C, B, N, O and Si elemental maps from EELS obtained on a nano-layered CxByNz material deposited onto a Si wafer (along with the TEM image, showing the scattering contrast of the layers)
Such kinds of study may generate new knowledge on both the material investigated and the investigation technique. A good example of this is our achievement in advanced electron holography imaging of graphene, thanks to the unique expertise of CEMES in the field. Electron holography enables to precisely analyze the stacking over large fields of view (several µm) yet with a nanometer resolution, as well as graphene morphology and local deformation. This opened the route to scrutinize in a same image the stacking nature as well as the number of stacked layers. Modelling the Van der Waals interaction was used to accurately estimate the contribution of carbon atoms in various stacks to the mean inner potential of the layer probed by the electron beam.
Phase contour TEM image obtained from the electron holography analysis of a single graphenic flake obtained from mechanical exfoliation of large graphite crystals. The image serves as a mapping of the local number of graphenes in the flake. Each color corresponds to a different number of piled-up graphenes, from 1 to 5 and more (black color correspond to no phase shif t, i.e., holes in the flake, or the surrounding empty space). The mapping requires to take a hologram image first, then to reconstruct the phase image from it, then to discretize the latter by tracing the contour every 0.06 rad of phase difference. (Cs-corrected F20 Tecnai microscope, operated at 100kV, with the biprisme voltage at 160 V).