Influence of local magnification effects in the atom probe for silicon nanocrystals doped by indium

Atom probe tomography (APT) is a powerful tool to study the 3-dimensional structure of materials with sub-nanometer spatial resolution. This allows us to study the location of atoms such as dopant positions in nanocrystals (NCs) with high accuracy. However, one of the limitations for the spatial resolution are the effects of local magnification when there are multiple elements with different evaporation rates in the atom probe specimen. For example, in the system of silicon (Si) NCs embedded in SiO2, the difference in the local evaporation field between Si NCs and SiO2 results in a non-uniform sequence of evaporation and this affects the accuracy of the 3-dimensional reconstruction of the atom probe experiment (i.e. over/under estimation of the number of doped atoms in the Si NCs). In this study, we use indium (In) as a dopant to investigate the local magnification effects. Due to the very low solubility of In-atoms in Si, the detected In-atoms inside of Si NCs can be attributed to the local magnification effects and we can quantitatively estimate the number of atoms which are projected inside of Si NCs due to the trajectory artefact. This approach provides a model system to quantify and correct local magnification effects which allows a more precise and advanced study of Si nanostructures.