Electron tomography of regularly shaped nanostructures under non-linear image acquisition

Electron tomography allows the 3D quantitative characterization of nanostructures, provided a monotonic relationship is fulfilled between the projected signal and the atomic number and thickness of the specimen. This requirement is not satisfied if the micrographs are affected by (i) diffraction contrast, (ii) detector saturation or (iii) contrast inversion due to absorption (high-angle scattering) at high thickness. Artefacts related to the non-monotonic tomography acquisition are examined using computer simulations and experimental tilt series of tungsten tips and CeO₂ nanoparticles. Conditions are derived under which in spite of the non-linear artefacts the information is sufficient for reconstructing the 3D morphology of convex objects by geometric tomography.