New Imaging Technique Sees Elements that Are “Invisible” to Common Methods

The Science

Electrons can extend our view of microscopic objects well beyond what’s possible with visible light, all the way to the atomic scale. A popular method in electron microscopy for looking at tough, resilient materials in atomic detail is scanning transmission electron microscopy, but the highly focused beam of electrons used can easily destroy delicate samples including light metals. Molecular Foundry scientists developed a new imaging technique that greatly improves images of light elements using fewer electrons.

The Impact

The MIDI-STEM method may solve the challenge of seeing structures with a mixture of heavy and light elements in close proximity, thereby allowing scientists to use high-resolution electron microscopy on a broader set of hybrid materials.

Summary

To address the damage caused by scanning transmission electron microscopy, or STEM, a team at the Molecular Foundry developed a new imaging technique, tested on samples of nanoscale gold and carbon, that greatly improves images of light elements using fewer electrons. The newly demonstrated technique, dubbed MIDI-STEM, for matched illumination and detector interferometry scanning transmission electron microscopy (STEM), combines STEM with an optical device called a phase plate that modifies the alternating peak-to-trough, wave-like properties (called the phase) of the electron beam. This phase plate modifies the electron beam in a way that allows scientists to measure subtle changes in a material, even revealing materials that would be invisible in traditional STEM imaging. The team who designed MIDI-STEM was brought together through the Foundry's new Theme Postdoc program, which tackles highly multidisciplinary research challenges that would result in the development of new capabilities for future users.

Funding

Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Work at the University of Oregon was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award No. DE-SC0010466.

Publications

C. Ophus, J. Ciston, J. Pierce, T. R. Harvey, J. Chess, B. J. McMorran, C. Czarnik, H. H. Rose, and P. Ercius, “Efficient linear phase contrast in scanning transmission electron microscopy with matched illumination and detector interferometry.” Nature Communications 7, 10719 (2016). [DOI: 10.1038/ncomms10719]