Maarten Wirix

Thermo Fisher Scientific, The Netherlands

One of the main challenges in conventional STEM techniques is the difficulty to fully image and interpret a lattice consisting of both high and low Z elements. While only high Z elements can be imaged in HAADF-STEM, (A)BF-STEM can display low Z elements, though atomic positions in the images are difficult to interpret as there is no clear contrast variation between different atoms (1).

Novel integrated differential phase contrast (iDPC) STEM imaging is instrumental in showing both low Z and high Z elements with clear contrast variation (2). iDPC STEM is based on center of mass (COM) based imaging (3), and its strength in simultaneous high and low Z detection has been shown experimentally in GaN (2, 4) and Ɣ-TiH (5) domains. Moreover, iDPC STEM images have also been shown to exhibit improved contrast in beam sensitive materials, exemplified with graphene (2).

In materials science, we are seeing an increasing particular interest in structures that are comprised of low Z elements and beam sensitive materials (i.e. 2D materials, zeolites, MOFs, etc.) requiring low dose imaging techniques. With an enhanced contrast as well as wide Z-range detection capability, iDPC STEM should be considered as the key sub-angstrom imaging method in these research areas.

1. Bosch, E.G.T. et al. Ultramicroscopy, 2015, 156, 59-72.
2. Lazić, I. et al. Ultramicroscopy, 2016, 160, 265-280.
3. Müller, K. et al. Nat. Commun., 2014, 5, 5653.
4. Yücelen, E. et al. Sci. Rep., 2018, 8, 2676.
5. de Graaf, S. et al. arXiv:1812.09118.