Principles and applications of ultrafast transmission electron microscopy

Abstract

Ultrafast transmission electron microscopy (UTEM) is an advanced experimental technique that integrates a femtosecond (fs) laser with transmission electron microscopy to capture material dynamic processes at exceptionally high spatiotemporal resolution. This review aims to provide an overview on the recent progresses on UTEM from technical principles, instrument developments to scientific applications and future prospects. The fundamental operation principle of UTEM involves exciting the sample with a pump laser/electric pulse, followed by probing with a time-delayed electron pulse. By precisely varying the delay time between the pump and probe pulses, electron imaging, diffraction or spectroscopy at fs-nanometer/atomic scale can be achieved. Based on these capabilities, these advances have recently culminated in techniques such as five-dimensional scanning transmission electron microscopy and Attosecond electron microscopy, which push the boundaries toward quantitative strain mapping and sub-cycle dynamics. UTEM has demonstrated significant applications in the study of microscopic dynamics in correlated materials, semiconductors, catalysts, nanophotonics, etc. It enables direct visualization of fundamental dynamic processes such as carrier relaxation, lattice vibrations, phase transitions, near-field evolution and magnetic domain switching, etc., thereby deepening the understanding of non-equilibrium states and providing critical insights for the design of novel functional devices. With ongoing advancements in fs electron sources and high-sensitivity electron detectors, the temporal resolution and detection sensitivity of UTEM continue to improve, highlighting its substantial potential in nanometer/atomic-scale ultrafast science. Future technique developments are expected to drive major breakthroughs in condensed matter physics, materials science, chemical reactions and even biological structure dynamics, offering a powerful tool for exploring the ultrafast microscopic world.

Keywords

Ultrafast transmission electron microscopy / spatiotemporal-resolved characterization / carrier dynamics / lattice dynamics / magnetic dynamics / attosecond electron microscopy

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