PhD position: Precise atomic-scale structure determination in thick nanostructures

Knowing where atoms are and how they are bonded is vital to understand the properties and performance of advanced materials. Among various atomic-scale characterisation methods, transmission electron microscopy has proven highly successful for precise structure determination. Breakthrough advances in fast-readout pixel detectors are enabling structure determination at unprecedented resolution. Despite these new tools, reliable structure determination remains restricted to ultrathin (a few nanometers thick) materials – a small subset of all materials of technological interest – as existing methods fail in thicker nanostructures due to multiple scattering of the probe electrons. Overcoming this limitation is the focus of much research [1-3].

This computational project could take several directions, including:

• Extending existing thin-object reconstruction strategies by developing iterative algorithms to correct for multiple scattering.
• Comparing phase retrieval strategies for determining the so-called scattering matrix with as few measurements as possible.
• Developing methods to characterise instrument aberrations from the data itself.
• Generalising methods to handle non-periodic structures.

References

[1] D. Ren, M. Chen, L. Waller & C. Ophus, ArXiv eprints (2018), arXiv:1807.03886

[2] H.G. Brown et al., Physical Review Letters 121 (2018) 266102

F. Wang, R.S. Pennington & C.T. Koch, Physical Review Letters 117 (2016) 015501