Student Seminar: 4D-STEM: Unlocking Hidden Information in Electron Diffraction

High-Resolution Transmission Electron Microscopy (HR-TEM) and Scanning Transmission Electron Microscopy (STEM) have long been the twin pillars of nanoscale characterization, offering phase-contrast atomic imaging and Z-contrast compositional mapping, respectively. However, while conventional electron diffraction provides vital reciprocal-space data, it historically lacks the spatial localization necessary to resolve the complex physics occurring at discrete interfaces and heterogeneous nanostructures. In this presentation, I will introduce Four-Dimensional Scanning Transmission Electron Microscopy (4D-STEM), a transformative technique that transcends traditional 2D intensity-based imaging. By utilizing high-speed pixelated detectors, 4D-STEM records a complete 2D convergent beam electron diffraction (CBED) pattern at every pixel of a 2D spatial scan. This creates a massive, information-rich data cube that effectively bridges the gap between real and reciprocal space.

I will briefly explain how “hidden” physical properties—such as sub-picometer lattice distortions and subtle symmetry breaking—are extracted through Center-of-Mass (CoM) analysis, Slide sideband (SSB), Maximum Likelihood (ML) and Electron multislice Ptychography. Through selected case studies, I will show how 4D-STEM quantitatively maps strain, light element disorder, anion displacement and structural dynamics that remain invisible under standard imaging conditions. This shift toward “information-rich” microscopy is currently advancing the study of quantum materials, catalysts, and beam-sensitive perovskites.