Data-efficient 4D-STEM in SEM: Beyond 2D Materials to Metallic Materials

TL;DR

This paper advances 4D-STEM in SEM by increasing speed, resolution, and applying it to diverse materials, enabling detailed imaging of nanostructures and in situ experiments.

Contribution

It introduces a faster, higher-resolution 4D-STEM method in SEM with novel geometry, expanding its application to various materials including alloys and FIB lamellae.

Findings

Enhanced acquisition rate by a factor of a few tenths using event-driven mode

Achieved a camera length of 160 mm for improved angular resolution

Successfully imaged nanostructured platinum-copper film and identified twins in copper

Abstract

Four-dimensional scanning transmission electron microscopy (4D-STEM) is a powerful tool that allows for the simultaneous acquisition of spatial and diffraction information, driven by recent advancements in direct electron detector technology. Although 4D-STEM has been predominantly developed for and used in conventional TEM and STEM, efforts are being made to implement the technique in scanning electron microscopy (SEM). In this paper, we push the boundaries of 4D-STEM in SEM and extend its capabilities in three key aspects: (1) faster acquisition rate with reduced data size, (2) higher angular resolution, and (3) application to various materials including conventional alloys and focused ion beam (FIB) lamella. Specifically, operating the MiniPIX Timepix3 detector in the event-driven mode significantly improves the acquisition rate by a factor of a few tenths compared to conventional frame-based mode, thereby opening up possibilities for integrating 4D-STEM into various in situ SEM testing. Furthermore, with a novel stage-detector geometry, a camera length of 160 mm is achieved which improves the angular resolution amplifying its utility, for example, magnetic or electric field imaging. Lastly, we successfully imaged a nanostructured platinum-copper thin film with a grain size of 16 nm and a thickness of 20 nm, and identified annealing twins in FIB-prepared polycrystalline copper using virtual darkfield imaging and orientation mapping. This work demonstrates the potential of synergetic combination of 4D-STEM with in situ experiments, and broadening its applications across a wide range of materials.