Towards predictive modelling of near-edge structures in electron energy loss spectra of AlN based ternary alloys

Abstract

Although electron energy loss near edge structure analysis provides a tool for experimentally probing unoccupied density of states, a detailed comparison with simulations is necessary in order to understand the origin of individual peaks. This paper presents a density functional theory based technique for predicting the N K-edge for ternary (quasi-binary) nitrogen alloys by adopting a core hole approach, a methodology that has been successful for binary nitride compounds. It is demonstrated that using the spectra of binary compounds for optimising the core hole charge ($0.35\,\mathrm{e}$ for cubic Ti$_{1-x}$Al$_x$N and $0.45\,\mathrm{e}$ for wurtzite Al$_x$Ga$_{1-x}$N), the predicted spectra evolutions of the ternary alloys agree well with the experiments. The spectral features are subsequently discussed in terms of the electronic structure and bonding of the alloys.