Monte Carlo Simulation and Experimental High-Angle Annular Dark Field Tomography

In the last 10 years, the transmission electron tomography technique was extensively used in biology applications to obtain 3D configurations of small organic structures [1]. Such bright field electron tomography is not generally used in material science applications as the diffraction effects result in strong artefacts during the reconstruction. Bragg’s diffractions are indeed present at certain angles during the acquisition of a bright field tilt series. High angle annular dark field (HAADF) imaging with a scanning transmission electron microscope (STEM) is not significantly affected by dynamic effects. Since the contrast of HAADF depends on material thickness and composition [2], this technique is a good candidate for tomographic acquisitions of materials science samples. However, the reconstruction algorithms have to be adapted and optimum experimental parameters are needed for high resolution three-dimensional (3D) dataset at the nanoscale. The CASINO Monte Carlo software [3] was developed to simulate the effect of parameters such as angular tilt range, angular coverage, beam energy and beam dosage on HAADF-STEM micrograph [4]. In this work, we use a Monte Carlo-based simulation method to accurately model the whole tomographic data acquisition process and test the reconstruction algorithm with these different parameters.