Measuring grain boundary segregation: tomographic atom probe field ion microscopy (APFIM) vs. analytical scanning transmission electron microscopy (STEM)

Grain boundary segregation is an important phenomenon in metallurgy and semiconductor technology. Some recent studies by tomographic atom probe field ion microscopy (APFIM) claim to have measured the interfacial excess of atoms segregated to grain boundaries with ultra-high precision, down to 0.01-0.02 atoms/nm2. This study critically evaluates these claims by simulations. It is shown that atom probe tomography is no 'magic bullet' and suffers similar physical constraints as analytical scanning transmission electron microscopy (STEM). Data analyses from both methods have much in common in terms of geometry, performance, systematic and statistical errors. It is shown that an analysis method previously developed for (S)TEM called conceptEM can also successfully be applied to APFIM data.