Real-time tilt undersampling optimization during electron tomography of beam sensitive samples using golden ratio scanning and RECAST3D

Abstract

Electron tomography is a widely used technique for 3D structural analysis of nanomaterials, but it can cause damage to samples due to high electron doses and long exposure times. To...

Low-Dose 4D-STEM Tomography for Beam-Sensitive Nanocomposites

“…One important issue when applying ET is the often significant accumulation of electron dose and therefore beam damage during the serial imaging, resulting in a transformed nanostructure that obstructs a trustworthy 3D reconstruction. ,, The relevance of this problem is even increased for MOFs that are particularly sensitive to electron radiation and which lose their crystallinity already at an accumulated dose of 5–30 electrons/Å 2 . − This amorphization process is often accompanied by a change in the morphology of MOF particles, particularly shrinkage. ,, Whereas amorphization is not an issue for nonatomically resolved tomography, shrinkage is synonymous with a change in the volume, which is not acceptable during tomogram acquisition. Various solutions to reduce the accumulated dose during serial imaging and thus mitigating beam damage have been proposed in the past, but often one has to accept a certain degree of change in the investigated particle. , However, especially when several 3D reconstructions are to be performed on one particle, for example, to investigate transformations as a result of in situ triggers, shrinkage of the sample by the electron beam is not acceptable …”

“…reduce the accumulated dose during serial imaging and thus mitigating beam damage have been proposed in the past, but often one has to accept a certain degree of change in the investigated particle. 12,21 However, especially when several 3D reconstructions are to be performed on one particle, for example, to investigate transformations as a result of in situ triggers, shrinkage of the sample by the electron beam is not acceptable. 9 An additional challenge for ET applied to MOF−metal nanocomposites is the different scattering power of the materials.…”

“…Despite the introduction of golden ratio scanning (GRS) in recent studies, we opted for sequential scanning due to the practical limitations of GRS in our 4D-STEM mode, particularly the challenges in real-time adjustments during tilt-series acquisition. 21 Notably, the large pixel size of 2.16 nm reduced the areal dose compared to atomically resolved images. The camera length was chosen to be relatively short (46 mm) to cover higher angles with the camera (0−134 mrad up to the diagonal maximum).…”

“…A tilt series was recorded with 10° increments from −70° to +70° with a 4D-STEM scan of 512 × 512 px (2.16 nm/px) in real space and 256 × 256 px in diffraction space (on a Timepix3 camera) at each tilt step. Despite the introduction of golden ratio scanning (GRS) in recent studies, we opted for sequential scanning due to the practical limitations of GRS in our 4D-STEM mode, particularly the challenges in real-time adjustments during tilt-series acquisition …”