LAUSR

Structural and compositional inhomogeneity is common in zeolites and considerably affects their properties. Thickness-limited lateral resolution, lack of depth resolution, and electron dose-constrained focusing limit local structural studies of zeolites in conventional transmission electron microscopy (TEM). We demonstrate that a multislice ptychography method based on four-dimensional scanning TEM (4D-STEM) data can overcome these limitations. Images obtained from a ~40-nanometer-thick MFI zeolite exhibited a lateral resolution of ~0.85 angstrom that enabled the identification of individual framework oxygen (O) atoms and the precise determination of the orientations of adsorbed molecules. Furthermore, a depth resolution of ~6.6 nanometers allowed probing of the three-dimensional distribution of O vacancies, as well as the phase boundaries in intergrown MFI and MEL zeolites. The 4D-STEM ptychography can be generally applied to other materials with similar high electron-beam sensitivity. Description Editor’s summary Zeolite structures are prone to structural and compositional inhomogeneities that can cause batch-to-batch variations in applications. However, imaging these variations is difficult in transmission electron microscopy (TEM) because zeolites are prone to electron beam damage at the doses needed for atomic resolution. Zhang et al. found that electron ptychography based on low-dose four-dimensional scanning TEM data could achieve subangstrom resolution. The authors resolved individual oxygen atom columns in various zeolites with specimen thicknesses of up to 40 nanometers and mapped the distribution of oxygen vacancies throughout a zeolite. Complex intergrown structures between different zeolite phases were also imaged. —Phil Szuromi Low-electron-dose ptychography reveals zeolite local structures such as oxygen vacancies and intergrowth phase boundaries.