LAUSR

The thickness and composition of a specimen are fundamental information for analyzing image, diffraction, and spectrum acquired by transmission electron microscopy (TEM). The thickness and composition maps are mainly obtained by spectroscopy, such as electron energy loss spectroscopy (EELS) or energy dispersive X-ray spectroscopy (EDS). Since these spectroscopies require a large electron dose, they cannot apply to electron-sensitive materials. In crystalline materials, as alternatives to spectroscopy, imaging and diffraction are used to measure the thickness and composition [1,2]. On the other hand, in non-crystalline materials, there are few alternatives to spectroscopy. Here, we focus on the diffraction patterns obtained by a pixelated detector. The thickness affects the number of scattering events, and the composition affects the scattering cross section. Thus, the diffraction pattern must contain the information of thickness and composition. Furthermore, by grace of the fast pixelated STEM detector, we can acquire the diffraction patterns at all scanning points (four-dimensional scanning TEM (4D-STEM)) [3]. We attempted to make the thickness and composition maps simultaneously from the diffraction patterns acquired by 4D-STEM. We picked up the thickness and composition from experimentally obtained diffraction patterns by comparing simulated diffraction patterns at various thicknesses and compositions. In the comparison, we used the radial distribution function (RDF) of the diffraction pattern because the diffraction pattern of non-crystalline material does not depend on the azimuthal angle.