Proton diffusion in amorphous SiO2 and hafnium silicate by Ab Initio molecular dynamics

We study proton diffusion in amorphous SiO2 and hafnium silicates at the atomic scale. In amorphous SiO2, ab initio molecular dynamics suggest that the dominant atomic process consists in cross-ring interoxygen hopping assisted by network vibrations. In hafnium silicates, we find that the proton localizes on O atoms bonded to Hf atoms, in accord with our static total-energy calculations. These results imply that in stacked gate oxides the proton preferentially localizes within the high-kappa oxide rather than within the SiO2 interlayer.