Microscopic mechanisms of radiation-induced proton density decay in SiO2 films

In order to understand the physics of radiation-induced proton density deca y in thin SiO2 films, we performed ab initio Hartree-Fock calculations of t he potential energy curves for the interaction between model oxide clusters and H in two charge states. The calculated results led to two separate pro posed mechanisms for proton density decay in thin SiO2 films: (1) electroni c excitation involving hot phonon levels of the ground electronic state at low photon-energy radiation and (2) electron capture by protons at high pho ton-energy radiation. The proposed mechanisms qualitatively explain recent experimental observations.