Will a Wiener Filter Decrease the Accuracy of HRTEM Displacement Measurements of Aperiodic Structures?

Abstract

Modern Cs-corrected high-resolution transmission electron microscopy (HRTEM) has pushed the resolution limit to sub-angstrom scale and has made possible the quantitative analyses of local aperiodic atomic structures. After images have been obtained, a Wiener filter is often used to improve the signal-to-noise ratio, especially for those samples containing both crystal and large amorphous components. However, a Wiener filter may introduce distortions in the original experimental images. From this point of view, having a fundamental understanding of the effect of a Wiener filter on the accuracy of atomic displacement measurements in aperiodic structures is important. In this work, we first review the principle of the Wiener filter and theoretically discuss the origin of the distortions induced in aperiodic structures by using a Wiener filter. Then, using hypothetical experimental systems that contains both aperiodic crystal structures and amorphous layers, we carried out synthetic experiments to quantitatively estimate the effect of the Wiener filter on the measurements of aperiodic displacements. Compared with the values for a non-filtered image, the signal-to-noise ratio was significantly improved, and the accuracy of the displacement measurement was not decreased when proper Wiener filter parameters were used. Such results are of great importance for the processing of HRTEM images.