INTRINSIC AND MODIFIED DEFECT STATES IN SILICA

Starting from a point defect involving a separated trivalent silicon and a non-bridging oxygen the optical properties of colour centres in pure silica are analysed. It is proposed that the silicon and oxygen states are charged in the annealed glass and that these are the precursors of the paramagnetic states produced with ionising radiation. A dipole centre in which the two defect ions share a common bond is described. This is used as a basis for analysing the colour centre properties of modified silica - the aim being to obtain a comprehensive picture of point defects in amorphous silicate networks. The effects of common impurities like water present in the different commercial forms of silica are also discussed. © 1979.