Quantitative chemical evaluation of dilute GaNAs using ADF STEM: Avoiding surface strain induced artifacts

The high angle annular dark field intensity (HAADF) in scanning transmission electron microscopy (STEM) can be used for a quantitative evaluation of the chemical composition in dilute GaNAs quantum wells by comparison with simulated intensities. As the scattered intensity is highly sensitive to surface strain fields originating from the quantum wells embedded in GaAs, the HAADF intensity is difficult to evaluate in a quantitative way as long as strain contrast cannot be distinguished from chemical contrast. We present a method to achieve full 2D HAADF STEM compositional mapping of GaNAs/GaAs quantum well systems by making use of information from two different camera lengths.

► Method for a quantitative analysis of GaNAs/GaAs without surface strain artifacts.
► Based on a combination of high- and low-angle ADF STEM imaging.
► Artifacts vanished by compensation of Huang scattering and dechanneling effects.
► Applicable for a large range of specimen parameters.
► Little experimental effort.