Modelling the interactions and diffusion of NO in amorphous SiO₂

Abstract

Nitric oxide (NO) is often used for the passivation of SiC/SiO 2 metal oxide semiconductor (MOS) devices. Although it is established experimentally, using XPS, EELS, and SIMS measurements, that the 4H-SiC/SiO 2 interface is extensively nitridated, the mechanisms of NO incorporation and diffusion in amorphous (a)-SiO 2 films are still poorly understood. We used Density Functional Theory (DFT) to simulate the incorporation and diffusion of NO through a-SiO 2 and correlate local steric environment in amorphous network to interstitial NO (NO i) incorporation energy and migration barriers. Shapes and volumes of structural cages in amorphous structures are characterised using a methodology based on the Voronoi Snetwork. Using an efficient sampling technique we identify the energy minima and transition states for neutral and negatively charged NO i molecules. Neutral NO i interacts with the amorphous network only weakly with the smallest incorporation energies in bigger cages. On the other hand NO −1 i binds at the network sites with wide O-Si-O bond angles, which also serve as the intrinsic precursor sites for electron trapping.

Review: understanding the properties of amorphous materials with high-performance computing methods

“…The approach adopted is to run an ensemble of simulations using classical MD and a full melt-quench trajectory, followed by relaxation with a hybrid functional (sometimes preceded by a relaxation with a non-hybrid functional) to give accurate electronic properties. This has been successfully applied to amorphous normalSiO2 [32], normalTiO2, ZnO [33], normalSm2normalO3 [34], normalAl2normalO3 [35] and normalHfO2 [36,37], to compute e.g. defect formation energies, and activation energies for diffusion.…”