Local estimation of lattice constants in HRTEM images

A model-based approach to estimate lattice constants from an atomically resolved HRTEM image is presented. The approach only utilizes the inherent periodicity of these images and does not require a centrosymmetric structure of the specimen. This allows the evaluation of, for instance, wurtzite-based materials like InGaN/GaN heterostructures. The lattice constants are determined within precisions below 3 pm from areas only a few unit cells large. This makes this method suitable for further strain/compositional analysis. Furthermore, the impact of the approximations of the true detectorʹs covariance matrices on the assessment of the model-based approach is investigated, and insights into the quality of these noise models of the detector are gained.