First-principles study of proton generation at the amorphous silica/silicon (100) interface

Hydrogen-related reactions at the amorphous SiO 2 (a-SiO 2 )/Si interface contribute to radiation-induced interface degradation. Their relative feasibility depends on the local defect environment. We used density functional theory and climbing-image nudged elastic band calculations to compare proton-generation pathways in representative configurations from four a-SiO 2 /Si(100) models. The reactions examined were direct dissociation of hydrogenated defects, H 2 dissociation at positively charged defects, and local proton transfer from water-passivated oxygen vacancies (H 2 O-V O ). Direct dissociation had barriers of approximately 1.76–3.0 eV. For H 2 dissociation, the barriers were approximately 1.3–2.3 eV, with the lowest value at a puckered oxygen vacancy. Selected H 2 O-V O configurations had lower barriers. The lower-barrier +1 pathway had a barrier of 0.58 eV and a reaction energy of +0.35 eV; the corresponding values for the lower-barrier +2 pathway were approximately 0.77 eV and + 0.11 eV. Although the +2 pathway had a higher forward barrier, it was less endothermic. Hybrid-functional single-point checks preserved this two-path ordering at geometries optimized with the Perdew-Burke-Ernzerhof functional. Both water-related pathways were competitive with the examined direct-dissociation and H 2 -dissociation routes because of their lower barriers. Their contribution to mobile-proton generation, however, also depends on precursor populations and migration beyond the local transfer step.