Fig. 2

A structural model of a graphene single/double layer. a The left figure is a plan view and the right figure shows a cross section of the structural model. b Phase of the simulated exit wave function. There are four geometrically different atom configurations: C-atoms in the top layer (blue dots), C-atoms in the upper layer that are not superimposed on those in the bottom layer (green dots), C-atoms in the bottom layer that are not superimposed on the top layer (yellow dots) and two superimposed C-atoms (brightest peaks, red dots) c The 3D propagation intensity. d An intensity slice across a x–z plane including the four geometrical configurations. e The intensity profile along z-direction for four different types of atom for two different g _max  = 4Å⁻¹ (dot line) and 1Å⁻¹ (solid line), respectively. The hidden atom can be clearly revealed in the intensity profile with g _max  = 4Å⁻¹. It smears out in the intensity profile with g _max  = 1Å⁻¹. f Mass circle of the four different atom configurations