Solving Complex Nanostructures With Ptychographic Atomic Electron Tomography

Abstract

Transmission electron microscopy (TEM) is a potent technique for the determination of three-dimensional atomic scale structure of samples in structural biology and materials science. In structural biology, three-dimensional structures of proteins are routinely determined using phase-contrast single-particle cryo-electron microscopy from thousands of identical proteins, and reconstructions have reached atomic resolution for specific proteins. In materials science, threedimensional atomic structures of complex nanomaterials have been determined using a combination of annular dark field (ADF) scanning transmission electron microscopic (STEM) tomography and subpixel localization of atomic peaks, in a method termed atomic electron tomography (AET). However, neither of these methods can determine the three-dimensional atomic structure of heterogeneous nanomaterials containing light elements. Here, we perform mixed-state electron ptychography from 34.5 million diffraction patterns to reconstruct a high-resolution tilt series of a double wall-carbon nanotube (DW-CNT), encapsulating a complex ZrTe sandwich structure. Class averaging of the resulting reconstructions and subpixel localization of the atomic peaks in the reconstructed volume reveals the complex three-dimensional atomic structure of the core-shell heterostructure with 17 pm precision. From these measurements, we solve the full Zr11Te50 structure, which contains a previously unobserved ZrTe2 phase in the core. The experimental realization of ptychographic atomic electron tomography (PAET) will allow for structural determination of a wide range of nanomaterials which are beam-sensitive or contain light elements.

Quantitative Scanning Transmission Electron Microscopy for Materials Science: Imaging, Diffraction, Spectroscopy, and Tomography

“…One of the next frontiers for AET will be to implement modalities such as phase contrast imaging that are more dose efficient and able to image light elements. Pelz et al (195) have experimentally demonstrated ptychographic AET, which they used to solve the structure of a complex ZrTe nanowire encapsulated in a DW-CNT, shown in Figure 10f. Pushing phase contrast methods to thicker specimens will require including multiple scattering in the reconstruction algorithm.…”