4.5 and 5.5 eV, the green channel is between 5.5 and 6.5 eV and the blue channel is between 6.9 and 7.9 eV. For the \(\pi + \sigma\) plasmon, the cyan channel is between 17 and 18 eV and the mageneta channel is between 23.5 and 24.5 eV. (c) The energy of the plasmon peaks plotted as a function of position between −13 nm and +13 nm with 0 centred on the approximate position of the graphene layer.