Electron trapping at point defects on hydroxylated silica surfaces

The origin of electron trapping and negative charging of hydroxylated silica surfaces is predicted based on accurate quantum-mechanical calculations. The calculated electron affinities of the two dominant neutral paramagnetic defects, the nonbridging oxygen center, equivalent to Si-O(center dot), and the silicon dangling bond, equivalent to Si(center dot), demonstrate that both defects are deep electron traps and can form the corresponding negatively charged defects. We predict the structure and optical absorption energies of these diamagnetic defects.