Interaction of hydrogen with defects in a-SiO 2

Abstract

In this paper, the current understanding of the role of hydrogen in passivating and creating defects in irradiated MOS samples is reviewed. The first ab initio calculation of the energies of activation and reaction of the dissociation of H 2 molecules at the E′ 1 defect in α-quartz, and for a simple model for the E′ γ defect in a-SiO 2 is prestented. The effects of various improvements to standard Hartree-Fock theory, including perturbative configuration interaction and improved basis sets, were studied. It is found that the qualitative picture of H 2 dissociation is insensitive to these improvements. The estimates of the energies of reaction and activation in the adiabatic approximation are 0.25 eV and 0.78 eV, respectively. The latter energy is roughly twice the activation energy reported by Li et al. The probable sources of error are explored and it is concluded that quantum effects (zero point energy and tunneling are probably crucial for modeling this dissociation reaction. The first ab initio study of the preferred conformation of the proton in a-SiO 2 and a preliminary semiempirical calculation of the activation energy for proton hopping are also presented.