Microscopic mechanisms of radiation-induced proton density decay in SiO/sub 2/ films

Aggregation and Stabilization of Carboxylic Acid Functionalized Halloysite Nanotubes (HNT-COOH)

“…Protons in solution tend to form positively charged oxonium complexes with oxygen atoms connected to two Si atoms on the surface of HNT-COOH. The proton-oxygen bond length was found to be 1.01 Å, which is in good agreement with previous theoretical and experimental studies . Two nanotube molecules connect with each other through oxonium ions, which are the most stable sites for the protons.…”

Proton mobility in a-SiO/sub 2/

“…These facts have been also corroborated by recent quantum mechanical calculations [6,7]. However, a number of issues related to the chemistry and the physics of mobile protons in a-SiO, remain to be addressed.…”

“…What is most often referred to as the "proton" is almost certainly associated with an oxygen atom to form a threecoordinate oxygen center as shown in Figure 1. This assumption is supported by recent theoretical calculations [6,7,11] which suggest that a positively charged H forms a Si-(OH')-Si complex. Therefore, an obvious model for the motion of the positive charge through a-SiO, can be described as "a sequence of hops", where the hydrogen atom and positive charge move from one oxygen to a neighboring oxygen as shown by the arrows in Figure 1.…”

Theoretical modeling of photon- and electron-stimulated Na and K desorption fromSiO2

“…4 ϩSiO 2 system; however in that case, due to the high value of the hydrogen ionization potential, the two diabatic curves cross. 8 The second process is that involving a Na atom bound to a defect like the NBO center, wSi-O-Na. Here the situation is more complicated.…”

“…A similar interpretation has been previously reported for the emission of hydrogen by electron trapping at protons in silica. 8 In this study we present a theoretical model based on the interaction of Na ϩ and Na with regular and defect sites of silica. In particular, we focus on the transition energies associated with the Na species incorporated in the lattice and on the mechanisms that can lead to a release of Na atoms under irradiation.…”