Figure 2: Electron reflectivity in a LEEM experiment as a function of in-plane momentum and energy.
From: Nanoscale measurements of unoccupied band dispersion in few-layer graphene
(a) Two-dimensional (2D) false-colour representation of IV-curves for different in-plane momenta 
. The minimum in the IV-curves of monolayer graphene (narrow blue band near the bottom) shifts to higher energies for non-zero 
. (b) Similar behaviour is observed for the minima (two blue bands) in bilayer graphene and (c) trilayer graphene. For all figures, 
is varied from M to Γ to K. The data at the Γ-point are the IV-curves in Fig. 1b. White data points stem from Lorentzian fits to the individual IV-curves to determine the energetic position of the minima. (d) μVLEED measurement on an exfoliated graphite flake showing very similar global behaviour to a–c, apart from the discrete blue bands now being one continuous band. All four plots reflect the unoccupied 2D band structure of the respective material, where high reflected intensity (red) corresponds to band gaps and low intensity (blue) to electronic states in the solid that couple to the incoming/reflected plane wave electron beams. The dark red area at very low energies is formed by the mirror mode. Its curvature is described by the parabolic dispersion of electrons in vacuum (black dashed line in Fig. 2a).
