Positron trap centers in x-ray and γ-ray irradiated SiO2

Using Doppler broadening annihilation spectroscopy, we investigated the properties of irradiated samples of SiO2/Si(100) with 117 nm thick oxide layer, grown in dry O2 on p- and n-type substrates. These samples were irradiated with γ rays and x rays at doses in the range of 7×104–9×106 rad and 50–2000 mJ/cm2, respectively. The changes observed in the Doppler broadening line shape parameter after irradiation and its recovery during isochronal annealing were used to obtain an activation energy of 1.48–1.61 eV required for annealing the defects.