Dissociation of GaN$^{2+}$ and AlN$^{2+}$ in APT: Electronic structure and stability in strong DC field

David Zanuttini (1, 2) , François Vurpillot (2) , J. Douady (1) , E. Jacquet (1) , P.-M. Anglade (1) , B. Gervais (1)

1 CIMAP - UMR 6252 - Centre de recherche sur les Ions, les MAtériaux et la Photonique
2 GPM - Groupe de physique des matériaux

We investigate from a theoretical point of view the stability of AlN2+ and GaN2+ dications produced under high static electric fields like those reached in Atom Probe Tomography (APT) experiments. By means of quantum chemical calculations of the electronic structure of these molecules, we show that their stability is governed by two independent processes. On the one hand, the spin-orbit coupling allows some molecular excited states to dissociate by inter-system crossing. On the other hand, the action of the electric field lowers the potential energy barrier, which ensures the dication stability in standard conditions. We present a detailed example of field emission dynamics in the specific case of the 11Δ states for a parabolic tip, which captures the essentials of the process by means of a simplified model. We show that the dissociation dynamics of AlN2+ and GaN2+ is completely different despite the strong resemblance of their electronic structure.

Domaines: Science des matériaux [cond-mat.mtrl-sci]

David Zanuttini, François Vurpillot, J. Douady, E. Jacquet, P.-M. Anglade, et al.. Dissociation of GaN$^{2+}$ and AlN$^{2+}$ in APT: Electronic structure and stability in strong DC field. Journal of Chemical Physics, 2018, 149 (13), pp.134310. ⟨10.1063/1.5036933⟩. ⟨hal-02061759⟩