Three-dimensional structural and compositional inhomogeneity in zeolites unraveled by low-dose electron ptychography

TL;DR

This paper introduces a 4D-STEM ptychography technique that achieves high-resolution 3D imaging of zeolites, revealing detailed structural and compositional inhomogeneities previously unresolvable by conventional TEM.

Contribution

The study demonstrates a novel 4D-STEM ptychography method that overcomes limitations of traditional TEM, providing ultrahigh lateral and depth resolution for detailed 3D analysis of zeolites.

Findings

Achieved ~0.85 Å lateral resolution enabling identification of individual oxygen atoms.

Attained ~6.6 nm depth resolution for 3D probing of vacancies and phase boundaries.

Unveiled complex intergrowth structures in zeolites in three dimensions.

Abstract

Structural and compositional inhomogeneity is common in zeolites and considerably affects their properties. Conventional transmission electron microscopy (TEM) cannot provide sufficient information on local structures in zeolites due to the thickness-limited lateral resolution, lack of depth resolution, and electron dose-constrained focusing. We demonstrate that a multislice ptychography method based on four-dimensional scanning TEM (4D-STEM) data can overcome these limitations. The 4D-STEM ptychography image obtained from a ~40-nm thick MFI zeolite exhibits an ultrahigh lateral resolution of ~0.85 {\AA}, enabling the unambiguous identification of individual framework oxygen (O) atoms and the precise determination of the orientations of adsorbed molecules. Furthermore, a depth resolution of ~6.6 nm is achieved, allowing the three-dimensional probing of O vacancies and phase boundaries in zeolites. The results of the 4D-STEM ptychography provide an unprecedented complete understanding of the intergrowth of MFI and MEL zeolites in three dimensions. The 4D-STEM ptychography can be generally applied to various zeolites and other materials with similar electron beam sensitivity.