Secondary signal imaging (SSI) electron tomography (SSI-ET): A new three-dimensional metrology for mesoscale specimens in transmission electron microscope

• We demonstrated a new electron tomography technique for mesoscale specimens.
• The SSI-ET tomogram provides remarkable visibility of the surface features.
• The contrast mechanism of the SSI in TEM is revealed by Monte Carlo simulations.

We have demonstrated a new electron tomography technique utilizing the secondary signals (secondary electrons and backscattered electrons) for ultra thick (a few μm) specimens. The Monte Carlo electron scattering simulations reveal that the amount of backscattered electrons generated by 200 and 300 keV incident electrons is a monotonic function of the sample thickness and this causes the thickness contrast satisfying the projection requirement for the tomographic reconstruction. Additional contribution of the secondary electrons emitted from the edges of the specimens enhances the visibility of the surface features. The acquired SSI tilt series of the specimen having mesoscopic dimensions are successfully reconstructed verifying that this new technique, so called the secondary signal imaging electron tomography (SSI-ET), can directly be utilized for 3D structural analysis of mesoscale structures.