Lattice defects continued clustering

For the samples after high-fluence irradiation (state O2), the nature of the defects is different in He- and Ar-irradiated samples because and resistivities showed different behavior in spite of the close agreement of the Ao variations. However, the main origin of the Ao decrease is the same in both samples and is thought to be due to vacancies that did not recombine with Nb interstitials because these agglomerate into clusters or precipitates. This is suggested because of the continuous increase of the concentration of off-lattice-site Nb atoms in spite of an Ao decrease during the irradiation up to this irradiation state. 

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