Positron annihilation lifetime and doppler broadening spectroscopies studies of defects in nano TiN crystal under gamma irradiation and high temperature

In this study, TiN nanocrystals underwent initial irradiation at room temperature using a ⁶⁰Co gamma source, employing four absorption doses (50, 200, 900, and 3500 kGy) within a Gamma MRX-25 unit. Subsequently, they were subjected to heating at 1173 K in a Linn™ HT-1800 oven under vacuum conditions of 10^–6 Torr for Positron analysis. The investigation into the mechanism of defect formation employed annihilation lifetime and Doppler broadening annihilation spectroscopies. Pertaining to the Positron Annihilation Lifetime Spectroscopy (PALS) studies, two distinct lifetime components were discerned across all samples. The τ1 lifetime component ranged between 155 and 159 ps. A marginal reduction (from 81.67 to 81.51%) was observed in the corresponding I1 intensity. Analysis of the S parameter derived from Doppler Broadening Annihilation Spectroscopy (DBAS) furnished insights into the presence of vacancy defects within the TiN nanocrystals. The diminishing trend in the S parameter with increasing positron energy or depth of positron implantation indicates a decline in the density and concentration of subsurface defects.