Assessment of lower-voltage TEM performance using 3D Fourier transform of through-focus series

We assess the imaging performance of a transmission electron microscopy (TEM) system operated at a relatively low acceleration voltage using the three-dimensional (3D) Fourier transform of through-focus images. Although a single diffractogram and the Thon diagram cannot distinguish between the linear and non-linear TEM imaging terms, the 3D Fourier transform allows us to evaluate linear imaging terms, resulting in a conclusive assessment of TEM performance. Using this method, information transfer up to 98pm is demonstrated for an 80kV TEM system equipped with a spherical aberration corrector and a monochromator. We also revisit the Young fringe method in the light of the 3D Fourier transform, and have found a considerable amount of non-linear terms in Young fringes at 80kV even from a typical standard specimen, such as an amorphous Ge thin film. ► We assess the performance of TEM using 3D Fourier transform of through-focus images. ► The method can discriminate between the linear and non-linear TEM imaging terms. ► High resolution of 98pm is achieved using 80kV Cs-corrected TEM with monochromator. ► We also revisit the Young fringe method in the light of the 3D Fourier transform.