Irradiation-induced effects were investigated by using an  in situ  transmission electron microscopic technique which permitted transmission electron microscopic images, and photoluminescence and cathodoluminescence spectra, to be obtained simultaneously. The results showed that luminescence intensities at wavelengths of 565, 725 and 850nm remained the same during irradiation at 20K. However, the intensities decreased during annealing at 90K, after irradiation at 20K. It was suggested that the Frenkel defects which were introduced by irradiation at 20K were no longer frozen at temperatures ranging from 20 to 90K, and that thermal migration of interstitials resulted in the formation of complexes that were associated with a non-radiative recombination center. Under irradiation, the luminescence intensities which were measured at 90K decreased with dose. An analysis of the rates of decrease indicated that the complexes were associated with 2 or more interstitials.

Y.Ohno, S.Takeda: Journal of Electron Microscopy, 1996, 45[1], 73-8