Abstract
The random network of non-crystalline SiO2, like fused silica or the oxide grown on a Si substrate in dry oxygen atmosphere, is investigated on the basis of the transport properties of hydrogen (fused silica) and oxygen (oxide layer on Si substrate). It is proved that diffusion of both hydrogen and oxygen are anomalous in the sense of percolation theory. A representative set of experimental results concerning the annealing kinetics of atomic hydrogen in Suprasil glasses, and oxide growth on Si surfaces, is explained by looking at transport theory in a percolation cluster. Transport coefficients with related activation energies and (random-) fractal-like parameters are obtained: their numerical values allow a deeper understanding of structural features related to the non-homogeneous SiO2 network. In particular the disordered SiO2 network turns out to be not a continuous random lattice but rather a granular random lattice containing grains and percolation pathways connected to relaxed bonds.