Cathodoluminescence of crystalline and amorphous SiO₂ and GeO₂

Cathodoluminescence (CL) and its temperature-dose behaviour are presented for di•erent crystalline and amorphous modifications of SiO₂ and GeO₂ as well as for Ge-doped SiO₂ layers. The crystalline samples include four-fold coordinated Si and Ge in hexagonal quartz and quartz-like crystals, respectively, as well six-fold coordinated atoms in tetragonal rutile-like crystals. The detected luminescence bands, in general, are attributed to three optical active luminescence centres: the two-fold coordinated silicon ( =Si:) and germanium ( =Ge:) centre, respectively, the nonbridging oxygen hole centre (NBOHC) and the self trapped exciton (STE). The first ones, the oxygen deficient centres (ODC), are especially developed in both, in the tetragonal crystal rutile-like modifications as well as in glassy states. The huge violet luminescence in Ge-implanted SiO₂-layers is attributed to the two-fold coordinated Ge in the silica matrix.