Fast versus conventional HAADF-STEM tomography: advantages and challenges

Electron tomography has evolved into a powerful technique to study the three-dimensional (3D) structure of functional nanomaterials. Conventionally, electron tomography experiments are based on acquiring tilt series of projection images with an increment of 1-2 ̊ over an angular range that is as large as possible. Although the acquisition of such a tilt series is mostly automated, even under ideal conditions approximately 1 hour is required to obtain all 2D projection images. This is clearly a major drawback when a large number or samples needs to be investigated or when dynamic effects appear during in-situ experiments. It is furthermore clear that 3D studies of radiation sensitive materials are extremely challenging since samples will degrade when long acquisition times are required. One of the emerging challenges in the field of electron tomography is therefore to accelerate the acquisition of tilt series for tomography. At the same time, the quality of the tomographic reconstructions should be maintained and enable one to obtain reliable and quantitative parameters such as e.g. particle size and surface morphology.