Detective quantum efficiency of electron ptychography techniques

Session

Poster Session One

Authors

Mr Felix Bennemann (1), Prof Peter Nellist (1), Prof Angus Kirkland (1)

Affiliations

1. University of Oxford

Keywords

4D-STEM, phase-sensitive, ptychography

Abstract text

Electron Ptychography (EP) is an imaging technique that has emerged as a promising approach to achieve high-resolution imaging of various materials. Despite its growing popularity, the field is still in its infancy, and there is a lack of systematic comparisons between different EP methods. Some measure of contrast transfer is available for certain techniques like single sideband (SSB) ptychography in the form of an analytical phase contrast transfer function (PCTF) [1]. PCTF functions have also been simulated for the extended ptychographic iteration engine (ePIE) algorithm [2]. For other techniques such as the Wigner distribution deconvolution, there doesn’t exist a PCTF. Therefore, while the PCTF is useful to compare SSB and ePIE there is little practical application relating it to experimental parameters such as the dose. 

Here we demonstrate how cascaded linear systems theory [3] can be used to develop analytical expressions for the spatial frequency dependent detective quantum efficiency (DQE) of various ptychographic imaging techniques. The expressions are compared with simulation data for verification. This gives experimentalists the ability to analytically calculate the dose required for imaging a certain size feature with a given EP technique.

References

1. Yang, H., Pennycook, T. J., & Nellist, P. D. (2015). Efficient phase contrast imaging in STEM using a pixelated detector. Part II: Optimisation of imaging conditions. Ultramicroscopy, 151, 232–239. https://doi.org/10.1016/j.ultramic.2014.10.013
2. O’Leary, C. M., Martinez, G. T., Liberti, E., Humphry, M. J., Kirkland, A. I., & Nellist, P. D. (2021). Contrast transfer and noise considerations in focused-probe electron ptychography. Ultramicroscopy, 221, 113189. https://doi.org/10.1016/j.ultramic.2020.113189
3. Cunningham, I. A., Westmore, M. S., & Fenster, A. (1994). A spatial-frequency dependent quantum accounting diagram and detective quantum efficiency model of signal and noise propagation in cascaded imaging systems. Medical Physics, 21(3), 417–427. https://doi.org/10.1118/1.597401