Direct detection imaging technology is relatively new to electron microscopy as compared to the
traditional detection of high energy electrons by using the scintillator and optical technology. However,
with the aid of many modern technology developments in recent years, direct detection imaging has
brought fundamental changes to the world of single particle cryoEM in structural biology where atomic
(or near atomic) resolution structures of many difficult biomolecules can be obtained in days instead of
months or years [1-2]. With the overwhelming success achieved in just a few years scientists working in
the field of cryoEM and structure biology have claimed the top prize in science [3].
Direct detection imaging technology has also started to impact electron microscopy applications in
materials science. Early success includes atomic resolution imaging of extremely beam sensitive
materials such as metal-organic-frameworks (MOFs) [4], high temporal resolution in-situ TEM [5], and
electron counting EELS (electron energy loss spectroscopy) [6], etc. Due to the wide range of
applications in materials science, direct detection imaging technology will have even more impact on
advanced electron microscopy applications.
Contrast to the traditional imaging technology, direct detection imaging cameras remove the scintillator
and the optical component by allowing high energy electrons to directly hit the imaging sensor to form
an image. Furthermore, due to the high-speed sensor readout, direct detection imaging cameras can
separate individual electrons fast enough in the imaging sensor for electron counting. One of the critical
benefits of direct detection and electron counting is the elimination of imaging sensor readout noise to
increase the ability to detect electrons under extremely weak illumination conditions. This is often
referred to as high detective quantum efficiency (DQE) in the literatures.
In this presentation, I will explain the basic concept of direct detection and electron counting, review the
successful examples already achieved in materials science, and attempt to provide a future outlook for
electron microscopy in materials science.
References
[1] X. M. Li et al., Electron counting and beam-induced motion correction enable near-atomicresolution
single-particle cryo-EM. Nat Methods 10, 584-590 (2013)
[2] H.W. Wang et al., Biological cryo-electron microscopy in China. Protein Science 26, 16-31 (2016).
[3] https://www.nobelprize.org/prizes/chemistry/2017/press-release/The Nobel Prize in Chemistry 2017. [4] Y. Zhu et al., Unravelling surface and interfacial structures of a metal–organic framework by
transmission electron microscopy. Nat Mater. 16, 532-537 (2017).
[5] H.G. Liao et al., Facet development during platinum nanocube growth. Science, 345, 916-919 (2014)
[6] J. L. Hart et al., Direct Detection Electron Energy-Loss Spectroscopy: A Method to Push the Limits
of Resolution and Sensitivity. Scientific Reports, 7, 8243-8256 (2017)