Abstract
The ability to obtain three-dimensional (3-D) information about morphologies of nanostructures elucidates many interesting properties of materials in both physical and biological sciences. Here we demonstrate a novel method in scanning transmission electron microscopy (STEM) that gives a fast and reliable assessment of the 3-D configuration of curvilinear nanostructures, all without needing to tilt the sample through an arc. Using one-dimensional crystalline defects known as dislocations as a prototypical example of a complex curvilinear object, we demonstrate their 3-D reconstruction two orders of magnitude faster than by standard tilt-arc TEM tomographic techniques, from data recorded by selecting different ray paths of the convergent STEM probe. Due to its speed and immunity to problems associated with a tilt arc, the tilt-less 3-D imaging offers important advantages for investigations of radiation-sensitive, polycrystalline, or magnetic materials. Further, by using a segmented detector, the total electron dose is reduced to a single STEM raster scan acquisition; our tilt-less approach will therefore open new avenues for real-time 3-D electron imaging of dynamic processes.
Highlights
Accurate insights into the physical and chemical properties of nanoscale materials and devices are critical for controlling their functionality[1]
By taking advantage of a sophisticated, proprietary image processing algorithm, we reduce the data input required for 3-D reconstruction to just two images taken at different incident beam angles, thereby increasing the efficiency of data acquisition by one to two orders of magnitude compared to standard Transmission electron microscopy (TEM) tomography techniques
As the electron beam transmits through the specimen it undergoes coherent elastic scattering, resulting in the formation of a convergent-beam electron diffraction (CBED) pattern in the back focal plane (BFP) of the objective lens[34]
Summary
Accurate insights into the physical and chemical properties of nanoscale materials and devices are critical for controlling their functionality[1]. While in an X-ray CAT (computer-aided tomography or computed axial tomography) scanner this is done by keeping the object fixed and rotating the source and detectors around the object, in standard TEM tomography the source and detectors are fixed and the object is rotated, typically acquiring a sequence of projected images of the same properties at small angular intervals over a relatively large tilt arc (typically >100 images over ±60–70° angular range)[11]. Associated with this methodology are a number of challenges. By taking advantage of a sophisticated, proprietary image processing algorithm, we reduce the data input required for 3-D reconstruction to just two images taken at different incident beam angles (effectively a tilt-less “stereoscopic pair”), thereby increasing the efficiency of data acquisition by one to two orders of magnitude compared to standard TEM tomography techniques
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