Atomic scale high-angle annular dark field STEM analysis of the N configuration in dilute nitrides of GaAs

Abstract

While high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) has been successfully used for the analysis of heavy atoms in a lighter matrix, the detection of light atoms in a heavy matrix remains challenging. In this paper, we show that the combination of first-principles total-energy calculations with aberration-corrected HAADF-STEM experimental and simulated images can be used to overcome this problem. The application of this methodology to the analysis of dilute nitrides of GaAs points to the existence of a major proportion of ${(2{\text{N}}_{\text{As}})}_{\text{nn}}$ in the alloy, which is a relatively stable configuration in GaAsN as revealed by our energetic calculations. Our study has allowed us to shed light in the effect of the local distortion of the lattice due to different configuration of atoms in HAADF-STEM imaging.