Defect formation analysis in gamma-irradiated titanium nitride nanocrystals: predictions from positron annihilation studies

The study investigates the effect of gamma radiation on defect formation in 20 nm titanium nitride (TiN) nanocrystals through positron annihilation lifetime (PALS) and Doppler broadening spectroscopy (DBS) studies. PALS studies were performed at atmospheric pressure, and DBS studies were performed under high vacuum conditions of 10 −9 Torr. Gamma irradiation of the samples was performed in MRX-25 gamma device using 60 Co isotope with 1.27 MeV energy at absorption doses of 50, 200, 900, and 3500 kGy. Two lifetime components were observed in the PALS results. Under the influence of gamma radiation, τ 1 increases from 170 to 179 ps, and τ 2 increases from 325 to 398 ps. As the radiation dose increases, the intensity corresponding to the short lifetime component I 1 increases (from 75.6 to 81.2%), and I 2 decreases (from 24.4 to 18.7%). PALS calculations were performed using the MICA package and a lifetime of 171 ps was determined for the 1Ti vacancy. With the help of Doppler broadening spectroscopy, information about the change and type of defects in the TiN nanocrystal along the volume was behavior of by studying S and W parameters. The results showed that the functionality of the material is optimal at gamma radiation doses not exceeding 3000 kGy.