Photoelectric properties and the energy gap of SiO2

The difference in the photoelectric spectra of SiO2 obtained by different authors is shown to be due to the secondary current injected by the metal electrode when this latter is in direct contact with the insulator. The photoelectric response obtained with blocking electrodes as well as the comparison between the afterglow properties and the decomposition of excitons in SiO2 indicate a band gap of about 11.5 eV.