Abstract
Knowing the three-dimensional structural information of materials at the nanometer scale is essential to understanding complex material properties. Electron tomography retrieves three-dimensional structural information using a tilt series of two-dimensional images. In this paper, we report an alternative combination of electron ptychography with the inverse multislice method. We demonstrate depth sectioning of a nanostructured material into slices with 0.34 nm lateral resolution and with a corresponding depth resolution of about 24–30 nm. This three-dimensional imaging method has potential applications for the three-dimensional structure determination of a range of objects, ranging from inorganic nanostructures to biological macromolecules.
Highlights
Knowing the three-dimensional structural information of materials at the nanometer scale is essential to understanding complex material properties
Transmission electron microscopy (TEM) has been extensively used for structural analysis in both physical and biological sciences for many decades, where under carefully defined optical conditions, the structure of 3D objects can be interpreted from two-dimensional (2D) images[3,4,5]
For X-rays, the projection approximation is generally valid even for a relatively thick specimens at high tilt angles, before significant multiple scattering occurs. This approximation breaks down at modest specimen thickness for electrons due to their larger interaction cross section[3], which leads to multiple scattering. This multiple scattering is often accounted for in image simulations using the multislice method[20, 21], and an inverse multislice method has been recently incorporated into ptychographic reconstruction algorithms, whereby the exit surface wave function of an object is calculated slice by slice as the wave is transmitted through the sample
Summary
Knowing the three-dimensional structural information of materials at the nanometer scale is essential to understanding complex material properties. For X-rays, the projection approximation is generally valid even for a relatively thick specimens at high tilt angles, before significant multiple scattering occurs This approximation breaks down at modest specimen thickness for electrons due to their larger interaction cross section[3], which leads to multiple scattering. This multiple scattering is often accounted for in image simulations using the multislice method[20, 21], and an inverse multislice (invMS) method has been recently incorporated into ptychographic reconstruction algorithms, whereby the exit surface wave function of an object is calculated slice by slice as the wave is transmitted through the sample. An alternative geometry that can be used to retrieve the object transmission function from an array of far-field diffraction patterns is to record these by moving a known, finite-sized (defocused) probe over a sample with partial a 101 nm g
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