An infra-red spectroscopic study was made of defects that were introduced into Czochralski-type samples by fast neutron irradiation at room temperature, followed by annealing. Two new localized vibrational modes were detected at 914 and 1000/cm. They were correlated with intermediate defect stages between VO and VO2 centers. The most likely candidate was suggested to be a [VO+Oi] structure, in which a VO pair was trapped near to an interstitial O atom. Semi-empirical calculations of the frequency shifts of the isolated Oi and VO centers, when they came together into a [VO+Oi] structure, were in general accord with the proposed assignment.

C.A.Londos, G.I.Georgiou, L.G.Fytros, N.Sarlis: Solid State Phenomena, 1996, 47-48, 281-6