Electron spin resonance of electron irradiated germanium dioxide

Irradiation of hexagonal germanium dioxide by fast electrons has been found to produce two paramagnetic centres. These are the oxygen vacancy, and the other is tentatively assigned to an oxygen vacancy-interstitial pair. The threshold energy for the production of both centres is 120+or- 5 keV, corresponding to a displacement for the oxygen atom of 18.1+or-0.1 eV. Annealing studies yield a unique activation energy of 1.1 eV at temperatures above 450 K for the retrapping of electrons at the oxygen vacancy. Below this temperature no unique activation energy for the annihilation of the vacancy by mobile oxygen atoms was found. For the supposed oxygen vacancy-interstitial pair two activation energies of 0.4 eV and 0.8 eV were found, corresponding to the displacement of oxygen atoms to two different interstitial sites.